# mix.exs

defp deps do
  # Add the dependency
  [
    {:oauth2, "~> 2.0"},
    {:hackney, "~> 1.18"} # depending on what tesla adapter you use
  ]
end

OAuth2.Client.put_serializer(client, "application/vnd.api+json", Jason)
OAuth2.Client.put_serializer(client, "application/xml", MyApp.Parsers.XML)

defmodule MyApp.Parsers.XML do
  def encode!(data), do: # ...
  def decode!(binary), do: # ...
end

config :oauth2, adapter: Tesla.Adapter.Mint

config :oauth2, middleware: [
  Tesla.Middleware.Retry,
  {Tesla.Middleware.Fuse, name: :example}
]

config :oauth2, debug: true

# Initialize a client with client_id, client_secret, site, and redirect_uri.
# The strategy option is optional as it defaults to `OAuth2.Strategy.AuthCode`.

client = OAuth2.Client.new([
  strategy: OAuth2.Strategy.AuthCode, #default
  client_id: "client_id",
  client_secret: "abc123",
  site: "https://auth.example.com",
  redirect_uri: "https://example.com/auth/callback"
])

# Generate the authorization URL and redirect the user to the provider.
OAuth2.Client.authorize_url!(client)
# => "https://auth.example.com/oauth/authorize?client_id=client_id&redirect_uri=https%3A%2F%2Fexample.com%2Fauth%2Fcallback&response_type=code"

# Use the authorization code returned from the provider to obtain an access token.
client = OAuth2.Client.get_token!(client, code: "someauthcode")

# Use the access token to make a request for resources
resource = OAuth2.Client.get!(client, "/api/resource").body

# Initializing a client with the strategy `OAuth2.Strategy.ClientCredentials`

client = OAuth2.Client.new([
  strategy: OAuth2.Strategy.ClientCredentials,
  client_id: "client_id",
  client_secret: "abc123",
  site: "https://auth.example.com"
])

# Request a token from with the newly created client
# Token will be stored inside the `%OAuth2.Client{}` struct (client.token)
client = OAuth2.Client.get_token!(client)

# client.token contains the `%OAuth2.AccessToken{}` struct

# raw access token
access_token = client.token.access_token

# raw refresh token - use a client with `OAuth2.Strategy.Refresh` for refreshing the token
refresh_token = client.token.refresh_token

refresh_client = OAuth2.Client.new([
  strategy: OAuth2.Strategy.Refresh,
  client_id: "client_id",
  client_secret: "abc123",
  site: "https://auth.example.com",
  params: %{"refresh_token" => refresh_token}
])

# refresh_client.token contains the `%OAuth2.AccessToken{}` struct again
refresh_client = OAuth2.Client.get_token!(refresh_client)

defmodule GitHub do
  use OAuth2.Strategy

  # Public API

  def client do
    OAuth2.Client.new([
      strategy: __MODULE__,
      client_id: System.get_env("GITHUB_CLIENT_ID"),
      client_secret: System.get_env("GITHUB_CLIENT_SECRET"),
      redirect_uri: "http://myapp.com/auth/callback",
      site: "https://api.github.com",
      authorize_url: "https://github.com/login/oauth/authorize",
      token_url: "https://github.com/login/oauth/access_token"
    ])
    |> OAuth2.Client.put_serializer("application/json", Jason)
  end

  def authorize_url! do
    OAuth2.Client.authorize_url!(client(), scope: "user,public_repo")
  end

  # you can pass options to the underlying http library via `opts` parameter
  def get_token!(params \\ [], headers \\ [], opts \\ []) do
    OAuth2.Client.get_token!(client(), params, headers, opts)
  end

  # Strategy Callbacks

  def authorize_url(client, params) do
    OAuth2.Strategy.AuthCode.authorize_url(client, params)
  end

  def get_token(client, params, headers) do
    client
    |> put_header("accept", "application/json")
    |> OAuth2.Strategy.AuthCode.get_token(params, headers)
  end
end

GitHub.authorize_url!

client = GitHub.get_token!(code: code)

user = OAuth2.Client.get!(client, "/user").body

# Or
case OAuth2.Client.get(client, "/user") do
  {:ok, %OAuth2.Response{body: user}} ->
    user
  {:error, %OAuth2.Response{status_code: 401, body: body}} ->
    Logger.error("Unauthorized token")
  {:error, %OAuth2.Error{reason: reason}} ->
    Logger.error("Error: #{inspect reason}")
end