[rust-lightning] / lightning-invoice / src / utils.rs

//! Convenient utilities to create an invoice.

use crate::{CreationError, Currency, Invoice, InvoiceBuilder, SignOrCreationError};

use crate::{prelude::*, Description, InvoiceDescription, Sha256};
use bech32::ToBase32;
use bitcoin_hashes::Hash;
use lightning::chain;
use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
use lightning::chain::keysinterface::{Recipient, NodeSigner, SignerProvider, EntropySource};
use lightning::ln::{PaymentHash, PaymentSecret};
use lightning::ln::channelmanager::{ChannelDetails, ChannelManager, MIN_FINAL_CLTV_EXPIRY_DELTA};
use lightning::ln::channelmanager::{PhantomRouteHints, MIN_CLTV_EXPIRY_DELTA};
use lightning::ln::inbound_payment::{create, create_from_hash, ExpandedKey};
use lightning::routing::gossip::RoutingFees;
use lightning::routing::router::{RouteHint, RouteHintHop, Router};
use lightning::util::logger::Logger;
use secp256k1::PublicKey;
use core::ops::Deref;
use core::time::Duration;

/// Utility to create an invoice that can be paid to one of multiple nodes, or a "phantom invoice."
/// See [`PhantomKeysManager`] for more information on phantom node payments.
///
/// `phantom_route_hints` parameter:
/// * Contains channel info for all nodes participating in the phantom invoice
/// * Entries are retrieved from a call to [`ChannelManager::get_phantom_route_hints`] on each
///   participating node
/// * It is fine to cache `phantom_route_hints` and reuse it across invoices, as long as the data is
///   updated when a channel becomes disabled or closes
/// * Note that if too many channels are included in [`PhantomRouteHints::channels`], the invoice
///   may be too long for QR code scanning. To fix this, `PhantomRouteHints::channels` may be pared
///   down
///
/// `payment_hash` can be specified if you have a specific need for a custom payment hash (see the difference
/// between [`ChannelManager::create_inbound_payment`] and [`ChannelManager::create_inbound_payment_for_hash`]).
/// If `None` is provided for `payment_hash`, then one will be created.
///
/// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
/// in excess of the current time.
///
/// `duration_since_epoch` is the current time since epoch in seconds.
///
/// You can specify a custom `min_final_cltv_expiry_delta`, or let LDK default it to
/// [`MIN_FINAL_CLTV_EXPIRY_DELTA`]. The provided expiry must be at least [`MIN_FINAL_CLTV_EXPIRY_DELTA`] - 3.
/// Note that LDK will add a buffer of 3 blocks to the delta to allow for up to a few new block
/// confirmations during routing.
///
/// Note that the provided `keys_manager`'s `NodeSigner` implementation must support phantom
/// invoices in its `sign_invoice` implementation ([`PhantomKeysManager`] satisfies this
/// requirement).
///
/// [`PhantomKeysManager`]: lightning::chain::keysinterface::PhantomKeysManager
/// [`ChannelManager::get_phantom_route_hints`]: lightning::ln::channelmanager::ChannelManager::get_phantom_route_hints
/// [`ChannelManager::create_inbound_payment`]: lightning::ln::channelmanager::ChannelManager::create_inbound_payment
/// [`ChannelManager::create_inbound_payment_for_hash`]: lightning::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
/// [`PhantomRouteHints::channels`]: lightning::ln::channelmanager::PhantomRouteHints::channels
/// [`MIN_FINAL_CLTV_EXPIRY_DETLA`]: lightning::ln::channelmanager::MIN_FINAL_CLTV_EXPIRY_DELTA
///
/// This can be used in a `no_std` environment, where [`std::time::SystemTime`] is not
/// available and the current time is supplied by the caller.
pub fn create_phantom_invoice<ES: Deref, NS: Deref, L: Deref>(
        amt_msat: Option<u64>, payment_hash: Option<PaymentHash>, description: String,
        invoice_expiry_delta_secs: u32, phantom_route_hints: Vec<PhantomRouteHints>, entropy_source: ES,
        node_signer: NS, logger: L, network: Currency, min_final_cltv_expiry_delta: Option<u16>, duration_since_epoch: Duration,
) -> Result<Invoice, SignOrCreationError<()>>
where
        ES::Target: EntropySource,
        NS::Target: NodeSigner,
        L::Target: Logger,
{
        let description = Description::new(description).map_err(SignOrCreationError::CreationError)?;
        let description = InvoiceDescription::Direct(&description,);
        _create_phantom_invoice::<ES, NS, L>(
                amt_msat, payment_hash, description, invoice_expiry_delta_secs, phantom_route_hints,
                entropy_source, node_signer, logger, network, min_final_cltv_expiry_delta, duration_since_epoch,
        )
}

/// Utility to create an invoice that can be paid to one of multiple nodes, or a "phantom invoice."
/// See [`PhantomKeysManager`] for more information on phantom node payments.
///
/// `phantom_route_hints` parameter:
/// * Contains channel info for all nodes participating in the phantom invoice
/// * Entries are retrieved from a call to [`ChannelManager::get_phantom_route_hints`] on each
///   participating node
/// * It is fine to cache `phantom_route_hints` and reuse it across invoices, as long as the data is
///   updated when a channel becomes disabled or closes
/// * Note that if too many channels are included in [`PhantomRouteHints::channels`], the invoice
///   may be too long for QR code scanning. To fix this, `PhantomRouteHints::channels` may be pared
///   down
///
/// `description_hash` is a SHA-256 hash of the description text
///
/// `payment_hash` can be specified if you have a specific need for a custom payment hash (see the difference
/// between [`ChannelManager::create_inbound_payment`] and [`ChannelManager::create_inbound_payment_for_hash`]).
/// If `None` is provided for `payment_hash`, then one will be created.
///
/// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
/// in excess of the current time.
///
/// `duration_since_epoch` is the current time since epoch in seconds.
///
/// Note that the provided `keys_manager`'s `NodeSigner` implementation must support phantom
/// invoices in its `sign_invoice` implementation ([`PhantomKeysManager`] satisfies this
/// requirement).
///
/// [`PhantomKeysManager`]: lightning::chain::keysinterface::PhantomKeysManager
/// [`ChannelManager::get_phantom_route_hints`]: lightning::ln::channelmanager::ChannelManager::get_phantom_route_hints
/// [`ChannelManager::create_inbound_payment`]: lightning::ln::channelmanager::ChannelManager::create_inbound_payment
/// [`ChannelManager::create_inbound_payment_for_hash`]: lightning::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
/// [`PhantomRouteHints::channels`]: lightning::ln::channelmanager::PhantomRouteHints::channels
///
/// This can be used in a `no_std` environment, where [`std::time::SystemTime`] is not
/// available and the current time is supplied by the caller.
pub fn create_phantom_invoice_with_description_hash<ES: Deref, NS: Deref, L: Deref>(
        amt_msat: Option<u64>, payment_hash: Option<PaymentHash>, invoice_expiry_delta_secs: u32,
        description_hash: Sha256, phantom_route_hints: Vec<PhantomRouteHints>, entropy_source: ES,
        node_signer: NS, logger: L, network: Currency, min_final_cltv_expiry_delta: Option<u16>, duration_since_epoch: Duration,
) -> Result<Invoice, SignOrCreationError<()>>
where
        ES::Target: EntropySource,
        NS::Target: NodeSigner,
        L::Target: Logger,
{
        _create_phantom_invoice::<ES, NS, L>(
                amt_msat, payment_hash, InvoiceDescription::Hash(&description_hash),
                invoice_expiry_delta_secs, phantom_route_hints, entropy_source, node_signer, logger, network,
                min_final_cltv_expiry_delta, duration_since_epoch,
        )
}

fn _create_phantom_invoice<ES: Deref, NS: Deref, L: Deref>(
        amt_msat: Option<u64>, payment_hash: Option<PaymentHash>, description: InvoiceDescription,
        invoice_expiry_delta_secs: u32, phantom_route_hints: Vec<PhantomRouteHints>, entropy_source: ES,
        node_signer: NS, logger: L, network: Currency, min_final_cltv_expiry_delta: Option<u16>, duration_since_epoch: Duration,
) -> Result<Invoice, SignOrCreationError<()>>
where
        ES::Target: EntropySource,
        NS::Target: NodeSigner,
        L::Target: Logger,
{

        if phantom_route_hints.is_empty() {
                return Err(SignOrCreationError::CreationError(
                        CreationError::MissingRouteHints,
                ));
        }

        if min_final_cltv_expiry_delta.is_some() && min_final_cltv_expiry_delta.unwrap().saturating_add(3) < MIN_FINAL_CLTV_EXPIRY_DELTA {
                return Err(SignOrCreationError::CreationError(CreationError::MinFinalCltvExpiryDeltaTooShort));
        }

        let invoice = match description {
                InvoiceDescription::Direct(description) => {
                        InvoiceBuilder::new(network).description(description.0.clone())
                }
                InvoiceDescription::Hash(hash) => InvoiceBuilder::new(network).description_hash(hash.0),
        };

        // If we ever see performance here being too slow then we should probably take this ExpandedKey as a parameter instead.
        let keys = ExpandedKey::new(&node_signer.get_inbound_payment_key_material());
        let (payment_hash, payment_secret) = if let Some(payment_hash) = payment_hash {
                let payment_secret = create_from_hash(
                        &keys,
                        amt_msat,
                        payment_hash,
                        invoice_expiry_delta_secs,
                        duration_since_epoch
                                .as_secs(),
                        min_final_cltv_expiry_delta,
                )
                .map_err(|_| SignOrCreationError::CreationError(CreationError::InvalidAmount))?;
                (payment_hash, payment_secret)
        } else {
                create(
                        &keys,
                        amt_msat,
                        invoice_expiry_delta_secs,
                        &entropy_source,
                        duration_since_epoch
                                .as_secs(),
                        min_final_cltv_expiry_delta,
                )
                .map_err(|_| SignOrCreationError::CreationError(CreationError::InvalidAmount))?
        };

        log_trace!(logger, "Creating phantom invoice from {} participating nodes with payment hash {}",
                phantom_route_hints.len(), log_bytes!(payment_hash.0));

        let mut invoice = invoice
                .duration_since_epoch(duration_since_epoch)
                .payment_hash(Hash::from_slice(&payment_hash.0).unwrap())
                .payment_secret(payment_secret)
                .min_final_cltv_expiry_delta(
                        // Add a buffer of 3 to the delta if present, otherwise use LDK's minimum.
                        min_final_cltv_expiry_delta.map(|x| x.saturating_add(3)).unwrap_or(MIN_FINAL_CLTV_EXPIRY_DELTA).into())
                .expiry_time(Duration::from_secs(invoice_expiry_delta_secs.into()));
        if let Some(amt) = amt_msat {
                invoice = invoice.amount_milli_satoshis(amt);
        }

        for PhantomRouteHints { channels, phantom_scid, real_node_pubkey } in phantom_route_hints {
                log_trace!(logger, "Generating phantom route hints for node {}",
                        log_pubkey!(real_node_pubkey));
                let mut route_hints = filter_channels(channels, amt_msat, &logger);

                // If we have any public channel, the route hints from `filter_channels` will be empty.
                // In that case we create a RouteHint on which we will push a single hop with the phantom
                // route into the invoice, and let the sender find the path to the `real_node_pubkey`
                // node by looking at our public channels.
                if route_hints.is_empty() {
                        route_hints.push(RouteHint(vec![]))
                }
                for mut route_hint in route_hints {
                        route_hint.0.push(RouteHintHop {
                                src_node_id: real_node_pubkey,
                                short_channel_id: phantom_scid,
                                fees: RoutingFees {
                                        base_msat: 0,
                                        proportional_millionths: 0,
                                },
                                cltv_expiry_delta: MIN_CLTV_EXPIRY_DELTA,
                                htlc_minimum_msat: None,
                                htlc_maximum_msat: None,});
                        invoice = invoice.private_route(route_hint.clone());
                }
        }

        let raw_invoice = match invoice.build_raw() {
                Ok(inv) => inv,
                Err(e) => return Err(SignOrCreationError::CreationError(e))
        };
        let hrp_str = raw_invoice.hrp.to_string();
        let hrp_bytes = hrp_str.as_bytes();
        let data_without_signature = raw_invoice.data.to_base32();
        let signed_raw_invoice = raw_invoice.sign(|_| node_signer.sign_invoice(hrp_bytes, &data_without_signature, Recipient::PhantomNode));
        match signed_raw_invoice {
                Ok(inv) => Ok(Invoice::from_signed(inv).unwrap()),
                Err(e) => Err(SignOrCreationError::SignError(e))
        }
}

#[cfg(feature = "std")]
/// Utility to construct an invoice. Generally, unless you want to do something like a custom
/// cltv_expiry, this is what you should be using to create an invoice. The reason being, this
/// method stores the invoice's payment secret and preimage in `ChannelManager`, so (a) the user
/// doesn't have to store preimage/payment secret information and (b) `ChannelManager` can verify
/// that the payment secret is valid when the invoice is paid.
///
/// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
/// in excess of the current time.
///
/// You can specify a custom `min_final_cltv_expiry_delta`, or let LDK default it to
/// [`MIN_FINAL_CLTV_EXPIRY_DELTA`]. The provided expiry must be at least [`MIN_FINAL_CLTV_EXPIRY_DELTA`].
/// Note that LDK will add a buffer of 3 blocks to the delta to allow for up to a few new block
/// confirmations during routing.
///
/// [`MIN_FINAL_CLTV_EXPIRY_DETLA`]: lightning::ln::channelmanager::MIN_FINAL_CLTV_EXPIRY_DELTA
pub fn create_invoice_from_channelmanager<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description: String, invoice_expiry_delta_secs: u32,
        min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
where
        M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
        T::Target: BroadcasterInterface,
        ES::Target: EntropySource,
        NS::Target: NodeSigner,
        SP::Target: SignerProvider,
        F::Target: FeeEstimator,
        R::Target: Router,
        L::Target: Logger,
{
        use std::time::SystemTime;
        let duration = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)
                .expect("for the foreseeable future this shouldn't happen");
        create_invoice_from_channelmanager_and_duration_since_epoch(
                channelmanager, node_signer, logger, network, amt_msat,
                description, duration, invoice_expiry_delta_secs, min_final_cltv_expiry_delta,
        )
}

#[cfg(feature = "std")]
/// Utility to construct an invoice. Generally, unless you want to do something like a custom
/// cltv_expiry, this is what you should be using to create an invoice. The reason being, this
/// method stores the invoice's payment secret and preimage in `ChannelManager`, so (a) the user
/// doesn't have to store preimage/payment secret information and (b) `ChannelManager` can verify
/// that the payment secret is valid when the invoice is paid.
/// Use this variant if you want to pass the `description_hash` to the invoice.
///
/// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
/// in excess of the current time.
///
/// You can specify a custom `min_final_cltv_expiry_delta`, or let LDK default it to
/// [`MIN_FINAL_CLTV_EXPIRY_DELTA`]. The provided expiry must be at least [`MIN_FINAL_CLTV_EXPIRY_DELTA`].
/// Note that LDK will add a buffer of 3 blocks to the delta to allow for up to a few new block
/// confirmations during routing.
///
/// [`MIN_FINAL_CLTV_EXPIRY_DETLA`]: lightning::ln::channelmanager::MIN_FINAL_CLTV_EXPIRY_DELTA
pub fn create_invoice_from_channelmanager_with_description_hash<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description_hash: Sha256,
        invoice_expiry_delta_secs: u32, min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
where
        M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
        T::Target: BroadcasterInterface,
        ES::Target: EntropySource,
        NS::Target: NodeSigner,
        SP::Target: SignerProvider,
        F::Target: FeeEstimator,
        R::Target: Router,
        L::Target: Logger,
{
        use std::time::SystemTime;

        let duration = SystemTime::now()
                .duration_since(SystemTime::UNIX_EPOCH)
                .expect("for the foreseeable future this shouldn't happen");

        create_invoice_from_channelmanager_with_description_hash_and_duration_since_epoch(
                channelmanager, node_signer, logger, network, amt_msat,
                description_hash, duration, invoice_expiry_delta_secs, min_final_cltv_expiry_delta,
        )
}

/// See [`create_invoice_from_channelmanager_with_description_hash`]
/// This version can be used in a `no_std` environment, where [`std::time::SystemTime`] is not
/// available and the current time is supplied by the caller.
pub fn create_invoice_from_channelmanager_with_description_hash_and_duration_since_epoch<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description_hash: Sha256,
        duration_since_epoch: Duration, invoice_expiry_delta_secs: u32, min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
                where
                        M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
                        T::Target: BroadcasterInterface,
                        ES::Target: EntropySource,
                        NS::Target: NodeSigner,
                        SP::Target: SignerProvider,
                        F::Target: FeeEstimator,
                        R::Target: Router,
                        L::Target: Logger,
{
        _create_invoice_from_channelmanager_and_duration_since_epoch(
                channelmanager, node_signer, logger, network, amt_msat,
                InvoiceDescription::Hash(&description_hash),
                duration_since_epoch, invoice_expiry_delta_secs, min_final_cltv_expiry_delta,
        )
}

/// See [`create_invoice_from_channelmanager`]
/// This version can be used in a `no_std` environment, where [`std::time::SystemTime`] is not
/// available and the current time is supplied by the caller.
pub fn create_invoice_from_channelmanager_and_duration_since_epoch<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description: String, duration_since_epoch: Duration,
        invoice_expiry_delta_secs: u32, min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
                where
                        M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
                        T::Target: BroadcasterInterface,
                        ES::Target: EntropySource,
                        NS::Target: NodeSigner,
                        SP::Target: SignerProvider,
                        F::Target: FeeEstimator,
                        R::Target: Router,
                        L::Target: Logger,
{
        _create_invoice_from_channelmanager_and_duration_since_epoch(
                channelmanager, node_signer, logger, network, amt_msat,
                InvoiceDescription::Direct(
                        &Description::new(description).map_err(SignOrCreationError::CreationError)?,
                ),
                duration_since_epoch, invoice_expiry_delta_secs, min_final_cltv_expiry_delta,
        )
}

fn _create_invoice_from_channelmanager_and_duration_since_epoch<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description: InvoiceDescription,
        duration_since_epoch: Duration, invoice_expiry_delta_secs: u32, min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
                where
                        M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
                        T::Target: BroadcasterInterface,
                        ES::Target: EntropySource,
                        NS::Target: NodeSigner,
                        SP::Target: SignerProvider,
                        F::Target: FeeEstimator,
                        R::Target: Router,
                        L::Target: Logger,
{
        if min_final_cltv_expiry_delta.is_some() && min_final_cltv_expiry_delta.unwrap().saturating_add(3) < MIN_FINAL_CLTV_EXPIRY_DELTA {
                return Err(SignOrCreationError::CreationError(CreationError::MinFinalCltvExpiryDeltaTooShort));
        }

        // `create_inbound_payment` only returns an error if the amount is greater than the total bitcoin
        // supply.
        let (payment_hash, payment_secret) = channelmanager
                .create_inbound_payment(amt_msat, invoice_expiry_delta_secs, min_final_cltv_expiry_delta)
                .map_err(|()| SignOrCreationError::CreationError(CreationError::InvalidAmount))?;
        _create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash(
                channelmanager, node_signer, logger, network, amt_msat, description, duration_since_epoch,
                invoice_expiry_delta_secs, payment_hash, payment_secret, min_final_cltv_expiry_delta)
}

/// See [`create_invoice_from_channelmanager_and_duration_since_epoch`]
/// This version allows for providing a custom [`PaymentHash`] for the invoice.
/// This may be useful if you're building an on-chain swap or involving another protocol where
/// the payment hash is also involved outside the scope of lightning.
pub fn create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description: String, duration_since_epoch: Duration,
        invoice_expiry_delta_secs: u32, payment_hash: PaymentHash, min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
        where
                M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
                T::Target: BroadcasterInterface,
                ES::Target: EntropySource,
                NS::Target: NodeSigner,
                SP::Target: SignerProvider,
                F::Target: FeeEstimator,
                R::Target: Router,
                L::Target: Logger,
{
        let payment_secret = channelmanager
                .create_inbound_payment_for_hash(payment_hash, amt_msat, invoice_expiry_delta_secs,
                        min_final_cltv_expiry_delta)
                .map_err(|()| SignOrCreationError::CreationError(CreationError::InvalidAmount))?;
        _create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash(
                channelmanager, node_signer, logger, network, amt_msat,
                InvoiceDescription::Direct(
                        &Description::new(description).map_err(SignOrCreationError::CreationError)?,
                ),
                duration_since_epoch, invoice_expiry_delta_secs, payment_hash, payment_secret,
                min_final_cltv_expiry_delta,
        )
}

fn _create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>(
        channelmanager: &ChannelManager<M, T, ES, NS, SP, F, R, L>, node_signer: NS, logger: L,
        network: Currency, amt_msat: Option<u64>, description: InvoiceDescription, duration_since_epoch: Duration,
        invoice_expiry_delta_secs: u32, payment_hash: PaymentHash, payment_secret: PaymentSecret,
        min_final_cltv_expiry_delta: Option<u16>,
) -> Result<Invoice, SignOrCreationError<()>>
        where
                M::Target: chain::Watch<<SP::Target as SignerProvider>::Signer>,
                T::Target: BroadcasterInterface,
                ES::Target: EntropySource,
                NS::Target: NodeSigner,
                SP::Target: SignerProvider,
                F::Target: FeeEstimator,
                R::Target: Router,
                L::Target: Logger,
{
        let our_node_pubkey = channelmanager.get_our_node_id();
        let channels = channelmanager.list_channels();

        if min_final_cltv_expiry_delta.is_some() && min_final_cltv_expiry_delta.unwrap().saturating_add(3) < MIN_FINAL_CLTV_EXPIRY_DELTA {
                return Err(SignOrCreationError::CreationError(CreationError::MinFinalCltvExpiryDeltaTooShort));
        }

        log_trace!(logger, "Creating invoice with payment hash {}", log_bytes!(payment_hash.0));

        let invoice = match description {
                InvoiceDescription::Direct(description) => {
                        InvoiceBuilder::new(network).description(description.0.clone())
                }
                InvoiceDescription::Hash(hash) => InvoiceBuilder::new(network).description_hash(hash.0),
        };

        let mut invoice = invoice
                .duration_since_epoch(duration_since_epoch)
                .payee_pub_key(our_node_pubkey)
                .payment_hash(Hash::from_slice(&payment_hash.0).unwrap())
                .payment_secret(payment_secret)
                .basic_mpp()
                .min_final_cltv_expiry_delta(
                        // Add a buffer of 3 to the delta if present, otherwise use LDK's minimum.
                        min_final_cltv_expiry_delta.map(|x| x.saturating_add(3)).unwrap_or(MIN_FINAL_CLTV_EXPIRY_DELTA).into())
                .expiry_time(Duration::from_secs(invoice_expiry_delta_secs.into()));
        if let Some(amt) = amt_msat {
                invoice = invoice.amount_milli_satoshis(amt);
        }

        let route_hints = filter_channels(channels, amt_msat, &logger);
        for hint in route_hints {
                invoice = invoice.private_route(hint);
        }

        let raw_invoice = match invoice.build_raw() {
                Ok(inv) => inv,
                Err(e) => return Err(SignOrCreationError::CreationError(e))
        };
        let hrp_str = raw_invoice.hrp.to_string();
        let hrp_bytes = hrp_str.as_bytes();
        let data_without_signature = raw_invoice.data.to_base32();
        let signed_raw_invoice = raw_invoice.sign(|_| node_signer.sign_invoice(hrp_bytes, &data_without_signature, Recipient::Node));
        match signed_raw_invoice {
                Ok(inv) => Ok(Invoice::from_signed(inv).unwrap()),
                Err(e) => Err(SignOrCreationError::SignError(e))
        }
}

/// Filters the `channels` for an invoice, and returns the corresponding `RouteHint`s to include
/// in the invoice.
///
/// The filtering is based on the following criteria:
/// * Only one channel per counterparty node
/// * If the counterparty has a channel that is above the `min_inbound_capacity_msat` + 10% scaling
///   factor (to allow some margin for change in inbound), select the channel with the lowest
///   inbound capacity that is above this threshold.
/// * If no `min_inbound_capacity_msat` is specified, or the counterparty has no channels above the
///   minimum + 10% scaling factor, select the channel with the highest inbound capacity per counterparty.
/// * Prefer channels with capacity at least `min_inbound_capacity_msat` and where the channel
///   `is_usable` (i.e. the peer is connected).
/// * If any public channel exists, only public [`RouteHint`]s will be returned.
/// * If any public, announced, channel exists (i.e. a channel with 7+ confs, to ensure the
///   announcement has had a chance to propagate), no [`RouteHint`]s will be returned, as the
///   sender is expected to find the path by looking at the public channels instead.
fn filter_channels<L: Deref>(
        channels: Vec<ChannelDetails>, min_inbound_capacity_msat: Option<u64>, logger: &L
) -> Vec<RouteHint> where L::Target: Logger {
        let mut filtered_channels: HashMap<PublicKey, ChannelDetails> = HashMap::new();
        let min_inbound_capacity = min_inbound_capacity_msat.unwrap_or(0);
        let mut min_capacity_channel_exists = false;
        let mut online_channel_exists = false;
        let mut online_min_capacity_channel_exists = false;
        let mut has_pub_unconf_chan = false;

        log_trace!(logger, "Considering {} channels for invoice route hints", channels.len());
        for channel in channels.into_iter().filter(|chan| chan.is_channel_ready) {
                if channel.get_inbound_payment_scid().is_none() || channel.counterparty.forwarding_info.is_none() {
                        log_trace!(logger, "Ignoring channel {} for invoice route hints", log_bytes!(channel.channel_id));
                        continue;
                }

                if channel.is_public {
                        if channel.confirmations.is_some() && channel.confirmations < Some(7) {
                                // If we have a public channel, but it doesn't have enough confirmations to (yet)
                                // be in the public network graph (and have gotten a chance to propagate), include
                                // route hints but only for public channels to protect private channel privacy.
                                has_pub_unconf_chan = true;
                        } else {
                                // If any public channel exists, return no hints and let the sender
                                // look at the public channels instead.
                                log_trace!(logger, "Not including channels in invoice route hints on account of public channel {}",
                                        log_bytes!(channel.channel_id));
                                return vec![]
                        }
                }

                if channel.inbound_capacity_msat >= min_inbound_capacity {
                        if !min_capacity_channel_exists {
                                log_trace!(logger, "Channel with enough inbound capacity exists for invoice route hints");
                                min_capacity_channel_exists = true;
                        }

                        if channel.is_usable {
                                online_min_capacity_channel_exists = true;
                        }
                }

                if channel.is_usable && !online_channel_exists {
                        log_trace!(logger, "Channel with connected peer exists for invoice route hints");
                        online_channel_exists = true;
                }

                match filtered_channels.entry(channel.counterparty.node_id) {
                        hash_map::Entry::Occupied(mut entry) => {
                                let current_max_capacity = entry.get().inbound_capacity_msat;
                                // If this channel is public and the previous channel is not, ensure we replace the
                                // previous channel to avoid announcing non-public channels.
                                let new_now_public = channel.is_public && !entry.get().is_public;
                                // Decide whether we prefer the currently selected channel with the node to the new one,
                                // based on their inbound capacity. 
                                let prefer_current = prefer_current_channel(min_inbound_capacity_msat, current_max_capacity,
                                        channel.inbound_capacity_msat);
                                // If the public-ness of the channel has not changed (in which case simply defer to
                                // `new_now_public), and this channel has more desirable inbound than the incumbent,
                                // prefer to include this channel.
                                let new_channel_preferable = channel.is_public == entry.get().is_public && !prefer_current;

                                if new_now_public || new_channel_preferable {
                                        log_trace!(logger,
                                                "Preferring counterparty {} channel {} (SCID {:?}, {} msats) over {} (SCID {:?}, {} msats) for invoice route hints",
                                                log_pubkey!(channel.counterparty.node_id),
                                                log_bytes!(channel.channel_id), channel.short_channel_id,
                                                channel.inbound_capacity_msat,
                                                log_bytes!(entry.get().channel_id), entry.get().short_channel_id,
                                                current_max_capacity);
                                        entry.insert(channel);
                                } else {
                                        log_trace!(logger,
                                                "Preferring counterparty {} channel {} (SCID {:?}, {} msats) over {} (SCID {:?}, {} msats) for invoice route hints",
                                                log_pubkey!(channel.counterparty.node_id),
                                                log_bytes!(entry.get().channel_id), entry.get().short_channel_id,
                                                current_max_capacity,
                                                log_bytes!(channel.channel_id), channel.short_channel_id,
                                                channel.inbound_capacity_msat);
                                }
                        }
                        hash_map::Entry::Vacant(entry) => {
                                entry.insert(channel);
                        }
                }
        }

        let route_hint_from_channel = |channel: ChannelDetails| {
                let forwarding_info = channel.counterparty.forwarding_info.as_ref().unwrap();
                RouteHint(vec![RouteHintHop {
                        src_node_id: channel.counterparty.node_id,
                        short_channel_id: channel.get_inbound_payment_scid().unwrap(),
                        fees: RoutingFees {
                                base_msat: forwarding_info.fee_base_msat,
                                proportional_millionths: forwarding_info.fee_proportional_millionths,
                        },
                        cltv_expiry_delta: forwarding_info.cltv_expiry_delta,
                        htlc_minimum_msat: channel.inbound_htlc_minimum_msat,
                        htlc_maximum_msat: channel.inbound_htlc_maximum_msat,}])
        };
        // If all channels are private, prefer to return route hints which have a higher capacity than
        // the payment value and where we're currently connected to the channel counterparty.
        // Even if we cannot satisfy both goals, always ensure we include *some* hints, preferring
        // those which meet at least one criteria.
        filtered_channels
                .into_iter()
                .map(|(_, channel)| channel)
                .filter(|channel| {
                        let has_enough_capacity = channel.inbound_capacity_msat >= min_inbound_capacity;
                        let include_channel = if has_pub_unconf_chan {
                                // If we have a public channel, but it doesn't have enough confirmations to (yet)
                                // be in the public network graph (and have gotten a chance to propagate), include
                                // route hints but only for public channels to protect private channel privacy.
                                channel.is_public
                        } else if online_min_capacity_channel_exists {
                                has_enough_capacity && channel.is_usable
                        } else if min_capacity_channel_exists && online_channel_exists {
                                // If there are some online channels and some min_capacity channels, but no
                                // online-and-min_capacity channels, just include the min capacity ones and ignore
                                // online-ness.
                                has_enough_capacity
                        } else if min_capacity_channel_exists {
                                has_enough_capacity
                        } else if online_channel_exists {
                                channel.is_usable
                        } else { true };

                        if include_channel {
                                log_trace!(logger, "Including channel {} in invoice route hints",
                                        log_bytes!(channel.channel_id));
                        } else if !has_enough_capacity {
                                log_trace!(logger, "Ignoring channel {} without enough capacity for invoice route hints",
                                        log_bytes!(channel.channel_id));
                        } else {
                                debug_assert!(!channel.is_usable || (has_pub_unconf_chan && !channel.is_public));
                                log_trace!(logger, "Ignoring channel {} with disconnected peer",
                                        log_bytes!(channel.channel_id));
                        }

                        include_channel
                })
                .map(route_hint_from_channel)
                .collect::<Vec<RouteHint>>()
}

/// prefer_current_channel chooses a channel to use for route hints between a currently selected and candidate
/// channel based on the inbound capacity of each channel and the minimum inbound capacity requested for the hints,
/// returning true if the current channel should be preferred over the candidate channel.
/// * If no minimum amount is requested, the channel with the most inbound is chosen to maximize the chances that a
///   payment of any size will succeed.
/// * If we have channels with inbound above our minimum requested inbound (plus a 10% scaling factor, expressed as a
///   percentage) then we choose the lowest inbound channel with above this amount. If we have sufficient inbound
///   channels, we don't want to deplete our larger channels with small payments (the off-chain version of "grinding
///   our change").
/// * If no channel above our minimum amount exists, then we just prefer the channel with the most inbound to give
///   payments the best chance of succeeding in multiple parts.
fn prefer_current_channel(min_inbound_capacity_msat: Option<u64>, current_channel: u64,
        candidate_channel: u64) -> bool {

        // If no min amount is given for the hints, err of the side of caution and choose the largest channel inbound to
        // maximize chances of any payment succeeding.
        if min_inbound_capacity_msat.is_none() {
                return current_channel > candidate_channel
        }

        let scaled_min_inbound = min_inbound_capacity_msat.unwrap() * 110;
        let current_sufficient = current_channel * 100 >= scaled_min_inbound;
        let candidate_sufficient = candidate_channel * 100 >= scaled_min_inbound;

        if current_sufficient && candidate_sufficient {
                return current_channel < candidate_channel
        } else if current_sufficient {
                return true
        } else if candidate_sufficient {
                return false
        }

        current_channel > candidate_channel
}

#[cfg(test)]
mod test {
        use core::time::Duration;
        use crate::{Currency, Description, InvoiceDescription, SignOrCreationError, CreationError};
        use bitcoin_hashes::{Hash, sha256};
        use bitcoin_hashes::sha256::Hash as Sha256;
        use lightning::chain::keysinterface::{EntropySource, PhantomKeysManager};
        use lightning::events::{MessageSendEvent, MessageSendEventsProvider, Event};
        use lightning::ln::{PaymentPreimage, PaymentHash};
        use lightning::ln::channelmanager::{PhantomRouteHints, MIN_FINAL_CLTV_EXPIRY_DELTA, PaymentId};
        use lightning::ln::functional_test_utils::*;
        use lightning::ln::msgs::ChannelMessageHandler;
        use lightning::routing::router::{PaymentParameters, RouteParameters, find_route};
        use lightning::util::test_utils;
        use lightning::util::config::UserConfig;
        use crate::utils::create_invoice_from_channelmanager_and_duration_since_epoch;
        use std::collections::HashSet;

        #[test]
        fn test_prefer_current_channel() {
                // No minimum, prefer larger candidate channel.
                assert_eq!(crate::utils::prefer_current_channel(None, 100, 200), false);

                // No minimum, prefer larger current channel.
                assert_eq!(crate::utils::prefer_current_channel(None, 200, 100), true);

                // Minimum set, prefer current channel over minimum + buffer.
                assert_eq!(crate::utils::prefer_current_channel(Some(100), 115, 100), true);

                // Minimum set, prefer candidate channel over minimum + buffer.
                assert_eq!(crate::utils::prefer_current_channel(Some(100), 105, 125), false);
                
                // Minimum set, both channels sufficient, prefer smaller current channel.
                assert_eq!(crate::utils::prefer_current_channel(Some(100), 115, 125), true);
                
                // Minimum set, both channels sufficient, prefer smaller candidate channel.
                assert_eq!(crate::utils::prefer_current_channel(Some(100), 200, 160), false);

                // Minimum set, neither sufficient, prefer larger current channel.
                assert_eq!(crate::utils::prefer_current_channel(Some(200), 100, 50), true);

                // Minimum set, neither sufficient, prefer larger candidate channel.
                assert_eq!(crate::utils::prefer_current_channel(Some(200), 100, 150), false);
        }


        #[test]
        fn test_from_channelmanager() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 10001);
                let non_default_invoice_expiry_secs = 4200;
                let invoice = create_invoice_from_channelmanager_and_duration_since_epoch(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), "test".to_string(), Duration::from_secs(1234567),
                        non_default_invoice_expiry_secs, None).unwrap();
                assert_eq!(invoice.amount_pico_btc(), Some(100_000));
                // If no `min_final_cltv_expiry_delta` is specified, then it should be `MIN_FINAL_CLTV_EXPIRY_DELTA`.
                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
                assert_eq!(invoice.description(), InvoiceDescription::Direct(&Description("test".to_string())));
                assert_eq!(invoice.expiry_time(), Duration::from_secs(non_default_invoice_expiry_secs.into()));

                // Invoice SCIDs should always use inbound SCID aliases over the real channel ID, if one is
                // available.
                let chan = &nodes[1].node.list_usable_channels()[0];
                assert_eq!(invoice.route_hints().len(), 1);
                assert_eq!(invoice.route_hints()[0].0.len(), 1);
                assert_eq!(invoice.route_hints()[0].0[0].short_channel_id, chan.inbound_scid_alias.unwrap());

                assert_eq!(invoice.route_hints()[0].0[0].htlc_minimum_msat, chan.inbound_htlc_minimum_msat);
                assert_eq!(invoice.route_hints()[0].0[0].htlc_maximum_msat, chan.inbound_htlc_maximum_msat);

                let payment_params = PaymentParameters::from_node_id(invoice.recover_payee_pub_key(),
                                invoice.min_final_cltv_expiry_delta() as u32)
                        .with_features(invoice.features().unwrap().clone())
                        .with_route_hints(invoice.route_hints());
                let route_params = RouteParameters {
                        payment_params,
                        final_value_msat: invoice.amount_milli_satoshis().unwrap(),
                };
                let first_hops = nodes[0].node.list_usable_channels();
                let network_graph = &node_cfgs[0].network_graph;
                let logger = test_utils::TestLogger::new();
                let scorer = test_utils::TestScorer::new();
                let random_seed_bytes = chanmon_cfgs[1].keys_manager.get_secure_random_bytes();
                let route = find_route(
                        &nodes[0].node.get_our_node_id(), &route_params, network_graph,
                        Some(&first_hops.iter().collect::<Vec<_>>()), &logger, &scorer, &random_seed_bytes
                ).unwrap();

                let payment_event = {
                        let mut payment_hash = PaymentHash([0; 32]);
                        payment_hash.0.copy_from_slice(&invoice.payment_hash().as_ref()[0..32]);
                        nodes[0].node.send_payment(&route, payment_hash, &Some(*invoice.payment_secret()), PaymentId(payment_hash.0)).unwrap();
                        let mut added_monitors = nodes[0].chain_monitor.added_monitors.lock().unwrap();
                        assert_eq!(added_monitors.len(), 1);
                        added_monitors.clear();

                        let mut events = nodes[0].node.get_and_clear_pending_msg_events();
                        assert_eq!(events.len(), 1);
                        SendEvent::from_event(events.remove(0))

                };
                nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
                nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &payment_event.commitment_msg);
                let mut added_monitors = nodes[1].chain_monitor.added_monitors.lock().unwrap();
                assert_eq!(added_monitors.len(), 1);
                added_monitors.clear();
                let events = nodes[1].node.get_and_clear_pending_msg_events();
                assert_eq!(events.len(), 2);
        }

        fn do_create_invoice_min_final_cltv_delta(with_custom_delta: bool) {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                let custom_min_final_cltv_expiry_delta = Some(50);

                let invoice = crate::utils::create_invoice_from_channelmanager_and_duration_since_epoch(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), "".into(), Duration::from_secs(1234567), 3600,
                        if with_custom_delta { custom_min_final_cltv_expiry_delta } else { None },
                ).unwrap();
                assert_eq!(invoice.min_final_cltv_expiry_delta(), if with_custom_delta {
                        custom_min_final_cltv_expiry_delta.unwrap() + 3 /* Buffer */} else { MIN_FINAL_CLTV_EXPIRY_DELTA } as u64);
        }

        #[test]
        fn test_create_invoice_custom_min_final_cltv_delta() {
                do_create_invoice_min_final_cltv_delta(true);
                do_create_invoice_min_final_cltv_delta(false);
        }

        #[test]
        fn create_invoice_min_final_cltv_delta_equals_htlc_fail_buffer() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                let custom_min_final_cltv_expiry_delta = Some(21);

                let invoice = crate::utils::create_invoice_from_channelmanager_and_duration_since_epoch(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), "".into(), Duration::from_secs(1234567), 3600,
                        custom_min_final_cltv_expiry_delta,
                ).unwrap();
                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
        }

        #[test]
        fn test_create_invoice_with_description_hash() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                let description_hash = crate::Sha256(Hash::hash("Testing description_hash".as_bytes()));
                let invoice = crate::utils::create_invoice_from_channelmanager_with_description_hash_and_duration_since_epoch(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), description_hash, Duration::from_secs(1234567), 3600, None,
                ).unwrap();
                assert_eq!(invoice.amount_pico_btc(), Some(100_000));
                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
                assert_eq!(invoice.description(), InvoiceDescription::Hash(&crate::Sha256(Sha256::hash("Testing description_hash".as_bytes()))));
        }

        #[test]
        fn test_create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                let payment_hash = PaymentHash([0; 32]);
                let invoice = crate::utils::create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_hash(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), "test".to_string(), Duration::from_secs(1234567), 3600,
                        payment_hash, None,
                ).unwrap();
                assert_eq!(invoice.amount_pico_btc(), Some(100_000));
                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
                assert_eq!(invoice.description(), InvoiceDescription::Direct(&Description("test".to_string())));
                assert_eq!(invoice.payment_hash(), &sha256::Hash::from_slice(&payment_hash.0[..]).unwrap());
        }

        #[test]
        fn test_hints_has_only_public_confd_channels() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let mut config = test_default_channel_config();
                config.channel_handshake_config.minimum_depth = 1;
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[Some(config), Some(config)]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);

                // Create a private channel with lots of capacity and a lower value public channel (without
                // confirming the funding tx yet).
                let unannounced_scid = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 0);
                let conf_tx = create_chan_between_nodes_with_value_init(&nodes[0], &nodes[1], 10_000, 0);

                // Before the channel is available, we should include the unannounced_scid.
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(unannounced_scid.0.short_channel_id_alias.unwrap());
                match_invoice_routes(Some(5000), &nodes[1], scid_aliases.clone());

                // However after we mine the funding tx and exchange channel_ready messages for the public
                // channel we'll immediately switch to including it as a route hint, even though it isn't
                // yet announced.
                let pub_channel_scid = mine_transaction(&nodes[0], &conf_tx);
                let node_a_pub_channel_ready = get_event_msg!(nodes[0], MessageSendEvent::SendChannelReady, nodes[1].node.get_our_node_id());
                nodes[1].node.handle_channel_ready(&nodes[0].node.get_our_node_id(), &node_a_pub_channel_ready);

                assert_eq!(mine_transaction(&nodes[1], &conf_tx), pub_channel_scid);
                let events = nodes[1].node.get_and_clear_pending_msg_events();
                assert_eq!(events.len(), 2);
                if let MessageSendEvent::SendChannelReady { msg, .. } = &events[0] {
                        nodes[0].node.handle_channel_ready(&nodes[1].node.get_our_node_id(), msg);
                } else { panic!(); }
                if let MessageSendEvent::SendChannelUpdate { msg, .. } = &events[1] {
                        nodes[0].node.handle_channel_update(&nodes[1].node.get_our_node_id(), msg);
                } else { panic!(); }

                nodes[1].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &get_event_msg!(nodes[0], MessageSendEvent::SendChannelUpdate, nodes[1].node.get_our_node_id()));

                expect_channel_ready_event(&nodes[0], &nodes[1].node.get_our_node_id());
                expect_channel_ready_event(&nodes[1], &nodes[0].node.get_our_node_id());

                scid_aliases.clear();
                scid_aliases.insert(node_a_pub_channel_ready.short_channel_id_alias.unwrap());
                match_invoice_routes(Some(5000), &nodes[1], scid_aliases.clone());
                // This also applies even if the amount is more than the payment amount, to ensure users
                // dont screw up their privacy.
                match_invoice_routes(Some(50_000_000), &nodes[1], scid_aliases.clone());

                // The same remains true until the channel has 7 confirmations, at which point we include
                // no hints.
                connect_blocks(&nodes[1], 5);
                match_invoice_routes(Some(5000), &nodes[1], scid_aliases.clone());
                connect_blocks(&nodes[1], 1);
                get_event_msg!(nodes[1], MessageSendEvent::SendAnnouncementSignatures, nodes[0].node.get_our_node_id());
                match_invoice_routes(Some(5000), &nodes[1], HashSet::new());
        }

        #[test]
        fn test_hints_includes_single_channels_to_nodes() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let chan_1_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 100000, 10001);
                let chan_2_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 2, 0, 100000, 10001);

                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_1_0.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_2_0.0.short_channel_id_alias.unwrap());

                match_invoice_routes(Some(5000), &nodes[0], scid_aliases);
        }

        #[test]
        fn test_hints_has_only_lowest_inbound_capacity_channel_above_minimum() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);

                let _chan_1_0_inbound_below_amt = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 10_000, 0);
                let _chan_1_0_large_inbound_above_amt = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 500_000, 0);
                let chan_1_0_low_inbound_above_amt = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 200_000, 0);

                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_1_0_low_inbound_above_amt.0.short_channel_id_alias.unwrap());
                match_invoice_routes(Some(100_000_000), &nodes[0], scid_aliases);
        }

        #[test]
        fn test_hints_has_only_online_channels() {
                let chanmon_cfgs = create_chanmon_cfgs(4);
                let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
                let nodes = create_network(4, &node_cfgs, &node_chanmgrs);
                let chan_a = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 10_000_000, 0);
                let chan_b = create_unannounced_chan_between_nodes_with_value(&nodes, 2, 0, 10_000_000, 0);
                let _chan_c = create_unannounced_chan_between_nodes_with_value(&nodes, 3, 0, 1_000_000, 0);

                // With all peers connected we should get all hints that have sufficient value
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_a.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_b.0.short_channel_id_alias.unwrap());

                match_invoice_routes(Some(1_000_000_000), &nodes[0], scid_aliases.clone());

                // With only one sufficient-value peer connected we should only get its hint
                scid_aliases.remove(&chan_b.0.short_channel_id_alias.unwrap());
                nodes[0].node.peer_disconnected(&nodes[2].node.get_our_node_id());
                match_invoice_routes(Some(1_000_000_000), &nodes[0], scid_aliases.clone());

                // If we don't have any sufficient-value peers connected we should get all hints with
                // sufficient value, even though there is a connected insufficient-value peer.
                scid_aliases.insert(chan_b.0.short_channel_id_alias.unwrap());
                nodes[0].node.peer_disconnected(&nodes[1].node.get_our_node_id());
                match_invoice_routes(Some(1_000_000_000), &nodes[0], scid_aliases);
        }

        #[test]
        fn test_forwarding_info_not_assigned_channel_excluded_from_hints() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let chan_1_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 100000, 10001);

                // Create an unannonced channel between `nodes[2]` and `nodes[0]`, for which the
                // `msgs::ChannelUpdate` is never handled for the node(s). As the `msgs::ChannelUpdate`
                // is never handled, the `channel.counterparty.forwarding_info` is never assigned.
                let mut private_chan_cfg = UserConfig::default();
                private_chan_cfg.channel_handshake_config.announced_channel = false;
                let temporary_channel_id = nodes[2].node.create_channel(nodes[0].node.get_our_node_id(), 1_000_000, 500_000_000, 42, Some(private_chan_cfg)).unwrap();
                let open_channel = get_event_msg!(nodes[2], MessageSendEvent::SendOpenChannel, nodes[0].node.get_our_node_id());
                nodes[0].node.handle_open_channel(&nodes[2].node.get_our_node_id(), &open_channel);
                let accept_channel = get_event_msg!(nodes[0], MessageSendEvent::SendAcceptChannel, nodes[2].node.get_our_node_id());
                nodes[2].node.handle_accept_channel(&nodes[0].node.get_our_node_id(), &accept_channel);

                let tx = sign_funding_transaction(&nodes[2], &nodes[0], 1_000_000, temporary_channel_id);

                let conf_height = core::cmp::max(nodes[2].best_block_info().1 + 1, nodes[0].best_block_info().1 + 1);
                confirm_transaction_at(&nodes[2], &tx, conf_height);
                connect_blocks(&nodes[2], CHAN_CONFIRM_DEPTH - 1);
                confirm_transaction_at(&nodes[0], &tx, conf_height);
                connect_blocks(&nodes[0], CHAN_CONFIRM_DEPTH - 1);
                let as_channel_ready = get_event_msg!(nodes[2], MessageSendEvent::SendChannelReady, nodes[0].node.get_our_node_id());
                nodes[2].node.handle_channel_ready(&nodes[0].node.get_our_node_id(), &get_event_msg!(nodes[0], MessageSendEvent::SendChannelReady, nodes[2].node.get_our_node_id()));
                get_event_msg!(nodes[2], MessageSendEvent::SendChannelUpdate, nodes[0].node.get_our_node_id());
                nodes[0].node.handle_channel_ready(&nodes[2].node.get_our_node_id(), &as_channel_ready);
                get_event_msg!(nodes[0], MessageSendEvent::SendChannelUpdate, nodes[2].node.get_our_node_id());
                expect_channel_ready_event(&nodes[0], &nodes[2].node.get_our_node_id());
                expect_channel_ready_event(&nodes[2], &nodes[0].node.get_our_node_id());

                // As `msgs::ChannelUpdate` was never handled for the participating node(s) of the second
                // channel, the channel will never be assigned any `counterparty.forwarding_info`.
                // Therefore only `chan_1_0` should be included in the hints.
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_1_0.0.short_channel_id_alias.unwrap());
                match_invoice_routes(Some(5000), &nodes[0], scid_aliases);
        }

        #[test]
        fn test_no_hints_if_a_mix_between_public_and_private_channel_exists() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let _chan_1_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 100000, 10001);

                let chan_2_0 = create_announced_chan_between_nodes_with_value(&nodes, 2, 0, 100000, 10001);
                nodes[2].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_2_0.1);
                nodes[0].node.handle_channel_update(&nodes[2].node.get_our_node_id(), &chan_2_0.0);

                // Ensure that the invoice doesn't include any route hints for any of `nodes[0]` channels,
                // even though all channels between `nodes[1]` and `nodes[0]` are private, as there is a
                // public channel between `nodes[2]` and `nodes[0]`
                match_invoice_routes(Some(5000), &nodes[0], HashSet::new());
        }

        #[test]
        fn test_only_public_channels_includes_no_channels_in_hints() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let chan_1_0 = create_announced_chan_between_nodes_with_value(&nodes, 1, 0, 100000, 10001);
                nodes[0].node.handle_channel_update(&nodes[1].node.get_our_node_id(), &chan_1_0.0);
                nodes[1].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_1_0.1);

                let chan_2_0 = create_announced_chan_between_nodes_with_value(&nodes, 2, 0, 100000, 10001);
                nodes[2].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_2_0.1);
                nodes[0].node.handle_channel_update(&nodes[2].node.get_our_node_id(), &chan_2_0.0);

                // As all of `nodes[0]` channels are public, no channels should be included in the hints
                match_invoice_routes(Some(5000), &nodes[0], HashSet::new());
        }

        #[test]
        fn test_channels_with_lower_inbound_capacity_than_invoice_amt_hints_filtering() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let chan_1_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 0, 100_000, 0);
                let chan_2_0 = create_unannounced_chan_between_nodes_with_value(&nodes, 2, 0, 1_000_000, 0);

                // As the invoice amt is 1 msat above chan_1_0's inbound capacity, it shouldn't be included
                let mut scid_aliases_99_000_001_msat = HashSet::new();
                scid_aliases_99_000_001_msat.insert(chan_2_0.0.short_channel_id_alias.unwrap());

                match_invoice_routes(Some(99_000_001), &nodes[0], scid_aliases_99_000_001_msat);

                // As the invoice amt is exactly at chan_1_0's inbound capacity, it should be included
                let mut scid_aliases_99_000_000_msat = HashSet::new();
                scid_aliases_99_000_000_msat.insert(chan_1_0.0.short_channel_id_alias.unwrap());
                scid_aliases_99_000_000_msat.insert(chan_2_0.0.short_channel_id_alias.unwrap());

                match_invoice_routes(Some(99_000_000), &nodes[0], scid_aliases_99_000_000_msat);

                // As the invoice amt is above all channels' inbound capacity, they will still be included
                let mut scid_aliases_2_000_000_000_msat = HashSet::new();
                scid_aliases_2_000_000_000_msat.insert(chan_1_0.0.short_channel_id_alias.unwrap());
                scid_aliases_2_000_000_000_msat.insert(chan_2_0.0.short_channel_id_alias.unwrap());

                match_invoice_routes(Some(2_000_000_000), &nodes[0], scid_aliases_2_000_000_000_msat);

                // An invoice with no specified amount should include all channels in the route hints.
                let mut scid_aliases_no_specified_amount = HashSet::new();
                scid_aliases_no_specified_amount.insert(chan_1_0.0.short_channel_id_alias.unwrap());
                scid_aliases_no_specified_amount.insert(chan_2_0.0.short_channel_id_alias.unwrap());

                match_invoice_routes(None, &nodes[0], scid_aliases_no_specified_amount);
        }

        fn match_invoice_routes<'a, 'b: 'a, 'c: 'b>(
                invoice_amt: Option<u64>,
                invoice_node: &Node<'a, 'b, 'c>,
                mut chan_ids_to_match: HashSet<u64>
        ) {
                let invoice = create_invoice_from_channelmanager_and_duration_since_epoch(
                        invoice_node.node, invoice_node.keys_manager, invoice_node.logger,
                        Currency::BitcoinTestnet, invoice_amt, "test".to_string(), Duration::from_secs(1234567),
                        3600, None).unwrap();
                let hints = invoice.private_routes();

                for hint in hints {
                        let hint_short_chan_id = (hint.0).0[0].short_channel_id;
                        assert!(chan_ids_to_match.remove(&hint_short_chan_id));
                }
                assert!(chan_ids_to_match.is_empty(), "Unmatched short channel ids: {:?}", chan_ids_to_match);
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_receive() {
                do_test_multi_node_receive(true);
                do_test_multi_node_receive(false);
        }

        #[cfg(feature = "std")]
        fn do_test_multi_node_receive(user_generated_pmt_hash: bool) {
                let mut chanmon_cfgs = create_chanmon_cfgs(3);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let chan_0_1 = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 10001);
                nodes[0].node.handle_channel_update(&nodes[1].node.get_our_node_id(), &chan_0_1.1);
                nodes[1].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_0_1.0);
                let chan_0_2 = create_announced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);
                nodes[0].node.handle_channel_update(&nodes[2].node.get_our_node_id(), &chan_0_2.1);
                nodes[2].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_0_2.0);

                let payment_amt = 10_000;
                let route_hints = vec![
                        nodes[1].node.get_phantom_route_hints(),
                        nodes[2].node.get_phantom_route_hints(),
                ];

                let user_payment_preimage = PaymentPreimage([1; 32]);
                let payment_hash = if user_generated_pmt_hash {
                        Some(PaymentHash(Sha256::hash(&user_payment_preimage.0[..]).into_inner()))
                } else {
                        None
                };
                let non_default_invoice_expiry_secs = 4200;

                let invoice =
                        crate::utils::create_phantom_invoice::<&test_utils::TestKeysInterface, &test_utils::TestKeysInterface, &test_utils::TestLogger>(
                                Some(payment_amt), payment_hash, "test".to_string(), non_default_invoice_expiry_secs,
                                route_hints, nodes[1].keys_manager, nodes[1].keys_manager, nodes[1].logger,
                                Currency::BitcoinTestnet, None, Duration::from_secs(1234567)
                        ).unwrap();
                let (payment_hash, payment_secret) = (PaymentHash(invoice.payment_hash().into_inner()), *invoice.payment_secret());
                let payment_preimage = if user_generated_pmt_hash {
                        user_payment_preimage
                } else {
                        nodes[1].node.get_payment_preimage(payment_hash, payment_secret).unwrap()
                };

                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
                assert_eq!(invoice.description(), InvoiceDescription::Direct(&Description("test".to_string())));
                assert_eq!(invoice.route_hints().len(), 2);
                assert_eq!(invoice.expiry_time(), Duration::from_secs(non_default_invoice_expiry_secs.into()));
                assert!(!invoice.features().unwrap().supports_basic_mpp());

                let payment_params = PaymentParameters::from_node_id(invoice.recover_payee_pub_key(),
                                invoice.min_final_cltv_expiry_delta() as u32)
                        .with_features(invoice.features().unwrap().clone())
                        .with_route_hints(invoice.route_hints());
                let params = RouteParameters {
                        payment_params,
                        final_value_msat: invoice.amount_milli_satoshis().unwrap(),
                };
                let first_hops = nodes[0].node.list_usable_channels();
                let network_graph = &node_cfgs[0].network_graph;
                let logger = test_utils::TestLogger::new();
                let scorer = test_utils::TestScorer::new();
                let random_seed_bytes = chanmon_cfgs[1].keys_manager.get_secure_random_bytes();
                let route = find_route(
                        &nodes[0].node.get_our_node_id(), &params, network_graph,
                        Some(&first_hops.iter().collect::<Vec<_>>()), &logger, &scorer, &random_seed_bytes
                ).unwrap();
                let (payment_event, fwd_idx) = {
                        let mut payment_hash = PaymentHash([0; 32]);
                        payment_hash.0.copy_from_slice(&invoice.payment_hash().as_ref()[0..32]);
                        nodes[0].node.send_payment(&route, payment_hash, &Some(*invoice.payment_secret()), PaymentId(payment_hash.0)).unwrap();
                        let mut added_monitors = nodes[0].chain_monitor.added_monitors.lock().unwrap();
                        assert_eq!(added_monitors.len(), 1);
                        added_monitors.clear();

                        let mut events = nodes[0].node.get_and_clear_pending_msg_events();
                        assert_eq!(events.len(), 1);
                        let fwd_idx = match events[0] {
                                MessageSendEvent::UpdateHTLCs { node_id, .. } => {
                                        if node_id == nodes[1].node.get_our_node_id() {
                                                1
                                        } else { 2 }
                                },
                                _ => panic!("Unexpected event")
                        };
                        (SendEvent::from_event(events.remove(0)), fwd_idx)
                };
                nodes[fwd_idx].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
                commitment_signed_dance!(nodes[fwd_idx], nodes[0], &payment_event.commitment_msg, false, true);

                // Note that we have to "forward pending HTLCs" twice before we see the PaymentClaimable as
                // this "emulates" the payment taking two hops, providing some privacy to make phantom node
                // payments "look real" by taking more time.
                expect_pending_htlcs_forwardable_ignore!(nodes[fwd_idx]);
                nodes[fwd_idx].node.process_pending_htlc_forwards();
                expect_pending_htlcs_forwardable_ignore!(nodes[fwd_idx]);
                nodes[fwd_idx].node.process_pending_htlc_forwards();

                let payment_preimage_opt = if user_generated_pmt_hash { None } else { Some(payment_preimage) };
                expect_payment_claimable!(&nodes[fwd_idx], payment_hash, payment_secret, payment_amt, payment_preimage_opt, route.paths[0].last().unwrap().pubkey);
                do_claim_payment_along_route(&nodes[0], &[&vec!(&nodes[fwd_idx])[..]], false, payment_preimage);
                let events = nodes[0].node.get_and_clear_pending_events();
                assert_eq!(events.len(), 2);
                match events[0] {
                        Event::PaymentSent { payment_preimage: ref ev_preimage, payment_hash: ref ev_hash, ref fee_paid_msat, .. } => {
                                assert_eq!(payment_preimage, *ev_preimage);
                                assert_eq!(payment_hash, *ev_hash);
                                assert_eq!(fee_paid_msat, &Some(0));
                        },
                        _ => panic!("Unexpected event")
                }
                match events[1] {
                        Event::PaymentPathSuccessful { payment_hash: hash, .. } => {
                                assert_eq!(hash, Some(payment_hash));
                        },
                        _ => panic!("Unexpected event")
                }
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_hints_has_htlc_min_max_values() {
                let mut chanmon_cfgs = create_chanmon_cfgs(3);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 10001);
                create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);

                let payment_amt = 20_000;
                let (payment_hash, _payment_secret) = nodes[1].node.create_inbound_payment(Some(payment_amt), 3600, None).unwrap();
                let route_hints = vec![
                        nodes[1].node.get_phantom_route_hints(),
                        nodes[2].node.get_phantom_route_hints(),
                ];

                let invoice = crate::utils::create_phantom_invoice::<&test_utils::TestKeysInterface,
                        &test_utils::TestKeysInterface, &test_utils::TestLogger>(Some(payment_amt), Some(payment_hash),
                                "test".to_string(), 3600, route_hints, nodes[1].keys_manager, nodes[1].keys_manager,
                                nodes[1].logger, Currency::BitcoinTestnet, None, Duration::from_secs(1234567)).unwrap();

                let chan_0_1 = &nodes[1].node.list_usable_channels()[0];
                assert_eq!(invoice.route_hints()[0].0[0].htlc_minimum_msat, chan_0_1.inbound_htlc_minimum_msat);
                assert_eq!(invoice.route_hints()[0].0[0].htlc_maximum_msat, chan_0_1.inbound_htlc_maximum_msat);

                let chan_0_2 = &nodes[2].node.list_usable_channels()[0];
                assert_eq!(invoice.route_hints()[1].0[0].htlc_minimum_msat, chan_0_2.inbound_htlc_minimum_msat);
                assert_eq!(invoice.route_hints()[1].0[0].htlc_maximum_msat, chan_0_2.inbound_htlc_maximum_msat);
        }

        #[test]
        #[cfg(feature = "std")]
        fn create_phantom_invoice_with_description_hash() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let payment_amt = 20_000;
                let route_hints = vec![
                        nodes[1].node.get_phantom_route_hints(),
                        nodes[2].node.get_phantom_route_hints(),
                ];

                let description_hash = crate::Sha256(Hash::hash("Description hash phantom invoice".as_bytes()));
                let non_default_invoice_expiry_secs = 4200;
                let invoice = crate::utils::create_phantom_invoice_with_description_hash::<
                        &test_utils::TestKeysInterface, &test_utils::TestKeysInterface, &test_utils::TestLogger,
                >(
                        Some(payment_amt), None, non_default_invoice_expiry_secs, description_hash,
                        route_hints, nodes[1].keys_manager, nodes[1].keys_manager, nodes[1].logger,
                        Currency::BitcoinTestnet, None, Duration::from_secs(1234567),
                )
                .unwrap();
                assert_eq!(invoice.amount_pico_btc(), Some(200_000));
                assert_eq!(invoice.min_final_cltv_expiry_delta(), MIN_FINAL_CLTV_EXPIRY_DELTA as u64);
                assert_eq!(invoice.expiry_time(), Duration::from_secs(non_default_invoice_expiry_secs.into()));
                assert_eq!(invoice.description(), InvoiceDescription::Hash(&crate::Sha256(Sha256::hash("Description hash phantom invoice".as_bytes()))));
        }

        #[test]
        #[cfg(feature = "std")]
        fn create_phantom_invoice_with_custom_payment_hash_and_custom_min_final_cltv_delta() {
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let payment_amt = 20_000;
                let route_hints = vec![
                        nodes[1].node.get_phantom_route_hints(),
                        nodes[2].node.get_phantom_route_hints(),
                ];
                let user_payment_preimage = PaymentPreimage([1; 32]);
                let payment_hash = Some(PaymentHash(Sha256::hash(&user_payment_preimage.0[..]).into_inner()));
                let non_default_invoice_expiry_secs = 4200;
                let min_final_cltv_expiry_delta = Some(100);
                let duration_since_epoch = Duration::from_secs(1234567);
                let invoice = crate::utils::create_phantom_invoice::<&test_utils::TestKeysInterface,
                        &test_utils::TestKeysInterface, &test_utils::TestLogger>(Some(payment_amt), payment_hash,
                                "".to_string(), non_default_invoice_expiry_secs, route_hints, nodes[1].keys_manager, nodes[1].keys_manager,
                                nodes[1].logger, Currency::BitcoinTestnet, min_final_cltv_expiry_delta, duration_since_epoch).unwrap();
                assert_eq!(invoice.amount_pico_btc(), Some(200_000));
                assert_eq!(invoice.min_final_cltv_expiry_delta(), (min_final_cltv_expiry_delta.unwrap() + 3) as u64);
                assert_eq!(invoice.expiry_time(), Duration::from_secs(non_default_invoice_expiry_secs.into()));
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_hints_includes_single_channels_to_participating_nodes() {
                let mut chanmon_cfgs = create_chanmon_cfgs(3);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let chan_0_1 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 10001);
                let chan_0_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);

                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_1.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_0_2.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(10_000),
                        &nodes[1],
                        vec![&nodes[1], &nodes[2],],
                        scid_aliases,
                        false
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_hints_includes_one_channel_of_each_counterparty_nodes_per_participating_node() {
                let mut chanmon_cfgs = create_chanmon_cfgs(4);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[3].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
                let nodes = create_network(4, &node_cfgs, &node_chanmgrs);

                let chan_0_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);
                let chan_0_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 3, 1000000, 10001);
                let chan_1_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 3, 3_000_000, 10005);

                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_0_3.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_1_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(10_000),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases,
                        false
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_forwarding_info_not_assigned_channel_excluded_from_hints() {
                let mut chanmon_cfgs = create_chanmon_cfgs(4);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[3].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
                let nodes = create_network(4, &node_cfgs, &node_chanmgrs);

                let chan_0_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);
                let chan_0_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 3, 1000000, 10001);

                // Create an unannonced channel between `nodes[1]` and `nodes[3]`, for which the
                // `msgs::ChannelUpdate` is never handled for the node(s). As the `msgs::ChannelUpdate`
                // is never handled, the `channel.counterparty.forwarding_info` is never assigned.
                let mut private_chan_cfg = UserConfig::default();
                private_chan_cfg.channel_handshake_config.announced_channel = false;
                let temporary_channel_id = nodes[1].node.create_channel(nodes[3].node.get_our_node_id(), 1_000_000, 500_000_000, 42, Some(private_chan_cfg)).unwrap();
                let open_channel = get_event_msg!(nodes[1], MessageSendEvent::SendOpenChannel, nodes[3].node.get_our_node_id());
                nodes[3].node.handle_open_channel(&nodes[1].node.get_our_node_id(), &open_channel);
                let accept_channel = get_event_msg!(nodes[3], MessageSendEvent::SendAcceptChannel, nodes[1].node.get_our_node_id());
                nodes[1].node.handle_accept_channel(&nodes[3].node.get_our_node_id(), &accept_channel);

                let tx = sign_funding_transaction(&nodes[1], &nodes[3], 1_000_000, temporary_channel_id);

                let conf_height = core::cmp::max(nodes[1].best_block_info().1 + 1, nodes[3].best_block_info().1 + 1);
                confirm_transaction_at(&nodes[1], &tx, conf_height);
                connect_blocks(&nodes[1], CHAN_CONFIRM_DEPTH - 1);
                confirm_transaction_at(&nodes[3], &tx, conf_height);
                connect_blocks(&nodes[3], CHAN_CONFIRM_DEPTH - 1);
                let as_channel_ready = get_event_msg!(nodes[1], MessageSendEvent::SendChannelReady, nodes[3].node.get_our_node_id());
                nodes[1].node.handle_channel_ready(&nodes[3].node.get_our_node_id(), &get_event_msg!(nodes[3], MessageSendEvent::SendChannelReady, nodes[1].node.get_our_node_id()));
                get_event_msg!(nodes[1], MessageSendEvent::SendChannelUpdate, nodes[3].node.get_our_node_id());
                nodes[3].node.handle_channel_ready(&nodes[1].node.get_our_node_id(), &as_channel_ready);
                get_event_msg!(nodes[3], MessageSendEvent::SendChannelUpdate, nodes[1].node.get_our_node_id());
                expect_channel_ready_event(&nodes[1], &nodes[3].node.get_our_node_id());
                expect_channel_ready_event(&nodes[3], &nodes[1].node.get_our_node_id());

                // As `msgs::ChannelUpdate` was never handled for the participating node(s) of the third
                // channel, the channel will never be assigned any `counterparty.forwarding_info`.
                // Therefore only `chan_0_3` should be included in the hints for `nodes[3]`.
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_0_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(10_000),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases,
                        false
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_with_only_public_channels_hints_includes_only_phantom_route() {
                let mut chanmon_cfgs = create_chanmon_cfgs(3);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let chan_0_1 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, 10001);

                let chan_2_0 = create_announced_chan_between_nodes_with_value(&nodes, 2, 0, 100000, 10001);
                nodes[2].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_2_0.1);
                nodes[0].node.handle_channel_update(&nodes[2].node.get_our_node_id(), &chan_2_0.0);

                // Hints should include `chan_0_1` from as `nodes[1]` only have private channels, but not
                // `chan_0_2` as `nodes[2]` only has public channels.
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_1.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(10_000),
                        &nodes[1],
                        vec![&nodes[1], &nodes[2],],
                        scid_aliases,
                        true
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_with_mixed_public_and_private_channel_hints_includes_only_phantom_route() {
                let mut chanmon_cfgs = create_chanmon_cfgs(4);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
                let nodes = create_network(4, &node_cfgs, &node_chanmgrs);

                let chan_0_2 = create_announced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);
                nodes[0].node.handle_channel_update(&nodes[2].node.get_our_node_id(), &chan_0_2.1);
                nodes[2].node.handle_channel_update(&nodes[0].node.get_our_node_id(), &chan_0_2.0);
                let _chan_1_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 2, 100000, 10001);

                let chan_0_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 3, 100000, 10001);

                // Hints should include `chan_0_3` from as `nodes[3]` only have private channels, and no
                // channels for `nodes[2]` as it contains a mix of public and private channels.
                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(10_000),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases,
                        true
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_hints_has_only_lowest_inbound_channel_above_minimum() {
                let mut chanmon_cfgs = create_chanmon_cfgs(3);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);

                let _chan_0_1_below_amt = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 100_000, 0);
                let _chan_0_1_above_amt_high_inbound = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 500_000, 0);
                let chan_0_1_above_amt_low_inbound = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 1, 180_000, 0);
                let chan_0_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 100000, 10001);

                let mut scid_aliases = HashSet::new();
                scid_aliases.insert(chan_0_1_above_amt_low_inbound.0.short_channel_id_alias.unwrap());
                scid_aliases.insert(chan_0_2.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(100_000_000),
                        &nodes[1],
                        vec![&nodes[1], &nodes[2],],
                        scid_aliases,
                        false
                );
        }

        #[test]
        #[cfg(feature = "std")]
        fn test_multi_node_channels_inbound_capacity_lower_than_invoice_amt_filtering() {
                let mut chanmon_cfgs = create_chanmon_cfgs(4);
                let seed_1 = [42u8; 32];
                let seed_2 = [43u8; 32];
                let cross_node_seed = [44u8; 32];
                chanmon_cfgs[1].keys_manager.backing = PhantomKeysManager::new(&seed_1, 43, 44, &cross_node_seed);
                chanmon_cfgs[2].keys_manager.backing = PhantomKeysManager::new(&seed_2, 43, 44, &cross_node_seed);
                let node_cfgs = create_node_cfgs(4, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(4, &node_cfgs, &[None, None, None, None]);
                let nodes = create_network(4, &node_cfgs, &node_chanmgrs);

                let chan_0_2 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 2, 1_000_000, 0);
                let chan_0_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 0, 3, 100_000, 0);
                let chan_1_3 = create_unannounced_chan_between_nodes_with_value(&nodes, 1, 3, 200_000, 0);

                // Since the invoice 1 msat above chan_0_3's inbound capacity, it should be filtered out.
                let mut scid_aliases_99_000_001_msat = HashSet::new();
                scid_aliases_99_000_001_msat.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases_99_000_001_msat.insert(chan_1_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(99_000_001),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases_99_000_001_msat,
                        false
                );

                // Since the invoice is exactly at chan_0_3's inbound capacity, it should be included.
                let mut scid_aliases_99_000_000_msat = HashSet::new();
                scid_aliases_99_000_000_msat.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases_99_000_000_msat.insert(chan_0_3.0.short_channel_id_alias.unwrap());
                scid_aliases_99_000_000_msat.insert(chan_1_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(99_000_000),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases_99_000_000_msat,
                        false
                );

                // Since the invoice is above all of `nodes[2]` channels' inbound capacity, all of
                // `nodes[2]` them should be included.
                let mut scid_aliases_300_000_000_msat = HashSet::new();
                scid_aliases_300_000_000_msat.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases_300_000_000_msat.insert(chan_0_3.0.short_channel_id_alias.unwrap());
                scid_aliases_300_000_000_msat.insert(chan_1_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        Some(300_000_000),
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases_300_000_000_msat,
                        false
                );

                // Since the no specified amount, all channels should included.
                let mut scid_aliases_no_specified_amount = HashSet::new();
                scid_aliases_no_specified_amount.insert(chan_0_2.0.short_channel_id_alias.unwrap());
                scid_aliases_no_specified_amount.insert(chan_0_3.0.short_channel_id_alias.unwrap());
                scid_aliases_no_specified_amount.insert(chan_1_3.0.short_channel_id_alias.unwrap());

                match_multi_node_invoice_routes(
                        None,
                        &nodes[2],
                        vec![&nodes[2], &nodes[3],],
                        scid_aliases_no_specified_amount,
                        false
                );
        }

        #[cfg(feature = "std")]
        fn match_multi_node_invoice_routes<'a, 'b: 'a, 'c: 'b>(
                invoice_amt: Option<u64>,
                invoice_node: &Node<'a, 'b, 'c>,
                network_multi_nodes: Vec<&Node<'a, 'b, 'c>>,
                mut chan_ids_to_match: HashSet<u64>,
                nodes_contains_public_channels: bool
        ){
                let phantom_route_hints = network_multi_nodes.iter()
                        .map(|node| node.node.get_phantom_route_hints())
                        .collect::<Vec<PhantomRouteHints>>();
                let phantom_scids = phantom_route_hints.iter()
                        .map(|route_hint| route_hint.phantom_scid)
                        .collect::<HashSet<u64>>();

                let invoice = crate::utils::create_phantom_invoice::<&test_utils::TestKeysInterface,
                        &test_utils::TestKeysInterface, &test_utils::TestLogger>(invoice_amt, None, "test".to_string(),
                                3600, phantom_route_hints, invoice_node.keys_manager, invoice_node.keys_manager,
                                invoice_node.logger, Currency::BitcoinTestnet, None, Duration::from_secs(1234567)).unwrap();

                let invoice_hints = invoice.private_routes();

                for hint in invoice_hints {
                        let hints = &(hint.0).0;
                        match hints.len() {
                                1 => {
                                        assert!(nodes_contains_public_channels);
                                        let phantom_scid = hints[0].short_channel_id;
                                        assert!(phantom_scids.contains(&phantom_scid));
                                },
                                2 => {
                                        let hint_short_chan_id = hints[0].short_channel_id;
                                        assert!(chan_ids_to_match.remove(&hint_short_chan_id));
                                        let phantom_scid = hints[1].short_channel_id;
                                        assert!(phantom_scids.contains(&phantom_scid));
                                },
                                _ => panic!("Incorrect hint length generated")
                        }
                }
                assert!(chan_ids_to_match.is_empty(), "Unmatched short channel ids: {:?}", chan_ids_to_match);
        }

        #[test]
        fn test_create_invoice_fails_with_invalid_custom_min_final_cltv_expiry_delta() {
                let chanmon_cfgs = create_chanmon_cfgs(2);
                let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
                let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
                let result = crate::utils::create_invoice_from_channelmanager_and_duration_since_epoch(
                        nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::BitcoinTestnet,
                        Some(10_000), "Some description".into(), Duration::from_secs(1234567), 3600, Some(MIN_FINAL_CLTV_EXPIRY_DELTA - 4),
                );
                match result {
                        Err(SignOrCreationError::CreationError(CreationError::MinFinalCltvExpiryDeltaTooShort)) => {},
                        _ => panic!(),
                }
        }
}