add tests and update Readme, #1

.travis.yml

@@ -0,0 +1,9 @@
+language: elixir
+elixir:
+  - 1.8
+env:
+  - MIX_ENV=test
+script:
+  - mix test
+after_success:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,2 +1,42 @@
 # elixir-base58-encode
 https://hex.pm/packages/b58
+
+
+This module provide the `encode/1` function which takes a binary and returns
+its base58 representation
+
+1. Add the package to you dependencies
+
+  ```
+  defp deps do
+    [b58: "~> 0.1.0"]
+  end
+  ```
+
+  and run `mix deps.get`
+
+2. Call the `encode` fundtion with a binary as parameter:
+
+ ```
+ > Base58Encode.encode("foo")
+ > "bQbp"
+ ```
+
+ if the parameter is not a binary the function will return `:error`
+
+ ```
+ > Base58Encode.encode(42)
+ > "bQbp"
+ ```
+
+The alphabet used for base58 is:
+`123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz`
+
+For more information about the implementation of this module see the issue 1:
+[How to encode a string to base58](https://github.com/dwyl/base58encode/issues/1)
+
+Read the following for more information about binary in Elixir:
+https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html
+
+Wikipedia page for base58:
+https://en.wikipedia.org/wiki/Base56

lib/base58encode.ex

@@ -1,21 +1,45 @@
 defmodule Base58Encode do
+  @moduledoc """
+  Provides the encode function which takes a binary and return it's
+  reprentation in base58
+  """
 
- def encode(binary) do
-  {decimal, _} = Integer.parse(Base.encode16(binary), 16)
-  codes = get_codes(decimal, [])
-  codes_to_string(codes)
+  @doc """
+  ## Examples
+
+    iex> Base58Encode.encode("hello")
+    "Cn8eVZg"
+
+    iex> Base58Encode.encode(42)
+    :error
+  """
+
+ def encode(binary) when is_binary(binary) do
+   case Integer.parse(Base.encode16(binary), 16) do
+      :error -> :error
+
+      {decimal, _} ->
+        codes = get_codes(decimal, [])
+        codes_to_string(codes)
+   end
  end
 
+ # If the parameter is not a binary, return an error
+ def encode(_), do: :error
+
+
+# return a list of codes (codepoint of base58)
  defp get_codes(int, codes) do
    rest = div(int, 58)
    code = rem(int, 58)
    if  rest == 0 do
      [code | codes]
    else
      get_codes(rest, [code | codes])
-  end
+   end
  end
 
+ # match codepoints to the alphabet of base58
  defp codes_to_string(codes) do
   alphabet =  [ '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',
                 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L',
@@ -25,7 +49,7 @@ defmodule Base58Encode do
                 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' ]
 
   codes
-  |> Enum.map(fn c -> Enum.at(alphabet, c) end)
+  |> Enum.map(&(Enum.at(alphabet, &1)))
   |> Enum.join()
  end
 

test/base58_encode_test.exs

@@ -0,0 +1,18 @@
+defmodule Base58EncodeTest do
+  use ExUnit.Case
+  doctest Base58Encode
+
+  describe "Testing encode function" do
+    test "returns base58 for the string foo" do
+      assert "bQbp" == Base58Encode.encode("foo")
+    end
+
+    test "returns error if parameter is not a binary" do
+      assert :error == Base58Encode.encode(23)
+    end
+
+    test "returns z when binary is represented by 57" do
+      assert "z" == Base58Encode.encode(<<57>>)
+    end
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()