From 72fb43f950815ef7a655c39f47610c835ac155d0 Mon Sep 17 00:00:00 2001
From: ThomasV <thomasv@electrum.org>
Date: Sat, 25 Feb 2023 12:23:34 +0100
Subject: [PATCH] lnworker: do not assume MPP in num_sats_can_receive

---
 electrum/lnworker.py        | 23 +++++------------------
 electrum/submarine_swaps.py |  7 +------
 2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/electrum/lnworker.py b/electrum/lnworker.py
index f83166df3..6dc9b32c6 100644
--- a/electrum/lnworker.py
+++ b/electrum/lnworker.py
@@ -2161,11 +2161,9 @@ class LNWallet(LNWorker):
             return channels
 
     def num_sats_can_receive(self, deltas=None) -> Decimal:
-        """Return a conservative estimate of max sat value we can realistically receive
-        in a single payment. (MPP is allowed)
-
-        The theoretical max would be `sum(chan.available_to_spend(REMOTE) for chan in self.channels)`,
-        but that would require a sender using MPP to magically guess all our channel liquidities.
+        """
+        We no longer assume the sender to send MPP on different channels,
+        because channel liquidities are hard to guess
         """
         if deltas is None:
             deltas = {}
@@ -2182,12 +2180,10 @@ class LNWallet(LNWorker):
             recv_chan_msats = [recv_capacity(chan) for chan in recv_channels]
         if not recv_chan_msats:
             return Decimal(0)
-        can_receive_msat = max(
-            max(recv_chan_msats),       # single-part payment baseline
-            sum(recv_chan_msats) // 2,  # heuristic for MPP
-        )
+        can_receive_msat = max(recv_chan_msats)
         return Decimal(can_receive_msat) / 1000
 
+
     def _suggest_channels_for_rebalance(self, direction, amount_sat) -> Sequence[Tuple[Channel, int]]:
         """
         Suggest a channel and amount to send/receive with that channel, so that we will be able to receive/send amount_sat
@@ -2297,15 +2293,6 @@ class LNWallet(LNWorker):
         return await self.pay_invoice(
             invoice, channels=[chan1])
 
-    def num_sats_can_receive_no_mpp(self) -> Decimal:
-        with self.lock:
-            channels = [
-                c for c in self.channels.values()
-                if c.is_active() and not c.is_frozen_for_receiving()
-            ]
-            can_receive = max([c.available_to_spend(REMOTE) for c in channels]) if channels else 0
-        return Decimal(can_receive) / 1000
-
     def can_receive_invoice(self, invoice: Invoice) -> bool:
         assert invoice.is_lightning()
         return (invoice.get_amount_sat() or 0) <= self.num_sats_can_receive()
diff --git a/electrum/submarine_swaps.py b/electrum/submarine_swaps.py
index cd62f98d8..55defd265 100644
--- a/electrum/submarine_swaps.py
+++ b/electrum/submarine_swaps.py
@@ -241,11 +241,6 @@ class SwapManager(Logger):
         callback = lambda: self._claim_swap(swap)
         self.lnwatcher.add_callback(swap.lockup_address, callback)
 
-    def num_sats_can_receive(self):
-        # finding how to do MPP is too hard for sender,
-        # might result in our coins being locked
-        return self.lnworker.num_sats_can_receive_no_mpp()
-
     async def normal_swap(
             self,
             *,
@@ -678,7 +673,7 @@ class SwapManager(Logger):
     def max_amount_forward_swap(self) -> Optional[int]:
         """ returns None if we cannot swap """
         max_swap_amt_ln = self.get_max_amount()
-        max_recv_amt_ln = int(self.num_sats_can_receive())
+        max_recv_amt_ln = int(self.lnworker.num_sats_can_receive())
         max_amt_ln = int(min(max_swap_amt_ln, max_recv_amt_ln))
         max_amt_oc = self.get_send_amount(max_amt_ln, is_reverse=False) or 0
         min_amt_oc = self.get_send_amount(self.get_min_amount(), is_reverse=False) or 0