Use SemanticError in OfferBuilder::build
[rust-lightning] / lightning-invoice / src / payment.rs
index e8e296294016f4ba8b9eb954e3d0df9f0c68d65f..96b20958fb7453517a085dec9bae44a29a2f6fb0 100644 (file)
 //! and payee using information provided by the payer and from the payee's [`Invoice`], when
 //! applicable.
 //!
-//! [`InvoicePayer`] is parameterized by a [`LockableScore`], which it uses for scoring failed and
-//! successful payment paths upon receiving [`Event::PaymentPathFailed`] and
-//! [`Event::PaymentPathSuccessful`] events, respectively.
+//! [`InvoicePayer`] uses its [`Router`] parameterization for optionally notifying scorers upon
+//! receiving the [`Event::PaymentPathFailed`] and [`Event::PaymentPathSuccessful`] events.
+//! It also does the same for payment probe failure and success events using [`Event::ProbeFailed`]
+//! and [`Event::ProbeSuccessful`].
 //!
 //! [`InvoicePayer`] is capable of retrying failed payments. It accomplishes this by implementing
 //! [`EventHandler`] which decorates a user-provided handler. It will intercept any
 //! # extern crate lightning_invoice;
 //! # extern crate secp256k1;
 //! #
-//! # #[cfg(feature = "no-std")]
-//! # extern crate core2;
-//! #
+//! # use lightning::io;
 //! # use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 //! # use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 //! # use lightning::ln::msgs::LightningError;
 //! # use lightning::routing::gossip::NodeId;
-//! # use lightning::routing::router::{Route, RouteHop, RouteParameters};
+//! # use lightning::routing::router::{InFlightHtlcs, Route, RouteHop, RouteParameters, Router};
 //! # use lightning::routing::scoring::{ChannelUsage, Score};
 //! # use lightning::util::events::{Event, EventHandler, EventsProvider};
 //! # use lightning::util::logger::{Logger, Record};
 //! # use lightning::util::ser::{Writeable, Writer};
 //! # use lightning_invoice::Invoice;
-//! # use lightning_invoice::payment::{InvoicePayer, Payer, Retry, Router};
+//! # use lightning_invoice::payment::{InvoicePayer, Payer, Retry, ScoringRouter};
 //! # use secp256k1::PublicKey;
 //! # use std::cell::RefCell;
 //! # use std::ops::Deref;
 //! #
-//! # #[cfg(not(feature = "std"))]
-//! # use core2::io;
-//! # #[cfg(feature = "std")]
-//! # use std::io;
-//! #
 //! # struct FakeEventProvider {}
 //! # impl EventsProvider for FakeEventProvider {
 //! #     fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {}
 //! #     fn node_id(&self) -> PublicKey { unimplemented!() }
 //! #     fn first_hops(&self) -> Vec<ChannelDetails> { unimplemented!() }
 //! #     fn send_payment(
-//! #         &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>
-//! #     ) -> Result<PaymentId, PaymentSendFailure> { unimplemented!() }
+//! #         &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>,
+//! #         payment_id: PaymentId
+//! #     ) -> Result<(), PaymentSendFailure> { unimplemented!() }
 //! #     fn send_spontaneous_payment(
-//! #         &self, route: &Route, payment_preimage: PaymentPreimage
-//! #     ) -> Result<PaymentId, PaymentSendFailure> { unimplemented!() }
+//! #         &self, route: &Route, payment_preimage: PaymentPreimage, payment_id: PaymentId,
+//! #     ) -> Result<(), PaymentSendFailure> { unimplemented!() }
 //! #     fn retry_payment(
 //! #         &self, route: &Route, payment_id: PaymentId
 //! #     ) -> Result<(), PaymentSendFailure> { unimplemented!() }
 //! #
 //! # struct FakeRouter {}
 //! # impl Router for FakeRouter {
-//! #     fn find_route<S: Score>(
-//! #         &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
-//! #         first_hops: Option<&[&ChannelDetails]>, scorer: &S
+//! #     fn find_route(
+//! #         &self, payer: &PublicKey, params: &RouteParameters,
+//! #         first_hops: Option<&[&ChannelDetails]>, _inflight_htlcs: InFlightHtlcs
 //! #     ) -> Result<Route, LightningError> { unimplemented!() }
 //! # }
+//! # impl ScoringRouter for FakeRouter {
+//! #     fn notify_payment_path_failed(&self, path: &[&RouteHop], short_channel_id: u64) {  unimplemented!() }
+//! #     fn notify_payment_path_successful(&self, path: &[&RouteHop]) {  unimplemented!() }
+//! #     fn notify_payment_probe_successful(&self, path: &[&RouteHop]) {  unimplemented!() }
+//! #     fn notify_payment_probe_failed(&self, path: &[&RouteHop], short_channel_id: u64) { unimplemented!() }
+//! # }
 //! #
 //! # struct FakeScorer {}
 //! # impl Writeable for FakeScorer {
 //! # let router = FakeRouter {};
 //! # let scorer = RefCell::new(FakeScorer {});
 //! # let logger = FakeLogger {};
-//! let invoice_payer = InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+//! let invoice_payer = InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 //!
 //! let invoice = "...";
 //! if let Ok(invoice) = invoice.parse::<Invoice>() {
@@ -145,12 +146,11 @@ use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 use lightning::ln::msgs::LightningError;
 use lightning::routing::gossip::NodeId;
-use lightning::routing::scoring::{ChannelUsage, LockableScore, Score};
-use lightning::routing::router::{PaymentParameters, Route, RouteHop, RouteParameters};
+use lightning::routing::router::{InFlightHtlcs, PaymentParameters, Route, RouteHop, RouteParameters, Router};
 use lightning::util::errors::APIError;
 use lightning::util::events::{Event, EventHandler};
 use lightning::util::logger::Logger;
-use time_utils::Time;
+use crate::time_utils::Time;
 use crate::sync::Mutex;
 
 use secp256k1::PublicKey;
@@ -167,25 +167,23 @@ use std::time::SystemTime;
 /// See [module-level documentation] for details.
 ///
 /// [module-level documentation]: crate::payment
-pub type InvoicePayer<P, R, S, L, E> = InvoicePayerUsingTime::<P, R, S, L, E, ConfiguredTime>;
+pub type InvoicePayer<P, R, L, E> = InvoicePayerUsingTime::<P, R, L, E, ConfiguredTime>;
 
 #[cfg(not(feature = "no-std"))]
 type ConfiguredTime = std::time::Instant;
 #[cfg(feature = "no-std")]
-use time_utils;
+use crate::time_utils;
 #[cfg(feature = "no-std")]
 type ConfiguredTime = time_utils::Eternity;
 
 /// (C-not exported) generally all users should use the [`InvoicePayer`] type alias.
-pub struct InvoicePayerUsingTime<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time>
+pub struct InvoicePayerUsingTime<P: Deref, R: ScoringRouter, L: Deref, E: EventHandler, T: Time>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        payer: P,
        router: R,
-       scorer: S,
        logger: L,
        event_handler: E,
        /// Caches the overall attempts at making a payment, which is updated prior to retrying.
@@ -209,49 +207,6 @@ impl<T: Time> PaymentInfo<T> {
        }
 }
 
-/// Used to store information about all the HTLCs that are inflight across all payment attempts
-struct AccountForInFlightHtlcs<'a, S: Score> {
-       scorer: &'a mut S,
-       /// Maps a channel's short channel id and its direction to the liquidity used up.
-       inflight_htlcs: HashMap<(u64, bool), u64>,
-}
-
-#[cfg(c_bindings)]
-impl<'a, S:Score> lightning::util::ser::Writeable for AccountForInFlightHtlcs<'a, S> {
-       fn write<W: lightning::util::ser::Writer>(&self, writer: &mut W) -> Result<(), std::io::Error> { self.scorer.write(writer) }
-}
-
-impl<'a, S: Score> Score for AccountForInFlightHtlcs<'a, S> {
-       fn channel_penalty_msat(&self, short_channel_id: u64, source: &NodeId, target: &NodeId, usage: ChannelUsage) -> u64 {
-               if let Some(used_liqudity) = self.inflight_htlcs.get(&(short_channel_id, source < target)) {
-                       let usage = ChannelUsage {
-                               inflight_htlc_msat: usage.inflight_htlc_msat + used_liqudity,
-                               ..usage
-                       };
-
-                       self.scorer.channel_penalty_msat(short_channel_id, source, target, usage)
-               } else {
-                       self.scorer.channel_penalty_msat(short_channel_id, source, target, usage)
-               }
-       }
-
-       fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
-               self.scorer.payment_path_failed(path, short_channel_id)
-       }
-
-       fn payment_path_successful(&mut self, path: &[&RouteHop]) {
-               self.scorer.payment_path_successful(path)
-       }
-
-       fn probe_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
-               self.scorer.probe_failed(path, short_channel_id)
-       }
-
-       fn probe_successful(&mut self, path: &[&RouteHop]) {
-               self.scorer.probe_successful(path)
-       }
-}
-
 /// Storing minimal payment attempts information required for determining if a outbound payment can
 /// be retried.
 #[derive(Clone, Copy)]
@@ -287,6 +242,18 @@ impl<T: Time> Display for PaymentAttempts<T> {
 }
 
 /// A trait defining behavior of an [`Invoice`] payer.
+///
+/// While the behavior of [`InvoicePayer`] provides idempotency of duplicate `send_*payment` calls
+/// with the same [`PaymentHash`], it is up to the `Payer` to provide idempotency across restarts.
+///
+/// [`ChannelManager`] provides idempotency for duplicate payments with the same [`PaymentId`].
+///
+/// In order to trivially ensure idempotency for payments, the default `Payer` implementation
+/// reuses the [`PaymentHash`] bytes as the [`PaymentId`]. Custom implementations wishing to
+/// provide payment idempotency with a different idempotency key (i.e. [`PaymentId`]) should map
+/// the [`Invoice`] or spontaneous payment target pubkey to their own idempotency key.
+///
+/// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
 pub trait Payer {
        /// Returns the payer's node id.
        fn node_id(&self) -> PublicKey;
@@ -296,13 +263,14 @@ pub trait Payer {
 
        /// Sends a payment over the Lightning Network using the given [`Route`].
        fn send_payment(
-               &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>
-       ) -> Result<PaymentId, PaymentSendFailure>;
+               &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>,
+               payment_id: PaymentId
+       ) -> Result<(), PaymentSendFailure>;
 
        /// Sends a spontaneous payment over the Lightning Network using the given [`Route`].
        fn send_spontaneous_payment(
-               &self, route: &Route, payment_preimage: PaymentPreimage
-       ) -> Result<PaymentId, PaymentSendFailure>;
+               &self, route: &Route, payment_preimage: PaymentPreimage, payment_id: PaymentId
+       ) -> Result<(), PaymentSendFailure>;
 
        /// Retries a failed payment path for the [`PaymentId`] using the given [`Route`].
        fn retry_payment(&self, route: &Route, payment_id: PaymentId) -> Result<(), PaymentSendFailure>;
@@ -311,13 +279,28 @@ pub trait Payer {
        fn abandon_payment(&self, payment_id: PaymentId);
 }
 
-/// A trait defining behavior for routing an [`Invoice`] payment.
-pub trait Router {
-       /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values.
-       fn find_route<S: Score>(
-               &self, payer: &PublicKey, route_params: &RouteParameters, payment_hash: &PaymentHash,
-               first_hops: Option<&[&ChannelDetails]>, scorer: &S
-       ) -> Result<Route, LightningError>;
+/// A trait defining behavior for a [`Router`] implementation that also supports scoring channels
+/// based on payment and probe success/failure.
+///
+/// [`Router`]: lightning::routing::router::Router
+pub trait ScoringRouter: Router {
+       /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values. Includes
+       /// `PaymentHash` and `PaymentId` to be able to correlate the request with a specific payment.
+       fn find_route_with_id(
+               &self, payer: &PublicKey, route_params: &RouteParameters,
+               first_hops: Option<&[&ChannelDetails]>, inflight_htlcs: InFlightHtlcs,
+               _payment_hash: PaymentHash, _payment_id: PaymentId
+       ) -> Result<Route, LightningError> {
+               self.find_route(payer, route_params, first_hops, inflight_htlcs)
+       }
+       /// Lets the router know that payment through a specific path has failed.
+       fn notify_payment_path_failed(&self, path: &[&RouteHop], short_channel_id: u64);
+       /// Lets the router know that payment through a specific path was successful.
+       fn notify_payment_path_successful(&self, path: &[&RouteHop]);
+       /// Lets the router know that a payment probe was successful.
+       fn notify_payment_probe_successful(&self, path: &[&RouteHop]);
+       /// Lets the router know that a payment probe failed.
+       fn notify_payment_probe_failed(&self, path: &[&RouteHop], short_channel_id: u64);
 }
 
 /// Strategies available to retry payment path failures for an [`Invoice`].
@@ -359,10 +342,9 @@ pub enum PaymentError {
        Sending(PaymentSendFailure),
 }
 
-impl<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time> InvoicePayerUsingTime<P, R, S, L, E, T>
+impl<P: Deref, R: ScoringRouter, L: Deref, E: EventHandler, T: Time> InvoicePayerUsingTime<P, R, L, E, T>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        /// Creates an invoice payer that retries failed payment paths.
@@ -370,12 +352,11 @@ where
        /// Will forward any [`Event::PaymentPathFailed`] events to the decorated `event_handler` once
        /// `retry` has been exceeded for a given [`Invoice`].
        pub fn new(
-               payer: P, router: R, scorer: S, logger: L, event_handler: E, retry: Retry
+               payer: P, router: R, logger: L, event_handler: E, retry: Retry
        ) -> Self {
                Self {
                        payer,
                        router,
-                       scorer,
                        logger,
                        event_handler,
                        payment_cache: Mutex::new(HashMap::new()),
@@ -385,36 +366,76 @@ where
 
        /// Pays the given [`Invoice`], caching it for later use in case a retry is needed.
        ///
-       /// You should ensure that the `invoice.payment_hash()` is unique and the same payment_hash has
-       /// never been paid before. Because [`InvoicePayer`] is stateless no effort is made to do so
-       /// for you.
+       /// [`Invoice::payment_hash`] is used as the [`PaymentId`], which ensures idempotency as long
+       /// as the payment is still pending. Once the payment completes or fails, you must ensure that
+       /// a second payment with the same [`PaymentHash`] is never sent.
+       ///
+       /// If you wish to use a different payment idempotency token, see
+       /// [`Self::pay_invoice_with_id`].
        pub fn pay_invoice(&self, invoice: &Invoice) -> Result<PaymentId, PaymentError> {
+               let payment_id = PaymentId(invoice.payment_hash().into_inner());
+               self.pay_invoice_with_id(invoice, payment_id).map(|()| payment_id)
+       }
+
+       /// Pays the given [`Invoice`] with a custom idempotency key, caching the invoice for later use
+       /// in case a retry is needed.
+       ///
+       /// Note that idempotency is only guaranteed as long as the payment is still pending. Once the
+       /// payment completes or fails, no idempotency guarantees are made.
+       ///
+       /// You should ensure that the [`Invoice::payment_hash`] is unique and the same [`PaymentHash`]
+       /// has never been paid before.
+       ///
+       /// See [`Self::pay_invoice`] for a variant which uses the [`PaymentHash`] for the idempotency
+       /// token.
+       pub fn pay_invoice_with_id(&self, invoice: &Invoice, payment_id: PaymentId) -> Result<(), PaymentError> {
                if invoice.amount_milli_satoshis().is_none() {
                        Err(PaymentError::Invoice("amount missing"))
                } else {
-                       self.pay_invoice_using_amount(invoice, None)
+                       self.pay_invoice_using_amount(invoice, None, payment_id)
                }
        }
 
        /// Pays the given zero-value [`Invoice`] using the given amount, caching it for later use in
        /// case a retry is needed.
        ///
-       /// You should ensure that the `invoice.payment_hash()` is unique and the same payment_hash has
-       /// never been paid before. Because [`InvoicePayer`] is stateless no effort is made to do so
-       /// for you.
+       /// [`Invoice::payment_hash`] is used as the [`PaymentId`], which ensures idempotency as long
+       /// as the payment is still pending. Once the payment completes or fails, you must ensure that
+       /// a second payment with the same [`PaymentHash`] is never sent.
+       ///
+       /// If you wish to use a different payment idempotency token, see
+       /// [`Self::pay_zero_value_invoice_with_id`].
        pub fn pay_zero_value_invoice(
                &self, invoice: &Invoice, amount_msats: u64
        ) -> Result<PaymentId, PaymentError> {
+               let payment_id = PaymentId(invoice.payment_hash().into_inner());
+               self.pay_zero_value_invoice_with_id(invoice, amount_msats, payment_id).map(|()| payment_id)
+       }
+
+       /// Pays the given zero-value [`Invoice`] using the given amount and custom idempotency key,
+       /// caching the invoice for later use in case a retry is needed.
+       ///
+       /// Note that idempotency is only guaranteed as long as the payment is still pending. Once the
+       /// payment completes or fails, no idempotency guarantees are made.
+       ///
+       /// You should ensure that the [`Invoice::payment_hash`] is unique and the same [`PaymentHash`]
+       /// has never been paid before.
+       ///
+       /// See [`Self::pay_zero_value_invoice`] for a variant which uses the [`PaymentHash`] for the
+       /// idempotency token.
+       pub fn pay_zero_value_invoice_with_id(
+               &self, invoice: &Invoice, amount_msats: u64, payment_id: PaymentId
+       ) -> Result<(), PaymentError> {
                if invoice.amount_milli_satoshis().is_some() {
                        Err(PaymentError::Invoice("amount unexpected"))
                } else {
-                       self.pay_invoice_using_amount(invoice, Some(amount_msats))
+                       self.pay_invoice_using_amount(invoice, Some(amount_msats), payment_id)
                }
        }
 
        fn pay_invoice_using_amount(
-               &self, invoice: &Invoice, amount_msats: Option<u64>
-       ) -> Result<PaymentId, PaymentError> {
+               &self, invoice: &Invoice, amount_msats: Option<u64>, payment_id: PaymentId
+       ) -> Result<(), PaymentError> {
                debug_assert!(invoice.amount_milli_satoshis().is_some() ^ amount_msats.is_some());
 
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
@@ -437,7 +458,7 @@ where
                };
 
                let send_payment = |route: &Route| {
-                       self.payer.send_payment(route, payment_hash, &payment_secret)
+                       self.payer.send_payment(route, payment_hash, &payment_secret, payment_id)
                };
 
                self.pay_internal(&route_params, payment_hash, send_payment)
@@ -447,13 +468,41 @@ where
        /// Pays `pubkey` an amount using the hash of the given preimage, caching it for later use in
        /// case a retry is needed.
        ///
-       /// You should ensure that `payment_preimage` is unique and that its `payment_hash` has never
-       /// been paid before. Because [`InvoicePayer`] is stateless no effort is made to do so for you.
+       /// The hash of the [`PaymentPreimage`] is used as the [`PaymentId`], which ensures idempotency
+       /// as long as the payment is still pending. Once the payment completes or fails, you must
+       /// ensure that a second payment with the same [`PaymentPreimage`] is never sent.
        pub fn pay_pubkey(
                &self, pubkey: PublicKey, payment_preimage: PaymentPreimage, amount_msats: u64,
                final_cltv_expiry_delta: u32
        ) -> Result<PaymentId, PaymentError> {
                let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+               let payment_id = PaymentId(payment_hash.0);
+               self.do_pay_pubkey(pubkey, payment_preimage, payment_hash, payment_id, amount_msats,
+                               final_cltv_expiry_delta)
+                       .map(|()| payment_id)
+       }
+
+       /// Pays `pubkey` an amount using the hash of the given preimage and a custom idempotency key,
+       /// caching the invoice for later use in case a retry is needed.
+       ///
+       /// Note that idempotency is only guaranteed as long as the payment is still pending. Once the
+       /// payment completes or fails, no idempotency guarantees are made.
+       ///
+       /// You should ensure that the [`PaymentPreimage`] is unique and the corresponding
+       /// [`PaymentHash`] has never been paid before.
+       pub fn pay_pubkey_with_id(
+               &self, pubkey: PublicKey, payment_preimage: PaymentPreimage, payment_id: PaymentId,
+               amount_msats: u64, final_cltv_expiry_delta: u32
+       ) -> Result<(), PaymentError> {
+               let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+               self.do_pay_pubkey(pubkey, payment_preimage, payment_hash, payment_id, amount_msats,
+                               final_cltv_expiry_delta)
+       }
+
+       fn do_pay_pubkey(
+               &self, pubkey: PublicKey, payment_preimage: PaymentPreimage, payment_hash: PaymentHash,
+               payment_id: PaymentId, amount_msats: u64, final_cltv_expiry_delta: u32
+       ) -> Result<(), PaymentError> {
                match self.payment_cache.lock().unwrap().entry(payment_hash) {
                        hash_map::Entry::Occupied(_) => return Err(PaymentError::Invoice("payment pending")),
                        hash_map::Entry::Vacant(entry) => entry.insert(PaymentInfo::new()),
@@ -466,15 +515,15 @@ where
                };
 
                let send_payment = |route: &Route| {
-                       self.payer.send_spontaneous_payment(route, payment_preimage)
+                       self.payer.send_spontaneous_payment(route, payment_preimage, payment_id)
                };
                self.pay_internal(&route_params, payment_hash, send_payment)
                        .map_err(|e| { self.payment_cache.lock().unwrap().remove(&payment_hash); e })
        }
 
-       fn pay_internal<F: FnOnce(&Route) -> Result<PaymentId, PaymentSendFailure> + Copy>(
+       fn pay_internal<F: FnOnce(&Route) -> Result<(), PaymentSendFailure> + Copy>(
                &self, params: &RouteParameters, payment_hash: PaymentHash, send_payment: F,
-       ) -> Result<PaymentId, PaymentError> {
+       ) -> Result<(), PaymentError> {
                #[cfg(feature = "std")] {
                        if has_expired(params) {
                                log_trace!(self.logger, "Invoice expired prior to send for payment {}", log_bytes!(payment_hash.0));
@@ -486,16 +535,15 @@ where
                let first_hops = self.payer.first_hops();
                let inflight_htlcs = self.create_inflight_map();
                let route = self.router.find_route(
-                       &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &AccountForInFlightHtlcs { scorer: &mut self.scorer.lock(), inflight_htlcs }
+                       &payer, &params, Some(&first_hops.iter().collect::<Vec<_>>()), inflight_htlcs
                ).map_err(|e| PaymentError::Routing(e))?;
 
                match send_payment(&route) {
-                       Ok(payment_id) => {
+                       Ok(()) => {
                                for path in route.paths {
                                        self.process_path_inflight_htlcs(payment_hash, path);
                                }
-                               Ok(payment_id)
+                               Ok(())
                        },
                        Err(e) => match e {
                                PaymentSendFailure::ParameterError(_) => Err(e),
@@ -530,13 +578,13 @@ where
                                                // consider the payment sent, so return `Ok()` here, ignoring any retry
                                                // errors.
                                                let _ = self.retry_payment(payment_id, payment_hash, &retry_data);
-                                               Ok(payment_id)
+                                               Ok(())
                                        } else {
                                                // This may happen if we send a payment and some paths fail, but
                                                // only due to a temporary monitor failure or the like, implying
                                                // they're really in-flight, but we haven't sent the initial
                                                // HTLC-Add messages yet.
-                                               Ok(payment_id)
+                                               Ok(())
                                        }
                                },
                        },
@@ -591,8 +639,7 @@ where
                let inflight_htlcs = self.create_inflight_map();
 
                let route = self.router.find_route(
-                       &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &AccountForInFlightHtlcs { scorer: &mut self.scorer.lock(), inflight_htlcs }
+                       &payer, &params, Some(&first_hops.iter().collect::<Vec<_>>()), inflight_htlcs
                );
 
                if route.is_err() {
@@ -645,13 +692,12 @@ where
                self.payment_cache.lock().unwrap().remove(payment_hash);
        }
 
-       /// Given a [`PaymentHash`], this function looks up inflight path attempts in the payment_cache.
-       /// Then, it uses the path information inside the cache to construct a HashMap mapping a channel's
-       /// short channel id and direction to the amount being sent through it.
+       /// Use path information in the payment_cache to construct a HashMap mapping a channel's short
+       /// channel id and direction to the amount being sent through it.
        ///
        /// This function should be called whenever we need information about currently used up liquidity
        /// across payments.
-       fn create_inflight_map(&self) -> HashMap<(u64, bool), u64> {
+       fn create_inflight_map(&self) -> InFlightHtlcs {
                let mut total_inflight_map: HashMap<(u64, bool), u64> = HashMap::new();
                // Make an attempt at finding existing payment information from `payment_cache`. If it
                // does not exist, it probably is a fresh payment and we can just return an empty
@@ -683,7 +729,7 @@ where
                        }
                }
 
-               total_inflight_map
+               InFlightHtlcs::new(total_inflight_map)
        }
 }
 
@@ -698,10 +744,9 @@ fn has_expired(route_params: &RouteParameters) -> bool {
        } else { false }
 }
 
-impl<P: Deref, R: Router, S: Deref, L: Deref, E: EventHandler, T: Time> EventHandler for InvoicePayerUsingTime<P, R, S, L, E, T>
+impl<P: Deref, R: ScoringRouter, L: Deref, E: EventHandler, T: Time> EventHandler for InvoicePayerUsingTime<P, R, L, E, T>
 where
        P::Target: Payer,
-       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
 {
        fn handle_event(&self, event: &Event) {
@@ -721,7 +766,7 @@ where
                        } => {
                                if let Some(short_channel_id) = short_channel_id {
                                        let path = path.iter().collect::<Vec<_>>();
-                                       self.scorer.lock().payment_path_failed(&path, *short_channel_id);
+                                       self.router.notify_payment_path_failed(&path, *short_channel_id)
                                }
 
                                if payment_id.is_none() {
@@ -744,7 +789,7 @@ where
                        },
                        Event::PaymentPathSuccessful { path, .. } => {
                                let path = path.iter().collect::<Vec<_>>();
-                               self.scorer.lock().payment_path_successful(&path);
+                               self.router.notify_payment_path_successful(&path);
                        },
                        Event::PaymentSent { payment_hash, .. } => {
                                let mut payment_cache = self.payment_cache.lock().unwrap();
@@ -756,13 +801,13 @@ where
                        Event::ProbeSuccessful { payment_hash, path, .. } => {
                                log_trace!(self.logger, "Probe payment {} of {}msat was successful", log_bytes!(payment_hash.0), path.last().unwrap().fee_msat);
                                let path = path.iter().collect::<Vec<_>>();
-                               self.scorer.lock().probe_successful(&path);
+                               self.router.notify_payment_probe_successful(&path);
                        },
                        Event::ProbeFailed { payment_hash, path, short_channel_id, .. } => {
                                if let Some(short_channel_id) = short_channel_id {
                                        log_trace!(self.logger, "Probe payment {} of {}msat failed at channel {}", log_bytes!(payment_hash.0), path.last().unwrap().fee_msat, *short_channel_id);
                                        let path = path.iter().collect::<Vec<_>>();
-                                       self.scorer.lock().probe_failed(&path, *short_channel_id);
+                                       self.router.notify_payment_probe_failed(&path, *short_channel_id);
                                }
                        },
                        _ => {},
@@ -777,7 +822,7 @@ where
 mod tests {
        use super::*;
        use crate::{InvoiceBuilder, Currency};
-       use utils::create_invoice_from_channelmanager_and_duration_since_epoch;
+       use crate::utils::{ScorerAccountingForInFlightHtlcs, create_invoice_from_channelmanager_and_duration_since_epoch};
        use bitcoin_hashes::sha256::Hash as Sha256;
        use lightning::ln::PaymentPreimage;
        use lightning::ln::channelmanager;
@@ -785,17 +830,18 @@ mod tests {
        use lightning::ln::functional_test_utils::*;
        use lightning::ln::msgs::{ChannelMessageHandler, ErrorAction, LightningError};
        use lightning::routing::gossip::{EffectiveCapacity, NodeId};
-       use lightning::routing::router::{PaymentParameters, Route, RouteHop};
-       use lightning::routing::scoring::ChannelUsage;
+       use lightning::routing::router::{InFlightHtlcs, PaymentParameters, Route, RouteHop, Router};
+       use lightning::routing::scoring::{ChannelUsage, LockableScore, Score};
        use lightning::util::test_utils::TestLogger;
        use lightning::util::errors::APIError;
        use lightning::util::events::{Event, EventsProvider, MessageSendEvent, MessageSendEventsProvider};
        use secp256k1::{SecretKey, PublicKey, Secp256k1};
        use std::cell::RefCell;
        use std::collections::VecDeque;
+       use std::ops::DerefMut;
        use std::time::{SystemTime, Duration};
-       use time_utils::tests::SinceEpoch;
-       use DEFAULT_EXPIRY_TIME;
+       use crate::time_utils::tests::SinceEpoch;
+       use crate::DEFAULT_EXPIRY_TIME;
        use lightning::util::errors::APIError::{ChannelUnavailable, MonitorUpdateInProgress};
 
        fn invoice(payment_preimage: PaymentPreimage) -> Invoice {
@@ -875,11 +921,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -904,11 +949,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -949,11 +993,10 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                assert!(invoice_payer.pay_invoice(&invoice).is_ok());
        }
@@ -971,11 +1014,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(PaymentId([1; 32]));
                let event = Event::PaymentPathFailed {
@@ -1016,11 +1058,10 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1074,13 +1115,12 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
-               type InvoicePayerUsingSinceEpoch <P, R, S, L, E> = InvoicePayerUsingTime::<P, R, S, L, E, SinceEpoch>;
+               type InvoicePayerUsingSinceEpoch <P, R, L, E> = InvoicePayerUsingTime::<P, R, L, E, SinceEpoch>;
 
                let invoice_payer =
-                       InvoicePayerUsingSinceEpoch::new(&payer, router, &scorer, &logger, event_handler, Retry::Timeout(Duration::from_secs(120)));
+                       InvoicePayerUsingSinceEpoch::new(&payer, router, &logger, event_handler, Retry::Timeout(Duration::from_secs(120)));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1116,11 +1156,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1148,11 +1187,10 @@ mod tests {
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
                let payer = TestPayer::new();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = expired_invoice(payment_preimage);
@@ -1173,11 +1211,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router,  &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1214,11 +1251,10 @@ mod tests {
                        .fails_on_attempt(2)
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1248,11 +1284,10 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
@@ -1284,11 +1319,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
 
@@ -1324,10 +1358,9 @@ mod tests {
        fn fails_paying_invoice_with_routing_errors() {
                let payer = TestPayer::new();
                let router = FailingRouter {};
-               let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, |_: &_| {}, Retry::Attempts(0));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
@@ -1347,11 +1380,10 @@ mod tests {
                let payer = TestPayer::new()
                        .fails_on_attempt(1)
                        .expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, |_: &_| {}, Retry::Attempts(0));
 
                match invoice_payer.pay_invoice(&invoice) {
                        Err(PaymentError::Sending(_)) => {},
@@ -1371,11 +1403,10 @@ mod tests {
                let final_value_msat = 100;
 
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id =
                        Some(invoice_payer.pay_zero_value_invoice(&invoice, final_value_msat).unwrap());
@@ -1394,11 +1425,10 @@ mod tests {
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
                let payer = TestPayer::new();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router,  &logger, event_handler, Retry::Attempts(0));
 
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
@@ -1425,11 +1455,10 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::Spontaneous(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_pubkey(
                                pubkey, payment_preimage, final_value_msat, final_cltv_expiry_delta
@@ -1478,13 +1507,13 @@ mod tests {
                let payer = TestPayer::new()
                        .expect_send(Amount::ForInvoice(final_value_msat))
                        .expect_send(Amount::OnRetry(final_value_msat / 2));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new().expect(TestResult::PaymentFailure {
+               let scorer = TestScorer::new().expect(TestResult::PaymentFailure {
                        path: path.clone(), short_channel_id: path[0].short_channel_id,
-               }));
+               });
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                let event = Event::PaymentPathFailed {
@@ -1513,14 +1542,13 @@ mod tests {
 
                // Expect that scorer is given short_channel_id upon handling the event.
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        .expect(TestResult::PaymentSuccess { path: route.paths[0].clone() })
-                       .expect(TestResult::PaymentSuccess { path: route.paths[1].clone() })
-               );
+                       .expect(TestResult::PaymentSuccess { path: route.paths[1].clone() });
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
                let event = Event::PaymentPathSuccessful {
@@ -1546,23 +1574,22 @@ mod tests {
                let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
                let route = TestRouter::route_for_value(final_value_msat);
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
 
                let inflight_map = invoice_payer.create_inflight_map();
                // First path check
-               assert_eq!(inflight_map.get(&(0, false)).unwrap().clone(), 94);
-               assert_eq!(inflight_map.get(&(1, true)).unwrap().clone(), 84);
-               assert_eq!(inflight_map.get(&(2, false)).unwrap().clone(), 64);
+               assert_eq!(inflight_map.0.get(&(0, false)).unwrap().clone(), 94);
+               assert_eq!(inflight_map.0.get(&(1, true)).unwrap().clone(), 84);
+               assert_eq!(inflight_map.0.get(&(2, false)).unwrap().clone(), 64);
 
                // Second path check
-               assert_eq!(inflight_map.get(&(3, false)).unwrap().clone(), 74);
-               assert_eq!(inflight_map.get(&(4, false)).unwrap().clone(), 64);
+               assert_eq!(inflight_map.0.get(&(3, false)).unwrap().clone(), 74);
+               assert_eq!(inflight_map.0.get(&(4, false)).unwrap().clone(), 64);
 
                invoice_payer.handle_event(&Event::PaymentPathSuccessful {
                        payment_id, payment_hash, path: route.paths[0].clone()
@@ -1570,13 +1597,13 @@ mod tests {
 
                let inflight_map = invoice_payer.create_inflight_map();
 
-               assert_eq!(inflight_map.get(&(0, false)), None);
-               assert_eq!(inflight_map.get(&(1, true)), None);
-               assert_eq!(inflight_map.get(&(2, false)), None);
+               assert_eq!(inflight_map.0.get(&(0, false)), None);
+               assert_eq!(inflight_map.0.get(&(1, true)), None);
+               assert_eq!(inflight_map.0.get(&(2, false)), None);
 
                // Second path should still be inflight
-               assert_eq!(inflight_map.get(&(3, false)).unwrap().clone(), 74);
-               assert_eq!(inflight_map.get(&(4, false)).unwrap().clone(), 64)
+               assert_eq!(inflight_map.0.get(&(3, false)).unwrap().clone(), 74);
+               assert_eq!(inflight_map.0.get(&(4, false)).unwrap().clone(), 64)
        }
 
        #[test]
@@ -1595,8 +1622,7 @@ mod tests {
                        .expect_send(Amount::ForInvoice(final_value_msat));
                let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
                let route = TestRouter::route_for_value(final_value_msat);
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        // 1st invoice, 1st path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        .expect_usage(ChannelUsage { amount_msat: 84, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
@@ -1610,11 +1636,11 @@ mod tests {
                        .expect_usage(ChannelUsage { amount_msat: 94, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        // 2nd invoice, 2nd path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 64, effective_capacity: EffectiveCapacity::Unknown } )
-                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 74, effective_capacity: EffectiveCapacity::Unknown } )
-               );
+                       .expect_usage(ChannelUsage { amount_msat: 74, inflight_htlc_msat: 74, effective_capacity: EffectiveCapacity::Unknown } );
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                // Succeed 1st path, leave 2nd path inflight
                let payment_id = invoice_payer.pay_invoice(&payment_invoice).unwrap();
@@ -1647,8 +1673,7 @@ mod tests {
                        .expect_send(Amount::OnRetry(final_value_msat / 2))
                        .expect_send(Amount::OnRetry(final_value_msat / 4));
                let final_value_msat = payment_invoice.amount_milli_satoshis().unwrap();
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new()
+               let scorer = TestScorer::new()
                        // 1st invoice, 1st path
                        .expect_usage(ChannelUsage { amount_msat: 64, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        .expect_usage(ChannelUsage { amount_msat: 84, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
@@ -1669,11 +1694,11 @@ mod tests {
                        .expect_usage(ChannelUsage { amount_msat: 46, inflight_htlc_msat: 0, effective_capacity: EffectiveCapacity::Unknown } )
                        // Retry 2, 2nd path
                        .expect_usage(ChannelUsage { amount_msat: 16, inflight_htlc_msat: 64 + 32, effective_capacity: EffectiveCapacity::Unknown } )
-                       .expect_usage(ChannelUsage { amount_msat: 26, inflight_htlc_msat: 74 + 32 + 10, effective_capacity: EffectiveCapacity::Unknown } )
-               );
+                       .expect_usage(ChannelUsage { amount_msat: 26, inflight_htlc_msat: 74 + 32 + 10, effective_capacity: EffectiveCapacity::Unknown } );
+               let router = TestRouter::new(scorer);
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(2));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(2));
 
                // Fail 1st path, leave 2nd path inflight
                let payment_id = Some(invoice_payer.pay_invoice(&payment_invoice).unwrap());
@@ -1722,18 +1747,17 @@ mod tests {
                                ]))
                        .expect_send(Amount::ForInvoice(final_value_msat));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                invoice_payer.pay_invoice(&invoice_to_pay).unwrap();
                let inflight_map = invoice_payer.create_inflight_map();
 
                // Only the second path, which failed with `MonitorUpdateInProgress` should be added to our
                // inflight map because retries are disabled.
-               assert_eq!(inflight_map.len(), 2);
+               assert_eq!(inflight_map.0.len(), 2);
        }
 
        #[test]
@@ -1754,22 +1778,27 @@ mod tests {
                                ]))
                        .expect_send(Amount::ForInvoice(final_value_msat));
 
-               let router = TestRouter {};
-               let scorer = RefCell::new(TestScorer::new());
+               let router = TestRouter::new(TestScorer::new());
                let logger = TestLogger::new();
                let invoice_payer =
-                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, Retry::Attempts(0));
+                       InvoicePayer::new(&payer, router, &logger, event_handler, Retry::Attempts(0));
 
                invoice_payer.pay_invoice(&invoice_to_pay).unwrap();
                let inflight_map = invoice_payer.create_inflight_map();
 
                // All paths successful, hence we check of the existence of all 5 hops.
-               assert_eq!(inflight_map.len(), 5);
+               assert_eq!(inflight_map.0.len(), 5);
        }
 
-       struct TestRouter;
+       struct TestRouter {
+               scorer: RefCell<TestScorer>,
+       }
 
        impl TestRouter {
+               fn new(scorer: TestScorer) -> Self {
+                       TestRouter { scorer: RefCell::new(scorer) }
+               }
+
                fn route_for_value(final_value_msat: u64) -> Route {
                        Route {
                                paths: vec![
@@ -1843,12 +1872,14 @@ mod tests {
        }
 
        impl Router for TestRouter {
-               fn find_route<S: Score>(
-                       &self, payer: &PublicKey, route_params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, scorer: &S
+               fn find_route(
+                       &self, payer: &PublicKey, route_params: &RouteParameters,
+                       _first_hops: Option<&[&ChannelDetails]>, inflight_htlcs: InFlightHtlcs
                ) -> Result<Route, LightningError> {
                        // Simulate calling the Scorer just as you would in find_route
                        let route = Self::route_for_value(route_params.final_value_msat);
+                       let mut locked_scorer = self.scorer.lock();
+                       let scorer = ScorerAccountingForInFlightHtlcs::new(locked_scorer.deref_mut(), inflight_htlcs);
                        for path in route.paths {
                                let mut aggregate_msat = 0u64;
                                for (idx, hop) in path.iter().rev().enumerate() {
@@ -1875,17 +1906,45 @@ mod tests {
                }
        }
 
+       impl ScoringRouter for TestRouter {
+               fn notify_payment_path_failed(&self, path: &[&RouteHop], short_channel_id: u64) {
+                       self.scorer.lock().payment_path_failed(path, short_channel_id);
+               }
+
+               fn notify_payment_path_successful(&self, path: &[&RouteHop]) {
+                       self.scorer.lock().payment_path_successful(path);
+               }
+
+               fn notify_payment_probe_successful(&self, path: &[&RouteHop]) {
+                       self.scorer.lock().probe_successful(path);
+               }
+
+               fn notify_payment_probe_failed(&self, path: &[&RouteHop], short_channel_id: u64) {
+                       self.scorer.lock().probe_failed(path, short_channel_id);
+               }
+       }
+
        struct FailingRouter;
 
        impl Router for FailingRouter {
-               fn find_route<S: Score>(
-                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+               fn find_route(
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _first_hops: Option<&[&ChannelDetails]>,
+                       _inflight_htlcs: InFlightHtlcs,
                ) -> Result<Route, LightningError> {
                        Err(LightningError { err: String::new(), action: ErrorAction::IgnoreError })
                }
        }
 
+       impl ScoringRouter for FailingRouter {
+               fn notify_payment_path_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
+       }
+
        struct TestScorer {
                event_expectations: Option<VecDeque<TestResult>>,
                scorer_expectations: RefCell<Option<VecDeque<ChannelUsage>>>,
@@ -1918,7 +1977,7 @@ mod tests {
 
        #[cfg(c_bindings)]
        impl lightning::util::ser::Writeable for TestScorer {
-               fn write<W: lightning::util::ser::Writer>(&self, _: &mut W) -> Result<(), std::io::Error> { unreachable!(); }
+               fn write<W: lightning::util::ser::Writer>(&self, _: &mut W) -> Result<(), lightning::io::Error> { unreachable!(); }
        }
 
        impl Score for TestScorer {
@@ -1947,7 +2006,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_failed call: {:?}", actual_path),
                                }
                        }
                }
@@ -1961,7 +2020,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
                                        },
-                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_successful call: {:?}", actual_path),
                                }
                        }
                }
@@ -1975,7 +2034,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_failed call: {:?}", actual_path),
                                }
                        }
                }
@@ -1988,7 +2047,7 @@ mod tests {
                                        Some(TestResult::PaymentSuccess { path }) => {
                                                panic!("Unexpected successful payment path: {:?}", path)
                                        },
-                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                                       None => panic!("Unexpected notify_payment_path_successful call: {:?}", actual_path),
                                }
                        }
                }
@@ -2061,13 +2120,13 @@ mod tests {
                        self
                }
 
-               fn check_attempts(&self) -> Result<PaymentId, PaymentSendFailure> {
+               fn check_attempts(&self) -> Result<(), PaymentSendFailure> {
                        let mut attempts = self.attempts.borrow_mut();
                        *attempts += 1;
 
                        match self.failing_on_attempt.borrow_mut().remove(&*attempts) {
                                Some(failure) => Err(failure),
-                               None => Ok(PaymentId([1; 32])),
+                               None => Ok(())
                        }
                }
 
@@ -2105,15 +2164,15 @@ mod tests {
 
                fn send_payment(
                        &self, route: &Route, _payment_hash: PaymentHash,
-                       _payment_secret: &Option<PaymentSecret>
-               ) -> Result<PaymentId, PaymentSendFailure> {
+                       _payment_secret: &Option<PaymentSecret>, _payment_id: PaymentId,
+               ) -> Result<(), PaymentSendFailure> {
                        self.check_value_msats(Amount::ForInvoice(route.get_total_amount()));
                        self.check_attempts()
                }
 
                fn send_spontaneous_payment(
-                       &self, route: &Route, _payment_preimage: PaymentPreimage,
-               ) -> Result<PaymentId, PaymentSendFailure> {
+                       &self, route: &Route, _payment_preimage: PaymentPreimage, _payment_id: PaymentId,
+               ) -> Result<(), PaymentSendFailure> {
                        self.check_value_msats(Amount::Spontaneous(route.get_total_amount()));
                        self.check_attempts()
                }
@@ -2122,7 +2181,7 @@ mod tests {
                        &self, route: &Route, _payment_id: PaymentId
                ) -> Result<(), PaymentSendFailure> {
                        self.check_value_msats(Amount::OnRetry(route.get_total_amount()));
-                       self.check_attempts().map(|_| ())
+                       self.check_attempts()
                }
 
                fn abandon_payment(&self, _payment_id: PaymentId) { }
@@ -2132,13 +2191,22 @@ mod tests {
        struct ManualRouter(RefCell<VecDeque<Result<Route, LightningError>>>);
 
        impl Router for ManualRouter {
-               fn find_route<S: Score>(
-                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
-                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+               fn find_route(
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _first_hops: Option<&[&ChannelDetails]>,
+                       _inflight_htlcs: InFlightHtlcs
                ) -> Result<Route, LightningError> {
                        self.0.borrow_mut().pop_front().unwrap()
                }
        }
+       impl ScoringRouter for ManualRouter {
+               fn notify_payment_path_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
+
+               fn notify_payment_path_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_successful(&self, _path: &[&RouteHop]) {}
+
+               fn notify_payment_probe_failed(&self, _path: &[&RouteHop], _short_channel_id: u64) {}
+       }
        impl ManualRouter {
                fn expect_find_route(&self, result: Result<Route, LightningError>) {
                        self.0.borrow_mut().push_back(result);
@@ -2193,12 +2261,11 @@ mod tests {
                router.expect_find_route(Ok(route.clone()));
 
                let event_handler = |_: &_| { panic!(); };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
-                       &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),
-                       duration_since_epoch(), 3600).unwrap())
+                       &nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::Bitcoin,
+                       Some(100_010_000), "Invoice".to_string(), duration_since_epoch(), 3600).unwrap())
                        .is_ok());
                let htlc_msgs = nodes[0].node.get_and_clear_pending_msg_events();
                assert_eq!(htlc_msgs.len(), 2);
@@ -2239,12 +2306,11 @@ mod tests {
                router.expect_find_route(Ok(route.clone()));
 
                let event_handler = |_: &_| { panic!(); };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
-                       &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),
-                       duration_since_epoch(), 3600).unwrap())
+                       &nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::Bitcoin,
+                       Some(100_010_000), "Invoice".to_string(), duration_since_epoch(), 3600).unwrap())
                        .is_ok());
                let htlc_msgs = nodes[0].node.get_and_clear_pending_msg_events();
                assert_eq!(htlc_msgs.len(), 2);
@@ -2321,12 +2387,11 @@ mod tests {
                        let event_checker = expected_events.borrow_mut().pop_front().unwrap();
                        event_checker(event);
                };
-               let scorer = RefCell::new(TestScorer::new());
-               let invoice_payer = InvoicePayer::new(nodes[0].node, router, &scorer, nodes[0].logger, event_handler, Retry::Attempts(1));
+               let invoice_payer = InvoicePayer::new(nodes[0].node, router, nodes[0].logger, event_handler, Retry::Attempts(1));
 
                assert!(invoice_payer.pay_invoice(&create_invoice_from_channelmanager_and_duration_since_epoch(
-                       &nodes[1].node, nodes[1].keys_manager, Currency::Bitcoin, Some(100_010_000), "Invoice".to_string(),
-                       duration_since_epoch(), 3600).unwrap())
+                       &nodes[1].node, nodes[1].keys_manager, nodes[1].logger, Currency::Bitcoin,
+                       Some(100_010_000), "Invoice".to_string(), duration_since_epoch(), 3600).unwrap())
                        .is_ok());
                let htlc_updates = SendEvent::from_node(&nodes[0]);
                check_added_monitors!(nodes[0], 1);