Merge pull request #50 from Glutexo/hash

✨ Hash the filename using MD5

lib/hash.ex

@@ -0,0 +1,18 @@
+defmodule Hash do
+  def md5(data, fmt) do
+    hash(:md5, data)
+    |> format(fmt)
+  end
+
+  def format(data, :bin) do
+    data
+  end
+
+  def format(data, :hex) do
+    Base.encode16(data, case: :lower)
+  end
+
+  def hash(func, data) do
+    :crypto.hash(func, data)
+  end
+end

lib/onigumo.ex

@@ -56,6 +56,6 @@ defmodule Onigumo do
   end
 
   def create_file_name(url) do
-    Base.url_encode64(url, padding: false)
+    Hash.md5(url, :hex)
   end
 end

test/hash_test.exs

@@ -0,0 +1,81 @@
+defmodule HashTest do
+  use ExUnit.Case
+
+  @known_md5s [
+    {
+      "",
+      "d41d8cd98f00b204e9800998ecf8427e",
+      <<212, 29, 140, 217, 143, 0, 178, 4, 233, 128, 9, 152, 236, 248, 66, 126>>
+    },
+    {
+      "onigumo",
+      "3d8425b6ea2efe0fa78075492c719ffe",
+      <<61, 132, 37, 182, 234, 46, 254, 15, 167, 128, 117, 73, 44, 113, 159, 254>>
+    },
+    {
+      "https://www.example.com/",
+      "dcbfe5ad9e8af3495ca4582e364c1bce",
+      <<220, 191, 229, 173, 158, 138, 243, 73, 92, 164, 88, 46, 54, 76, 27, 206>>
+    }
+  ]
+
+  @binary_hash <<61, 132, 37, 182, 234, 46, 254, 15, 167, 128, 117, 73, 44, 113, 159, 254>>
+  @formatted_hashes [
+    {
+      :bin,
+      <<61, 132, 37, 182, 234, 46, 254, 15, 167, 128, 117, 73, 44, 113, 159, 254>>
+    },
+    {
+      :hex,
+      "3d8425b6ea2efe0fa78075492c719ffe"
+    }
+  ]
+
+  @known_hash_data "onigumo"
+  @known_hashes [
+    {
+      :md5,
+      <<61, 132, 37, 182, 234, 46, 254, 15, 167, 128, 117, 73, 44, 113, 159, 254>>
+    },
+    {
+      :sha256,
+      <<233, 125, 4, 183, 163, 127, 108, 247, 107, 107, 129, 176, 45, 233, 210, 255, 218, 34, 202,
+        51, 112, 158, 160, 220, 15, 109, 229, 143, 188, 196, 45, 128>>
+    },
+    {
+      :sha512,
+      <<215, 171, 58, 63, 123, 94, 7, 206, 21, 30, 63, 150, 208, 35, 179, 69, 235, 190, 128, 183,
+        0, 89, 237, 183, 155, 8, 190, 178, 233, 240, 157, 95, 187, 200, 110, 163, 116, 55, 57, 63,
+        73, 16, 192, 76, 15, 236, 126, 106, 117, 209, 199, 43, 231, 192, 105, 122, 247, 100, 47,
+        100, 178, 231, 31, 217>>
+    }
+  ]
+
+  test("hash MD5 known value in hexadecimal") do
+    for {data, hash_hex, _} <- @known_md5s do
+      hash = Hash.md5(data, :hex)
+      assert(hash == hash_hex)
+    end
+  end
+
+  test("hash MD5 known value in binary") do
+    for {data, _, hash_bin} <- @known_md5s do
+      hash = Hash.md5(data, :bin)
+      assert(hash == hash_bin)
+    end
+  end
+
+  test("format a binary hash") do
+    for {format, hash} <- @formatted_hashes do
+      formatted = Hash.format(@binary_hash, format)
+      assert(formatted == hash)
+    end
+  end
+
+  test("hash a known value") do
+    for {func, known_hash} <- @known_hashes do
+      computed_hash = Hash.hash(func, @known_hash_data)
+      assert(computed_hash == known_hash)
+    end
+  end
+end

test/onigumo_test.exs

@@ -94,11 +94,8 @@ defmodule OnigumoTest do
     input_url = "https://onigumo.local/hello.html"
     created_file_name = Onigumo.create_file_name(input_url)
 
-    expected_file_name = Base.url_encode64(input_url, padding: false)
+    expected_file_name = Hash.md5(input_url, :hex)
     assert(created_file_name == expected_file_name)
-
-    unexpected_file_name = Base.url_encode64(input_url, padding: true)
-    assert(created_file_name != unexpected_file_name)
   end
 
   defp prepare_response(url) do
@@ -118,7 +115,7 @@ defmodule OnigumoTest do
   end
 
   defp assert_downloaded(url, tmp_dir) do
-    file_name = Base.url_encode64(url, padding: false)
+    file_name = Onigumo.create_file_name(url)
     output_path = Path.join(tmp_dir, file_name)
     read_output = File.read!(output_path)
     expected_output = body(url)