From 01c11eecb0f42e7d7f40bd23478506768a753423 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Wed, 13 Apr 2022 06:29:07 +0200
Subject: [PATCH] Custom encoding can use startTuple() and finishTuple()

---
 contractabi/decoding.nim              | 11 ++---
 contractabi/encoding.nim              | 22 ++++-----
 tests/contractabi/testCustomTypes.nim | 71 ++++++++++++++++++++++-----
 3 files changed, 76 insertions(+), 28 deletions(-)

diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index ba4375c..7283d94 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -43,11 +43,10 @@ func index(decoder: var AbiDecoder): var int =
 func `index=`(decoder: var AbiDecoder, value: int) =
   decoder.currentTuple.index = value
 
-func startTuple(decoder: var AbiDecoder): ?!void =
+func startTuple*(decoder: var AbiDecoder) =
   decoder.stack.add(Tuple.init(decoder.index))
-  success()
 
-func finishTuple(decoder: var AbiDecoder) =
+func finishTuple*(decoder: var AbiDecoder) =
   doAssert decoder.stack.len > 1, "unable to finish a tuple that hasn't started"
   let tupl = decoder.stack.pop()
   decoder.index = tupl.index
@@ -134,7 +133,7 @@ func decode(decoder: var AbiDecoder, T: type seq[byte]): ?!T =
 
 func decode[T: tuple](decoder: var AbiDecoder, _: typedesc[T]): ?!T =
   var tupl: T
-  ?decoder.startTuple()
+  decoder.startTuple()
   for element in tupl.fields:
     element = ?decoder.read(typeof(element))
   decoder.finishTuple()
@@ -143,7 +142,7 @@ func decode[T: tuple](decoder: var AbiDecoder, _: typedesc[T]): ?!T =
 func decode[T](decoder: var AbiDecoder, _: type seq[T]): ?!seq[T] =
   var sequence: seq[T]
   let len = ?decoder.read(uint64)
-  ?decoder.startTuple()
+  decoder.startTuple()
   for _ in 0..<len:
     sequence.add(?decoder.read(T))
   decoder.finishTuple()
@@ -151,7 +150,7 @@ func decode[T](decoder: var AbiDecoder, _: type seq[T]): ?!seq[T] =
 
 func decode[I,T](decoder: var AbiDecoder, _: type array[I,T]): ?!array[I,T] =
   var arr: array[I, T]
-  ?decoder.startTuple()
+  decoder.startTuple()
   for i in 0..<arr.len:
     arr[i] = ?decoder.read(T)
   decoder.finishTuple()
diff --git a/contractabi/encoding.nim b/contractabi/encoding.nim
index 1b42964..88dd7c8 100644
--- a/contractabi/encoding.nim
+++ b/contractabi/encoding.nim
@@ -57,7 +57,7 @@ func postpone(encoder: var AbiEncoder, bytes: seq[byte]) =
 func setDynamic(encoder: var AbiEncoder) =
   encoder.stack[^1].dynamic = true
 
-func startTuple(encoder: var AbiEncoder) =
+func startTuple*(encoder: var AbiEncoder) =
   encoder.stack.add(Tuple())
 
 func encode(encoder: var AbiEncoder, tupl: Tuple) =
@@ -67,7 +67,7 @@ func encode(encoder: var AbiEncoder, tupl: Tuple) =
   else:
     encoder.append(tupl.finish())
 
-func finishTuple(encoder: var AbiEncoder) =
+func finishTuple*(encoder: var AbiEncoder) =
   encoder.encode(encoder.stack.pop())
 
 func pad(encoder: var AbiEncoder, len: int, padding=0'u8) =
@@ -131,25 +131,25 @@ func encode(encoder: var AbiEncoder, tupl: tuple) =
     encoder.write(element)
   encoder.finishTuple()
 
+func finish(encoder: var AbiEncoder): Tuple =
+  doAssert encoder.stack.len == 1, "not all tuples were finished"
+  doAssert encoder.stack[0].bytes.len mod 32 == 0, "encoding invariant broken"
+  encoder.stack[0]
+
 func write*[T](encoder: var AbiEncoder, value: T) =
   var writer = AbiEncoder.init()
   writer.encode(value)
-  encoder.encode(writer.stack[0])
-
-func finish(encoder: var AbiEncoder): seq[byte] =
-  doAssert encoder.stack.len == 1, "not all tuples were finished"
-  doAssert encoder.stack[0].bytes.len mod 32 == 0, "encoding invariant broken"
-  encoder.stack[0].bytes
+  encoder.encode(writer.finish())
 
 func encode*[T](_: type AbiEncoder, value: T): seq[byte] =
   var encoder = AbiEncoder.init()
   encoder.write(value)
-  encoder.finish()
+  encoder.finish().bytes
 
 proc isDynamic*(_: type AbiEncoder, T: type): bool {.compileTime.} =
   var encoder = AbiEncoder.init()
-  encoder.encode(T.default)
-  encoder.stack[^1].dynamic
+  encoder.write(T.default)
+  encoder.finish().dynamic
 
 proc isStatic*(_: type AbiEncoder, T: type): bool {.compileTime.} =
   not AbiEncoder.isDynamic(T)
diff --git a/tests/contractabi/testCustomTypes.nim b/tests/contractabi/testCustomTypes.nim
index 13ae90d..9e61b54 100644
--- a/tests/contractabi/testCustomTypes.nim
+++ b/tests/contractabi/testCustomTypes.nim
@@ -2,30 +2,79 @@ import std/unittest
 import pkg/questionable/results
 import contractabi
 
-type CustomType = object
-  a: uint16
-  b: string
+type
+  Custom1 = object
+    a: uint16
+    b: string
+  Custom2 = object
+    a: uint16
+    b: string
+  Custom3 = object
+    a: uint16
+    b: string
 
-func encode(encoder: var AbiEncoder, custom: CustomType) =
+func encode(encoder: var AbiEncoder, custom: Custom1) =
   encoder.write( (custom.a, custom.b) )
 
-func decode(decoder: var AbiDecoder, T: type CustomType): ?!T =
+func decode(decoder: var AbiDecoder, T: type Custom1): ?!T =
   let (a, b) = ?decoder.read( (uint16, string) )
-  success CustomType(a: a, b: b)
+  success Custom1(a: a, b: b)
+
+func encode(encoder: var AbiEncoder, custom: Custom2) =
+  encoder.startTuple()
+  encoder.write(custom.a)
+  encoder.write(custom.b)
+  encoder.finishTuple()
+
+func decode(decoder: var AbiDecoder, T: type Custom2): ?!T =
+  var custom: T
+  decoder.startTuple()
+  custom.a = ?decoder.read(uint16)
+  custom.b = ?decoder.read(string)
+  decoder.finishTuple()
+  success custom
+
+func encode(encoder: var AbiEncoder, custom: Custom3) =
+  encoder.startTuple()
+  encoder.write(custom.a)
+  encoder.write(custom.b)
+  # missing: encoder.finishTuple()
+
+func decode(decoder: var AbiDecoder, T: type Custom3): ?!T =
+  var custom: T
+  decoder.startTuple()
+  custom.a = ?decoder.read(uint16)
+  custom.b = ?decoder.read(string)
+  # missing: decoder.finishTuple()
+  success custom
 
 suite "custom types":
 
-  let custom = CustomType(a: 42, b: "ultimate answer")
+  let custom1 = Custom1(a: 42, b: "ultimate answer")
+  let custom2 = Custom2(a: 42, b: "ultimate answer")
+  let custom3 = Custom3(a: 42, b: "ultimate answer")
 
   test "can be encoded":
-    check AbiEncoder.encode(custom) == AbiEncoder.encode( (custom.a, custom.b) )
+    check:
+      AbiEncoder.encode(custom1) == AbiEncoder.encode( (custom1.a, custom1.b) )
 
   test "can be decoded":
-    let encoding = AbiEncoder.encode(custom)
-    check AbiDecoder.decode(encoding, CustomType) == success custom
+    let encoding = AbiEncoder.encode(custom1)
+    check AbiDecoder.decode(encoding, Custom1) == success custom1
 
   test "can be embedded in tuples, arrays and sequences":
-    let embedding = (custom, [custom], @[custom])
+    let embedding = (custom1, [custom1], @[custom1])
     let encoding = AbiEncoder.encode(embedding)
     let decoded = AbiDecoder.decode(encoding, typeof(embedding))
     check !decoded == embedding
+
+  test "can use startTuple() and finishTuple()":
+    let encoding = AbiEncoder.encode(custom2)
+    check AbiDecoder.decode(encoding, Custom2) == success custom2
+
+  test "fail when finishTuple() is missing":
+    expect AssertionDefect:
+      discard AbiEncoder.encode(custom3)
+    let encoding = AbiEncoder.encode( (custom3.a, custom3.b) )
+    expect AssertionDefect:
+      discard AbiDecoder.decode(encoding, Custom3)