add get_scores method on ProbabilisticScorer

Allows access to the scorer state. An example use case is an LSP
exposing the global network view in its scorer over http to light
clients.

Author: joostjager

lightning/src/routing/scoring.rs

@@ -1148,6 +1148,11 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ProbabilisticScorer<G, L> whe
 	pub fn set(&mut self, external_scores: ChannelLiquidities) {
 		_ = mem::replace(&mut self.channel_liquidities, external_scores);
 	}
+
+	/// Returns the current scores.
+	pub fn get_scores(&self) -> ChannelLiquidities {
+		self.channel_liquidities.clone()
+	}
 }
 
 impl ChannelLiquidity {
@@ -3943,6 +3948,37 @@ mod tests {
 			Some(0.0));
 	}
 
+	#[test]
+	fn get_scores() {
+		let logger = TestLogger::new();
+		let network_graph = network_graph(&logger);
+		let params = ProbabilisticScoringFeeParameters {
+			liquidity_penalty_multiplier_msat: 1_000,
+			..ProbabilisticScoringFeeParameters::zero_penalty()
+		};
+		let mut scorer = ProbabilisticScorer::new(ProbabilisticScoringDecayParameters::default(), &network_graph, &logger);
+		let source = source_node_id();
+		let usage = ChannelUsage {
+			amount_msat: 500,
+			inflight_htlc_msat: 0,
+			effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
+		};
+		let successful_path = payment_path_for_amount(200);
+		let channel = &network_graph.read_only().channel(42).unwrap().to_owned();
+		let (info, _) = channel.as_directed_from(&source).unwrap();
+		let candidate = CandidateRouteHop::PublicHop(PublicHopCandidate {
+			info,
+			short_channel_id: 41,
+		});
+
+		scorer.payment_path_successful(&successful_path, Duration::ZERO);
+		assert_eq!(scorer.channel_penalty_msat(&candidate, usage, &params), 301);
+
+		// Get the scores and assert that both channels are present in the returned struct.
+		let scores = scorer.get_scores();
+		assert_eq!(scores.iter().count(), 2);
+	}
+
 	#[test]
 	fn combined_scorer() {
 		let logger = TestLogger::new();