Add Destination (abstraction for either channel id or eth address)

nitro/basics.nim

@@ -3,9 +3,11 @@ import pkg/questionable/results
 import pkg/stint
 import ./uint48
 import ./ethaddress
+import ./destination
 
 export questionable
 export results
 export stint
 export uint48
 export ethaddress
+export destination

nitro/destination.nim

@@ -0,0 +1,25 @@
+import pkg/questionable
+import pkg/questionable/results
+import pkg/stew/byteutils
+import ./ethaddress
+
+include questionable/errorban
+
+type Destination* = distinct array[32, byte]
+
+proc toArray*(destination: Destination): array[32, byte] =
+  array[32, byte](destination)
+
+proc `$`*(destination: Destination): string =
+  destination.toArray().toHex()
+
+proc parse*(_: type Destination, s: string): ?Destination =
+   Destination(array[32, byte].fromHex(s)).catch.toOption()
+
+proc `==`*(a, b: Destination): bool {.borrow.}
+
+proc toDestination*(address: EthAddress): Destination =
+  var bytes: array[32, byte]
+  for i in 0..<20:
+    bytes[12 + i] = array[20, byte](address)[i]
+  Destination(bytes)

nitro/protocol/abi.nim

@@ -99,6 +99,9 @@ proc encode(encoder: var AbiEncoder, bytes: seq[byte]) =
 proc encode(encoder: var AbiEncoder, address: EthAddress) =
   encoder.padleft(address.toArray)
 
+proc encode(encoder: var AbiEncoder, destination: Destination) =
+  encoder.encode(destination.toArray)
+
 proc encode[I, T](encoder: var AbiEncoder, value: array[I, T]) =
   encoder.startTuple()
   for element in value:

nitro/protocol/channel.nim

@@ -12,11 +12,11 @@ type
     participants*: seq[EthAddress]
     chainId*: UInt256
 
-proc getChannelId*(channel: ChannelDefinition): array[32, byte] =
+proc getChannelId*(channel: ChannelDefinition): Destination =
   var encoder= AbiEncoder.init()
   encoder.startTuple()
   encoder.write(channel.chainId)
   encoder.write(channel.participants)
   encoder.write(channel.nonce)
   encoder.finishTuple()
-  keccak256.digest(encoder.finish()).data
+  Destination(keccak256.digest(encoder.finish()).data)

nitro/protocol/outcome.nim

@@ -20,11 +20,11 @@ type
       guarantee*: Guarantee
   Allocation* = distinct seq[AllocationItem]
   AllocationItem* = object
-    destination*: array[32, byte]
+    destination*: Destination
     amount*: UInt256
   Guarantee* = object
-    targetChannelId*: array[32, byte]
-    destinations*: seq[array[32, byte]]
+    targetChannelId*: Destination
+    destinations*: seq[Destination]
 
 proc encode*(encoder: var AbiEncoder, guarantee: Guarantee) =
   encoder.startTuple()

tests/nitro/examples.nim

@@ -27,6 +27,9 @@ proc example*(_: type UInt128): UInt128 =
 proc example*(_: type EthAddress): EthAddress =
   EthAddress(array[20, byte].example)
 
+proc example*(_: type Destination): Destination =
+  Destination(array[32, byte].example)
+
 proc example*(_: type ChannelDefinition): ChannelDefinition =
   ChannelDefinition(
     nonce: UInt48.example,
@@ -36,14 +39,14 @@ proc example*(_: type ChannelDefinition): ChannelDefinition =
 
 proc example*(_: type AllocationItem): AllocationItem =
   AllocationItem(
-    destination: array[32, byte].example,
+    destination: Destination.example,
     amount: UInt256.example
   )
 
 proc example*(_: type Guarantee): Guarantee =
   Guarantee(
-    targetChannelId: array[32, byte].example,
-    destinations: seq[array[32, byte]].example
+    targetChannelId: Destination.example,
+    destinations: seq[Destination].example
   )
 
 proc example*(_: type Allocation): Allocation =

tests/nitro/protocol/testChannel.nim

@@ -16,7 +16,7 @@ suite "channel definition":
     encoder.finishTuple()
     let encoded = encoder.finish()
     let hashed = keccak256.digest(encoded).data
-    check getChannelId(channel) == hashed
+    check getChannelId(channel) == Destination(hashed)
 
   test "produces same id as javascript implementation":
     let channel = ChannelDefinition(
@@ -26,7 +26,7 @@ suite "channel definition":
         EthAddress.fromHex("24b905Dcc8A11C0FE57C2592f3D25f0447402C10").get()
       ]
     )
-    let expected = array[32, byte].fromHex(
+    let expected = Destination.parse(
       "4f8cce57e9fe88edaab05234972eaf0c2d183e4f6b175aff293375fbe4d5d7cc"
-    )
+    ).get()
     check getChannelId(channel) == expected

tests/nitro/protocol/testOutcome.nim

@@ -96,9 +96,9 @@ suite "outcome":
         ).get(),
         allocation: Allocation(@[
           AllocationItem(
-            destination: array[32, byte].fromHex(
+            destination: Destination.parse(
               "f1918e8562236eb17adc8502332f4c9c82bc14e19bfc0aa10ab674ff75b3d2f3"
-            ),
+            ).get(),
             amount: 0x05.u256
           )
         ])
@@ -109,13 +109,13 @@ suite "outcome":
           "1E90B49563da16D2537CA1Ddd9b1285279103D93"
         ).get(),
         guarantee: Guarantee(
-          targetChannelId: array[32, byte].fromHex(
+          targetChannelId: Destination.parse(
             "cac1bb71f0a97c8ac94ca9546b43178a9ad254c7b757ac07433aa6df35cd8089"
-          ),
+          ).get(),
           destinations: @[
-            array[32, byte].fromHex(
+            Destination.parse(
               "f1918e8562236eb17adc8502332f4c9c82bc14e19bfc0aa10ab674ff75b3d2f3"
-            )
+            ).get()
           ]
         )
       )