function that returns map from commitment number to list of HTLCs

electrum/lnchan.py

@@ -579,14 +579,14 @@ class Channel(PrintError):
           unsettled_local + remote_settled - local_settled
         return remote_msat, local_msat
 
-    def included_htlcs(self, subject, htlc_initiator):
+    def included_htlcs(self, subject, htlc_initiator, only_pending=True):
         """
         return filter of non-dust htlcs for subjects commitment transaction, initiated by given party
         """
         feerate = self.pending_feerate(subject)
         conf = self.config[subject]
         weight = HTLC_SUCCESS_WEIGHT if subject != htlc_initiator else HTLC_TIMEOUT_WEIGHT
-        htlcs = self.htlcs(htlc_initiator, only_pending=True)
+        htlcs = self.htlcs(htlc_initiator, only_pending=only_pending)
         fee_for_htlc = lambda htlc: htlc.amount_msat // 1000 - (weight * feerate // 1000)
         return filter(lambda htlc: fee_for_htlc(htlc) >= conf.dust_limit_sat, htlcs)
 
@@ -853,6 +853,21 @@ class Channel(PrintError):
         assert tx.is_complete()
         return tx
 
+    def included_htlcs_in_latest_ctxs(self):
+        """ A map from commitment number to list of HTLCs in
+            their latest two commitment transactions.
+            The oldest might have been revoked.  """
+        old_htlcs = list(self.included_htlcs(REMOTE, REMOTE, only_pending=False)) \
+                  + list(self.included_htlcs(REMOTE, LOCAL,  only_pending=False))
+
+        old_logs = dict(self.lock_in_htlc_changes(LOCAL))
+        new_htlcs = list(self.included_htlcs(REMOTE, REMOTE)) \
+                  + list(self.included_htlcs(REMOTE, LOCAL))
+        self.log = old_logs
+
+        return {self.config[REMOTE].ctn:   old_htlcs,
+                self.config[REMOTE].ctn+1: new_htlcs, }
+
 def maybe_create_sweeptx_for_their_ctx_to_remote(chan, ctx, their_pcp: bytes,
                                                  sweep_address) -> Optional[EncumberedTransaction]:
     assert isinstance(their_pcp, bytes)

electrum/tests/test_lnchan.py

@@ -199,6 +199,11 @@ class TestChannel(unittest.TestCase):
         alice_channel, bob_channel = self.alice_channel, self.bob_channel
         htlc = self.htlc
 
+        ctn_to_htlcs = alice_channel.included_htlcs_in_latest_ctxs()
+        self.assertEqual(list(ctn_to_htlcs.keys()), [0,1])
+        self.assertEqual(ctn_to_htlcs[0], [])
+        self.assertEqual(ctn_to_htlcs[1], [htlc])
+
         # Next alice commits this change by sending a signature message. Since
         # we expect the messages to be ordered, Bob will receive the HTLC we
         # just sent before he receives this signature, so the signature will
@@ -273,6 +278,12 @@ class TestChannel(unittest.TestCase):
         alice_channel.receive_htlc_settle(preimage, self.aliceHtlcIndex)
 
         bobSig2, bobHtlcSigs2 = bob_channel.sign_next_commitment()
+
+        ctn_to_htlcs = bob_channel.included_htlcs_in_latest_ctxs()
+        self.assertEqual(list(ctn_to_htlcs.keys()), [1,2])
+        self.assertEqual(len(ctn_to_htlcs[1]), 1)
+        self.assertEqual(len(ctn_to_htlcs[2]), 0)
+
         alice_channel.receive_new_commitment(bobSig2, bobHtlcSigs2)
 
         aliceRevocation2, _ = alice_channel.revoke_current_commitment()