Fix (and DRY) the conditionals before calling `peer_disconnected`
[rust-lightning] / lightning / src / offers / refund.rs
index 1e5c0f80a77dbc8f70a034e2be98bbb25fcb47a1..fff33873954a6f92ab55ad2de8d326447dafd0ac 100644 (file)
 //! Data structures and encoding for refunds.
 //!
 //! A [`Refund`] is an "offer for money" and is typically constructed by a merchant and presented
-//! directly to the customer. The recipient responds with an `Invoice` to be paid.
+//! directly to the customer. The recipient responds with an [`Invoice`] to be paid.
 //!
 //! This is an [`InvoiceRequest`] produced *not* in response to an [`Offer`].
 //!
+//! [`Invoice`]: crate::offers::invoice::Invoice
 //! [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 //! [`Offer`]: crate::offers::offer::Offer
 //!
@@ -77,8 +78,10 @@ use core::convert::TryFrom;
 use core::str::FromStr;
 use core::time::Duration;
 use crate::io;
+use crate::ln::PaymentHash;
 use crate::ln::features::InvoiceRequestFeatures;
 use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+use crate::offers::invoice::{BlindedPayInfo, InvoiceBuilder};
 use crate::offers::invoice_request::{InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef};
 use crate::offers::offer::{OfferTlvStream, OfferTlvStreamRef};
 use crate::offers::parse::{Bech32Encode, ParseError, ParsedMessage, SemanticError};
@@ -102,8 +105,8 @@ pub struct RefundBuilder {
 }
 
 impl RefundBuilder {
-       /// Creates a new builder for a refund using the [`Refund::payer_id`] for signing invoices. Use
-       /// a different pubkey per refund to avoid correlating refunds.
+       /// 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
        /// [`Refund::amount_msats`].
@@ -115,9 +118,9 @@ impl RefundBuilder {
                }
 
                let refund = RefundContents {
-                       payer: PayerContents(metadata), metadata: None, description, absolute_expiry: None,
-                       issuer: None, paths: None, chain: None, amount_msats,
-                       features: InvoiceRequestFeatures::empty(), payer_id, payer_note: None,
+                       payer: PayerContents(metadata), description, absolute_expiry: None, issuer: None,
+                       paths: None, chain: None, amount_msats, features: InvoiceRequestFeatures::empty(),
+                       quantity: None, payer_id, payer_note: None,
                };
 
                Ok(RefundBuilder { refund })
@@ -159,6 +162,20 @@ impl RefundBuilder {
                self
        }
 
+       /// Sets [`Refund::quantity`] of items. This is purely for informational purposes. It is useful
+       /// when the refund pertains to an [`Invoice`] that paid for more than one item from an
+       /// [`Offer`] as specified by [`InvoiceRequest::quantity`].
+       ///
+       /// Successive calls to this method will override the previous setting.
+       ///
+       /// [`Invoice`]: crate::offers::invoice::Invoice
+       /// [`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
+       }
+
        /// Sets the [`Refund::payer_note`].
        ///
        /// Successive calls to this method will override the previous setting.
@@ -183,25 +200,35 @@ impl RefundBuilder {
        }
 }
 
-/// A `Refund` is a request to send an `Invoice` without a preceding [`Offer`].
+#[cfg(test)]
+impl RefundBuilder {
+       fn features_unchecked(mut self, features: InvoiceRequestFeatures) -> Self {
+               self.refund.features = features;
+               self
+       }
+}
+
+/// A `Refund` is a request to send an [`Invoice`] without a preceding [`Offer`].
 ///
 /// Typically, after an invoice is paid, the recipient may publish a refund allowing the sender to
 /// recoup their funds. A refund may be used more generally as an "offer for money", such as with a
 /// bitcoin ATM.
 ///
+/// [`Invoice`]: crate::offers::invoice::Invoice
 /// [`Offer`]: crate::offers::offer::Offer
 #[derive(Clone, Debug)]
 pub struct Refund {
-       bytes: Vec<u8>,
-       contents: RefundContents,
+       pub(super) bytes: Vec<u8>,
+       pub(super) contents: RefundContents,
 }
 
-/// The contents of a [`Refund`], which may be shared with an `Invoice`.
+/// The contents of a [`Refund`], which may be shared with an [`Invoice`].
+///
+/// [`Invoice`]: crate::offers::invoice::Invoice
 #[derive(Clone, Debug)]
-struct RefundContents {
+pub(super) struct RefundContents {
        payer: PayerContents,
        // offer fields
-       metadata: Option<Vec<u8>>,
        description: String,
        absolute_expiry: Option<Duration>,
        issuer: Option<String>,
@@ -210,6 +237,7 @@ struct RefundContents {
        chain: Option<ChainHash>,
        amount_msats: u64,
        features: InvoiceRequestFeatures,
+       quantity: Option<u64>,
        payer_id: PublicKey,
        payer_note: Option<String>,
 }
@@ -231,13 +259,7 @@ impl Refund {
        /// Whether the refund has expired.
        #[cfg(feature = "std")]
        pub 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,
-               }
+               self.contents.is_expired()
        }
 
        /// The issuer of the refund, possibly beginning with `user@domain` or `domain`. Intended to be
@@ -277,7 +299,15 @@ impl Refund {
                &self.contents.features
        }
 
-       /// A possibly transient pubkey used to sign the refund.
+       /// The quantity of an item that refund is for.
+       pub fn quantity(&self) -> Option<u64> {
+               self.contents.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.contents.payer_id
        }
@@ -286,6 +316,51 @@ impl Refund {
        pub fn payer_note(&self) -> Option<PrintableString> {
                self.contents.payer_note.as_ref().map(|payer_note| PrintableString(payer_note.as_str()))
        }
+
+       /// Creates an [`Invoice`] for the refund with the given required fields.
+       ///
+       /// Unless [`InvoiceBuilder::relative_expiry`] is set, the invoice will expire two hours after
+       /// calling this method in `std` builds. For `no-std` builds, a final [`Duration`] parameter
+       /// must be given, which is used to set [`Invoice::created_at`] since [`std::time::SystemTime`]
+       /// is not available.
+       ///
+       /// The caller is expected to remember the preimage of `payment_hash` in order to
+       /// claim a payment for the invoice.
+       ///
+       /// The `signing_pubkey` is required to sign the invoice since refunds are not in response to an
+       /// offer, which does have a `signing_pubkey`.
+       ///
+       /// The `payment_paths` parameter is useful for maintaining the payment recipient's privacy. It
+       /// must contain one or more elements ordered from most-preferred to least-preferred, if there's
+       /// a preference. Note, however, that any privacy is lost if a public node id is used for
+       /// `signing_pubkey`.
+       ///
+       /// Errors if the request contains unknown required features.
+       ///
+       /// [`Invoice`]: crate::offers::invoice::Invoice
+       /// [`Invoice::created_at`]: crate::offers::invoice::Invoice::created_at
+       pub fn respond_with(
+               &self, payment_paths: Vec<(BlindedPath, BlindedPayInfo)>, payment_hash: PaymentHash,
+               signing_pubkey: PublicKey,
+               #[cfg(any(test, not(feature = "std")))]
+               created_at: Duration
+       ) -> Result<InvoiceBuilder, SemanticError> {
+               if self.features().requires_unknown_bits() {
+                       return Err(SemanticError::UnknownRequiredFeatures);
+               }
+
+               #[cfg(all(not(test), feature = "std"))]
+               let created_at = std::time::SystemTime::now()
+                       .duration_since(std::time::SystemTime::UNIX_EPOCH)
+                       .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
+
+               InvoiceBuilder::for_refund(self, payment_paths, created_at, payment_hash, signing_pubkey)
+       }
+
+       #[cfg(test)]
+       fn as_tlv_stream(&self) -> RefundTlvStreamRef {
+               self.contents.as_tlv_stream()
+       }
 }
 
 impl AsRef<[u8]> for Refund {
@@ -295,7 +370,18 @@ impl AsRef<[u8]> for Refund {
 }
 
 impl RefundContents {
-       fn chain(&self) -> ChainHash {
+       #[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(super) fn chain(&self) -> ChainHash {
                self.chain.unwrap_or_else(|| self.implied_chain())
        }
 
@@ -310,7 +396,7 @@ impl RefundContents {
 
                let offer = OfferTlvStreamRef {
                        chains: None,
-                       metadata: self.metadata.as_ref(),
+                       metadata: None,
                        currency: None,
                        amount: None,
                        description: Some(&self.description),
@@ -331,7 +417,7 @@ impl RefundContents {
                        chain: self.chain.as_ref(),
                        amount: Some(self.amount_msats),
                        features,
-                       quantity: None,
+                       quantity: self.quantity,
                        payer_id: Some(&self.payer_id),
                        payer_note: self.payer_note.as_ref(),
                };
@@ -412,6 +498,10 @@ impl TryFrom<RefundTlvStream> for RefundContents {
                        Some(metadata) => PayerContents(metadata),
                };
 
+               if metadata.is_some() {
+                       return Err(SemanticError::UnexpectedMetadata);
+               }
+
                if chains.is_some() {
                        return Err(SemanticError::UnexpectedChain);
                }
@@ -449,20 +539,14 @@ impl TryFrom<RefundTlvStream> for RefundContents {
 
                let features = features.unwrap_or_else(InvoiceRequestFeatures::empty);
 
-               // TODO: Check why this isn't in the spec.
-               if quantity.is_some() {
-                       return Err(SemanticError::UnexpectedQuantity);
-               }
-
                let payer_id = match payer_id {
                        None => return Err(SemanticError::MissingPayerId),
                        Some(payer_id) => payer_id,
                };
 
-               // TODO: Should metadata be included?
                Ok(RefundContents {
-                       payer, metadata, description, absolute_expiry, issuer, paths, chain, amount_msats,
-                       features, payer_id, payer_note,
+                       payer, description, absolute_expiry, issuer, paths, chain, amount_msats, features,
+                       quantity, payer_id, payer_note,
                })
        }
 }
@@ -472,3 +556,485 @@ impl core::fmt::Display for Refund {
                self.fmt_bech32_str(f)
        }
 }
+
+#[cfg(test)]
+mod tests {
+       use super::{Refund, RefundBuilder, RefundTlvStreamRef};
+
+       use bitcoin::blockdata::constants::ChainHash;
+       use bitcoin::network::constants::Network;
+       use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, SecretKey};
+       use core::convert::TryFrom;
+       use core::time::Duration;
+       use crate::ln::features::{InvoiceRequestFeatures, OfferFeatures};
+       use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+       use crate::offers::invoice_request::InvoiceRequestTlvStreamRef;
+       use crate::offers::offer::OfferTlvStreamRef;
+       use crate::offers::parse::{ParseError, SemanticError};
+       use crate::offers::payer::PayerTlvStreamRef;
+       use crate::onion_message::{BlindedHop, BlindedPath};
+       use crate::util::ser::{BigSize, Writeable};
+       use crate::util::string::PrintableString;
+
+       fn payer_pubkey() -> PublicKey {
+               let secp_ctx = Secp256k1::new();
+               KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap()).public_key()
+       }
+
+       fn pubkey(byte: u8) -> PublicKey {
+               let secp_ctx = Secp256k1::new();
+               PublicKey::from_secret_key(&secp_ctx, &privkey(byte))
+       }
+
+       fn privkey(byte: u8) -> SecretKey {
+               SecretKey::from_slice(&[byte; 32]).unwrap()
+       }
+
+       trait ToBytes {
+               fn to_bytes(&self) -> Vec<u8>;
+       }
+
+       impl<'a> ToBytes for RefundTlvStreamRef<'a> {
+               fn to_bytes(&self) -> Vec<u8> {
+                       let mut buffer = Vec::new();
+                       self.write(&mut buffer).unwrap();
+                       buffer
+               }
+       }
+
+       #[test]
+       fn builds_refund_with_defaults() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+
+               let mut buffer = Vec::new();
+               refund.write(&mut buffer).unwrap();
+
+               assert_eq!(refund.bytes, buffer.as_slice());
+               assert_eq!(refund.metadata(), &[1; 32]);
+               assert_eq!(refund.description(), PrintableString("foo"));
+               assert_eq!(refund.absolute_expiry(), None);
+               #[cfg(feature = "std")]
+               assert!(!refund.is_expired());
+               assert_eq!(refund.paths(), &[]);
+               assert_eq!(refund.issuer(), None);
+               assert_eq!(refund.chain(), ChainHash::using_genesis_block(Network::Bitcoin));
+               assert_eq!(refund.amount_msats(), 1000);
+               assert_eq!(refund.features(), &InvoiceRequestFeatures::empty());
+               assert_eq!(refund.payer_id(), payer_pubkey());
+               assert_eq!(refund.payer_note(), None);
+
+               assert_eq!(
+                       refund.as_tlv_stream(),
+                       (
+                               PayerTlvStreamRef { metadata: Some(&vec![1; 32]) },
+                               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: None,
+                               },
+                               InvoiceRequestTlvStreamRef {
+                                       chain: None,
+                                       amount: Some(1000),
+                                       features: None,
+                                       quantity: None,
+                                       payer_id: Some(&payer_pubkey()),
+                                       payer_note: None,
+                               },
+                       ),
+               );
+
+               if let Err(e) = Refund::try_from(buffer) {
+                       panic!("error parsing refund: {:?}", e);
+               }
+       }
+
+       #[test]
+       fn fails_building_refund_with_invalid_amount() {
+               match RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), MAX_VALUE_MSAT + 1) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, SemanticError::InvalidAmount),
+               }
+       }
+
+       #[test]
+       fn builds_refund_with_absolute_expiry() {
+               let future_expiry = Duration::from_secs(u64::max_value());
+               let past_expiry = Duration::from_secs(0);
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .absolute_expiry(future_expiry)
+                       .build()
+                       .unwrap();
+               let (_, tlv_stream, _) = refund.as_tlv_stream();
+               #[cfg(feature = "std")]
+               assert!(!refund.is_expired());
+               assert_eq!(refund.absolute_expiry(), Some(future_expiry));
+               assert_eq!(tlv_stream.absolute_expiry, Some(future_expiry.as_secs()));
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .absolute_expiry(future_expiry)
+                       .absolute_expiry(past_expiry)
+                       .build()
+                       .unwrap();
+               let (_, tlv_stream, _) = refund.as_tlv_stream();
+               #[cfg(feature = "std")]
+               assert!(refund.is_expired());
+               assert_eq!(refund.absolute_expiry(), Some(past_expiry));
+               assert_eq!(tlv_stream.absolute_expiry, Some(past_expiry.as_secs()));
+       }
+
+       #[test]
+       fn builds_refund_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 refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .path(paths[0].clone())
+                       .path(paths[1].clone())
+                       .build()
+                       .unwrap();
+               let (_, offer_tlv_stream, invoice_request_tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.paths(), paths.as_slice());
+               assert_eq!(refund.payer_id(), pubkey(42));
+               assert_ne!(pubkey(42), pubkey(44));
+               assert_eq!(offer_tlv_stream.paths, Some(&paths));
+               assert_eq!(invoice_request_tlv_stream.payer_id, Some(&pubkey(42)));
+       }
+
+       #[test]
+       fn builds_refund_with_issuer() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .issuer("bar".into())
+                       .build()
+                       .unwrap();
+               let (_, tlv_stream, _) = refund.as_tlv_stream();
+               assert_eq!(refund.issuer(), Some(PrintableString("bar")));
+               assert_eq!(tlv_stream.issuer, Some(&String::from("bar")));
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .issuer("bar".into())
+                       .issuer("baz".into())
+                       .build()
+                       .unwrap();
+               let (_, tlv_stream, _) = refund.as_tlv_stream();
+               assert_eq!(refund.issuer(), Some(PrintableString("baz")));
+               assert_eq!(tlv_stream.issuer, Some(&String::from("baz")));
+       }
+
+       #[test]
+       fn builds_refund_with_chain() {
+               let mainnet = ChainHash::using_genesis_block(Network::Bitcoin);
+               let testnet = ChainHash::using_genesis_block(Network::Testnet);
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .chain(Network::Bitcoin)
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.chain(), mainnet);
+               assert_eq!(tlv_stream.chain, None);
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .chain(Network::Testnet)
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.chain(), testnet);
+               assert_eq!(tlv_stream.chain, Some(&testnet));
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .chain(Network::Regtest)
+                       .chain(Network::Testnet)
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.chain(), testnet);
+               assert_eq!(tlv_stream.chain, Some(&testnet));
+       }
+
+       #[test]
+       fn builds_refund_with_quantity() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .quantity(10)
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.quantity(), Some(10));
+               assert_eq!(tlv_stream.quantity, Some(10));
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .quantity(10)
+                       .quantity(1)
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.quantity(), Some(1));
+               assert_eq!(tlv_stream.quantity, Some(1));
+       }
+
+       #[test]
+       fn builds_refund_with_payer_note() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .payer_note("bar".into())
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.payer_note(), Some(PrintableString("bar")));
+               assert_eq!(tlv_stream.payer_note, Some(&String::from("bar")));
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .payer_note("bar".into())
+                       .payer_note("baz".into())
+                       .build().unwrap();
+               let (_, _, tlv_stream) = refund.as_tlv_stream();
+               assert_eq!(refund.payer_note(), Some(PrintableString("baz")));
+               assert_eq!(tlv_stream.payer_note, Some(&String::from("baz")));
+       }
+
+       #[test]
+       fn parses_refund_with_metadata() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.0.metadata = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingPayerMetadata));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_description() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.description = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingDescription));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_amount() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.amount = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingAmount));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.amount = Some(MAX_VALUE_MSAT + 1);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::InvalidAmount));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_payer_id() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.payer_id = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingPayerId));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_optional_fields() {
+               let past_expiry = Duration::from_secs(0);
+               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 refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .absolute_expiry(past_expiry)
+                       .issuer("bar".into())
+                       .path(paths[0].clone())
+                       .path(paths[1].clone())
+                       .chain(Network::Testnet)
+                       .features_unchecked(InvoiceRequestFeatures::unknown())
+                       .quantity(10)
+                       .payer_note("baz".into())
+                       .build()
+                       .unwrap();
+               match refund.to_string().parse::<Refund>() {
+                       Ok(refund) => {
+                               assert_eq!(refund.absolute_expiry(), Some(past_expiry));
+                               #[cfg(feature = "std")]
+                               assert!(refund.is_expired());
+                               assert_eq!(refund.paths(), &paths[..]);
+                               assert_eq!(refund.issuer(), Some(PrintableString("bar")));
+                               assert_eq!(refund.chain(), ChainHash::using_genesis_block(Network::Testnet));
+                               assert_eq!(refund.features(), &InvoiceRequestFeatures::unknown());
+                               assert_eq!(refund.quantity(), Some(10));
+                               assert_eq!(refund.payer_note(), Some(PrintableString("baz")));
+                       },
+                       Err(e) => panic!("error parsing refund: {:?}", e),
+               }
+       }
+
+       #[test]
+       fn fails_parsing_refund_with_unexpected_fields() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let metadata = vec![42; 32];
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.metadata = Some(&metadata);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedMetadata));
+                       },
+               }
+
+               let chains = vec![ChainHash::using_genesis_block(Network::Testnet)];
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.chains = Some(&chains);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedChain));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.currency = Some(&b"USD");
+               tlv_stream.1.amount = Some(1000);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedAmount));
+                       },
+               }
+
+               let features = OfferFeatures::unknown();
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.features = Some(&features);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedFeatures));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.quantity_max = Some(10);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedQuantity));
+                       },
+               }
+
+               let node_id = payer_pubkey();
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.node_id = Some(&node_id);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedSigningPubkey));
+                       },
+               }
+       }
+
+       #[test]
+       fn fails_parsing_refund_with_extra_tlv_records() {
+               let secp_ctx = Secp256k1::new();
+               let keys = KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], keys.public_key(), 1000).unwrap()
+                       .build().unwrap();
+
+               let mut encoded_refund = Vec::new();
+               refund.write(&mut encoded_refund).unwrap();
+               BigSize(1002).write(&mut encoded_refund).unwrap();
+               BigSize(32).write(&mut encoded_refund).unwrap();
+               [42u8; 32].write(&mut encoded_refund).unwrap();
+
+               match Refund::try_from(encoded_refund) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, ParseError::Decode(DecodeError::InvalidValue)),
+               }
+       }
+}