Use `crate::prelude::*` rather than specific imports
[rust-lightning] / lightning / src / offers / refund.rs
index 2c8dffeb1516abfa7961d144581d412657861c2a..73b48521ae670659bb4781f7f670a694b862dea2 100644 (file)
@@ -18,6 +18,8 @@
 //! [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 //! [`Offer`]: crate::offers::offer::Offer
 //!
+//! # Example
+//!
 //! ```
 //! extern crate bitcoin;
 //! extern crate core;
 //! # Ok(())
 //! # }
 //! ```
+//!
+//! # Note
+//!
+//! If constructing a [`Refund`] for use with a [`ChannelManager`], use
+//! [`ChannelManager::create_refund_builder`] instead of [`RefundBuilder::new`].
+//!
+//! [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+//! [`ChannelManager::create_refund_builder`]: crate::ln::channelmanager::ChannelManager::create_refund_builder
 
 use bitcoin::blockdata::constants::ChainHash;
 use bitcoin::network::constants::Network;
 use bitcoin::secp256k1::{PublicKey, Secp256k1, self};
-use core::convert::TryFrom;
+use core::hash::{Hash, Hasher};
 use core::ops::Deref;
 use core::str::FromStr;
 use core::time::Duration;
@@ -82,10 +92,11 @@ use crate::sign::EntropySource;
 use crate::io;
 use crate::blinded_path::BlindedPath;
 use crate::ln::PaymentHash;
+use crate::ln::channelmanager::PaymentId;
 use crate::ln::features::InvoiceRequestFeatures;
 use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
 use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
-use crate::offers::invoice::{BlindedPayInfo, DerivedSigningPubkey, ExplicitSigningPubkey, InvoiceBuilder};
+use crate::offers::invoice::BlindedPayInfo;
 use crate::offers::invoice_request::{InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef};
 use crate::offers::offer::{OfferTlvStream, OfferTlvStreamRef};
 use crate::offers::parse::{Bech32Encode, Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
@@ -94,6 +105,16 @@ use crate::offers::signer::{Metadata, MetadataMaterial, self};
 use crate::util::ser::{SeekReadable, WithoutLength, Writeable, Writer};
 use crate::util::string::PrintableString;
 
+#[cfg(not(c_bindings))]
+use {
+       crate::offers::invoice::{DerivedSigningPubkey, ExplicitSigningPubkey, InvoiceBuilder},
+};
+#[cfg(c_bindings)]
+use {
+       crate::offers::invoice::{InvoiceWithDerivedSigningPubkeyBuilder, InvoiceWithExplicitSigningPubkeyBuilder},
+};
+
+#[allow(unused_imports)]
 use crate::prelude::*;
 
 #[cfg(feature = "std")]
@@ -113,12 +134,31 @@ pub struct RefundBuilder<'a, T: secp256k1::Signing> {
        secp_ctx: Option<&'a Secp256k1<T>>,
 }
 
-impl<'a> RefundBuilder<'a, secp256k1::SignOnly> {
+/// Builds a [`Refund`] for the "offer for money" flow.
+///
+/// See [module-level documentation] for usage.
+///
+/// [module-level documentation]: self
+#[cfg(c_bindings)]
+pub struct RefundMaybeWithDerivedMetadataBuilder<'a> {
+       refund: RefundContents,
+       secp_ctx: Option<&'a Secp256k1<secp256k1::All>>,
+}
+
+macro_rules! refund_explicit_metadata_builder_methods { () => {
        /// Creates a new builder for a refund using the [`Refund::payer_id`] for the public node id to
        /// send to if no [`Refund::paths`] are set. Otherwise, it may be a transient pubkey.
        ///
-       /// Additionally, sets the required [`Refund::description`], [`Refund::metadata`], and
+       /// Additionally, sets the required [`Refund::description`], [`Refund::payer_metadata`], and
        /// [`Refund::amount_msats`].
+       ///
+       /// # Note
+       ///
+       /// If constructing a [`Refund`] for use with a [`ChannelManager`], use
+       /// [`ChannelManager::create_refund_builder`] instead of [`RefundBuilder::new`].
+       ///
+       /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+       /// [`ChannelManager::create_refund_builder`]: crate::ln::channelmanager::ChannelManager::create_refund_builder
        pub fn new(
                description: String, metadata: Vec<u8>, payer_id: PublicKey, amount_msats: u64
        ) -> Result<Self, Bolt12SemanticError> {
@@ -136,9 +176,11 @@ impl<'a> RefundBuilder<'a, secp256k1::SignOnly> {
                        secp_ctx: None,
                })
        }
-}
+} }
 
-impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
+macro_rules! refund_builder_methods { (
+       $self: ident, $self_type: ty, $return_type: ty, $return_value: expr, $secp_context: ty $(, $self_mut: tt)?
+) => {
        /// Similar to [`RefundBuilder::new`] except, if [`RefundBuilder::path`] is called, the payer id
        /// is derived from the given [`ExpandedKey`] and nonce. This provides sender privacy by using a
        /// different payer id for each refund, assuming a different nonce is used.  Otherwise, the
@@ -147,18 +189,22 @@ impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
        /// Also, sets the metadata when [`RefundBuilder::build`] is called such that it can be used to
        /// verify that an [`InvoiceRequest`] was produced for the refund given an [`ExpandedKey`].
        ///
+       /// The `payment_id` is encrypted in the metadata and should be unique. This ensures that only
+       /// one invoice will be paid for the refund and that payments can be uniquely identified.
+       ///
        /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
        /// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
        pub fn deriving_payer_id<ES: Deref>(
                description: String, node_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES,
-               secp_ctx: &'a Secp256k1<T>, amount_msats: u64
+               secp_ctx: &'a Secp256k1<$secp_context>, amount_msats: u64, payment_id: PaymentId
        ) -> Result<Self, Bolt12SemanticError> where ES::Target: EntropySource {
                if amount_msats > MAX_VALUE_MSAT {
                        return Err(Bolt12SemanticError::InvalidAmount);
                }
 
                let nonce = Nonce::from_entropy_source(entropy_source);
-               let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES);
+               let payment_id = Some(payment_id);
+               let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES, payment_id);
                let metadata = Metadata::DerivedSigningPubkey(derivation_material);
                Ok(Self {
                        refund: RefundContents {
@@ -174,17 +220,17 @@ impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
        /// already passed is valid and can be checked for using [`Refund::is_expired`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn absolute_expiry(mut self, absolute_expiry: Duration) -> Self {
-               self.refund.absolute_expiry = Some(absolute_expiry);
-               self
+       pub fn absolute_expiry($($self_mut)* $self: $self_type, absolute_expiry: Duration) -> $return_type {
+               $self.refund.absolute_expiry = Some(absolute_expiry);
+               $return_value
        }
 
        /// Sets the [`Refund::issuer`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn issuer(mut self, issuer: String) -> Self {
-               self.refund.issuer = Some(issuer);
-               self
+       pub fn issuer($($self_mut)* $self: $self_type, issuer: String) -> $return_type {
+               $self.refund.issuer = Some(issuer);
+               $return_value
        }
 
        /// Adds a blinded path to [`Refund::paths`]. Must include at least one path if only connected
@@ -192,18 +238,26 @@ impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
        ///
        /// 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.refund.paths.get_or_insert_with(Vec::new).push(path);
-               self
+       pub fn path($($self_mut)* $self: $self_type, path: BlindedPath) -> $return_type {
+               $self.refund.paths.get_or_insert_with(Vec::new).push(path);
+               $return_value
        }
 
        /// Sets the [`Refund::chain`] of the given [`Network`] for paying an invoice. If not
        /// called, [`Network::Bitcoin`] is assumed.
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn chain(mut self, network: Network) -> Self {
-               self.refund.chain = Some(ChainHash::using_genesis_block(network));
-               self
+       pub fn chain($self: $self_type, network: Network) -> $return_type {
+               $self.chain_hash(ChainHash::using_genesis_block(network))
+       }
+
+       /// Sets the [`Refund::chain`] of the given [`ChainHash`] for paying an invoice. If not called,
+       /// [`Network::Bitcoin`] is assumed.
+       ///
+       /// Successive calls to this method will override the previous setting.
+       pub(crate) fn chain_hash($($self_mut)* $self: $self_type, chain: ChainHash) -> $return_type {
+               $self.refund.chain = Some(chain);
+               $return_value
        }
 
        /// Sets [`Refund::quantity`] of items. This is purely for informational purposes. It is useful
@@ -215,60 +269,109 @@ impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
        /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
        /// [`InvoiceRequest::quantity`]: crate::offers::invoice_request::InvoiceRequest::quantity
        /// [`Offer`]: crate::offers::offer::Offer
-       pub fn quantity(mut self, quantity: u64) -> Self {
-               self.refund.quantity = Some(quantity);
-               self
+       pub fn quantity($($self_mut)* $self: $self_type, quantity: u64) -> $return_type {
+               $self.refund.quantity = Some(quantity);
+               $return_value
        }
 
        /// Sets the [`Refund::payer_note`].
        ///
        /// Successive calls to this method will override the previous setting.
-       pub fn payer_note(mut self, payer_note: String) -> Self {
-               self.refund.payer_note = Some(payer_note);
-               self
+       pub fn payer_note($($self_mut)* $self: $self_type, payer_note: String) -> $return_type {
+               $self.refund.payer_note = Some(payer_note);
+               $return_value
        }
 
        /// Builds a [`Refund`] after checking for valid semantics.
-       pub fn build(mut self) -> Result<Refund, Bolt12SemanticError> {
-               if self.refund.chain() == self.refund.implied_chain() {
-                       self.refund.chain = None;
+       pub fn build($($self_mut)* $self: $self_type) -> Result<Refund, Bolt12SemanticError> {
+               if $self.refund.chain() == $self.refund.implied_chain() {
+                       $self.refund.chain = None;
                }
 
                // Create the metadata for stateless verification of a Bolt12Invoice.
-               if self.refund.payer.0.has_derivation_material() {
-                       let mut metadata = core::mem::take(&mut self.refund.payer.0);
+               if $self.refund.payer.0.has_derivation_material() {
+                       let mut metadata = core::mem::take(&mut $self.refund.payer.0);
 
-                       if self.refund.paths.is_none() {
+                       if $self.refund.paths.is_none() {
                                metadata = metadata.without_keys();
                        }
 
-                       let mut tlv_stream = self.refund.as_tlv_stream();
+                       let mut tlv_stream = $self.refund.as_tlv_stream();
                        tlv_stream.0.metadata = None;
-                       if metadata.derives_keys() {
+                       if metadata.derives_payer_keys() {
                                tlv_stream.2.payer_id = None;
                        }
 
-                       let (derived_metadata, keys) = metadata.derive_from(tlv_stream, self.secp_ctx);
+                       let (derived_metadata, keys) = metadata.derive_from(tlv_stream, $self.secp_ctx);
                        metadata = derived_metadata;
                        if let Some(keys) = keys {
-                               self.refund.payer_id = keys.public_key();
+                               $self.refund.payer_id = keys.public_key();
                        }
 
-                       self.refund.payer.0 = metadata;
+                       $self.refund.payer.0 = metadata;
                }
 
                let mut bytes = Vec::new();
-               self.refund.write(&mut bytes).unwrap();
+               $self.refund.write(&mut bytes).unwrap();
+
+               Ok(Refund {
+                       bytes,
+                       #[cfg(not(c_bindings))]
+                       contents: $self.refund,
+                       #[cfg(c_bindings)]
+                       contents: $self.refund.clone(),
+               })
+       }
+} }
+
+#[cfg(test)]
+macro_rules! refund_builder_test_methods { (
+       $self: ident, $self_type: ty, $return_type: ty, $return_value: expr $(, $self_mut: tt)?
+) => {
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       pub(crate) fn clear_paths($($self_mut)* $self: $self_type) -> $return_type {
+               $self.refund.paths = None;
+               $return_value
+       }
 
-               Ok(Refund { bytes, contents: self.refund })
+       #[cfg_attr(c_bindings, allow(dead_code))]
+       fn features_unchecked($($self_mut)* $self: $self_type, features: InvoiceRequestFeatures) -> $return_type {
+               $self.refund.features = features;
+               $return_value
        }
+} }
+
+impl<'a> RefundBuilder<'a, secp256k1::SignOnly> {
+       refund_explicit_metadata_builder_methods!();
 }
 
-#[cfg(test)]
 impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
-       fn features_unchecked(mut self, features: InvoiceRequestFeatures) -> Self {
-               self.refund.features = features;
-               self
+       refund_builder_methods!(self, Self, Self, self, T, mut);
+
+       #[cfg(test)]
+       refund_builder_test_methods!(self, Self, Self, self, mut);
+}
+
+#[cfg(all(c_bindings, not(test)))]
+impl<'a> RefundMaybeWithDerivedMetadataBuilder<'a> {
+       refund_explicit_metadata_builder_methods!();
+       refund_builder_methods!(self, &mut Self, (), (), secp256k1::All);
+}
+
+#[cfg(all(c_bindings, test))]
+impl<'a> RefundMaybeWithDerivedMetadataBuilder<'a> {
+       refund_explicit_metadata_builder_methods!();
+       refund_builder_methods!(self, &mut Self, &mut Self, self, secp256k1::All);
+       refund_builder_test_methods!(self, &mut Self, &mut Self, self);
+}
+
+#[cfg(c_bindings)]
+impl<'a> From<RefundBuilder<'a, secp256k1::All>>
+for RefundMaybeWithDerivedMetadataBuilder<'a> {
+       fn from(builder: RefundBuilder<'a, secp256k1::All>) -> Self {
+               let RefundBuilder { refund, secp_ctx } = builder;
+
+               Self { refund, secp_ctx }
        }
 }
 
@@ -281,7 +384,6 @@ impl<'a, T: secp256k1::Signing> RefundBuilder<'a, T> {
 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 /// [`Offer`]: crate::offers::offer::Offer
 #[derive(Clone, Debug)]
-#[cfg_attr(test, derive(PartialEq))]
 pub struct Refund {
        pub(super) bytes: Vec<u8>,
        pub(super) contents: RefundContents,
@@ -319,7 +421,7 @@ impl Refund {
        ///
        /// If `None`, the refund does not expire.
        pub fn absolute_expiry(&self) -> Option<Duration> {
-               self.contents.absolute_expiry
+               self.contents.absolute_expiry()
        }
 
        /// Whether the refund has expired.
@@ -328,46 +430,51 @@ impl Refund {
                self.contents.is_expired()
        }
 
+       /// Whether the refund has expired given the duration since the Unix epoch.
+       pub fn is_expired_no_std(&self, duration_since_epoch: Duration) -> bool {
+               self.contents.is_expired_no_std(duration_since_epoch)
+       }
+
        /// The issuer of the refund, 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.as_ref().map(|issuer| PrintableString(issuer.as_str()))
+               self.contents.issuer()
        }
 
        /// Paths to the sender originating from publicly reachable nodes. Blinded paths provide sender
        /// privacy by obfuscating its node id.
        pub fn paths(&self) -> &[BlindedPath] {
-               self.contents.paths.as_ref().map(|paths| paths.as_slice()).unwrap_or(&[])
+               self.contents.paths()
        }
 
        /// An unpredictable series of bytes, typically containing information about the derivation of
        /// [`payer_id`].
        ///
        /// [`payer_id`]: Self::payer_id
-       pub fn metadata(&self) -> &[u8] {
+       pub fn payer_metadata(&self) -> &[u8] {
                self.contents.metadata()
        }
 
        /// A chain that the refund is valid for.
        pub fn chain(&self) -> ChainHash {
-               self.contents.chain.unwrap_or_else(|| self.contents.implied_chain())
+               self.contents.chain()
        }
 
        /// The amount to refund in msats (i.e., the minimum lightning-payable unit for [`chain`]).
        ///
        /// [`chain`]: Self::chain
        pub fn amount_msats(&self) -> u64 {
-               self.contents.amount_msats
+               self.contents.amount_msats()
        }
 
        /// Features pertaining to requesting an invoice.
        pub fn features(&self) -> &InvoiceRequestFeatures {
-               &self.contents.features
+               &self.contents.features()
        }
 
        /// The quantity of an item that refund is for.
        pub fn quantity(&self) -> Option<u64> {
-               self.contents.quantity
+               self.contents.quantity()
        }
 
        /// A public node id to send to in the case where there are no [`paths`]. Otherwise, a possibly
@@ -375,14 +482,16 @@ impl Refund {
        ///
        /// [`paths`]: Self::paths
        pub fn payer_id(&self) -> PublicKey {
-               self.contents.payer_id
+               self.contents.payer_id()
        }
 
        /// Payer provided note to include in the invoice.
        pub fn payer_note(&self) -> Option<PrintableString> {
-               self.contents.payer_note.as_ref().map(|payer_note| PrintableString(payer_note.as_str()))
+               self.contents.payer_note()
        }
+}
 
+macro_rules! respond_with_explicit_signing_pubkey_methods { ($self: ident, $builder: ty) => {
        /// Creates an [`InvoiceBuilder`] for the refund with the given required fields and using the
        /// [`Duration`] since [`std::time::SystemTime::UNIX_EPOCH`] as the creation time.
        ///
@@ -394,14 +503,14 @@ impl Refund {
        /// [`Duration`]: core::time::Duration
        #[cfg(feature = "std")]
        pub fn respond_with(
-               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               &$self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
                signing_pubkey: PublicKey,
-       ) -> Result<InvoiceBuilder<ExplicitSigningPubkey>, Bolt12SemanticError> {
+       ) -> Result<$builder, Bolt12SemanticError> {
                let created_at = std::time::SystemTime::now()
                        .duration_since(std::time::SystemTime::UNIX_EPOCH)
                        .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
 
-               self.respond_with_no_std(payment_paths, payment_hash, signing_pubkey, created_at)
+               $self.respond_with_no_std(payment_paths, payment_hash, signing_pubkey, created_at)
        }
 
        /// Creates an [`InvoiceBuilder`] for the refund with the given required fields.
@@ -427,16 +536,18 @@ impl Refund {
        ///
        /// [`Bolt12Invoice::created_at`]: crate::offers::invoice::Bolt12Invoice::created_at
        pub fn respond_with_no_std(
-               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               &$self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
                signing_pubkey: PublicKey, created_at: Duration
-       ) -> Result<InvoiceBuilder<ExplicitSigningPubkey>, Bolt12SemanticError> {
-               if self.features().requires_unknown_bits() {
+       ) -> Result<$builder, Bolt12SemanticError> {
+               if $self.features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }
 
-               InvoiceBuilder::for_refund(self, payment_paths, created_at, payment_hash, signing_pubkey)
+               <$builder>::for_refund($self, payment_paths, created_at, payment_hash, signing_pubkey)
        }
+} }
 
+macro_rules! respond_with_derived_signing_pubkey_methods { ($self: ident, $builder: ty) => {
        /// Creates an [`InvoiceBuilder`] for the refund using the given required fields and that uses
        /// derived signing keys to sign the [`Bolt12Invoice`].
        ///
@@ -447,9 +558,9 @@ impl Refund {
        /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
        #[cfg(feature = "std")]
        pub fn respond_using_derived_keys<ES: Deref>(
-               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               &$self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
                expanded_key: &ExpandedKey, entropy_source: ES
-       ) -> Result<InvoiceBuilder<DerivedSigningPubkey>, Bolt12SemanticError>
+       ) -> Result<$builder, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
@@ -457,7 +568,7 @@ impl Refund {
                        .duration_since(std::time::SystemTime::UNIX_EPOCH)
                        .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
 
-               self.respond_using_derived_keys_no_std(
+               $self.respond_using_derived_keys_no_std(
                        payment_paths, payment_hash, created_at, expanded_key, entropy_source
                )
        }
@@ -471,22 +582,36 @@ impl Refund {
        ///
        /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
        pub fn respond_using_derived_keys_no_std<ES: Deref>(
-               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               &$self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
                created_at: core::time::Duration, expanded_key: &ExpandedKey, entropy_source: ES
-       ) -> Result<InvoiceBuilder<DerivedSigningPubkey>, Bolt12SemanticError>
+       ) -> Result<$builder, Bolt12SemanticError>
        where
                ES::Target: EntropySource,
        {
-               if self.features().requires_unknown_bits() {
+               if $self.features().requires_unknown_bits() {
                        return Err(Bolt12SemanticError::UnknownRequiredFeatures);
                }
 
                let nonce = Nonce::from_entropy_source(entropy_source);
                let keys = signer::derive_keys(nonce, expanded_key);
-               InvoiceBuilder::for_refund_using_keys(self, payment_paths, created_at, payment_hash, keys)
+               <$builder>::for_refund_using_keys($self, payment_paths, created_at, payment_hash, keys)
        }
+} }
 
-       #[cfg(test)]
+#[cfg(not(c_bindings))]
+impl Refund {
+       respond_with_explicit_signing_pubkey_methods!(self, InvoiceBuilder<ExplicitSigningPubkey>);
+       respond_with_derived_signing_pubkey_methods!(self, InvoiceBuilder<DerivedSigningPubkey>);
+}
+
+#[cfg(c_bindings)]
+impl Refund {
+       respond_with_explicit_signing_pubkey_methods!(self, InvoiceWithExplicitSigningPubkeyBuilder);
+       respond_with_derived_signing_pubkey_methods!(self, InvoiceWithDerivedSigningPubkeyBuilder);
+}
+
+#[cfg(test)]
+impl Refund {
        fn as_tlv_stream(&self) -> RefundTlvStreamRef {
                self.contents.as_tlv_stream()
        }
@@ -498,20 +623,49 @@ impl AsRef<[u8]> for Refund {
        }
 }
 
+impl PartialEq for Refund {
+       fn eq(&self, other: &Self) -> bool {
+               self.bytes.eq(&other.bytes)
+       }
+}
+
+impl Eq for Refund {}
+
+impl Hash for Refund {
+       fn hash<H: Hasher>(&self, state: &mut H) {
+               self.bytes.hash(state);
+       }
+}
+
 impl RefundContents {
        pub fn description(&self) -> PrintableString {
                PrintableString(&self.description)
        }
 
+       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,
-               }
+               SystemTime::UNIX_EPOCH
+                       .elapsed()
+                       .map(|duration_since_epoch| self.is_expired_no_std(duration_since_epoch))
+                       .unwrap_or(false)
+       }
+
+       pub(super) fn is_expired_no_std(&self, duration_since_epoch: Duration) -> bool {
+               self.absolute_expiry
+                       .map(|absolute_expiry| duration_since_epoch > absolute_expiry)
+                       .unwrap_or(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 metadata(&self) -> &[u8] {
@@ -526,14 +680,37 @@ impl RefundContents {
                ChainHash::using_genesis_block(Network::Bitcoin)
        }
 
-       pub(super) fn derives_keys(&self) -> bool {
-               self.payer.0.derives_keys()
+       pub fn amount_msats(&self) -> u64 {
+               self.amount_msats
        }
 
-       pub(super) fn payer_id(&self) -> PublicKey {
+       /// Features pertaining to requesting an invoice.
+       pub fn features(&self) -> &InvoiceRequestFeatures {
+               &self.features
+       }
+
+       /// The quantity of an item that refund is for.
+       pub fn quantity(&self) -> Option<u64> {
+               self.quantity
+       }
+
+       /// A public node id to send to in the case where there are no [`paths`]. Otherwise, a possibly
+       /// transient pubkey.
+       ///
+       /// [`paths`]: Self::paths
+       pub fn payer_id(&self) -> PublicKey {
                self.payer_id
        }
 
+       /// Payer provided note to include in the invoice.
+       pub fn payer_note(&self) -> Option<PrintableString> {
+               self.payer_note.as_ref().map(|payer_note| PrintableString(payer_note.as_str()))
+       }
+
+       pub(super) fn derives_keys(&self) -> bool {
+               self.payer.0.derives_payer_keys()
+       }
+
        pub(super) fn as_tlv_stream(&self) -> RefundTlvStreamRef {
                let payer = PayerTlvStreamRef {
                        metadata: self.payer.0.as_bytes(),
@@ -704,15 +881,25 @@ impl core::fmt::Display for Refund {
 
 #[cfg(test)]
 mod tests {
-       use super::{Refund, RefundBuilder, RefundTlvStreamRef};
+       use super::{Refund, RefundTlvStreamRef};
+       #[cfg(not(c_bindings))]
+       use {
+               super::RefundBuilder,
+       };
+       #[cfg(c_bindings)]
+       use {
+               super::RefundMaybeWithDerivedMetadataBuilder as RefundBuilder,
+       };
 
        use bitcoin::blockdata::constants::ChainHash;
        use bitcoin::network::constants::Network;
        use bitcoin::secp256k1::{KeyPair, Secp256k1, SecretKey};
-       use core::convert::TryFrom;
+
        use core::time::Duration;
+
        use crate::blinded_path::{BlindedHop, BlindedPath};
        use crate::sign::KeyMaterial;
+       use crate::ln::channelmanager::PaymentId;
        use crate::ln::features::{InvoiceRequestFeatures, OfferFeatures};
        use crate::ln::inbound_payment::ExpandedKey;
        use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
@@ -723,6 +910,7 @@ mod tests {
        use crate::offers::test_utils::*;
        use crate::util::ser::{BigSize, Writeable};
        use crate::util::string::PrintableString;
+       use crate::prelude::*;
 
        trait ToBytes {
                fn to_bytes(&self) -> Vec<u8>;
@@ -745,7 +933,7 @@ mod tests {
                refund.write(&mut buffer).unwrap();
 
                assert_eq!(refund.bytes, buffer.as_slice());
-               assert_eq!(refund.metadata(), &[1; 32]);
+               assert_eq!(refund.payer_metadata(), &[1; 32]);
                assert_eq!(refund.description(), PrintableString("foo"));
                assert_eq!(refund.absolute_expiry(), None);
                #[cfg(feature = "std")]
@@ -806,9 +994,10 @@ mod tests {
                let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
                let entropy = FixedEntropy {};
                let secp_ctx = Secp256k1::new();
+               let payment_id = PaymentId([1; 32]);
 
                let refund = RefundBuilder
-                       ::deriving_payer_id(desc, node_id, &expanded_key, &entropy, &secp_ctx, 1000)
+                       ::deriving_payer_id(desc, node_id, &expanded_key, &entropy, &secp_ctx, 1000, payment_id)
                        .unwrap()
                        .build().unwrap();
                assert_eq!(refund.payer_id(), node_id);
@@ -819,7 +1008,10 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(invoice.verify(&expanded_key, &secp_ctx));
+               match invoice.verify(&expanded_key, &secp_ctx) {
+                       Ok(payment_id) => assert_eq!(payment_id, PaymentId([1; 32])),
+                       Err(()) => panic!("verification failed"),
+               }
 
                let mut tlv_stream = refund.as_tlv_stream();
                tlv_stream.2.amount = Some(2000);
@@ -832,7 +1024,7 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+               assert!(invoice.verify(&expanded_key, &secp_ctx).is_err());
 
                // Fails verification with altered metadata
                let mut tlv_stream = refund.as_tlv_stream();
@@ -847,7 +1039,7 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+               assert!(invoice.verify(&expanded_key, &secp_ctx).is_err());
        }
 
        #[test]
@@ -857,6 +1049,7 @@ mod tests {
                let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
                let entropy = FixedEntropy {};
                let secp_ctx = Secp256k1::new();
+               let payment_id = PaymentId([1; 32]);
 
                let blinded_path = BlindedPath {
                        introduction_node_id: pubkey(40),
@@ -868,7 +1061,7 @@ mod tests {
                };
 
                let refund = RefundBuilder
-                       ::deriving_payer_id(desc, node_id, &expanded_key, &entropy, &secp_ctx, 1000)
+                       ::deriving_payer_id(desc, node_id, &expanded_key, &entropy, &secp_ctx, 1000, payment_id)
                        .unwrap()
                        .path(blinded_path)
                        .build().unwrap();
@@ -879,7 +1072,10 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(invoice.verify(&expanded_key, &secp_ctx));
+               match invoice.verify(&expanded_key, &secp_ctx) {
+                       Ok(payment_id) => assert_eq!(payment_id, PaymentId([1; 32])),
+                       Err(()) => panic!("verification failed"),
+               }
 
                // Fails verification with altered fields
                let mut tlv_stream = refund.as_tlv_stream();
@@ -893,7 +1089,7 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+               assert!(invoice.verify(&expanded_key, &secp_ctx).is_err());
 
                // Fails verification with altered payer_id
                let mut tlv_stream = refund.as_tlv_stream();
@@ -908,13 +1104,14 @@ mod tests {
                        .unwrap()
                        .build().unwrap()
                        .sign(recipient_sign).unwrap();
-               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+               assert!(invoice.verify(&expanded_key, &secp_ctx).is_err());
        }
 
        #[test]
        fn builds_refund_with_absolute_expiry() {
                let future_expiry = Duration::from_secs(u64::max_value());
                let past_expiry = Duration::from_secs(0);
+               let now = future_expiry - Duration::from_secs(1_000);
 
                let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
                        .absolute_expiry(future_expiry)
@@ -923,6 +1120,7 @@ mod tests {
                let (_, tlv_stream, _) = refund.as_tlv_stream();
                #[cfg(feature = "std")]
                assert!(!refund.is_expired());
+               assert!(!refund.is_expired_no_std(now));
                assert_eq!(refund.absolute_expiry(), Some(future_expiry));
                assert_eq!(tlv_stream.absolute_expiry, Some(future_expiry.as_secs()));
 
@@ -934,6 +1132,7 @@ mod tests {
                let (_, tlv_stream, _) = refund.as_tlv_stream();
                #[cfg(feature = "std")]
                assert!(refund.is_expired());
+               assert!(refund.is_expired_no_std(now));
                assert_eq!(refund.absolute_expiry(), Some(past_expiry));
                assert_eq!(tlv_stream.absolute_expiry, Some(past_expiry.as_secs()));
        }