Offer TLV stream for BOLT 12

Add an Offer TLV stream that can be read or written. Reading checks for
unknown even fields but does not check whether the encoded offer's
semantics are correct.

Author: jkczyz

lightning/src/lib.rs

@@ -75,6 +75,7 @@ extern crate core;
 pub mod util;
 pub mod chain;
 pub mod ln;
+pub mod offers;
 pub mod routing;
 
 #[cfg(feature = "std")]

lightning/src/offers/mod.rs

@@ -0,0 +1,85 @@
+// 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.
+
+//! Implementation of Lightning Offers
+//! ([BOLT 12](https://github.com/lightning/bolts/blob/master/12-offer-encoding.md)).
+
+use bitcoin::bech32;
+use bitcoin::bech32::FromBase32;
+use bitcoin::hash_types::BlockHash;
+use bitcoin::secp256k1::{PublicKey, XOnlyPublicKey};
+use bitcoin::secp256k1::schnorr::Signature;
+use core::str::FromStr;
+use ln::PaymentHash;
+use ln::features::OfferFeatures;
+use ln::msgs::DecodeError;
+use util::ser::{HighZeroBytesDroppedVarInt, Readable, WithLength, WithoutLength};
+
+use prelude::*;
+
+/// An `offer` TLV stream without any semantic checks, apart from any checks performed when parsing
+/// the underlying types.
+struct OfferTlvStream {
+	_empty: (),
+	chains: Option<WithoutLength<Vec<BlockHash>>>,
+	currency: Option<WithoutLength<String>>,
+	amount: Option<HighZeroBytesDroppedVarInt<u64>>,
+	description: Option<WithoutLength<String>>,
+	features: Option<OfferFeatures>,
+	absolute_expiry: Option<HighZeroBytesDroppedVarInt<u64>>,
+	paths: Option<WithoutLength<Vec<BlindedPath>>>,
+	issuer: Option<WithoutLength<String>>,
+	quantity_min: Option<HighZeroBytesDroppedVarInt<u64>>,
+	quantity_max: Option<HighZeroBytesDroppedVarInt<u64>>,
+	recurrence: Option<Recurrence>,
+	node_id: Option<XOnlyPublicKey>,
+	send_invoice: Option<()>,
+	refund_for: Option<PaymentHash>,
+	signature: Option<Signature>,
+}
+
+impl_writeable_msg!(OfferTlvStream, { _empty }, {
+	(2, chains, option),
+	(6, currency, option),
+	(8, amount, option),
+	(10, description, option),
+	(12, features, option),
+	(14, absolute_expiry, option),
+	(16, paths, option),
+	(20, issuer, option),
+	(22, quantity_min, option),
+	(24, quantity_max, option),
+	(26, recurrence, option),
+	(30, node_id, option),
+	(34, refund_for, option),
+	(54, send_invoice, option),
+	(240, signature, option),
+});
+
+struct BlindedPath {
+	blinding: PublicKey,
+	path: WithLength<Vec<OnionMessagePath>, u8>,
+}
+
+impl_writeable!(BlindedPath, { blinding, path });
+
+struct OnionMessagePath {
+	node_id: PublicKey,
+	encrypted_recipient_data: Vec<u8>,
+}
+
+impl_writeable!(OnionMessagePath, { node_id, encrypted_recipient_data });
+
+// TODO: Remove once BOLT 12 test vectors are updated.
+struct Recurrence {
+	time_unit: u8,
+	period: HighZeroBytesDroppedVarInt<u32>,
+}
+
+impl_writeable!(Recurrence, { time_unit, period });