From e3c9aa436867b02e66f81c52c7dabc913ce74b52 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Wed, 19 Jan 2022 09:16:22 +0100
Subject: [PATCH] Add support for Ethereum addresses

---
 contractabi/address.nim            | 26 ++++++++++++++++++++++++++
 contractabi/decoding.nim           |  9 +++++++++
 contractabi/encoding.nim           |  5 +++++
 tests/contractabi/examples.nim     |  4 ++++
 tests/contractabi/testAddress.nim  | 25 +++++++++++++++++++++++++
 tests/contractabi/testDecoding.nim |  3 +++
 tests/contractabi/testEncoding.nim |  4 ++++
 tests/testAll.nim                  |  1 +
 8 files changed, 77 insertions(+)
 create mode 100644 contractabi/address.nim
 create mode 100644 tests/contractabi/testAddress.nim

diff --git a/contractabi/address.nim b/contractabi/address.nim
new file mode 100644
index 0000000..30fb6f6
--- /dev/null
+++ b/contractabi/address.nim
@@ -0,0 +1,26 @@
+import pkg/stew/byteutils
+import pkg/questionable
+import pkg/upraises
+
+push: {.upraises: [].}
+
+type
+  Address* = distinct array[20, byte]
+
+func init*(_: type Address, bytes: array[20, byte]): Address =
+  Address(bytes)
+
+func init*(_: type Address, hex: string): ?Address =
+  try:
+    let bytes = array[20, byte].fromHex(hex)
+    some Address.init(bytes)
+  except ValueError:
+    none Address
+
+func toArray*(address: Address): array[20, byte] =
+  array[20, byte](address)
+
+func `$`*(address: Address): string =
+  "0x" & toHex(address.toArray)
+
+func `==`*(a, b: Address): bool {.borrow.}
diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index f4123b3..ba4375c 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -5,6 +5,10 @@ import pkg/questionable/results
 import pkg/upraises
 import ./encoding
 import ./integers
+import ./address
+
+export stint
+export address
 
 push: {.upraises:[].}
 
@@ -114,6 +118,11 @@ func decode(decoder: var AbiDecoder, T: type enum): ?!T =
   else:
     failure "invalid enum value"
 
+func decode(decoder: var AbiDecoder, T: type Address): ?!T =
+  var bytes: array[20, byte]
+  bytes[0..<20] =(?decoder.read(20))[0..<20]
+  success T.init(bytes)
+
 func decode[I](decoder: var AbiDecoder, T: type array[I, byte]): ?!T =
   var arr: T
   arr[0..<arr.len] = ?decoder.read(arr.len, padRight)
diff --git a/contractabi/encoding.nim b/contractabi/encoding.nim
index 30a2a0a..1b42964 100644
--- a/contractabi/encoding.nim
+++ b/contractabi/encoding.nim
@@ -2,8 +2,10 @@ import pkg/stint
 import pkg/upraises
 import pkg/stew/byteutils
 import ./integers
+import ./address
 
 export stint
+export address
 
 push: {.upraises:[].}
 
@@ -95,6 +97,9 @@ func encode(encoder: var AbiEncoder, value: bool) =
 func encode(encoder: var AbiEncoder, value: enum) =
   encoder.encode(uint64(ord(value)))
 
+func encode(encoder: var AbiEncoder, value: Address) =
+  encoder.padleft(value.toArray)
+
 func encode[I](encoder: var AbiEncoder, bytes: array[I, byte]) =
   encoder.padright(bytes)
 
diff --git a/tests/contractabi/examples.nim b/tests/contractabi/examples.nim
index 7d9a745..07b2588 100644
--- a/tests/contractabi/examples.nim
+++ b/tests/contractabi/examples.nim
@@ -1,6 +1,7 @@
 import std/random
 import std/sequtils
 import pkg/stint
+import pkg/contractabi/address
 
 randomize()
 
@@ -23,3 +24,6 @@ proc example*(T: type StUint): T =
 
 proc example*(T: type StInt): T =
   cast[T](StUint[T.bits].example)
+
+proc example*(T: type Address): T =
+  Address.init(array[20, byte].example)
diff --git a/tests/contractabi/testAddress.nim b/tests/contractabi/testAddress.nim
new file mode 100644
index 0000000..847647e
--- /dev/null
+++ b/tests/contractabi/testAddress.nim
@@ -0,0 +1,25 @@
+import std/unittest
+import pkg/contractabi/address
+import pkg/questionable
+
+suite "Address":
+
+  let address = Address.init [
+    0x1'u8, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa,
+    0x1   , 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa
+  ]
+
+  test "can be converted to string":
+    check $address == "0x0102030405060708090a0102030405060708090a"
+
+  test "can be parsed from string":
+    check:
+      Address.init("0x0102030405060708090a0102030405060708090a") == some address
+
+  test "parsing fails when string does not contain proper hex":
+    check:
+      Address.init("0xfoo2030405060708090a0102030405060708090a") == none Address
+
+  test "parsing fails when string does not contain 20 bytes":
+    check:
+      Address.init("0x0102030405060708090a010203040506070809") == none Address
diff --git a/tests/contractabi/testDecoding.nim b/tests/contractabi/testDecoding.nim
index 3f4a848..8db1023 100644
--- a/tests/contractabi/testDecoding.nim
+++ b/tests/contractabi/testDecoding.nim
@@ -84,6 +84,9 @@ suite "ABI decoding":
     checkDecode(Int128)
     checkDecode(Int256)
 
+  test "decodes addresses":
+    checkDecode(Address.example)
+
   test "decodes byte arrays":
     checkDecode([1'u8, 2'u8, 3'u8])
     checkDecode(array[32, byte].example)
diff --git a/tests/contractabi/testEncoding.nim b/tests/contractabi/testEncoding.nim
index 809f855..9f7d844 100644
--- a/tests/contractabi/testEncoding.nim
+++ b/tests/contractabi/testEncoding.nim
@@ -59,6 +59,10 @@ suite "ABI encoding":
     check AbiEncoder.encode(-1.i256) == 0xFF'u8.repeat(32)
     check AbiEncoder.encode(-1.i128) == 0xFF'u8.repeat(32)
 
+  test "encodes addresses":
+    let address = Address.example
+    check AbiEncoder.encode(address) == 12.zeroes & @(address.toArray)
+
   test "encodes byte arrays":
     let bytes3 = [1'u8, 2'u8, 3'u8]
     check AbiEncoder.encode(bytes3) == @bytes3 & 29.zeroes
diff --git a/tests/testAll.nim b/tests/testAll.nim
index c3c66a0..14847a9 100644
--- a/tests/testAll.nim
+++ b/tests/testAll.nim
@@ -1,3 +1,4 @@
+import ./contractabi/testAddress
 import ./contractabi/testEncoding
 import ./contractabi/testDecoding
 import ./contractabi/testCustomTypes