github.ex

defmodule Api.OAuth.Github do
  use OK.Pipe

  @authorize_url "https://github.com/login/oauth/authorize"
  @token_url "https://github.com/login/oauth/access_token"
  @api_url_base "https://api.github.com"
  @base_url "http://localhost:4000"
  @client_id System.get_env("GITHUB_CLIENT_ID")
  @client_secret System.get_env("GITHUB_CLIENT_SECRET")

  def client(token) do
    middleware = [
      {Tesla.Middleware.BaseUrl, @api_url_base},
      Tesla.Middleware.JSON,
      {Tesla.Middleware.Headers,
       [
         {"authorization", "token: " <> token},
         {"User-Agent", "AuthKit:#{@client_id}"}
       ]}
    ]

    Tesla.client(middleware)
  end

  def get_url(state) do
    Tesla.get(@authorize_url,
      query: [
        response_type: "code",
        client_id: @client_id,
        state: state,
        redirect_uri: @base_url <> "/test"
      ]
    )
    ~>> Map.get(:headers)
    |> Enum.find(fn {x, _} -> x == "location" end)
    |> elem(1)
  end

  def get_token(code) do
    Tesla.get(@token_url,
      query: [
        grant_type: "authorization_code",
        client_id: @client_id,
        client_secret: @client_secret,
        redirect_uri: @base_url <> "/test",
        code: code
      ]
    )
    ~>> Map.get(:body)
    |> URI.decode_query()
    |> Map.get("access_token")
  end

  def generate_state do
    :crypto.strong_rand_bytes(25)
    |> Base.url_encode64()
    |> binary_part(0, 25)
  end

  def user_repos(client, username) do
    Tesla.get(client, "/users/" <> username <> "/repos")
  end

  def user_installations(client, username) do
    Tesla.get(client, "/user/installations")
  end
end