Mono-hop unidirectional payments

src/DotNetLightning.Core/Channel/Channel.fs

@@ -446,6 +446,32 @@ module Channel =
                 [] |> Ok
 
         // ---------- normal operation ---------
+        | ChannelState.Normal state, MonoHopUnidirectionalPayment op when state.LocalShutdown.IsSome || state.RemoteShutdown.IsSome ->
+            sprintf "Could not send mono-hop unidirectional payment %A since shutdown is already in progress." op
+            |> apiMisuse
+        | ChannelState.Normal state, MonoHopUnidirectionalPayment op ->
+            result {
+                let payment: MonoHopUnidirectionalPaymentMsg = {
+                    ChannelId = state.Commitments.ChannelId
+                    Amount = op.Amount
+                }
+                let commitments1 = state.Commitments.AddLocalProposal(payment)
+
+                let remoteCommit1 =
+                    match commitments1.RemoteNextCommitInfo with
+                    | RemoteNextCommitInfo.Waiting info -> info.NextRemoteCommit
+                    | RemoteNextCommitInfo.Revoked _info -> commitments1.RemoteCommit
+                let! reduced = remoteCommit1.Spec.Reduce(commitments1.RemoteChanges.ACKed, commitments1.LocalChanges.Proposed) |> expectTransactionError
+                do! Validation.checkOurMonoHopUnidirectionalPaymentIsAcceptableWithCurrentSpec reduced commitments1 payment
+                return [ WeAcceptedOperationMonoHopUnidirectionalPayment(payment, commitments1) ]
+            }
+        | ChannelState.Normal state, ApplyMonoHopUnidirectionalPayment msg ->
+            result {
+                let commitments1 = state.Commitments.AddRemoteProposal(msg)
+                let! reduced = commitments1.LocalCommit.Spec.Reduce (commitments1.LocalChanges.ACKed, commitments1.RemoteChanges.Proposed) |> expectTransactionError
+                do! Validation.checkTheirMonoHopUnidirectionalPaymentIsAcceptableWithCurrentSpec reduced commitments1 msg
+                return [ WeAcceptedMonoHopUnidirectionalPayment commitments1 ]
+            }
         | ChannelState.Normal state, AddHTLC op when state.LocalShutdown.IsSome || state.RemoteShutdown.IsSome ->
             sprintf "Could not add new HTLC %A since shutdown is already in progress." op
             |> apiMisuse
@@ -551,8 +577,8 @@ module Channel =
                                                  RemoteCommit = theirNextCommit
                                                  RemoteNextCommitInfo = RemoteNextCommitInfo.Revoked msg.NextPerCommitmentPoint
                                                  RemotePerCommitmentSecrets = remotePerCommitmentSecrets }
-                    let _result = Ok [ WeAcceptedRevokeAndACK commitments1 ]
-                    failwith "needs update"
+                    Console.WriteLine("WARNING: revocation is not implemented yet")
+                    Ok [ WeAcceptedRevokeAndACK(commitments1) ]
 
         | ChannelState.Normal state, ChannelCommand.Close cmd ->
             let localSPK = cmd.ScriptPubKey |> Option.defaultValue (state.Commitments.LocalParams.DefaultFinalScriptPubKey)
@@ -832,8 +858,12 @@ module Channel =
             { c with State = ChannelState.Normal data }
 
         // ----- normal operation --------
+        | WeAcceptedOperationMonoHopUnidirectionalPayment(_, newCommitments), ChannelState.Normal normalData ->
+            { c with State = ChannelState.Normal({ normalData with Commitments = newCommitments }) }
         | WeAcceptedOperationAddHTLC(_, newCommitments), ChannelState.Normal d ->
             { c with State = ChannelState.Normal({ d with Commitments = newCommitments }) }
+        | WeAcceptedMonoHopUnidirectionalPayment(newCommitments), ChannelState.Normal normalData ->
+            { c with State = ChannelState.Normal({ normalData with Commitments = newCommitments }) }
         | WeAcceptedUpdateAddHTLC(newCommitments), ChannelState.Normal d ->
             { c with State = ChannelState.Normal({ d with Commitments = newCommitments }) }
 

src/DotNetLightning.Core/Channel/ChannelError.fs

@@ -38,6 +38,7 @@ type ChannelError =
     // --- case they sent unacceptable msg ---
     | InvalidOpenChannel of InvalidOpenChannelError
     | InvalidAcceptChannel of InvalidAcceptChannelError
+    | InvalidMonoHopUnidirectionalPayment of InvalidMonoHopUnidirectionalPaymentError
     | InvalidUpdateAddHTLC of InvalidUpdateAddHTLCError
     | InvalidRevokeAndACK of InvalidRevokeAndACKError
     | InvalidUpdateFee of InvalidUpdateFeeError
@@ -71,6 +72,7 @@ type ChannelError =
         | TheyCannotAffordFee (_, _, _) -> Close
         | InvalidOpenChannel _ -> DistrustPeer
         | InvalidAcceptChannel _ -> DistrustPeer
+        | InvalidMonoHopUnidirectionalPayment _ -> Close
         | InvalidUpdateAddHTLC _ -> Close
         | InvalidRevokeAndACK _ -> Close
         | InvalidUpdateFee _ -> Close
@@ -141,6 +143,8 @@ type ChannelError =
             sprintf "Cannot close channel: %s" msg
         | InvalidOperationAddHTLC invalidOperationAddHTLCError ->
             sprintf "Invalid operation (add htlc): %s" invalidOperationAddHTLCError.Message
+        | InvalidMonoHopUnidirectionalPayment invalidMonoHopUnidirectionalPaymentError ->
+            sprintf "Invalid monohop-unidirectional payment: %s" invalidMonoHopUnidirectionalPaymentError.Message
 
 and ChannelConsumerAction =
     /// The error which should never happen.
@@ -181,6 +185,18 @@ and InvalidAcceptChannelError = {
     member this.Message =
         String.concat "; " this.Errors
 
+and InvalidMonoHopUnidirectionalPaymentError = {
+    NetworkMsg: MonoHopUnidirectionalPaymentMsg
+    Errors: string list
+}
+    with
+    static member Create msg e = {
+        NetworkMsg = msg
+        Errors = e
+    }
+    member this.Message =
+        String.concat "; " this.Errors
+
 and InvalidUpdateAddHTLCError = {
     NetworkMsg: UpdateAddHTLCMsg
     Errors: string list
@@ -504,6 +520,22 @@ module internal AcceptChannelMsgValidation =
 
         (check1 |> Validation.ofResult) *^> check2 *^> check3 *^> check4 *^> check5 *^> check6 *^> check7
 
+module UpdateMonoHopUnidirectionalPaymentWithContext =
+    let internal checkWeHaveSufficientFunds (state: Commitments) (currentSpec) =
+        let fees =
+            if state.LocalParams.IsFunder then
+                Transactions.commitTxFee state.RemoteParams.DustLimitSatoshis currentSpec
+            else
+                Money.Zero
+        let missing = currentSpec.ToRemote.ToMoney() - state.RemoteParams.ChannelReserveSatoshis - fees
+        if missing < Money.Zero then
+            sprintf "We don't have sufficient funds to send mono-hop unidirectional payment. current to_remote amount is: %A. Remote Channel Reserve is: %A. and fee is %A"
+                    (currentSpec.ToRemote.ToMoney())
+                    state.RemoteParams.ChannelReserveSatoshis
+                    fees
+            |> Error
+        else
+            Ok()
 
 module UpdateAddHTLCValidation =
     let internal checkExpiryIsNotPast (current: BlockHeight) (expiry) =
@@ -518,7 +550,23 @@ module UpdateAddHTLCValidation =
     let internal checkAmountIsLargerThanMinimum (htlcMinimum: LNMoney) (amount) =
         check (amount) (<) (htlcMinimum) "htlc value (%A) is too small. must be greater or equal to %A"
 
-
+module internal MonoHopUnidirectionalPaymentValidationWithContext =
+    let checkWeHaveSufficientFunds (state: Commitments) (currentSpec) =
+        let fees =
+            if state.LocalParams.IsFunder then
+                Transactions.commitTxFee state.RemoteParams.DustLimitSatoshis currentSpec
+            else
+                Money.Zero
+        let missing = currentSpec.ToRemote.ToMoney() - state.RemoteParams.ChannelReserveSatoshis - fees
+        if missing < Money.Zero then
+            sprintf "We don't have sufficient funds to send mono-hop unidirectional payment. current to_remote amount is: %A. Remote Channel Reserve is: %A. and fee is %A"
+                    (currentSpec.ToRemote.ToMoney())
+                    state.RemoteParams.ChannelReserveSatoshis
+                    fees
+            |> Error
+        else
+            Ok()
+
 module internal UpdateAddHTLCValidationWithContext =
     let checkLessThanHTLCValueInFlightLimit (currentSpec: CommitmentSpec) (limit) (add: UpdateAddHTLCMsg) =
         let htlcValueInFlight = currentSpec.HTLCs |> Map.toSeq |> Seq.sumBy (fun (_, v) -> v.Add.Amount)

src/DotNetLightning.Core/Channel/ChannelOperations.fs

@@ -15,6 +15,10 @@ open NBitcoin
 open ResultUtils
 open ResultUtils.Portability
 
+type OperationMonoHopUnidirectionalPayment = {
+    Amount: LNMoney
+}
+
 type OperationAddHTLC = {
     Amount: LNMoney
     PaymentHash: PaymentHash
@@ -203,6 +207,8 @@ type ChannelCommand =
     | CreateChannelReestablish
 
     // normal
+    | MonoHopUnidirectionalPayment of OperationMonoHopUnidirectionalPayment
+    | ApplyMonoHopUnidirectionalPayment of msg: MonoHopUnidirectionalPaymentMsg
     | AddHTLC of OperationAddHTLC
     | ApplyUpdateAddHTLC of msg: UpdateAddHTLCMsg * currentHeight: BlockHeight
     | FulfillHTLC of OperationFulfillHTLC

src/DotNetLightning.Core/Channel/ChannelTypes.fs

@@ -276,6 +276,9 @@ type ChannelEvent =
     | BothFundingLocked of nextState: Data.NormalData
 
     // -------- normal operation ------
+    | WeAcceptedOperationMonoHopUnidirectionalPayment of msg: MonoHopUnidirectionalPaymentMsg * newCommitments: Commitments
+    | WeAcceptedMonoHopUnidirectionalPayment of newCommitments: Commitments
+
     | WeAcceptedOperationAddHTLC of msg: UpdateAddHTLCMsg * newCommitments: Commitments
     | WeAcceptedUpdateAddHTLC of newCommitments: Commitments
 
@@ -368,6 +371,27 @@ type ChannelState =
             (fun v cc -> match cc with
                          | Normal _ -> Normal v
                          | _ -> cc )
+        member this.ChannelId: Option<ChannelId> =
+            match this with
+            | WaitForInitInternal
+            | WaitForOpenChannel _
+            | WaitForAcceptChannel _
+            | WaitForFundingTx _
+            | WaitForFundingCreated _ -> None
+            | WaitForFundingSigned data -> Some data.ChannelId
+            | WaitForFundingConfirmed data -> Some data.ChannelId
+            | WaitForFundingLocked data -> Some data.ChannelId
+            | Normal data -> Some data.ChannelId
+            | Shutdown data -> Some data.ChannelId
+            | Negotiating data -> Some data.ChannelId
+            | Closing data -> Some data.ChannelId
+            | Closed _
+            | Offline _
+            | Syncing _
+            | ErrFundingLost _
+            | ErrFundingTimeOut _
+            | ErrInformationLeak _ -> None
+
         member this.Phase =
             match this with
             | WaitForInitInternal
@@ -388,3 +412,25 @@ type ChannelState =
             | ErrFundingLost _
             | ErrFundingTimeOut _
             | ErrInformationLeak _ -> Abnormal
+
+        member this.Commitments: Option<Commitments> =
+            match this with
+            | WaitForInitInternal
+            | WaitForOpenChannel _
+            | WaitForAcceptChannel _
+            | WaitForFundingTx _
+            | WaitForFundingCreated _
+            | WaitForFundingSigned _ -> None
+            | WaitForFundingConfirmed data -> Some (data :> IHasCommitments).Commitments
+            | WaitForFundingLocked data -> Some (data :> IHasCommitments).Commitments
+            | Normal data -> Some (data :> IHasCommitments).Commitments
+            | Shutdown data -> Some (data :> IHasCommitments).Commitments
+            | Negotiating data -> Some (data :> IHasCommitments).Commitments
+            | Closing data -> Some (data :> IHasCommitments).Commitments
+            | Closed _
+            | Offline _
+            | Syncing _
+            | ErrFundingLost _
+            | ErrFundingTimeOut _
+            | ErrInformationLeak _ -> None
+

src/DotNetLightning.Core/Channel/ChannelValidation.fs

@@ -197,6 +197,13 @@ module internal Validation =
         *> AcceptChannelMsgValidation.checkConfigPermits conf.PeerChannelConfigLimits msg
         |> Result.mapError(InvalidAcceptChannelError.Create msg >> InvalidAcceptChannel)
 
+    let checkOurMonoHopUnidirectionalPaymentIsAcceptableWithCurrentSpec (currentSpec) (state: Commitments) (payment: MonoHopUnidirectionalPaymentMsg) =
+        Validation.ofResult(MonoHopUnidirectionalPaymentValidationWithContext.checkWeHaveSufficientFunds state currentSpec)
+        |> Result.mapError(fun errs -> InvalidMonoHopUnidirectionalPayment { NetworkMsg = payment; Errors = errs })
+
+    let checkTheirMonoHopUnidirectionalPaymentIsAcceptableWithCurrentSpec (currentSpec) (state: Commitments) (payment: MonoHopUnidirectionalPaymentMsg) =
+        Validation.ofResult(MonoHopUnidirectionalPaymentValidationWithContext.checkWeHaveSufficientFunds state currentSpec)
+        |> Result.mapError(fun errs -> InvalidMonoHopUnidirectionalPayment { NetworkMsg = payment; Errors = errs })
 
     let checkOperationAddHTLC (state: NormalData) (op: OperationAddHTLC) =
         Validation.ofResult(UpdateAddHTLCValidation.checkExpiryIsNotPast op.CurrentHeight op.Expiry)

src/DotNetLightning.Core/Channel/Commitments.fs

@@ -236,3 +236,39 @@ type Commitments = {
                      |> Money.Satoshis) - commitFee
 
             {Amounts.ToLocal = toLocalAmount; ToRemote = toRemoteAmount}
+
+        member this.SpendableBalance(): LNMoney =
+            let remoteCommit =
+                match this.RemoteNextCommitInfo with
+                | RemoteNextCommitInfo.Waiting info -> info.NextRemoteCommit
+                | RemoteNextCommitInfo.Revoked _info -> this.RemoteCommit
+            let reducedRes =
+                remoteCommit.Spec.Reduce(
+                    this.RemoteChanges.ACKed,
+                    this.LocalChanges.Proposed
+                )
+            let reduced =
+                match reducedRes with
+                | Error err ->
+                    failwithf
+                        "reducing commit failed even though we have not proposed any changes\
+                        error: %A"
+                        err
+                | Ok reduced -> reduced
+            let fees =
+                if this.LocalParams.IsFunder then
+                    Transactions.commitTxFee this.RemoteParams.DustLimitSatoshis reduced
+                    |> LNMoney.FromMoney
+                else
+                    LNMoney.Zero
+            let channelReserve =
+                this.RemoteParams.ChannelReserveSatoshis
+                |> LNMoney.FromMoney
+            let totalBalance = reduced.ToRemote
+            let untrimmedSpendableBalance = totalBalance - channelReserve - fees
+            let dustLimit =
+                this.RemoteParams.DustLimitSatoshis
+                |> LNMoney.FromMoney
+            let untrimmedMax = LNMoney.Min(untrimmedSpendableBalance, dustLimit)
+            let spendableBalance = LNMoney.Max(untrimmedMax, untrimmedSpendableBalance)
+            spendableBalance

src/DotNetLightning.Core/Crypto/ShaChain.fs

@@ -1,5 +1,7 @@
 namespace DotNetLightning.Crypto
 
+open System
+
 type Node = {
     Value: byte[]
     Height: int32
@@ -16,8 +18,9 @@ module ShaChain =
     let flip (_input: byte[]) (_index: uint64): byte[] =
         failwith "Not implemented: ShaChain::flip"
 
-    let addHash (_receiver: ShaChain) (_hash: byte[]) (_index: uint64) =
-        failwith "Not implemented: ShaChain::addHash"
+    let addHash (receiver: ShaChain) (_hash: byte[]) (_index: uint64) =
+        Console.WriteLine("WARNING: Not implemented: ShaChain::addHash")
+        receiver
 
     let getHash (_receiver: ShaChain)(_index: uint64) =
         failwith "Not implemented: ShaChain::getHash"

src/DotNetLightning.Core/Serialization/Msgs/Msgs.fs

@@ -104,6 +104,8 @@ module internal TypeFlag =
     let ReplyChannelRange = 264us
     [<Literal>]
     let GossipTimestampFilter = 265us
+    [<Literal>]
+    let MonoHopUnidirectionalPayment = 42198us
 
 type ILightningMsg = interface end
 type ISetupMsg = inherit ILightningMsg
@@ -195,6 +197,8 @@ module ILightningSerializable =
             deserialize<ReplyChannelRangeMsg>(ls) :> ILightningMsg
         | TypeFlag.GossipTimestampFilter ->
             deserialize<GossipTimestampFilterMsg>(ls) :> ILightningMsg
+        | TypeFlag.MonoHopUnidirectionalPayment ->
+            deserialize<MonoHopUnidirectionalPaymentMsg>(ls) :> ILightningMsg
         | x ->
             raise <| FormatException(sprintf "Unknown message type %d" x)
     let serializeWithFlags (ls: LightningWriterStream) (data: ILightningMsg) =
@@ -283,6 +287,9 @@ module ILightningSerializable =
         | :? GossipTimestampFilterMsg as d ->
             ls.Write(TypeFlag.GossipTimestampFilter, false)
             (d :> ILightningSerializable<GossipTimestampFilterMsg>).Serialize(ls)
+        | :? MonoHopUnidirectionalPaymentMsg as d ->
+            ls.Write(TypeFlag.MonoHopUnidirectionalPayment, false)
+            (d :> ILightningSerializable<MonoHopUnidirectionalPaymentMsg>).Serialize(ls)
         | x -> failwithf "%A is not known lightning message. This should never happen" x
 
 module LightningMsg =
@@ -1572,3 +1579,19 @@ type GossipTimestampFilterMsg = {
             ls.Write(this.FirstTimestamp, false)
             ls.Write(this.TimestampRange, false)
 
+[<CLIMutable>]
+type MonoHopUnidirectionalPaymentMsg = {
+    mutable ChannelId: ChannelId
+    mutable Amount: LNMoney
+}
+with
+    interface IHTLCMsg
+    interface IUpdateMsg
+    interface ILightningSerializable<MonoHopUnidirectionalPaymentMsg> with
+        member this.Deserialize(ls) =
+            this.ChannelId <- ls.ReadUInt256(true) |> ChannelId
+            this.Amount <- ls.ReadUInt64(false) |> LNMoney.MilliSatoshis
+        member this.Serialize(ls) =
+            ls.Write(this.ChannelId.Value.ToBytes())
+            ls.Write(this.Amount.MilliSatoshi, false)
+