[rust-lightning] / lightning / src / offers / offer.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! Data structures and encoding for `offer` messages.
//!
//! An [`Offer`] represents an "offer to be paid." It is typically constructed by a merchant and
//! published as a QR code to be scanned by a customer. The customer uses the offer to request an
//! invoice from the merchant to be paid.
//!
//! ```
//! extern crate bitcoin;
//! extern crate core;
//! extern crate lightning;
//!
//! use core::convert::TryFrom;
//! use core::num::NonZeroU64;
//! use core::time::Duration;
//!
//! use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, SecretKey};
//! use lightning::offers::offer::{Offer, OfferBuilder, Quantity};
//! use lightning::offers::parse::Bolt12ParseError;
//! use lightning::util::ser::{Readable, Writeable};
//!
//! # use lightning::blinded_path::BlindedPath;
//! # #[cfg(feature = "std")]
//! # use std::time::SystemTime;
//! #
//! # fn create_blinded_path() -> BlindedPath { unimplemented!() }
//! # fn create_another_blinded_path() -> BlindedPath { unimplemented!() }
//! #
//! # #[cfg(feature = "std")]
//! # fn build() -> Result<(), Bolt12ParseError> {
//! let secp_ctx = Secp256k1::new();
//! let keys = KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
//! let pubkey = PublicKey::from(keys);
//!
//! let expiration = SystemTime::now() + Duration::from_secs(24 * 60 * 60);
//! let offer = OfferBuilder::new("coffee, large".to_string(), pubkey)
//!     .amount_msats(20_000)
//!     .supported_quantity(Quantity::Unbounded)
//!     .absolute_expiry(expiration.duration_since(SystemTime::UNIX_EPOCH).unwrap())
//!     .issuer("Foo Bar".to_string())
//!     .path(create_blinded_path())
//!     .path(create_another_blinded_path())
//!     .build()?;
//!
//! // Encode as a bech32 string for use in a QR code.
//! let encoded_offer = offer.to_string();
//!
//! // Parse from a bech32 string after scanning from a QR code.
//! let offer = encoded_offer.parse::<Offer>()?;
//!
//! // Encode offer as raw bytes.
//! let mut bytes = Vec::new();
//! offer.write(&mut bytes).unwrap();
//!
//! // Decode raw bytes into an offer.
//! let offer = Offer::try_from(bytes)?;
//! # Ok(())
//! # }
//! ```

use bitcoin::blockdata::constants::ChainHash;
use bitcoin::network::constants::Network;
use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, self};
use core::convert::TryFrom;
use core::num::NonZeroU64;
use core::ops::Deref;
use core::str::FromStr;
use core::time::Duration;
use crate::sign::EntropySource;
use crate::io;
use crate::blinded_path::BlindedPath;
use crate::ln::features::OfferFeatures;
use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
use crate::ln::msgs::MAX_VALUE_MSAT;
use crate::offers::invoice_request::{DerivedPayerId, ExplicitPayerId, InvoiceRequestBuilder};
use crate::offers::merkle::TlvStream;
use crate::offers::parse::{Bech32Encode, Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
use crate::offers::signer::{Metadata, MetadataMaterial, self};
use crate::util::ser::{HighZeroBytesDroppedBigSize, WithoutLength, Writeable, Writer};
use crate::util::string::PrintableString;

use crate::prelude::*;

#[cfg(feature = "std")]
use std::time::SystemTime;

pub(super) const IV_BYTES: &[u8; IV_LEN] = b"LDK Offer ~~~~~~";

/// Builds an [`Offer`] for the "offer to be paid" flow.
///
/// See [module-level documentation] for usage.
///
/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
///
/// [module-level documentation]: self
pub struct OfferBuilder<'a, M: MetadataStrategy, T: secp256k1::Signing> {
        offer: OfferContents,
        metadata_strategy: core::marker::PhantomData<M>,
        secp_ctx: Option<&'a Secp256k1<T>>,
}

/// Indicates how [`Offer::metadata`] may be set.
///
/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
pub trait MetadataStrategy {}

/// [`Offer::metadata`] may be explicitly set or left empty.
///
/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
pub struct ExplicitMetadata {}

/// [`Offer::metadata`] will be derived.
///
/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
pub struct DerivedMetadata {}

impl MetadataStrategy for ExplicitMetadata {}
impl MetadataStrategy for DerivedMetadata {}

impl<'a> OfferBuilder<'a, ExplicitMetadata, secp256k1::SignOnly> {
        /// Creates a new builder for an offer setting the [`Offer::description`] and using the
        /// [`Offer::signing_pubkey`] for signing invoices. The associated secret key must be remembered
        /// while the offer is valid.
        ///
        /// Use a different pubkey per offer to avoid correlating offers.
        pub fn new(description: String, signing_pubkey: PublicKey) -> Self {
                OfferBuilder {
                        offer: OfferContents {
                                chains: None, metadata: None, amount: None, description,
                                features: OfferFeatures::empty(), absolute_expiry: None, issuer: None, paths: None,
                                supported_quantity: Quantity::One, signing_pubkey,
                        },
                        metadata_strategy: core::marker::PhantomData,
                        secp_ctx: None,
                }
        }

        /// Sets the [`Offer::metadata`] to the given bytes.
        ///
        /// Successive calls to this method will override the previous setting.
        pub fn metadata(mut self, metadata: Vec<u8>) -> Result<Self, Bolt12SemanticError> {
                self.offer.metadata = Some(Metadata::Bytes(metadata));
                Ok(self)
        }
}

impl<'a, T: secp256k1::Signing> OfferBuilder<'a, DerivedMetadata, T> {
        /// Similar to [`OfferBuilder::new`] except, if [`OfferBuilder::path`] is called, the signing
        /// pubkey is derived from the given [`ExpandedKey`] and [`EntropySource`]. This provides
        /// recipient privacy by using a different signing pubkey for each offer. Otherwise, the
        /// provided `node_id` is used for the signing pubkey.
        ///
        /// Also, sets the metadata when [`OfferBuilder::build`] is called such that it can be used by
        /// [`InvoiceRequest::verify`] to determine if the request was produced for the offer given an
        /// [`ExpandedKey`].
        ///
        /// [`InvoiceRequest::verify`]: crate::offers::invoice_request::InvoiceRequest::verify
        /// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
        pub fn deriving_signing_pubkey<ES: Deref>(
                description: String, node_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES,
                secp_ctx: &'a Secp256k1<T>
        ) -> Self where ES::Target: EntropySource {
                let nonce = Nonce::from_entropy_source(entropy_source);
                let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES);
                let metadata = Metadata::DerivedSigningPubkey(derivation_material);
                OfferBuilder {
                        offer: OfferContents {
                                chains: None, metadata: Some(metadata), amount: None, description,
                                features: OfferFeatures::empty(), absolute_expiry: None, issuer: None, paths: None,
                                supported_quantity: Quantity::One, signing_pubkey: node_id,
                        },
                        metadata_strategy: core::marker::PhantomData,
                        secp_ctx: Some(secp_ctx),
                }
        }
}

impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
        /// Adds the chain hash of the given [`Network`] to [`Offer::chains`]. If not called,
        /// the chain hash of [`Network::Bitcoin`] is assumed to be the only one supported.
        ///
        /// See [`Offer::chains`] on how this relates to the payment currency.
        ///
        /// Successive calls to this method will add another chain hash.
        pub fn chain(mut self, network: Network) -> Self {
                let chains = self.offer.chains.get_or_insert_with(Vec::new);
                let chain = ChainHash::using_genesis_block(network);
                if !chains.contains(&chain) {
                        chains.push(chain);
                }

                self
        }

        /// Sets the [`Offer::amount`] as an [`Amount::Bitcoin`].
        ///
        /// Successive calls to this method will override the previous setting.
        pub fn amount_msats(self, amount_msats: u64) -> Self {
                self.amount(Amount::Bitcoin { amount_msats })
        }

        /// Sets the [`Offer::amount`].
        ///
        /// Successive calls to this method will override the previous setting.
        pub(super) fn amount(mut self, amount: Amount) -> Self {
                self.offer.amount = Some(amount);
                self
        }

        /// Sets the [`Offer::absolute_expiry`] as seconds since the Unix epoch. Any expiry that has
        /// already passed is valid and can be checked for using [`Offer::is_expired`].
        ///
        /// Successive calls to this method will override the previous setting.
        pub fn absolute_expiry(mut self, absolute_expiry: Duration) -> Self {
                self.offer.absolute_expiry = Some(absolute_expiry);
                self
        }

        /// Sets the [`Offer::issuer`].
        ///
        /// Successive calls to this method will override the previous setting.
        pub fn issuer(mut self, issuer: String) -> Self {
                self.offer.issuer = Some(issuer);
                self
        }

        /// Adds a blinded path to [`Offer::paths`]. Must include at least one path if only connected by
        /// private channels or if [`Offer::signing_pubkey`] is not a public node id.
        ///
        /// Successive calls to this method will add another blinded path. Caller is responsible for not
        /// adding duplicate paths.
        pub fn path(mut self, path: BlindedPath) -> Self {
                self.offer.paths.get_or_insert_with(Vec::new).push(path);
                self
        }

        /// Sets the quantity of items for [`Offer::supported_quantity`]. If not called, defaults to
        /// [`Quantity::One`].
        ///
        /// Successive calls to this method will override the previous setting.
        pub fn supported_quantity(mut self, quantity: Quantity) -> Self {
                self.offer.supported_quantity = quantity;
                self
        }

        /// Builds an [`Offer`] from the builder's settings.
        pub fn build(mut self) -> Result<Offer, Bolt12SemanticError> {
                match self.offer.amount {
                        Some(Amount::Bitcoin { amount_msats }) => {
                                if amount_msats > MAX_VALUE_MSAT {
                                        return Err(Bolt12SemanticError::InvalidAmount);
                                }
                        },
                        Some(Amount::Currency { .. }) => return Err(Bolt12SemanticError::UnsupportedCurrency),
                        None => {},
                }

                if let Some(chains) = &self.offer.chains {
                        if chains.len() == 1 && chains[0] == self.offer.implied_chain() {
                                self.offer.chains = None;
                        }
                }

                Ok(self.build_without_checks())
        }

        fn build_without_checks(mut self) -> Offer {
                // Create the metadata for stateless verification of an InvoiceRequest.
                if let Some(mut metadata) = self.offer.metadata.take() {
                        if metadata.has_derivation_material() {
                                if self.offer.paths.is_none() {
                                        metadata = metadata.without_keys();
                                }

                                let mut tlv_stream = self.offer.as_tlv_stream();
                                debug_assert_eq!(tlv_stream.metadata, None);
                                tlv_stream.metadata = None;
                                if metadata.derives_keys() {
                                        tlv_stream.node_id = None;
                                }

                                let (derived_metadata, keys) = metadata.derive_from(tlv_stream, self.secp_ctx);
                                metadata = derived_metadata;
                                if let Some(keys) = keys {
                                        self.offer.signing_pubkey = keys.public_key();
                                }
                        }

                        self.offer.metadata = Some(metadata);
                }

                let mut bytes = Vec::new();
                self.offer.write(&mut bytes).unwrap();

                Offer { bytes, contents: self.offer }
        }
}

#[cfg(test)]
impl<'a, M: MetadataStrategy, T: secp256k1::Signing> OfferBuilder<'a, M, T> {
        fn features_unchecked(mut self, features: OfferFeatures) -> Self {
                self.offer.features = features;
                self
        }

        pub(super) fn build_unchecked(self) -> Offer {
                self.build_without_checks()
        }
}

/// An `Offer` is a potentially long-lived proposal for payment of a good or service.
///
/// An offer is a precursor to an [`InvoiceRequest`]. A merchant publishes an offer from which a
/// customer may request an [`Bolt12Invoice`] for a specific quantity and using an amount sufficient
/// to cover that quantity (i.e., at least `quantity * amount`). See [`Offer::amount`].
///
/// Offers may be denominated in currency other than bitcoin but are ultimately paid using the
/// latter.
///
/// Through the use of [`BlindedPath`]s, offers provide recipient privacy.
///
/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
#[derive(Clone, Debug)]
#[cfg_attr(test, derive(PartialEq))]
pub struct Offer {
        // The serialized offer. Needed when creating an `InvoiceRequest` if the offer contains unknown
        // fields.
        pub(super) bytes: Vec<u8>,
        pub(super) contents: OfferContents,
}

/// The contents of an [`Offer`], which may be shared with an [`InvoiceRequest`] or a
/// [`Bolt12Invoice`].
///
/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
#[derive(Clone, Debug)]
#[cfg_attr(test, derive(PartialEq))]
pub(super) struct OfferContents {
        chains: Option<Vec<ChainHash>>,
        metadata: Option<Metadata>,
        amount: Option<Amount>,
        description: String,
        features: OfferFeatures,
        absolute_expiry: Option<Duration>,
        issuer: Option<String>,
        paths: Option<Vec<BlindedPath>>,
        supported_quantity: Quantity,
        signing_pubkey: PublicKey,
}

impl Offer {
        // TODO: Return a slice once ChainHash has constants.
        // - https://github.com/rust-bitcoin/rust-bitcoin/pull/1283
        // - https://github.com/rust-bitcoin/rust-bitcoin/pull/1286
        /// The chains that may be used when paying a requested invoice (e.g., bitcoin mainnet).
        /// Payments must be denominated in units of the minimal lightning-payable unit (e.g., msats)
        /// for the selected chain.
        pub fn chains(&self) -> Vec<ChainHash> {
                self.contents.chains()
        }

        pub(super) fn implied_chain(&self) -> ChainHash {
                self.contents.implied_chain()
        }

        /// Returns whether the given chain is supported by the offer.
        pub fn supports_chain(&self, chain: ChainHash) -> bool {
                self.contents.supports_chain(chain)
        }

        // TODO: Link to corresponding method in `InvoiceRequest`.
        /// Opaque bytes set by the originator. Useful for authentication and validating fields since it
        /// is reflected in `invoice_request` messages along with all the other fields from the `offer`.
        pub fn metadata(&self) -> Option<&Vec<u8>> {
                self.contents.metadata()
        }

        /// The minimum amount required for a successful payment of a single item.
        pub fn amount(&self) -> Option<&Amount> {
                self.contents.amount()
        }

        /// A complete description of the purpose of the payment. Intended to be displayed to the user
        /// but with the caveat that it has not been verified in any way.
        pub fn description(&self) -> PrintableString {
                self.contents.description()
        }

        /// Features pertaining to the offer.
        pub fn features(&self) -> &OfferFeatures {
                &self.contents.features()
        }

        /// Duration since the Unix epoch when an invoice should no longer be requested.
        ///
        /// If `None`, the offer does not expire.
        pub fn absolute_expiry(&self) -> Option<Duration> {
                self.contents.absolute_expiry()
        }

        /// Whether the offer has expired.
        #[cfg(feature = "std")]
        pub fn is_expired(&self) -> bool {
                self.contents.is_expired()
        }

        /// The issuer of the offer, possibly beginning with `user@domain` or `domain`. Intended to be
        /// displayed to the user but with the caveat that it has not been verified in any way.
        pub fn issuer(&self) -> Option<PrintableString> {
                self.contents.issuer()
        }

        /// Paths to the recipient originating from publicly reachable nodes. Blinded paths provide
        /// recipient privacy by obfuscating its node id.
        pub fn paths(&self) -> &[BlindedPath] {
                self.contents.paths()
        }

        /// The quantity of items supported.
        pub fn supported_quantity(&self) -> Quantity {
                self.contents.supported_quantity()
        }

        /// Returns whether the given quantity is valid for the offer.
        pub fn is_valid_quantity(&self, quantity: u64) -> bool {
                self.contents.is_valid_quantity(quantity)
        }

        /// Returns whether a quantity is expected in an [`InvoiceRequest`] for the offer.
        ///
        /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
        pub fn expects_quantity(&self) -> bool {
                self.contents.expects_quantity()
        }

        /// The public key used by the recipient to sign invoices.
        pub fn signing_pubkey(&self) -> PublicKey {
                self.contents.signing_pubkey()
        }

        /// Similar to [`Offer::request_invoice`] except it:
        /// - derives the [`InvoiceRequest::payer_id`] such that a different key can be used for each
        ///   request, and
        /// - sets the [`InvoiceRequest::metadata`] when [`InvoiceRequestBuilder::build`] is called such
        ///   that it can be used by [`Bolt12Invoice::verify`] to determine if the invoice was requested
        ///   using a base [`ExpandedKey`] from which the payer id was derived.
        ///
        /// Useful to protect the sender's privacy.
        ///
        /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
        ///
        /// [`InvoiceRequest::payer_id`]: crate::offers::invoice_request::InvoiceRequest::payer_id
        /// [`InvoiceRequest::metadata`]: crate::offers::invoice_request::InvoiceRequest::metadata
        /// [`Bolt12Invoice::verify`]: crate::offers::invoice::Bolt12Invoice::verify
        /// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
        pub fn request_invoice_deriving_payer_id<'a, 'b, ES: Deref, T: secp256k1::Signing>(
                &'a self, expanded_key: &ExpandedKey, entropy_source: ES, secp_ctx: &'b Secp256k1<T>
        ) -> Result<InvoiceRequestBuilder<'a, 'b, DerivedPayerId, T>, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
                if self.features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }

                Ok(InvoiceRequestBuilder::deriving_payer_id(self, expanded_key, entropy_source, secp_ctx))
        }

        /// Similar to [`Offer::request_invoice_deriving_payer_id`] except uses `payer_id` for the
        /// [`InvoiceRequest::payer_id`] instead of deriving a different key for each request.
        ///
        /// Useful for recurring payments using the same `payer_id` with different invoices.
        ///
        /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
        ///
        /// [`InvoiceRequest::payer_id`]: crate::offers::invoice_request::InvoiceRequest::payer_id
        pub fn request_invoice_deriving_metadata<ES: Deref>(
                &self, payer_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES
        ) -> Result<InvoiceRequestBuilder<ExplicitPayerId, secp256k1::SignOnly>, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
                if self.features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }

                Ok(InvoiceRequestBuilder::deriving_metadata(self, payer_id, expanded_key, entropy_source))
        }

        /// Creates an [`InvoiceRequestBuilder`] for the offer with the given `metadata` and `payer_id`,
        /// which will be reflected in the `Bolt12Invoice` response.
        ///
        /// The `metadata` is useful for including information about the derivation of `payer_id` such
        /// that invoice response handling can be stateless. Also serves as payer-provided entropy while
        /// hashing in the signature calculation.
        ///
        /// This should not leak any information such as by using a simple BIP-32 derivation path.
        /// Otherwise, payments may be correlated.
        ///
        /// Errors if the offer contains unknown required features.
        ///
        /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
        ///
        /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
        pub fn request_invoice(
                &self, metadata: Vec<u8>, payer_id: PublicKey
        ) -> Result<InvoiceRequestBuilder<ExplicitPayerId, secp256k1::SignOnly>, Bolt12SemanticError> {
                if self.features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }

                Ok(InvoiceRequestBuilder::new(self, metadata, payer_id))
        }

        #[cfg(test)]
        pub(super) fn as_tlv_stream(&self) -> OfferTlvStreamRef {
                self.contents.as_tlv_stream()
        }
}

impl AsRef<[u8]> for Offer {
        fn as_ref(&self) -> &[u8] {
                &self.bytes
        }
}

impl OfferContents {
        pub fn chains(&self) -> Vec<ChainHash> {
                self.chains.as_ref().cloned().unwrap_or_else(|| vec![self.implied_chain()])
        }

        pub fn implied_chain(&self) -> ChainHash {
                ChainHash::using_genesis_block(Network::Bitcoin)
        }

        pub fn supports_chain(&self, chain: ChainHash) -> bool {
                self.chains().contains(&chain)
        }

        pub fn metadata(&self) -> Option<&Vec<u8>> {
                self.metadata.as_ref().and_then(|metadata| metadata.as_bytes())
        }

        pub fn amount(&self) -> Option<&Amount> {
                self.amount.as_ref()
        }

        pub fn description(&self) -> PrintableString {
                PrintableString(&self.description)
        }

        pub fn features(&self) -> &OfferFeatures {
                &self.features
        }

        pub fn absolute_expiry(&self) -> Option<Duration> {
                self.absolute_expiry
        }

        #[cfg(feature = "std")]
        pub(super) fn is_expired(&self) -> bool {
                match self.absolute_expiry {
                        Some(seconds_from_epoch) => match SystemTime::UNIX_EPOCH.elapsed() {
                                Ok(elapsed) => elapsed > seconds_from_epoch,
                                Err(_) => false,
                        },
                        None => false,
                }
        }

        pub fn issuer(&self) -> Option<PrintableString> {
                self.issuer.as_ref().map(|issuer| PrintableString(issuer.as_str()))
        }

        pub fn paths(&self) -> &[BlindedPath] {
                self.paths.as_ref().map(|paths| paths.as_slice()).unwrap_or(&[])
        }

        pub(super) fn check_amount_msats_for_quantity(
                &self, amount_msats: Option<u64>, quantity: Option<u64>
        ) -> Result<(), Bolt12SemanticError> {
                let offer_amount_msats = match self.amount {
                        None => 0,
                        Some(Amount::Bitcoin { amount_msats }) => amount_msats,
                        Some(Amount::Currency { .. }) => return Err(Bolt12SemanticError::UnsupportedCurrency),
                };

                if !self.expects_quantity() || quantity.is_some() {
                        let expected_amount_msats = offer_amount_msats.checked_mul(quantity.unwrap_or(1))
                                .ok_or(Bolt12SemanticError::InvalidAmount)?;
                        let amount_msats = amount_msats.unwrap_or(expected_amount_msats);

                        if amount_msats < expected_amount_msats {
                                return Err(Bolt12SemanticError::InsufficientAmount);
                        }

                        if amount_msats > MAX_VALUE_MSAT {
                                return Err(Bolt12SemanticError::InvalidAmount);
                        }
                }

                Ok(())
        }

        pub fn supported_quantity(&self) -> Quantity {
                self.supported_quantity
        }

        pub(super) fn check_quantity(&self, quantity: Option<u64>) -> Result<(), Bolt12SemanticError> {
                let expects_quantity = self.expects_quantity();
                match quantity {
                        None if expects_quantity => Err(Bolt12SemanticError::MissingQuantity),
                        Some(_) if !expects_quantity => Err(Bolt12SemanticError::UnexpectedQuantity),
                        Some(quantity) if !self.is_valid_quantity(quantity) => {
                                Err(Bolt12SemanticError::InvalidQuantity)
                        },
                        _ => Ok(()),
                }
        }

        fn is_valid_quantity(&self, quantity: u64) -> bool {
                match self.supported_quantity {
                        Quantity::Bounded(n) => quantity <= n.get(),
                        Quantity::Unbounded => quantity > 0,
                        Quantity::One => quantity == 1,
                }
        }

        fn expects_quantity(&self) -> bool {
                match self.supported_quantity {
                        Quantity::Bounded(_) => true,
                        Quantity::Unbounded => true,
                        Quantity::One => false,
                }
        }

        pub(super) fn signing_pubkey(&self) -> PublicKey {
                self.signing_pubkey
        }

        /// Verifies that the offer metadata was produced from the offer in the TLV stream.
        pub(super) fn verify<T: secp256k1::Signing>(
                &self, bytes: &[u8], key: &ExpandedKey, secp_ctx: &Secp256k1<T>
        ) -> Result<Option<KeyPair>, ()> {
                match self.metadata() {
                        Some(metadata) => {
                                let tlv_stream = TlvStream::new(bytes).range(OFFER_TYPES).filter(|record| {
                                        match record.r#type {
                                                OFFER_METADATA_TYPE => false,
                                                OFFER_NODE_ID_TYPE => !self.metadata.as_ref().unwrap().derives_keys(),
                                                _ => true,
                                        }
                                });
                                signer::verify_metadata(
                                        metadata, key, IV_BYTES, self.signing_pubkey(), tlv_stream, secp_ctx
                                )
                        },
                        None => Err(()),
                }
        }

        pub(super) fn as_tlv_stream(&self) -> OfferTlvStreamRef {
                let (currency, amount) = match &self.amount {
                        None => (None, None),
                        Some(Amount::Bitcoin { amount_msats }) => (None, Some(*amount_msats)),
                        Some(Amount::Currency { iso4217_code, amount }) => (
                                Some(iso4217_code), Some(*amount)
                        ),
                };

                let features = {
                        if self.features == OfferFeatures::empty() { None } else { Some(&self.features) }
                };

                OfferTlvStreamRef {
                        chains: self.chains.as_ref(),
                        metadata: self.metadata(),
                        currency,
                        amount,
                        description: Some(&self.description),
                        features,
                        absolute_expiry: self.absolute_expiry.map(|duration| duration.as_secs()),
                        paths: self.paths.as_ref(),
                        issuer: self.issuer.as_ref(),
                        quantity_max: self.supported_quantity.to_tlv_record(),
                        node_id: Some(&self.signing_pubkey),
                }
        }
}

impl Writeable for Offer {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                WithoutLength(&self.bytes).write(writer)
        }
}

impl Writeable for OfferContents {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                self.as_tlv_stream().write(writer)
        }
}

/// The minimum amount required for an item in an [`Offer`], denominated in either bitcoin or
/// another currency.
#[derive(Clone, Debug, PartialEq)]
pub enum Amount {
        /// An amount of bitcoin.
        Bitcoin {
                /// The amount in millisatoshi.
                amount_msats: u64,
        },
        /// An amount of currency specified using ISO 4712.
        Currency {
                /// The currency that the amount is denominated in.
                iso4217_code: CurrencyCode,
                /// The amount in the currency unit adjusted by the ISO 4712 exponent (e.g., USD cents).
                amount: u64,
        },
}

/// An ISO 4712 three-letter currency code (e.g., USD).
pub type CurrencyCode = [u8; 3];

/// Quantity of items supported by an [`Offer`].
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Quantity {
        /// Up to a specific number of items (inclusive). Use when more than one item can be requested
        /// but is limited (e.g., because of per customer or inventory limits).
        ///
        /// May be used with `NonZeroU64::new(1)` but prefer to use [`Quantity::One`] if only one item
        /// is supported.
        Bounded(NonZeroU64),
        /// One or more items. Use when more than one item can be requested without any limit.
        Unbounded,
        /// Only one item. Use when only a single item can be requested.
        One,
}

impl Quantity {
        fn to_tlv_record(&self) -> Option<u64> {
                match self {
                        Quantity::Bounded(n) => Some(n.get()),
                        Quantity::Unbounded => Some(0),
                        Quantity::One => None,
                }
        }
}

/// Valid type range for offer TLV records.
pub(super) const OFFER_TYPES: core::ops::Range<u64> = 1..80;

/// TLV record type for [`Offer::metadata`].
const OFFER_METADATA_TYPE: u64 = 4;

/// TLV record type for [`Offer::signing_pubkey`].
const OFFER_NODE_ID_TYPE: u64 = 22;

tlv_stream!(OfferTlvStream, OfferTlvStreamRef, OFFER_TYPES, {
        (2, chains: (Vec<ChainHash>, WithoutLength)),
        (OFFER_METADATA_TYPE, metadata: (Vec<u8>, WithoutLength)),
        (6, currency: CurrencyCode),
        (8, amount: (u64, HighZeroBytesDroppedBigSize)),
        (10, description: (String, WithoutLength)),
        (12, features: (OfferFeatures, WithoutLength)),
        (14, absolute_expiry: (u64, HighZeroBytesDroppedBigSize)),
        (16, paths: (Vec<BlindedPath>, WithoutLength)),
        (18, issuer: (String, WithoutLength)),
        (20, quantity_max: (u64, HighZeroBytesDroppedBigSize)),
        (OFFER_NODE_ID_TYPE, node_id: PublicKey),
});

impl Bech32Encode for Offer {
        const BECH32_HRP: &'static str = "lno";
}

impl FromStr for Offer {
        type Err = Bolt12ParseError;

        fn from_str(s: &str) -> Result<Self, <Self as FromStr>::Err> {
                Self::from_bech32_str(s)
        }
}

impl TryFrom<Vec<u8>> for Offer {
        type Error = Bolt12ParseError;

        fn try_from(bytes: Vec<u8>) -> Result<Self, Self::Error> {
                let offer = ParsedMessage::<OfferTlvStream>::try_from(bytes)?;
                let ParsedMessage { bytes, tlv_stream } = offer;
                let contents = OfferContents::try_from(tlv_stream)?;
                Ok(Offer { bytes, contents })
        }
}

impl TryFrom<OfferTlvStream> for OfferContents {
        type Error = Bolt12SemanticError;

        fn try_from(tlv_stream: OfferTlvStream) -> Result<Self, Self::Error> {
                let OfferTlvStream {
                        chains, metadata, currency, amount, description, features, absolute_expiry, paths,
                        issuer, quantity_max, node_id,
                } = tlv_stream;

                let metadata = metadata.map(|metadata| Metadata::Bytes(metadata));

                let amount = match (currency, amount) {
                        (None, None) => None,
                        (None, Some(amount_msats)) if amount_msats > MAX_VALUE_MSAT => {
                                return Err(Bolt12SemanticError::InvalidAmount);
                        },
                        (None, Some(amount_msats)) => Some(Amount::Bitcoin { amount_msats }),
                        (Some(_), None) => return Err(Bolt12SemanticError::MissingAmount),
                        (Some(iso4217_code), Some(amount)) => Some(Amount::Currency { iso4217_code, amount }),
                };

                let description = match description {
                        None => return Err(Bolt12SemanticError::MissingDescription),
                        Some(description) => description,
                };

                let features = features.unwrap_or_else(OfferFeatures::empty);

                let absolute_expiry = absolute_expiry
                        .map(|seconds_from_epoch| Duration::from_secs(seconds_from_epoch));

                let supported_quantity = match quantity_max {
                        None => Quantity::One,
                        Some(0) => Quantity::Unbounded,
                        Some(n) => Quantity::Bounded(NonZeroU64::new(n).unwrap()),
                };

                let signing_pubkey = match node_id {
                        None => return Err(Bolt12SemanticError::MissingSigningPubkey),
                        Some(node_id) => node_id,
                };

                Ok(OfferContents {
                        chains, metadata, amount, description, features, absolute_expiry, issuer, paths,
                        supported_quantity, signing_pubkey,
                })
        }
}

impl core::fmt::Display for Offer {
        fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
                self.fmt_bech32_str(f)
        }
}

#[cfg(test)]
mod tests {
        use super::{Amount, Offer, OfferBuilder, OfferTlvStreamRef, Quantity};

        use bitcoin::blockdata::constants::ChainHash;
        use bitcoin::network::constants::Network;
        use bitcoin::secp256k1::Secp256k1;
        use core::convert::TryFrom;
        use core::num::NonZeroU64;
        use core::time::Duration;
        use crate::blinded_path::{BlindedHop, BlindedPath};
        use crate::sign::KeyMaterial;
        use crate::ln::features::OfferFeatures;
        use crate::ln::inbound_payment::ExpandedKey;
        use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
        use crate::offers::parse::{Bolt12ParseError, Bolt12SemanticError};
        use crate::offers::test_utils::*;
        use crate::util::ser::{BigSize, Writeable};
        use crate::util::string::PrintableString;

        #[test]
        fn builds_offer_with_defaults() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42)).build().unwrap();

                let mut buffer = Vec::new();
                offer.write(&mut buffer).unwrap();

                assert_eq!(offer.bytes, buffer.as_slice());
                assert_eq!(offer.chains(), vec![ChainHash::using_genesis_block(Network::Bitcoin)]);
                assert!(offer.supports_chain(ChainHash::using_genesis_block(Network::Bitcoin)));
                assert_eq!(offer.metadata(), None);
                assert_eq!(offer.amount(), None);
                assert_eq!(offer.description(), PrintableString("foo"));
                assert_eq!(offer.features(), &OfferFeatures::empty());
                assert_eq!(offer.absolute_expiry(), None);
                #[cfg(feature = "std")]
                assert!(!offer.is_expired());
                assert_eq!(offer.paths(), &[]);
                assert_eq!(offer.issuer(), None);
                assert_eq!(offer.supported_quantity(), Quantity::One);
                assert_eq!(offer.signing_pubkey(), pubkey(42));

                assert_eq!(
                        offer.as_tlv_stream(),
                        OfferTlvStreamRef {
                                chains: None,
                                metadata: None,
                                currency: None,
                                amount: None,
                                description: Some(&String::from("foo")),
                                features: None,
                                absolute_expiry: None,
                                paths: None,
                                issuer: None,
                                quantity_max: None,
                                node_id: Some(&pubkey(42)),
                        },
                );

                if let Err(e) = Offer::try_from(buffer) {
                        panic!("error parsing offer: {:?}", e);
                }
        }

        #[test]
        fn builds_offer_with_chains() {
                let mainnet = ChainHash::using_genesis_block(Network::Bitcoin);
                let testnet = ChainHash::using_genesis_block(Network::Testnet);

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .chain(Network::Bitcoin)
                        .build()
                        .unwrap();
                assert!(offer.supports_chain(mainnet));
                assert_eq!(offer.chains(), vec![mainnet]);
                assert_eq!(offer.as_tlv_stream().chains, None);

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .chain(Network::Testnet)
                        .build()
                        .unwrap();
                assert!(offer.supports_chain(testnet));
                assert_eq!(offer.chains(), vec![testnet]);
                assert_eq!(offer.as_tlv_stream().chains, Some(&vec![testnet]));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .chain(Network::Testnet)
                        .chain(Network::Testnet)
                        .build()
                        .unwrap();
                assert!(offer.supports_chain(testnet));
                assert_eq!(offer.chains(), vec![testnet]);
                assert_eq!(offer.as_tlv_stream().chains, Some(&vec![testnet]));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .chain(Network::Bitcoin)
                        .chain(Network::Testnet)
                        .build()
                        .unwrap();
                assert!(offer.supports_chain(mainnet));
                assert!(offer.supports_chain(testnet));
                assert_eq!(offer.chains(), vec![mainnet, testnet]);
                assert_eq!(offer.as_tlv_stream().chains, Some(&vec![mainnet, testnet]));
        }

        #[test]
        fn builds_offer_with_metadata() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .metadata(vec![42; 32]).unwrap()
                        .build()
                        .unwrap();
                assert_eq!(offer.metadata(), Some(&vec![42; 32]));
                assert_eq!(offer.as_tlv_stream().metadata, Some(&vec![42; 32]));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .metadata(vec![42; 32]).unwrap()
                        .metadata(vec![43; 32]).unwrap()
                        .build()
                        .unwrap();
                assert_eq!(offer.metadata(), Some(&vec![43; 32]));
                assert_eq!(offer.as_tlv_stream().metadata, Some(&vec![43; 32]));
        }

        #[test]
        fn builds_offer_with_metadata_derived() {
                let desc = "foo".to_string();
                let node_id = recipient_pubkey();
                let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
                let entropy = FixedEntropy {};
                let secp_ctx = Secp256k1::new();

                let offer = OfferBuilder
                        ::deriving_signing_pubkey(desc, node_id, &expanded_key, &entropy, &secp_ctx)
                        .amount_msats(1000)
                        .build().unwrap();
                assert_eq!(offer.signing_pubkey(), node_id);

                let invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_ok());

                // Fails verification with altered offer field
                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.amount = Some(100);

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                let invoice_request = Offer::try_from(encoded_offer).unwrap()
                        .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_err());

                // Fails verification with altered metadata
                let mut tlv_stream = offer.as_tlv_stream();
                let metadata = tlv_stream.metadata.unwrap().iter().copied().rev().collect();
                tlv_stream.metadata = Some(&metadata);

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                let invoice_request = Offer::try_from(encoded_offer).unwrap()
                        .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_err());
        }

        #[test]
        fn builds_offer_with_derived_signing_pubkey() {
                let desc = "foo".to_string();
                let node_id = recipient_pubkey();
                let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
                let entropy = FixedEntropy {};
                let secp_ctx = Secp256k1::new();

                let blinded_path = BlindedPath {
                        introduction_node_id: pubkey(40),
                        blinding_point: pubkey(41),
                        blinded_hops: vec![
                                BlindedHop { blinded_node_id: pubkey(42), encrypted_payload: vec![0; 43] },
                                BlindedHop { blinded_node_id: node_id, encrypted_payload: vec![0; 44] },
                        ],
                };

                let offer = OfferBuilder
                        ::deriving_signing_pubkey(desc, node_id, &expanded_key, &entropy, &secp_ctx)
                        .amount_msats(1000)
                        .path(blinded_path)
                        .build().unwrap();
                assert_ne!(offer.signing_pubkey(), node_id);

                let invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_ok());

                // Fails verification with altered offer field
                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.amount = Some(100);

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                let invoice_request = Offer::try_from(encoded_offer).unwrap()
                        .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_err());

                // Fails verification with altered signing pubkey
                let mut tlv_stream = offer.as_tlv_stream();
                let signing_pubkey = pubkey(1);
                tlv_stream.node_id = Some(&signing_pubkey);

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                let invoice_request = Offer::try_from(encoded_offer).unwrap()
                        .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();
                assert!(invoice_request.verify(&expanded_key, &secp_ctx).is_err());
        }

        #[test]
        fn builds_offer_with_amount() {
                let bitcoin_amount = Amount::Bitcoin { amount_msats: 1000 };
                let currency_amount = Amount::Currency { iso4217_code: *b"USD", amount: 10 };

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .amount_msats(1000)
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.amount(), Some(&bitcoin_amount));
                assert_eq!(tlv_stream.amount, Some(1000));
                assert_eq!(tlv_stream.currency, None);

                let builder = OfferBuilder::new("foo".into(), pubkey(42))
                        .amount(currency_amount.clone());
                let tlv_stream = builder.offer.as_tlv_stream();
                assert_eq!(builder.offer.amount, Some(currency_amount.clone()));
                assert_eq!(tlv_stream.amount, Some(10));
                assert_eq!(tlv_stream.currency, Some(b"USD"));
                match builder.build() {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12SemanticError::UnsupportedCurrency),
                }

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .amount(currency_amount.clone())
                        .amount(bitcoin_amount.clone())
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(tlv_stream.amount, Some(1000));
                assert_eq!(tlv_stream.currency, None);

                let invalid_amount = Amount::Bitcoin { amount_msats: MAX_VALUE_MSAT + 1 };
                match OfferBuilder::new("foo".into(), pubkey(42)).amount(invalid_amount).build() {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12SemanticError::InvalidAmount),
                }
        }

        #[test]
        fn builds_offer_with_features() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .features_unchecked(OfferFeatures::unknown())
                        .build()
                        .unwrap();
                assert_eq!(offer.features(), &OfferFeatures::unknown());
                assert_eq!(offer.as_tlv_stream().features, Some(&OfferFeatures::unknown()));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .features_unchecked(OfferFeatures::unknown())
                        .features_unchecked(OfferFeatures::empty())
                        .build()
                        .unwrap();
                assert_eq!(offer.features(), &OfferFeatures::empty());
                assert_eq!(offer.as_tlv_stream().features, None);
        }

        #[test]
        fn builds_offer_with_absolute_expiry() {
                let future_expiry = Duration::from_secs(u64::max_value());
                let past_expiry = Duration::from_secs(0);

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .absolute_expiry(future_expiry)
                        .build()
                        .unwrap();
                #[cfg(feature = "std")]
                assert!(!offer.is_expired());
                assert_eq!(offer.absolute_expiry(), Some(future_expiry));
                assert_eq!(offer.as_tlv_stream().absolute_expiry, Some(future_expiry.as_secs()));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .absolute_expiry(future_expiry)
                        .absolute_expiry(past_expiry)
                        .build()
                        .unwrap();
                #[cfg(feature = "std")]
                assert!(offer.is_expired());
                assert_eq!(offer.absolute_expiry(), Some(past_expiry));
                assert_eq!(offer.as_tlv_stream().absolute_expiry, Some(past_expiry.as_secs()));
        }

        #[test]
        fn builds_offer_with_paths() {
                let paths = vec![
                        BlindedPath {
                                introduction_node_id: pubkey(40),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(43), encrypted_payload: vec![0; 43] },
                                        BlindedHop { blinded_node_id: pubkey(44), encrypted_payload: vec![0; 44] },
                                ],
                        },
                        BlindedPath {
                                introduction_node_id: pubkey(40),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(45), encrypted_payload: vec![0; 45] },
                                        BlindedHop { blinded_node_id: pubkey(46), encrypted_payload: vec![0; 46] },
                                ],
                        },
                ];

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .path(paths[0].clone())
                        .path(paths[1].clone())
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.paths(), paths.as_slice());
                assert_eq!(offer.signing_pubkey(), pubkey(42));
                assert_ne!(pubkey(42), pubkey(44));
                assert_eq!(tlv_stream.paths, Some(&paths));
                assert_eq!(tlv_stream.node_id, Some(&pubkey(42)));
        }

        #[test]
        fn builds_offer_with_issuer() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .issuer("bar".into())
                        .build()
                        .unwrap();
                assert_eq!(offer.issuer(), Some(PrintableString("bar")));
                assert_eq!(offer.as_tlv_stream().issuer, Some(&String::from("bar")));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .issuer("bar".into())
                        .issuer("baz".into())
                        .build()
                        .unwrap();
                assert_eq!(offer.issuer(), Some(PrintableString("baz")));
                assert_eq!(offer.as_tlv_stream().issuer, Some(&String::from("baz")));
        }

        #[test]
        fn builds_offer_with_supported_quantity() {
                let one = NonZeroU64::new(1).unwrap();
                let ten = NonZeroU64::new(10).unwrap();

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::One)
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.supported_quantity(), Quantity::One);
                assert_eq!(tlv_stream.quantity_max, None);

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Unbounded)
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.supported_quantity(), Quantity::Unbounded);
                assert_eq!(tlv_stream.quantity_max, Some(0));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Bounded(ten))
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.supported_quantity(), Quantity::Bounded(ten));
                assert_eq!(tlv_stream.quantity_max, Some(10));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Bounded(one))
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.supported_quantity(), Quantity::Bounded(one));
                assert_eq!(tlv_stream.quantity_max, Some(1));

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Bounded(ten))
                        .supported_quantity(Quantity::One)
                        .build()
                        .unwrap();
                let tlv_stream = offer.as_tlv_stream();
                assert_eq!(offer.supported_quantity(), Quantity::One);
                assert_eq!(tlv_stream.quantity_max, None);
        }

        #[test]
        fn fails_requesting_invoice_with_unknown_required_features() {
                match OfferBuilder::new("foo".into(), pubkey(42))
                        .features_unchecked(OfferFeatures::unknown())
                        .build().unwrap()
                        .request_invoice(vec![1; 32], pubkey(43))
                {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12SemanticError::UnknownRequiredFeatures),
                }
        }

        #[test]
        fn parses_offer_with_chains() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .chain(Network::Bitcoin)
                        .chain(Network::Testnet)
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }
        }

        #[test]
        fn parses_offer_with_amount() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .amount(Amount::Bitcoin { amount_msats: 1000 })
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.amount = Some(1000);
                tlv_stream.currency = Some(b"USD");

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                if let Err(e) = Offer::try_from(encoded_offer) {
                        panic!("error parsing offer: {:?}", e);
                }

                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.amount = None;
                tlv_stream.currency = Some(b"USD");

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                match Offer::try_from(encoded_offer) {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingAmount)),
                }

                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.amount = Some(MAX_VALUE_MSAT + 1);
                tlv_stream.currency = None;

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                match Offer::try_from(encoded_offer) {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)),
                }
        }

        #[test]
        fn parses_offer_with_description() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42)).build().unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.description = None;

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                match Offer::try_from(encoded_offer) {
                        Ok(_) => panic!("expected error"),
                        Err(e) => {
                                assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingDescription));
                        },
                }
        }

        #[test]
        fn parses_offer_with_paths() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .path(BlindedPath {
                                introduction_node_id: pubkey(40),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(43), encrypted_payload: vec![0; 43] },
                                        BlindedHop { blinded_node_id: pubkey(44), encrypted_payload: vec![0; 44] },
                                ],
                        })
                        .path(BlindedPath {
                                introduction_node_id: pubkey(40),
                                blinding_point: pubkey(41),
                                blinded_hops: vec![
                                        BlindedHop { blinded_node_id: pubkey(45), encrypted_payload: vec![0; 45] },
                                        BlindedHop { blinded_node_id: pubkey(46), encrypted_payload: vec![0; 46] },
                                ],
                        })
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let mut builder = OfferBuilder::new("foo".into(), pubkey(42));
                builder.offer.paths = Some(vec![]);

                let offer = builder.build().unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }
        }

        #[test]
        fn parses_offer_with_quantity() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::One)
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Unbounded)
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Bounded(NonZeroU64::new(10).unwrap()))
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let offer = OfferBuilder::new("foo".into(), pubkey(42))
                        .supported_quantity(Quantity::Bounded(NonZeroU64::new(1).unwrap()))
                        .build()
                        .unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }
        }

        #[test]
        fn parses_offer_with_node_id() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42)).build().unwrap();
                if let Err(e) = offer.to_string().parse::<Offer>() {
                        panic!("error parsing offer: {:?}", e);
                }

                let mut tlv_stream = offer.as_tlv_stream();
                tlv_stream.node_id = None;

                let mut encoded_offer = Vec::new();
                tlv_stream.write(&mut encoded_offer).unwrap();

                match Offer::try_from(encoded_offer) {
                        Ok(_) => panic!("expected error"),
                        Err(e) => {
                                assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingSigningPubkey));
                        },
                }
        }

        #[test]
        fn fails_parsing_offer_with_extra_tlv_records() {
                let offer = OfferBuilder::new("foo".into(), pubkey(42)).build().unwrap();

                let mut encoded_offer = Vec::new();
                offer.write(&mut encoded_offer).unwrap();
                BigSize(80).write(&mut encoded_offer).unwrap();
                BigSize(32).write(&mut encoded_offer).unwrap();
                [42u8; 32].write(&mut encoded_offer).unwrap();

                match Offer::try_from(encoded_offer) {
                        Ok(_) => panic!("expected error"),
                        Err(e) => assert_eq!(e, Bolt12ParseError::Decode(DecodeError::InvalidValue)),
                }
        }
}

#[cfg(test)]
mod bech32_tests {
        use super::{Bolt12ParseError, Offer};
        use bitcoin::bech32;
        use crate::ln::msgs::DecodeError;

        #[test]
        fn encodes_offer_as_bech32_without_checksum() {
                let encoded_offer = "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg";
                let offer = dbg!(encoded_offer.parse::<Offer>().unwrap());
                let reencoded_offer = offer.to_string();
                dbg!(reencoded_offer.parse::<Offer>().unwrap());
                assert_eq!(reencoded_offer, encoded_offer);
        }

        #[test]
        fn parses_bech32_encoded_offers() {
                let offers = [
                        // BOLT 12 test vectors
                        "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg",
                        "l+no1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg",
                        "lno1pqps7sjqpgt+yzm3qv4uxzmtsd3jjqer9wd3hy6tsw3+5k7msjzfpy7nz5yqcn+ygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd+5xvxg",
                        "lno1pqps7sjqpgt+ yzm3qv4uxzmtsd3jjqer9wd3hy6tsw3+  5k7msjzfpy7nz5yqcn+\nygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd+\r\n 5xvxg",
                ];
                for encoded_offer in &offers {
                        if let Err(e) = encoded_offer.parse::<Offer>() {
                                panic!("Invalid offer ({:?}): {}", e, encoded_offer);
                        }
                }
        }

        #[test]
        fn fails_parsing_bech32_encoded_offers_with_invalid_continuations() {
                let offers = [
                        // BOLT 12 test vectors
                        "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg+",
                        "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg+ ",
                        "+lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg",
                        "+ lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg",
                        "ln++o1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg",
                ];
                for encoded_offer in &offers {
                        match encoded_offer.parse::<Offer>() {
                                Ok(_) => panic!("Valid offer: {}", encoded_offer),
                                Err(e) => assert_eq!(e, Bolt12ParseError::InvalidContinuation),
                        }
                }

        }

        #[test]
        fn fails_parsing_bech32_encoded_offer_with_invalid_hrp() {
                let encoded_offer = "lni1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxg";
                match encoded_offer.parse::<Offer>() {
                        Ok(_) => panic!("Valid offer: {}", encoded_offer),
                        Err(e) => assert_eq!(e, Bolt12ParseError::InvalidBech32Hrp),
                }
        }

        #[test]
        fn fails_parsing_bech32_encoded_offer_with_invalid_bech32_data() {
                let encoded_offer = "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxo";
                match encoded_offer.parse::<Offer>() {
                        Ok(_) => panic!("Valid offer: {}", encoded_offer),
                        Err(e) => assert_eq!(e, Bolt12ParseError::Bech32(bech32::Error::InvalidChar('o'))),
                }
        }

        #[test]
        fn fails_parsing_bech32_encoded_offer_with_invalid_tlv_data() {
                let encoded_offer = "lno1pqps7sjqpgtyzm3qv4uxzmtsd3jjqer9wd3hy6tsw35k7msjzfpy7nz5yqcnygrfdej82um5wf5k2uckyypwa3eyt44h6txtxquqh7lz5djge4afgfjn7k4rgrkuag0jsd5xvxgqqqqq";
                match encoded_offer.parse::<Offer>() {
                        Ok(_) => panic!("Valid offer: {}", encoded_offer),
                        Err(e) => assert_eq!(e, Bolt12ParseError::Decode(DecodeError::InvalidValue)),
                }
        }
}