Invoice request parsing from bech32 strings

Implement Bech32Encode for InvoiceRequest, which supports creating and
parsing QR codes for the merchant-pays-user (e.g., refund, ATM) flow.

Author: jkczyz

lightning/src/offers/invoice_request.rs

@@ -55,10 +55,11 @@ use bitcoin::secp256k1::{Message, PublicKey, self};
 use bitcoin::secp256k1::schnorr::Signature;
 use core::convert::TryFrom;
 use io;
+use core::str::FromStr;
 use ln::features::OfferFeatures;
 use offers::merkle::{SignatureTlvStream, SignatureTlvStreamRef, self};
 use offers::offer::{Amount, Offer, OfferContents, OfferTlvStream, OfferTlvStreamRef, SendInvoiceOfferContents};
-use offers::parse::{ParseError, SemanticError};
+use offers::parse::{Bech32Encode, ParseError, SemanticError};
 use offers::payer::{PayerContents, PayerTlvStream, PayerTlvStreamRef};
 use util::ser::{Readable, WithoutLength, Writeable, Writer};
 
@@ -325,6 +326,12 @@ impl InvoiceRequestContents {
 	}
 }
 
+impl AsRef<[u8]> for InvoiceRequest {
+	fn as_ref(&self) -> &[u8] {
+		&self.bytes
+	}
+}
+
 impl Writeable for InvoiceRequest {
 	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 		WithoutLength(&self.bytes).write(writer)
@@ -355,6 +362,12 @@ tlv_stream!(InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef, {
 	(89, payer_note: String),
 });
 
+impl Bech32Encode for InvoiceRequest {
+	type TlvStream = FullInvoiceRequestTlvStream;
+
+	const BECH32_HRP: &'static str = "lnr";
+}
+
 type ParsedInvoiceRequest = (Vec<u8>, FullInvoiceRequestTlvStream);
 
 type FullInvoiceRequestTlvStream =
@@ -368,6 +381,15 @@ type PartialInvoiceRequestTlvStreamRef<'a> = (
 	InvoiceRequestTlvStreamRef<'a>,
 );
 
+impl FromStr for InvoiceRequest {
+	type Err = ParseError;
+
+	fn from_str(s: &str) -> Result<Self, <Self as FromStr>::Err> {
+		let (tlv_stream, bytes) = InvoiceRequest::from_bech32_str(s)?;
+		InvoiceRequest::try_from((bytes, tlv_stream))
+	}
+}
+
 impl TryFrom<ParsedInvoiceRequest> for InvoiceRequest {
 	type Error = ParseError;
 
@@ -451,3 +473,9 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 		})
 	}
 }
+
+impl core::fmt::Display for InvoiceRequest {
+	fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
+		self.fmt_bech32_str(f)
+	}
+}