Merge pull request #1208 from TheBlueMatt/2021-12-less-force-close
[rust-lightning] / lightning-invoice / src / payment.rs
index 1a7242b8ef6961ac0f6d60da1b929ffba0a1eb81..e785bb39264130a4895a25fd663e1b42560fd665 100644 (file)
@@ -7,12 +7,17 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-//! A module for paying Lightning invoices.
+//! A module for paying Lightning invoices and sending spontaneous payments.
 //!
-//! Defines an [`InvoicePayer`] utility for paying invoices, parameterized by [`Payer`] and
+//! Defines an [`InvoicePayer`] utility for sending payments, parameterized by [`Payer`] and
 //! [`Router`] traits. Implementations of [`Payer`] provide the payer's node id, channels, and means
 //! to send a payment over a [`Route`]. Implementations of [`Router`] find a [`Route`] between payer
-//! and payee using information provided by the payer and from the payee's [`Invoice`].
+//! 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`] 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;
 //! #
-//! # use lightning::ln::{PaymentHash, PaymentSecret};
+//! # use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 //! # use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 //! # use lightning::ln::msgs::LightningError;
-//! # use lightning::routing;
+//! # use lightning::routing::scoring::Score;
 //! # use lightning::routing::network_graph::NodeId;
 //! # use lightning::routing::router::{Route, RouteHop, RouteParameters};
 //! # 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, RetryAttempts, Router};
 //! # use secp256k1::key::PublicKey;
 //! #     fn send_payment(
 //! #         &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>
 //! #     ) -> Result<PaymentId, PaymentSendFailure> { unimplemented!() }
+//! #     fn send_spontaneous_payment(
+//! #         &self, route: &Route, payment_preimage: PaymentPreimage
+//! #     ) -> Result<PaymentId, PaymentSendFailure> { unimplemented!() }
 //! #     fn retry_payment(
 //! #         &self, route: &Route, payment_id: PaymentId
 //! #     ) -> Result<(), PaymentSendFailure> { unimplemented!() }
 //! # }
 //! #
-//! # struct FakeRouter {};
-//! # impl<S: routing::Score> Router<S> for FakeRouter {
+//! # struct FakeRouter {}
+//! # impl<S: Score> Router<S> for FakeRouter {
 //! #     fn find_route(
-//! #         &self, payer: &PublicKey, params: &RouteParameters,
+//! #         &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
 //! #         first_hops: Option<&[&ChannelDetails]>, scorer: &S
 //! #     ) -> Result<Route, LightningError> { unimplemented!() }
 //! # }
 //! #
-//! # struct FakeScorer {};
-//! # impl routing::Score for FakeScorer {
+//! # struct FakeScorer {}
+//! # impl Writeable for FakeScorer {
+//! #     fn write<W: Writer>(&self, w: &mut W) -> Result<(), std::io::Error> { unimplemented!(); }
+//! # }
+//! # impl Score for FakeScorer {
 //! #     fn channel_penalty_msat(
-//! #         &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId
+//! #         &self, _short_channel_id: u64, _send_amt: u64, _chan_amt: Option<u64>, _source: &NodeId, _target: &NodeId
 //! #     ) -> u64 { 0 }
 //! #     fn payment_path_failed(&mut self, _path: &[&RouteHop], _short_channel_id: u64) {}
+//! #     fn payment_path_successful(&mut self, _path: &[&RouteHop]) {}
 //! # }
 //! #
-//! # struct FakeLogger {};
+//! # struct FakeLogger {}
 //! # impl Logger for FakeLogger {
 //! #     fn log(&self, record: &Record) { unimplemented!() }
 //! # }
 //! let invoice_payer = InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 //!
 //! let invoice = "...";
-//! let invoice = invoice.parse::<Invoice>().unwrap();
-//! invoice_payer.pay_invoice(&invoice).unwrap();
+//! if let Ok(invoice) = invoice.parse::<Invoice>() {
+//!     invoice_payer.pay_invoice(&invoice).unwrap();
 //!
 //! # let event_provider = FakeEventProvider {};
-//! loop {
-//!     event_provider.process_pending_events(&invoice_payer);
+//!     loop {
+//!         event_provider.process_pending_events(&invoice_payer);
+//!     }
 //! }
 //! # }
 //! ```
 use crate::Invoice;
 
 use bitcoin_hashes::Hash;
+use bitcoin_hashes::sha256::Hash as Sha256;
 
-use lightning::ln::{PaymentHash, PaymentSecret};
+use lightning::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::ln::channelmanager::{ChannelDetails, PaymentId, PaymentSendFailure};
 use lightning::ln::msgs::LightningError;
-use lightning::routing;
-use lightning::routing::{LockableScore, Score};
+use lightning::routing::scoring::{LockableScore, Score};
 use lightning::routing::router::{Payee, Route, RouteParameters};
 use lightning::util::events::{Event, EventHandler};
 use lightning::util::logger::Logger;
@@ -130,12 +144,16 @@ use std::ops::Deref;
 use std::sync::Mutex;
 use std::time::{Duration, SystemTime};
 
-/// A utility for paying [`Invoice]`s.
+/// A utility for paying [`Invoice`]s and sending spontaneous payments.
+///
+/// See [module-level documentation] for details.
+///
+/// [module-level documentation]: crate::payment
 pub struct InvoicePayer<P: Deref, R, S: Deref, L: Deref, E>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
        E: EventHandler,
 {
@@ -162,16 +180,21 @@ pub trait Payer {
                &self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>
        ) -> Result<PaymentId, 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>;
+
        /// Retries a failed payment path for the [`PaymentId`] using the given [`Route`].
        fn retry_payment(&self, route: &Route, payment_id: PaymentId) -> Result<(), PaymentSendFailure>;
 }
 
 /// A trait defining behavior for routing an [`Invoice`] payment.
-pub trait Router<S: routing::Score> {
+pub trait Router<S: Score> {
        /// Finds a [`Route`] between `payer` and `payee` for a payment with the given values.
        fn find_route(
-               &self, payer: &PublicKey, params: &RouteParameters, first_hops: Option<&[&ChannelDetails]>,
-               scorer: &S
+               &self, payer: &PublicKey, params: &RouteParameters, payment_hash: &PaymentHash,
+               first_hops: Option<&[&ChannelDetails]>, scorer: &S
        ) -> Result<Route, LightningError>;
 }
 
@@ -197,8 +220,8 @@ pub enum PaymentError {
 impl<P: Deref, R, S: Deref, L: Deref, E> InvoicePayer<P, R, S, L, E>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
        E: EventHandler,
 {
@@ -273,13 +296,43 @@ where
                        final_cltv_expiry_delta: invoice.min_final_cltv_expiry() as u32,
                };
 
-               self.pay_internal(&params, payment_hash, &payment_secret)
+               let send_payment = |route: &Route| {
+                       self.payer.send_payment(route, payment_hash, &payment_secret)
+               };
+               self.pay_internal(&params, payment_hash, send_payment)
+                       .map_err(|e| { self.payment_cache.lock().unwrap().remove(&payment_hash); e })
+       }
+
+       /// 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.
+       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());
+               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(0),
+               };
+
+               let params = RouteParameters {
+                       payee: Payee::for_keysend(pubkey),
+                       final_value_msat: amount_msats,
+                       final_cltv_expiry_delta,
+               };
+
+               let send_payment = |route: &Route| {
+                       self.payer.send_spontaneous_payment(route, payment_preimage)
+               };
+               self.pay_internal(&params, payment_hash, send_payment)
                        .map_err(|e| { self.payment_cache.lock().unwrap().remove(&payment_hash); e })
        }
 
-       fn pay_internal(
-               &self, params: &RouteParameters, payment_hash: PaymentHash,
-               payment_secret: &Option<PaymentSecret>,
+       fn pay_internal<F: FnOnce(&Route) -> Result<PaymentId, PaymentSendFailure> + Copy>(
+               &self, params: &RouteParameters, payment_hash: PaymentHash, send_payment: F,
        ) -> Result<PaymentId, PaymentError> {
                if has_expired(params) {
                        log_trace!(self.logger, "Invoice expired prior to send for payment {}", log_bytes!(payment_hash.0));
@@ -289,13 +342,11 @@ where
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
                let route = self.router.find_route(
-                       &payer,
-                       params,
-                       Some(&first_hops.iter().collect::<Vec<_>>()),
-                       &self.scorer.lock(),
+                       &payer, params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
+                       &self.scorer.lock()
                ).map_err(|e| PaymentError::Routing(e))?;
 
-               match self.payer.send_payment(&route, payment_hash, payment_secret) {
+               match send_payment(&route) {
                        Ok(payment_id) => Ok(payment_id),
                        Err(e) => match e {
                                PaymentSendFailure::ParameterError(_) => Err(e),
@@ -308,7 +359,7 @@ where
                                        } else {
                                                *retry_count += 1;
                                                std::mem::drop(payment_cache);
-                                               Ok(self.pay_internal(params, payment_hash, payment_secret)?)
+                                               Ok(self.pay_internal(params, payment_hash, send_payment)?)
                                        }
                                },
                                PaymentSendFailure::PartialFailure { failed_paths_retry, payment_id, .. } => {
@@ -352,7 +403,10 @@ where
 
                let payer = self.payer.node_id();
                let first_hops = self.payer.first_hops();
-               let route = self.router.find_route(&payer, &params, Some(&first_hops.iter().collect::<Vec<_>>()), &self.scorer.lock());
+               let route = self.router.find_route(
+                       &payer, &params, &payment_hash, Some(&first_hops.iter().collect::<Vec<_>>()),
+                       &self.scorer.lock()
+               );
                if route.is_err() {
                        log_trace!(self.logger, "Failed to find a route for payment {}; not retrying (attempts: {})", log_bytes!(payment_hash.0), attempts);
                        return Err(());
@@ -400,8 +454,8 @@ fn has_expired(params: &RouteParameters) -> bool {
 impl<P: Deref, R, S: Deref, L: Deref, E> EventHandler for InvoicePayer<P, R, S, L, E>
 where
        P::Target: Payer,
-       R: for <'a> Router<<<S as Deref>::Target as routing::LockableScore<'a>>::Locked>,
-       S::Target: for <'a> routing::LockableScore<'a>,
+       R: for <'a> Router<<<S as Deref>::Target as LockableScore<'a>>::Locked>,
+       S::Target: for <'a> LockableScore<'a>,
        L::Target: Logger,
        E: EventHandler,
 {
@@ -429,6 +483,10 @@ where
 
                                if *all_paths_failed { self.payment_cache.lock().unwrap().remove(payment_hash); }
                        },
+                       Event::PaymentPathSuccessful { path, .. } => {
+                               let path = path.iter().collect::<Vec<_>>();
+                               self.scorer.lock().payment_path_successful(&path);
+                       },
                        Event::PaymentSent { payment_hash, .. } => {
                                let mut payment_cache = self.payment_cache.lock().unwrap();
                                let attempts = payment_cache
@@ -514,6 +572,10 @@ mod tests {
                        .unwrap()
        }
 
+       fn pubkey() -> PublicKey {
+               PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap()
+       }
+
        #[test]
        fn pays_invoice_on_first_attempt() {
                let event_handled = core::cell::RefCell::new(false);
@@ -522,8 +584,9 @@ mod tests {
                let payment_preimage = PaymentPreimage([1; 32]);
                let invoice = invoice(payment_preimage);
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
-               let payer = TestPayer::new();
+               let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let router = TestRouter {};
                let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
@@ -551,8 +614,8 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new()
-                       .expect_value_msat(final_value_msat)
-                       .expect_value_msat(final_value_msat / 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 logger = TestLogger::new();
@@ -583,6 +646,30 @@ mod tests {
                assert_eq!(*payer.attempts.borrow(), 2);
        }
 
+       #[test]
+       fn pays_invoice_on_partial_failure() {
+               let event_handler = |_: &_| { panic!() };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let retry = TestRouter::retry_for_invoice(&invoice);
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               let payer = TestPayer::new()
+                       .fails_with_partial_failure(retry.clone(), OnAttempt(1))
+                       .fails_with_partial_failure(retry, OnAttempt(2))
+                       .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 logger = TestLogger::new();
+               let invoice_payer =
+                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
+
+               assert!(invoice_payer.pay_invoice(&invoice).is_ok());
+       }
+
        #[test]
        fn retries_payment_path_for_unknown_payment() {
                let event_handled = core::cell::RefCell::new(false);
@@ -593,7 +680,9 @@ mod tests {
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
-               let payer = TestPayer::new();
+               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 logger = TestLogger::new();
@@ -636,9 +725,9 @@ mod tests {
                let final_value_msat = invoice.amount_milli_satoshis().unwrap();
 
                let payer = TestPayer::new()
-                       .expect_value_msat(final_value_msat)
-                       .expect_value_msat(final_value_msat / 2)
-                       .expect_value_msat(final_value_msat / 2);
+                       .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 logger = TestLogger::new();
@@ -688,15 +777,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -739,15 +830,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -781,7 +874,8 @@ mod tests {
 
                let payer = TestPayer::new()
                        .fails_on_attempt(2)
-                       .expect_value_msat(final_value_msat);
+                       .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 logger = TestLogger::new();
@@ -811,15 +905,17 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
                assert_eq!(*payer.attempts.borrow(), 1);
 
@@ -843,15 +939,19 @@ mod tests {
                let event_handled = core::cell::RefCell::new(false);
                let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
 
-               let payer = TestPayer::new();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(0));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                let payment_id = Some(invoice_payer.pay_invoice(&invoice).unwrap());
 
                // Cannot repay an invoice pending payment.
@@ -902,15 +1002,19 @@ mod tests {
 
        #[test]
        fn fails_paying_invoice_with_sending_errors() {
-               let payer = TestPayer::new().fails_on_attempt(1);
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+
+               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 logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, |_: &_| {}, RetryAttempts(0));
 
-               let payment_preimage = PaymentPreimage([1; 32]);
-               let invoice = invoice(payment_preimage);
                match invoice_payer.pay_invoice(&invoice) {
                        Err(PaymentError::Sending(_)) => {},
                        Err(_) => panic!("unexpected error"),
@@ -928,7 +1032,7 @@ mod tests {
                let payment_hash = PaymentHash(invoice.payment_hash().clone().into_inner());
                let final_value_msat = 100;
 
-               let payer = TestPayer::new().expect_value_msat(final_value_msat);
+               let payer = TestPayer::new().expect_send(Amount::ForInvoice(final_value_msat));
                let router = TestRouter {};
                let scorer = RefCell::new(TestScorer::new());
                let logger = TestLogger::new();
@@ -969,6 +1073,57 @@ mod tests {
                }
        }
 
+       #[test]
+       fn pays_pubkey_with_amount() {
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let pubkey = pubkey();
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+               let final_value_msat = 100;
+               let final_cltv_expiry_delta = 42;
+
+               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 logger = TestLogger::new();
+               let invoice_payer =
+                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
+
+               let payment_id = Some(invoice_payer.pay_pubkey(
+                               pubkey, payment_preimage, final_value_msat, final_cltv_expiry_delta
+                       ).unwrap());
+               assert_eq!(*payer.attempts.borrow(), 1);
+
+               let retry = RouteParameters {
+                       payee: Payee::for_keysend(pubkey),
+                       final_value_msat,
+                       final_cltv_expiry_delta,
+               };
+               let event = Event::PaymentPathFailed {
+                       payment_id,
+                       payment_hash,
+                       network_update: None,
+                       rejected_by_dest: false,
+                       all_paths_failed: false,
+                       path: vec![],
+                       short_channel_id: None,
+                       retry: Some(retry),
+               };
+               invoice_payer.handle_event(&event);
+               assert_eq!(*event_handled.borrow(), false);
+               assert_eq!(*payer.attempts.borrow(), 2);
+
+               invoice_payer.handle_event(&Event::PaymentSent {
+                       payment_id, payment_preimage, payment_hash, fee_paid_msat: None
+               });
+               assert_eq!(*event_handled.borrow(), true);
+               assert_eq!(*payer.attempts.borrow(), 2);
+       }
+
        #[test]
        fn scores_failed_channel() {
                let event_handled = core::cell::RefCell::new(false);
@@ -982,9 +1137,13 @@ mod tests {
                let short_channel_id = Some(path[0].short_channel_id);
 
                // Expect that scorer is given short_channel_id upon handling the event.
-               let payer = TestPayer::new();
+               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_channel_failure(short_channel_id.unwrap()));
+               let scorer = RefCell::new(TestScorer::new().expect(PaymentPath::Failure {
+                       path: path.clone(), short_channel_id: path[0].short_channel_id,
+               }));
                let logger = TestLogger::new();
                let invoice_payer =
                        InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
@@ -1003,6 +1162,39 @@ mod tests {
                invoice_payer.handle_event(&event);
        }
 
+       #[test]
+       fn scores_successful_channels() {
+               let event_handled = core::cell::RefCell::new(false);
+               let event_handler = |_: &_| { *event_handled.borrow_mut() = true; };
+
+               let payment_preimage = PaymentPreimage([1; 32]);
+               let invoice = invoice(payment_preimage);
+               let payment_hash = Some(PaymentHash(invoice.payment_hash().clone().into_inner()));
+               let final_value_msat = invoice.amount_milli_satoshis().unwrap();
+               let route = TestRouter::route_for_value(final_value_msat);
+
+               // 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()
+                       .expect(PaymentPath::Success { path: route.paths[0].clone() })
+                       .expect(PaymentPath::Success { path: route.paths[1].clone() })
+               );
+               let logger = TestLogger::new();
+               let invoice_payer =
+                       InvoicePayer::new(&payer, router, &scorer, &logger, event_handler, RetryAttempts(2));
+
+               let payment_id = invoice_payer.pay_invoice(&invoice).unwrap();
+               let event = Event::PaymentPathSuccessful {
+                       payment_id, payment_hash, path: route.paths[0].clone()
+               };
+               invoice_payer.handle_event(&event);
+               let event = Event::PaymentPathSuccessful {
+                       payment_id, payment_hash, path: route.paths[1].clone()
+               };
+               invoice_payer.handle_event(&event);
+       }
+
        struct TestRouter;
 
        impl TestRouter {
@@ -1046,13 +1238,10 @@ mod tests {
                }
        }
 
-       impl<S: routing::Score> Router<S> for TestRouter {
+       impl<S: Score> Router<S> for TestRouter {
                fn find_route(
-                       &self,
-                       _payer: &PublicKey,
-                       params: &RouteParameters,
-                       _first_hops: Option<&[&ChannelDetails]>,
-                       _scorer: &S,
+                       &self, _payer: &PublicKey, params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
                ) -> Result<Route, LightningError> {
                        Ok(Route {
                                payee: Some(params.payee.clone()), ..Self::route_for_value(params.final_value_msat)
@@ -1062,43 +1251,74 @@ mod tests {
 
        struct FailingRouter;
 
-       impl<S: routing::Score> Router<S> for FailingRouter {
+       impl<S: Score> Router<S> for FailingRouter {
                fn find_route(
-                       &self,
-                       _payer: &PublicKey,
-                       _params: &RouteParameters,
-                       _first_hops: Option<&[&ChannelDetails]>,
-                       _scorer: &S,
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
                ) -> Result<Route, LightningError> {
                        Err(LightningError { err: String::new(), action: ErrorAction::IgnoreError })
                }
        }
 
        struct TestScorer {
-               expectations: VecDeque<u64>,
+               expectations: Option<VecDeque<PaymentPath>>,
+       }
+
+       #[derive(Debug)]
+       enum PaymentPath {
+               Failure { path: Vec<RouteHop>, short_channel_id: u64 },
+               Success { path: Vec<RouteHop> },
        }
 
        impl TestScorer {
                fn new() -> Self {
                        Self {
-                               expectations: VecDeque::new(),
+                               expectations: None,
                        }
                }
 
-               fn expect_channel_failure(mut self, short_channel_id: u64) -> Self {
-                       self.expectations.push_back(short_channel_id);
+               fn expect(mut self, expectation: PaymentPath) -> Self {
+                       self.expectations.get_or_insert_with(|| VecDeque::new()).push_back(expectation);
                        self
                }
        }
 
-       impl routing::Score for TestScorer {
+       #[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!(); }
+       }
+
+       impl Score for TestScorer {
                fn channel_penalty_msat(
-                       &self, _short_channel_id: u64, _source: &NodeId, _target: &NodeId
+                       &self, _short_channel_id: u64, _send_amt: u64, _chan_amt: Option<u64>, _source: &NodeId, _target: &NodeId
                ) -> u64 { 0 }
 
-               fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
-                       if let Some(expected_short_channel_id) = self.expectations.pop_front() {
-                               assert_eq!(short_channel_id, expected_short_channel_id);
+               fn payment_path_failed(&mut self, actual_path: &[&RouteHop], actual_short_channel_id: u64) {
+                       if let Some(expectations) = &mut self.expectations {
+                               match expectations.pop_front() {
+                                       Some(PaymentPath::Failure { path, short_channel_id }) => {
+                                               assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
+                                               assert_eq!(actual_short_channel_id, short_channel_id);
+                                       },
+                                       Some(PaymentPath::Success { path }) => {
+                                               panic!("Unexpected successful payment path: {:?}", path)
+                                       },
+                                       None => panic!("Unexpected payment_path_failed call: {:?}", actual_path),
+                               }
+                       }
+               }
+
+               fn payment_path_successful(&mut self, actual_path: &[&RouteHop]) {
+                       if let Some(expectations) = &mut self.expectations {
+                               match expectations.pop_front() {
+                                       Some(PaymentPath::Failure { path, .. }) => {
+                                               panic!("Unexpected payment path failure: {:?}", path)
+                                       },
+                                       Some(PaymentPath::Success { path }) => {
+                                               assert_eq!(actual_path, &path.iter().collect::<Vec<_>>()[..]);
+                                       },
+                                       None => panic!("Unexpected payment_path_successful call: {:?}", actual_path),
+                               }
                        }
                }
        }
@@ -1109,55 +1329,77 @@ mod tests {
                                return;
                        }
 
-                       if !self.expectations.is_empty() {
-                               panic!("Unsatisfied channel failure expectations: {:?}", self.expectations);
+                       if let Some(expectations) = &self.expectations {
+                               if !expectations.is_empty() {
+                                       panic!("Unsatisfied scorer expectations: {:?}", expectations);
+                               }
                        }
                }
        }
 
        struct TestPayer {
-               expectations: core::cell::RefCell<VecDeque<u64>>,
+               expectations: core::cell::RefCell<VecDeque<Amount>>,
                attempts: core::cell::RefCell<usize>,
-               failing_on_attempt: Option<usize>,
+               failing_on_attempt: core::cell::RefCell<HashMap<usize, PaymentSendFailure>>,
+       }
+
+       #[derive(Clone, Debug, PartialEq, Eq)]
+       enum Amount {
+               ForInvoice(u64),
+               Spontaneous(u64),
+               OnRetry(u64),
        }
 
+       struct OnAttempt(usize);
+
        impl TestPayer {
                fn new() -> Self {
                        Self {
                                expectations: core::cell::RefCell::new(VecDeque::new()),
                                attempts: core::cell::RefCell::new(0),
-                               failing_on_attempt: None,
+                               failing_on_attempt: core::cell::RefCell::new(HashMap::new()),
                        }
                }
 
-               fn expect_value_msat(self, value_msat: u64) -> Self {
+               fn expect_send(self, value_msat: Amount) -> Self {
                        self.expectations.borrow_mut().push_back(value_msat);
                        self
                }
 
                fn fails_on_attempt(self, attempt: usize) -> Self {
-                       Self {
-                               expectations: core::cell::RefCell::new(self.expectations.borrow().clone()),
-                               attempts: core::cell::RefCell::new(0),
-                               failing_on_attempt: Some(attempt),
-                       }
+                       let failure = PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed);
+                       self.fails_with(failure, OnAttempt(attempt))
                }
 
-               fn check_attempts(&self) -> bool {
+               fn fails_with_partial_failure(self, retry: RouteParameters, attempt: OnAttempt) -> Self {
+                       self.fails_with(PaymentSendFailure::PartialFailure {
+                               results: vec![],
+                               failed_paths_retry: Some(retry),
+                               payment_id: PaymentId([1; 32]),
+                       }, attempt)
+               }
+
+               fn fails_with(self, failure: PaymentSendFailure, attempt: OnAttempt) -> Self {
+                       self.failing_on_attempt.borrow_mut().insert(attempt.0, failure);
+                       self
+               }
+
+               fn check_attempts(&self) -> Result<PaymentId, PaymentSendFailure> {
                        let mut attempts = self.attempts.borrow_mut();
                        *attempts += 1;
-                       match self.failing_on_attempt {
-                               None => true,
-                               Some(attempt) if attempt != *attempts => true,
-                               Some(_) => false,
+
+                       match self.failing_on_attempt.borrow_mut().remove(&*attempts) {
+                               Some(failure) => Err(failure),
+                               None => Ok(PaymentId([1; 32])),
                        }
                }
 
-               fn check_value_msats(&self, route: &Route) {
+               fn check_value_msats(&self, actual_value_msats: Amount) {
                        let expected_value_msats = self.expectations.borrow_mut().pop_front();
                        if let Some(expected_value_msats) = expected_value_msats {
-                               let actual_value_msats = route.get_total_amount();
                                assert_eq!(actual_value_msats, expected_value_msats);
+                       } else {
+                               panic!("Unexpected amount: {:?}", actual_value_msats);
                        }
                }
        }
@@ -1185,37 +1427,36 @@ mod tests {
                }
 
                fn send_payment(
-                       &self,
-                       route: &Route,
-                       _payment_hash: PaymentHash,
+                       &self, route: &Route, _payment_hash: PaymentHash,
                        _payment_secret: &Option<PaymentSecret>
                ) -> Result<PaymentId, PaymentSendFailure> {
-                       if self.check_attempts() {
-                               self.check_value_msats(route);
-                               Ok(PaymentId([1; 32]))
-                       } else {
-                               Err(PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed))
-                       }
+                       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.check_value_msats(Amount::Spontaneous(route.get_total_amount()));
+                       self.check_attempts()
                }
 
                fn retry_payment(
                        &self, route: &Route, _payment_id: PaymentId
                ) -> Result<(), PaymentSendFailure> {
-                       if self.check_attempts() {
-                               self.check_value_msats(route);
-                               Ok(())
-                       } else {
-                               Err(PaymentSendFailure::ParameterError(APIError::MonitorUpdateFailed))
-                       }
+                       self.check_value_msats(Amount::OnRetry(route.get_total_amount()));
+                       self.check_attempts().map(|_| ())
                }
        }
 
        // *** Full Featured Functional Tests with a Real ChannelManager ***
        struct ManualRouter(RefCell<VecDeque<Result<Route, LightningError>>>);
 
-       impl<S: routing::Score> Router<S> for ManualRouter {
-               fn find_route(&self, _payer: &PublicKey, _params: &RouteParameters, _first_hops: Option<&[&ChannelDetails]>, _scorer: &S)
-               -> Result<Route, LightningError> {
+       impl<S: Score> Router<S> for ManualRouter {
+               fn find_route(
+                       &self, _payer: &PublicKey, _params: &RouteParameters, _payment_hash: &PaymentHash,
+                       _first_hops: Option<&[&ChannelDetails]>, _scorer: &S
+               ) -> Result<Route, LightningError> {
                        self.0.borrow_mut().pop_front().unwrap()
                }
        }