From 469a8d4154aeb21c92df8ef371e8bc352bdd91c9 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Tue, 6 Apr 2021 12:25:47 +0200
Subject: [PATCH] JSON serialization of signed states

---
 nitro.nim                |  2 +
 nitro/json.nim           | 96 ++++++++++++++++++++++++++++++++++++++++
 tests/nitro/examples.nim |  6 +++
 tests/nitro/testJson.nim | 19 ++++++++
 tests/testAll.nim        |  1 +
 5 files changed, 124 insertions(+)
 create mode 100644 nitro/json.nim
 create mode 100644 tests/nitro/testJson.nim

diff --git a/nitro.nim b/nitro.nim
index 7c1afe6..1dd1e4d 100644
--- a/nitro.nim
+++ b/nitro.nim
@@ -1,5 +1,7 @@
 import ./nitro/protocol
 import ./nitro/wallet
+import ./nitro/json
 
 export protocol
 export wallet
+export json
diff --git a/nitro/json.nim b/nitro/json.nim
new file mode 100644
index 0000000..739313a
--- /dev/null
+++ b/nitro/json.nim
@@ -0,0 +1,96 @@
+import std/json
+import std/typetraits
+import pkg/stew/byteutils
+import ./basics
+import ./protocol
+import ./wallet/signedstate
+
+export signedstate
+
+push: {.upraises:[].}
+
+func `%`(value: Outcome | Allocation): JsonNode =
+  type Base = distinctBase(typeof value)
+  %(Base(value))
+
+func `%`(value: seq[byte]): JsonNode =
+  %value.toHex
+
+func `%`(value: EthAddress | Destination): JsonNode =
+  %($value)
+
+func `%`(value: UInt256): JsonNode =
+  %(value.toHex)
+
+func `%`(value: Signature): JsonNode =
+  %($value)
+
+func `%`(value: AllocationItem): JsonNode =
+  %*{
+    "destination": value.destination,
+    "amount": value.amount
+  }
+
+func toJson*(payment: SignedState): string =
+  $(%*payment)
+
+{.pop.}
+
+push: {.upraises: [ValueError].}
+
+func expectKind(node: JsonNode, kind: JsonNodeKind) =
+  if node.kind != kind:
+    let message = "expected " & $kind & ", got: " & $node.kind
+    raise newException(JsonKindError, message)
+
+func initFromJson*(bytes: var seq[byte], node: JsonNode, _: var string) =
+  node.expectKind(JString)
+  let parsed = seq[byte].fromHex(node.getStr)
+  if parsed.isOk:
+    bytes = parsed.get
+  else:
+    raise newException(ValueError, "invalid hex string")
+
+func initFromJson*(address: var EthAddress, node: JsonNode, _: var string) =
+  node.expectKind(JString)
+  let parsed = EthAddress.parse(node.getStr)
+  if parsed.isSome:
+    address = parsed.get
+  else:
+    raise newException(ValueError, "invalid ethereum address")
+
+func initFromJson*(dest: var Destination, node: JsonNode, _: var string) =
+  node.expectKind(JString)
+  let parsed = Destination.parse(node.getStr)
+  if parsed.isSome:
+    dest = parsed.get
+  else:
+    raise newException(ValueError, "invalid nitro destination")
+
+func initFromJson*(number: var UInt256, node: JsonNode, _: var string) =
+  node.expectKind(JString)
+  number = UInt256.fromHex(node.getStr)
+
+func initFromJson*(signature: var Signature, node: JsonNode, _: var string) =
+  node.expectKind(JString)
+  let parsed = Signature.parse(node.getStr)
+  if parsed.isSome:
+    signature = parsed.get
+  else:
+    raise newException(ValueError, "invalid signature")
+
+{.pop.}
+
+push: {.upraises: [].}
+
+proc fromJson*(_: type SignedState, json: string): ?SignedState =
+  try:
+    {.warning[UnsafeSetLen]: off.}
+    return parseJson(json).to(SignedState).some
+    {.warning[UnsafeSetLen]: on.}
+  except ValueError:
+    return SignedState.none
+  except Exception as error:
+    raise (ref Defect)(msg: error.msg, parent: error)
+
+{.pop.}
diff --git a/tests/nitro/examples.nim b/tests/nitro/examples.nim
index 1b0ca68..ae49195 100644
--- a/tests/nitro/examples.nim
+++ b/tests/nitro/examples.nim
@@ -83,3 +83,9 @@ proc example*(_: type Signature): Signature =
   let key = PrivateKey.random
   let state = State.example
   key.sign(state)
+
+proc example*(_: type SignedState): SignedState =
+  let state = State.example
+  let key = PrivateKey.random
+  let signature = key.sign(state)
+  SignedState(state: state, signatures: @[signature])
diff --git a/tests/nitro/testJson.nim b/tests/nitro/testJson.nim
new file mode 100644
index 0000000..8d3b49f
--- /dev/null
+++ b/tests/nitro/testJson.nim
@@ -0,0 +1,19 @@
+import ./basics
+
+suite "json serialization":
+
+  let payment = SignedState.example()
+
+  test "serializes signed states to json":
+    check payment.toJson.len > 0
+
+  test "deserializes signed state":
+    check SignedState.fromJson(payment.toJson) == payment.some
+
+  test "returns none when deserializing invalid json":
+    let invalid = "{"
+    check SignedState.fromJson(invalid).isNone
+
+  test "returns none when json cannot be converted to signed state":
+    let invalid = "{}"
+    check SignedState.fromJson(invalid).isNone
diff --git a/tests/testAll.nim b/tests/testAll.nim
index 3ed9f24..c747a70 100644
--- a/tests/testAll.nim
+++ b/tests/testAll.nim
@@ -4,5 +4,6 @@ import ./nitro/protocol/testOutcome
 import ./nitro/protocol/testState
 import ./nitro/protocol/testSignature
 import ./nitro/testWallet
+import ./nitro/testJson
 
 {.warning[UnusedImport]: off.}