From 707cc821b11748d74297925739f7e13ee06252e4 Mon Sep 17 00:00:00 2001
From: Jeffrey Czyz <jkczyz@gmail.com>
Date: Thu, 25 Jan 2024 16:16:56 -0600
Subject: [PATCH] WIP: Success probability for ProbabilisticScorer

---
 lightning/src/routing/router.rs  |  4 +++-
 lightning/src/routing/scoring.rs | 35 +++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 36ea344a21e..8368224df65 100644
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -183,7 +183,9 @@ impl<G: Deref<Target = NetworkGraph<L>> + Clone, L: Deref, S: Deref, SP: Sized,
 				let amount_msat = amount_msats;
 				let effective_capacity = info.effective_capacity();
 				let usage = ChannelUsage { amount_msat, inflight_htlc_msat: 0, effective_capacity };
-				let success_probability = scorer.channel_success_probability(scid, &info, usage);
+				let success_probability = scorer.channel_success_probability(
+					scid, &info, usage, &self.score_params
+				);
 
 				if !success_probability.is_finite() {
 					return None;
diff --git a/lightning/src/routing/scoring.rs b/lightning/src/routing/scoring.rs
index 342fd8c68ef..8f24539a222 100644
--- a/lightning/src/routing/scoring.rs
+++ b/lightning/src/routing/scoring.rs
@@ -118,7 +118,8 @@ pub trait ScoreLookUp {
 	/// This is useful to determine whether a channel should be included in a blinded path and the
 	/// preferred ordering of blinded paths.
 	fn channel_success_probability(
-		&self, _short_channel_id: u64, _info: &DirectedChannelInfo, _usage: ChannelUsage
+		&self, _short_channel_id: u64, _info: &DirectedChannelInfo, _usage: ChannelUsage,
+		_score_params: &Self::ScoreParams
 	) -> f64 { 0.5 }
 
 	/// Returns how certain any knowledge gained about the channel's liquidity balance is.
@@ -1251,6 +1252,27 @@ DirectedChannelLiquidity< L, BRT, T> {
 		liquidity_penalty_msat.saturating_add(amount_penalty_msat)
 	}
 
+	fn success_probability(
+		&self, usage: ChannelUsage, score_params: &ProbabilisticScoringFeeParameters
+	) -> f64 {
+		let amount_msat = usage.amount_msat;
+		let available_capacity = self.capacity_msat;
+		let max_liquidity_msat = self.max_liquidity_msat();
+		let min_liquidity_msat = core::cmp::min(self.min_liquidity_msat(), max_liquidity_msat);
+
+		if amount_msat <= min_liquidity_msat {
+			1.0
+		} else if amount_msat >= max_liquidity_msat {
+			0.0
+		} else {
+			let (numerator, denominator) = success_probability(
+				amount_msat, min_liquidity_msat, max_liquidity_msat, available_capacity,
+				score_params, false
+			);
+			numerator as f64 / denominator as f64
+		}
+	}
+
 	/// Returns the lower bound of the channel liquidity balance in this direction.
 	#[inline(always)]
 	fn min_liquidity_msat(&self) -> u64 {
@@ -1390,6 +1412,17 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ScoreLookUp for Probabilistic
 			.saturating_add(base_penalty_msat)
 	}
 
+	fn channel_success_probability(
+		&self, short_channel_id: u64, info: &DirectedChannelInfo, usage: ChannelUsage,
+		score_params: &ProbabilisticScoringFeeParameters
+	) -> f64 {
+		self.channel_liquidities
+			.get(&short_channel_id)
+			.unwrap_or(&ChannelLiquidity::new(Duration::ZERO))
+			.as_directed(info.source(), info.target(), usage.effective_capacity.as_msat())
+			.success_probability(usage, score_params)
+	}
+
 	fn channel_balance_certainty(&self, short_channel_id: u64, info: &DirectedChannelInfo) -> f64 {
 		self.channel_liquidities
 			.get(&short_channel_id)