+/// A wrapper around the various hop representations.
+///
+/// Used to construct a [`PathBuildingHop`] and to estimate [`EffectiveCapacity`].
+#[derive(Clone, Debug)]
+enum CandidateRouteHop<'a> {
+ /// A hop from the payer, where the outbound liquidity is known.
+ FirstHop {
+ details: &'a ChannelDetails,
+ },
+ /// A hop found in the [`NetworkGraph`], where the channel capacity may or may not be known.
+ PublicHop {
+ info: DirectedChannelInfoWithUpdate<'a>,
+ short_channel_id: u64,
+ },
+ /// A hop to the payee found in the payment invoice, though not necessarily a direct channel.
+ PrivateHop {
+ hint: &'a RouteHintHop,
+ }
+}
+
+impl<'a> CandidateRouteHop<'a> {
+ fn short_channel_id(&self) -> u64 {
+ match self {
+ CandidateRouteHop::FirstHop { details } => details.short_channel_id.unwrap(),
+ CandidateRouteHop::PublicHop { short_channel_id, .. } => *short_channel_id,
+ CandidateRouteHop::PrivateHop { hint } => hint.short_channel_id,
+ }
+ }
+
+ // NOTE: This may alloc memory so avoid calling it in a hot code path.
+ fn features(&self) -> ChannelFeatures {
+ match self {
+ CandidateRouteHop::FirstHop { details } => details.counterparty.features.to_context(),
+ CandidateRouteHop::PublicHop { info, .. } => info.channel().features.clone(),
+ CandidateRouteHop::PrivateHop { .. } => ChannelFeatures::empty(),
+ }
+ }
+
+ fn cltv_expiry_delta(&self) -> u32 {
+ match self {
+ CandidateRouteHop::FirstHop { .. } => 0,
+ CandidateRouteHop::PublicHop { info, .. } => info.direction().cltv_expiry_delta as u32,
+ CandidateRouteHop::PrivateHop { hint } => hint.cltv_expiry_delta as u32,
+ }
+ }
+
+ fn htlc_minimum_msat(&self) -> u64 {
+ match self {
+ CandidateRouteHop::FirstHop { .. } => 0,
+ CandidateRouteHop::PublicHop { info, .. } => info.direction().htlc_minimum_msat,
+ CandidateRouteHop::PrivateHop { hint } => hint.htlc_minimum_msat.unwrap_or(0),
+ }
+ }
+
+ fn fees(&self) -> RoutingFees {
+ match self {
+ CandidateRouteHop::FirstHop { .. } => RoutingFees {
+ base_msat: 0, proportional_millionths: 0,
+ },
+ CandidateRouteHop::PublicHop { info, .. } => info.direction().fees,
+ CandidateRouteHop::PrivateHop { hint } => hint.fees,
+ }
+ }
+
+ fn effective_capacity(&self) -> EffectiveCapacity {
+ match self {
+ CandidateRouteHop::FirstHop { details } => EffectiveCapacity::ExactLiquidity {
+ liquidity_msat: details.outbound_capacity_msat,
+ },
+ CandidateRouteHop::PublicHop { info, .. } => info.effective_capacity(),
+ CandidateRouteHop::PrivateHop { .. } => EffectiveCapacity::Infinite,
+ }
+ }