// 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 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.
//!
//! 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
//!
//! ```
//! extern crate bitcoin;
//! extern crate core;
//! extern crate lightning;
//!
//! use core::convert::TryFrom;
//! use core::time::Duration;
//!
//! use bitcoin::network::constants::Network;
//! use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, SecretKey};
//! use lightning::offers::parse::ParseError;
//! use lightning::offers::refund::{Refund, RefundBuilder};
//! use lightning::util::ser::{Readable, Writeable};
//!
//! # use lightning::onion_message::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<(), ParseError> {
//! 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 refund = RefundBuilder::new("coffee, large".to_string(), vec![1; 32], pubkey, 20_000)?
//!     .absolute_expiry(expiration.duration_since(SystemTime::UNIX_EPOCH).unwrap())
//!     .issuer("Foo Bar".to_string())
//!     .path(create_blinded_path())
//!     .path(create_another_blinded_path())
//!     .chain(Network::Bitcoin)
//!     .payer_note("refund for order #12345".to_string())
//!     .build()?;
//!
//! // Encode as a bech32 string for use in a QR code.
//! let encoded_refund = refund.to_string();
//!
//! // Parse from a bech32 string after scanning from a QR code.
//! let refund = encoded_refund.parse::<Refund>()?;
//!
//! // Encode refund as raw bytes.
//! let mut bytes = Vec::new();
//! refund.write(&mut bytes).unwrap();
//!
//! // Decode raw bytes into an refund.
//! let refund = Refund::try_from(bytes)?;
//! # Ok(())
//! # }
//! ```

use bitcoin::blockdata::constants::ChainHash;
use bitcoin::network::constants::Network;
use bitcoin::secp256k1::PublicKey;
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};
use crate::offers::payer::{PayerContents, PayerTlvStream, PayerTlvStreamRef};
use crate::onion_message::BlindedPath;
use crate::util::ser::{SeekReadable, WithoutLength, Writeable, Writer};
use crate::util::string::PrintableString;

use crate::prelude::*;

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

/// Builds a [`Refund`] for the "offer for money" flow.
///
/// See [module-level documentation] for usage.
///
/// [module-level documentation]: self
pub struct RefundBuilder {
	refund: RefundContents,
}

impl RefundBuilder {
	/// 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`].
	pub fn new(
		description: String, metadata: Vec<u8>, payer_id: PublicKey, amount_msats: u64
	) -> Result<Self, SemanticError> {
		if amount_msats > MAX_VALUE_MSAT {
			return Err(SemanticError::InvalidAmount);
		}

		let refund = RefundContents {
			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 })
	}

	/// Sets the [`Refund::absolute_expiry`] as seconds since the Unix epoch. Any expiry that has
	/// 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
	}

	/// 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
	}

	/// Adds a blinded path to [`Refund::paths`]. Must include at least one path if only connected
	/// by private channels or if [`Refund::payer_id`] 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.refund.paths.get_or_insert_with(Vec::new).push(path);
		self
	}

	/// 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
	}

	/// 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.
	pub fn payer_note(mut self, payer_note: String) -> Self {
		self.refund.payer_note = Some(payer_note);
		self
	}

	/// Builds a [`Refund`] after checking for valid semantics.
	pub fn build(mut self) -> Result<Refund, SemanticError> {
		if self.refund.chain() == self.refund.implied_chain() {
			self.refund.chain = None;
		}

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

		Ok(Refund {
			bytes,
			contents: self.refund,
		})
	}
}

#[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, PartialEq)]
pub struct Refund {
	pub(super) bytes: Vec<u8>,
	pub(super) contents: RefundContents,
}

/// The contents of a [`Refund`], which may be shared with an [`Invoice`].
///
/// [`Invoice`]: crate::offers::invoice::Invoice
#[derive(Clone, Debug, PartialEq)]
pub(super) struct RefundContents {
	payer: PayerContents,
	// offer fields
	description: String,
	absolute_expiry: Option<Duration>,
	issuer: Option<String>,
	paths: Option<Vec<BlindedPath>>,
	// invoice_request fields
	chain: Option<ChainHash>,
	amount_msats: u64,
	features: InvoiceRequestFeatures,
	quantity: Option<u64>,
	payer_id: PublicKey,
	payer_note: Option<String>,
}

impl Refund {
	/// A complete description of the purpose of the refund. 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 {
		PrintableString(&self.contents.description)
	}

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

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

	/// 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()))
	}

	/// 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(&[])
	}

	/// An unpredictable series of bytes, typically containing information about the derivation of
	/// [`payer_id`].
	///
	/// [`payer_id`]: Self::payer_id
	pub fn metadata(&self) -> &[u8] {
		&self.contents.payer.0
	}

	/// A chain that the refund is valid for.
	pub fn chain(&self) -> ChainHash {
		self.contents.chain.unwrap_or_else(|| self.contents.implied_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
	}

	/// Features pertaining to requesting an invoice.
	pub fn features(&self) -> &InvoiceRequestFeatures {
		&self.contents.features
	}

	/// 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
	}

	/// 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()))
	}

	/// Creates an [`Invoice`] for the refund with the given required fields and using the
	/// [`Duration`] since [`std::time::SystemTime::UNIX_EPOCH`] as the creation time.
	///
	/// See [`Refund::respond_with_no_std`] for further details where the aforementioned creation
	/// time is used for the `created_at` parameter.
	///
	/// [`Invoice`]: crate::offers::invoice::Invoice
	/// [`Duration`]: core::time::Duration
	#[cfg(feature = "std")]
	pub fn respond_with(
		&self, payment_paths: Vec<(BlindedPath, BlindedPayInfo)>, payment_hash: PaymentHash,
		signing_pubkey: PublicKey,
	) -> Result<InvoiceBuilder, SemanticError> {
		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)
	}

	/// Creates an [`Invoice`] for the refund with the given required fields.
	///
	/// Unless [`InvoiceBuilder::relative_expiry`] is set, the invoice will expire two hours after
	/// `created_at`, which is used to set [`Invoice::created_at`]. Useful for `no-std` builds where
	/// [`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_no_std(
		&self, payment_paths: Vec<(BlindedPath, BlindedPayInfo)>, payment_hash: PaymentHash,
		signing_pubkey: PublicKey, created_at: Duration
	) -> Result<InvoiceBuilder, SemanticError> {
		if self.features().requires_unknown_bits() {
			return Err(SemanticError::UnknownRequiredFeatures);
		}

		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 {
	fn as_ref(&self) -> &[u8] {
		&self.bytes
	}
}

impl RefundContents {
	#[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())
	}

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

	pub(super) fn as_tlv_stream(&self) -> RefundTlvStreamRef {
		let payer = PayerTlvStreamRef {
			metadata: Some(&self.payer.0),
		};

		let offer = OfferTlvStreamRef {
			chains: None,
			metadata: None,
			currency: None,
			amount: None,
			description: Some(&self.description),
			features: None,
			absolute_expiry: self.absolute_expiry.map(|duration| duration.as_secs()),
			paths: self.paths.as_ref(),
			issuer: self.issuer.as_ref(),
			quantity_max: None,
			node_id: None,
		};

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

		let invoice_request = InvoiceRequestTlvStreamRef {
			chain: self.chain.as_ref(),
			amount: Some(self.amount_msats),
			features,
			quantity: self.quantity,
			payer_id: Some(&self.payer_id),
			payer_note: self.payer_note.as_ref(),
		};

		(payer, offer, invoice_request)
	}
}

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

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

type RefundTlvStream = (PayerTlvStream, OfferTlvStream, InvoiceRequestTlvStream);

type RefundTlvStreamRef<'a> = (
	PayerTlvStreamRef<'a>,
	OfferTlvStreamRef<'a>,
	InvoiceRequestTlvStreamRef<'a>,
);

impl SeekReadable for RefundTlvStream {
	fn read<R: io::Read + io::Seek>(r: &mut R) -> Result<Self, DecodeError> {
		let payer = SeekReadable::read(r)?;
		let offer = SeekReadable::read(r)?;
		let invoice_request = SeekReadable::read(r)?;

		Ok((payer, offer, invoice_request))
	}
}

impl Bech32Encode for Refund {
	const BECH32_HRP: &'static str = "lnr";
}

impl FromStr for Refund {
	type Err = ParseError;

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

impl TryFrom<Vec<u8>> for Refund {
	type Error = ParseError;

	fn try_from(bytes: Vec<u8>) -> Result<Self, Self::Error> {
		let refund = ParsedMessage::<RefundTlvStream>::try_from(bytes)?;
		let ParsedMessage { bytes, tlv_stream } = refund;
		let contents = RefundContents::try_from(tlv_stream)?;

		Ok(Refund { bytes, contents })
	}
}

impl TryFrom<RefundTlvStream> for RefundContents {
	type Error = SemanticError;

	fn try_from(tlv_stream: RefundTlvStream) -> Result<Self, Self::Error> {
		let (
			PayerTlvStream { metadata: payer_metadata },
			OfferTlvStream {
				chains, metadata, currency, amount: offer_amount, description,
				features: offer_features, absolute_expiry, paths, issuer, quantity_max, node_id,
			},
			InvoiceRequestTlvStream { chain, amount, features, quantity, payer_id, payer_note },
		) = tlv_stream;

		let payer = match payer_metadata {
			None => return Err(SemanticError::MissingPayerMetadata),
			Some(metadata) => PayerContents(metadata),
		};

		if metadata.is_some() {
			return Err(SemanticError::UnexpectedMetadata);
		}

		if chains.is_some() {
			return Err(SemanticError::UnexpectedChain);
		}

		if currency.is_some() || offer_amount.is_some() {
			return Err(SemanticError::UnexpectedAmount);
		}

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

		if offer_features.is_some() {
			return Err(SemanticError::UnexpectedFeatures);
		}

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

		if quantity_max.is_some() {
			return Err(SemanticError::UnexpectedQuantity);
		}

		if node_id.is_some() {
			return Err(SemanticError::UnexpectedSigningPubkey);
		}

		let amount_msats = match amount {
			None => return Err(SemanticError::MissingAmount),
			Some(amount_msats) if amount_msats > MAX_VALUE_MSAT => {
				return Err(SemanticError::InvalidAmount);
			},
			Some(amount_msats) => amount_msats,
		};

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

		let payer_id = match payer_id {
			None => return Err(SemanticError::MissingPayerId),
			Some(payer_id) => payer_id,
		};

		Ok(RefundContents {
			payer, description, absolute_expiry, issuer, paths, chain, amount_msats, features,
			quantity, payer_id, payer_note,
		})
	}
}

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