From 5a18897947a2523059a4c1c5a3593d8032a09de9 Mon Sep 17 00:00:00 2001
From: Deon <deonsummers91@gmail.com>
Date: Tue, 29 May 2018 20:36:26 -0500
Subject: [PATCH] Added checksum methods

---
 lib/exw3.ex        | 28 ++++++++++++++++++++++++++++
 test/exw3_test.exs | 35 ++++++++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/lib/exw3.ex b/lib/exw3.ex
index bac58fa..5890067 100644
--- a/lib/exw3.ex
+++ b/lib/exw3.ex
@@ -23,6 +23,34 @@ defmodule ExW3 do
     Enum.join(["0x", bytes |> Base.encode16(case: :lower)], "")
   end
 
+	@spec to_checksum_address(binary()) :: binary()
+	@doc "returns a checksummed address"
+	def to_checksum_address(address) do
+    address = String.replace(address, ~r/^0x/, "")
+
+    {:ok, hash} = Ethereumex.HttpClient.web3_sha3(String.downcase(address))
+    non_prefix_hash = String.replace(hash, ~r/^0x/, "")
+    keccak_hash_list = non_prefix_hash
+    |> String.split("", trim: true)
+    |> Enum.map(fn (x) -> elem(Integer.parse(x, 16),0) end)
+
+    list_arr = for n <- 0..String.length(address)-1 do
+      number = Enum.at(keccak_hash_list, n)
+      cond do
+        number >= 8 -> String.upcase(String.at(address, n))
+        true -> String.downcase(String.at(address, n))
+      end
+    end
+
+    "0x" <> List.to_string(list_arr)
+  end
+	
+	@doc "checks if the address is a valid checksummed address"
+	@spec is_valid_checksum_address(binary()) :: boolean()
+  def is_valid_checksum_address(address) do
+    to_checksum_address(address) == address
+  end
+
   @spec accounts() :: list()
   @doc "returns all available accounts"
   def accounts do
diff --git a/test/exw3_test.exs b/test/exw3_test.exs
index 94cb267..1fac304 100644
--- a/test/exw3_test.exs
+++ b/test/exw3_test.exs
@@ -183,4 +183,37 @@ defmodule EXW3Test do
 
     assert ExW3.to_address(same_address) == Enum.at(context[:accounts], 0)
   end
-end
\ No newline at end of file
+
+  test "returns checksum for all caps address" do
+    assert ExW3.to_checksum_address(String.downcase("0x52908400098527886E0F7030069857D2E4169EE7")) == "0x52908400098527886E0F7030069857D2E4169EE7"
+    assert ExW3.to_checksum_address(String.downcase("0x8617E340B3D01FA5F11F306F4090FD50E238070D")) == "0x8617E340B3D01FA5F11F306F4090FD50E238070D"
+  end
+
+
+  test "returns checksumfor all lowercase address" do
+    assert ExW3.to_checksum_address(String.downcase("0xde709f2102306220921060314715629080e2fb77")) == "0xde709f2102306220921060314715629080e2fb77"
+    assert ExW3.to_checksum_address(String.downcase("0x27b1fdb04752bbc536007a920d24acb045561c26")) == "0x27b1fdb04752bbc536007a920d24acb045561c26"
+  end
+
+  test "returns checksum for normal addresses" do
+    assert ExW3.to_checksum_address(String.downcase("0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed")) == "0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed"
+    assert ExW3.to_checksum_address(String.downcase("0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359")) == "0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359"
+    assert ExW3.to_checksum_address(String.downcase("0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB")) == "0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB"
+    assert ExW3.to_checksum_address(String.downcase("0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb")) == "0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb"
+  end
+
+  test "returns valid check for is_valid_checksum_address()" do
+    assert ExW3.is_valid_checksum_address("0x52908400098527886E0F7030069857D2E4169EE7") == true
+    assert ExW3.is_valid_checksum_address("0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB") == true
+    assert ExW3.is_valid_checksum_address("0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb") == true
+    assert ExW3.is_valid_checksum_address("0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed") == true
+    assert ExW3.is_valid_checksum_address("0x27b1fdb04752bbc536007a920d24acb045561c26") == true
+    assert ExW3.is_valid_checksum_address("0xde709f2102306220921060314715629080e2fb77") == true
+    assert ExW3.is_valid_checksum_address("0x8617E340B3D01FA5F11F306F4090FD50E238070D") == true
+    assert ExW3.is_valid_checksum_address("0x52908400098527886E0F7030069857D2E4169EE7") == true
+  end
+
+  test "returns invalid check for is_valid_checksum_address()" do
+    assert ExW3.is_valid_checksum_address("0x2f015c60e0be116b1f0cd534704db9c92118fb6a") == false
+  end
+end