From 0f4c4d14658cd5418f8573c0eba4f18ce1e3b320 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Tue, 30 Nov 2021 16:22:52 +0100
Subject: [PATCH] Decode sequences and arrays

---
 contractabi/decoding.nim           | 15 +++++++++++++++
 contractabi/encoding.nim           |  8 ++++++++
 tests/contractabi/testDecoding.nim |  9 +++++++++
 tests/contractabi/testEncoding.nim |  6 ++++++
 4 files changed, 38 insertions(+)

diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index 6ca7823..24c9228 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -1,6 +1,7 @@
 import pkg/stint
 import pkg/stew/endians2
 import pkg/upraises
+import ./encoding
 
 push: {.upraises:[].}
 
@@ -93,6 +94,20 @@ func finish*(decoder: var AbiDecoder) =
   doAssert decoder.index == decoder.bytes.len, "unread trailing bytes found"
   doAssert decoder.index mod 32 == 0, "encoding variant broken"
 
+func read*[T](decoder: var AbiDecoder, _: type seq[T]): seq[T] =
+  let len = decoder.read(uint64)
+  decoder.startTuple(dynamic=true)
+  for _ in 0..<len:
+    result.add(decoder.read(T))
+  decoder.finishTuple()
+
+func read*[I,T](decoder: var AbiDecoder, _: type array[I,T]): array[I,T] =
+  const dynamic = AbiEncoder.isDynamic(T)
+  decoder.startTuple(dynamic)
+  for i in 0..<result.len:
+    result[i] = decoder.read(T)
+  decoder.finishTuple()
+
 func decode*(_: type AbiDecoder, bytes: seq[byte], T: type): T =
   var decoder = AbiDecoder.init(bytes)
   result = decoder.read(T)
diff --git a/contractabi/encoding.nim b/contractabi/encoding.nim
index 7174d7e..5f093c8 100644
--- a/contractabi/encoding.nim
+++ b/contractabi/encoding.nim
@@ -128,3 +128,11 @@ func encode*[T](_: type AbiEncoder, value: T): seq[byte] =
   var encoder = AbiEncoder.init()
   encoder.write(value)
   encoder.finish()
+
+proc isDynamic*(_: type AbiEncoder, T: type): bool {.compileTime.} =
+  var encoder = AbiEncoder.init()
+  encoder.encode(T.default)
+  encoder.stack[^1].dynamic
+
+proc isStatic*(_: type AbiEncoder, T: type): bool {.compileTime.} =
+  not AbiEncoder.isDynamic(T)
diff --git a/tests/contractabi/testDecoding.nim b/tests/contractabi/testDecoding.nim
index 6ddff96..01bd55b 100644
--- a/tests/contractabi/testDecoding.nim
+++ b/tests/contractabi/testDecoding.nim
@@ -186,3 +186,12 @@ suite "ABI decoding":
     decoder.finishTuple()
     decoder.finish()
 
+  test "decodes sequences":
+    checkDecode(@[seq[byte].example, seq[byte].example])
+
+  test "decodes arrays with static elements":
+    checkDecode([array[32, byte].example, array[32, byte].example])
+
+  test "decodes arrays with dynamic elements":
+    checkDecode([seq[byte].example, seq[byte].example])
+
diff --git a/tests/contractabi/testEncoding.nim b/tests/contractabi/testEncoding.nim
index 1f1ec25..24fe46a 100644
--- a/tests/contractabi/testEncoding.nim
+++ b/tests/contractabi/testEncoding.nim
@@ -171,5 +171,11 @@ suite "ABI encoding":
   test "encodes strings as UTF-8 byte sequence":
     check AbiEncoder.encode("hello!☺") == AbiEncoder.encode("hello!☺".toBytes)
 
+  test "can determine whether types are dynamic or static":
+    check static AbiEncoder.isStatic(uint8)
+    check static AbiEncoder.isDynamic(seq[byte])
+    check static AbiEncoder.isStatic(array[2, array[2, byte]])
+    check static AbiEncoder.isDynamic(array[2, seq[byte]])
+
 # https://medium.com/b2expand/abi-encoding-explanation-4f470927092d
 # https://docs.soliditylang.org/en/v0.8.1/abi-spec.html#formal-specification-of-the-encoding