Implement OffersMessageFlow functions

Author: shaavan

lightning/src/ln/channelmanager.rs

@@ -10202,7 +10202,7 @@ macro_rules! create_refund_builder { ($self: ident, $builder: ty) => {
 /// Sending multiple requests increases the chances of successful delivery in case some
 /// paths are unavailable. However, only one invoice for a given [`PaymentId`] will be paid,
 /// even if multiple invoices are received.
-const OFFERS_MESSAGE_REQUEST_LIMIT: usize = 10;
+pub const OFFERS_MESSAGE_REQUEST_LIMIT: usize = 10;
 
 impl<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, MR: Deref, L: Deref> ChannelManager<M, T, ES, NS, SP, F, R, MR, L>
 where

lightning/src/ln/inbound_payment.rs

@@ -194,7 +194,7 @@ pub fn create_from_hash(keys: &ExpandedKey, min_value_msat: Option<u64>, payment
 }
 
 #[cfg(async_payments)]
-pub(super) fn create_for_spontaneous_payment(
+pub(crate) fn create_for_spontaneous_payment(
 	keys: &ExpandedKey, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32,
 	current_time: u64, min_final_cltv_expiry_delta: Option<u16>
 ) -> Result<PaymentSecret, ()> {
@@ -213,7 +213,7 @@ pub(super) fn create_for_spontaneous_payment(
 	Ok(construct_payment_secret(&iv_bytes, &metadata_bytes, &keys.metadata_key))
 }
 
-pub(super) fn calculate_absolute_expiry(highest_seen_timestamp: u64, invoice_expiry_delta_secs: u32) -> u64 {
+pub(crate) fn calculate_absolute_expiry(highest_seen_timestamp: u64, invoice_expiry_delta_secs: u32) -> u64 {
 	// We assume that highest_seen_timestamp is pretty close to the current time - it's updated when
 	// we receive a new block with the maximum time we've seen in a header. It should never be more
 	// than two hours in the future.  Thus, we add two hours here as a buffer to ensure we