oauth2

# OAuth2 (Client)
> An Elixir OAuth2 Client
[![Build Status](https://travis-ci.org/scrogson/oauth2.svg?branch=master)](https://travis-ci.org/scrogson/oauth2)
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## Install
```elixir
# mix.exs
def application do
  # Add the application to your list of applications.
  # This will ensure that it will be included in a release.
  [applications: [:logger, :oauth2]]
end
defp deps do
  # Add the dependency
  [{:oauth2, "~> 0.9"}]
end
```
## Configure a serializer
This library can be configured to handle encoding and decoding requests and
responses automatically.
If you're using [Poison](https://hex.pm/packages/poison) for JSON in your
application, this library is already pre-configured to use it for `"application/json"`
request and response bodies. You will still need to include it as a dependency though.
If you need to handle different MIME types, you can simply configure it like so:
```elixir
# config/config.exs
config :oauth2,
  serializers: %{
    "application/vnd.api+json" => Poison,
    "application/xml" => MyApp.XmlParser,
  }
```
The `serializers` option is a map where the keys are MIME types and the values
are modules.
The modules are expected to export `encode!/1` and `decode!/1`.
```elixir
defmodule MyApp.XmlParser do
  def encode!(data), do: # ...
  def decode!(binary), do: # ...
end
```
## Debug mode
Some times its handy to see what's coming back from the response when getting
a token. You can configure OAuth2 to output the response like so:
```elixir
config :oauth2, debug: true
```
## Usage
Current implemented strategies:
- Authorization Code
- Password
- Client Credentials
### Authorization Code Flow (AuthCode Strategy)
```elixir
# 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
```
## Write Your Own Strategy
Here's an example strategy for GitHub:
```elixir
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"
    ])
  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_param(:client_secret, client.client_secret)
    |> put_header("accept", "application/json")
    |> OAuth2.Strategy.AuthCode.get_token(params, headers)
  end
end
```
Here's how you'd use the example GitHub strategy:
Generate the authorize URL and redirect the client for authorization.
```elixir
GitHub.authorize_url!
```
Capture the `code` in your callback route on your server and use it to obtain an access token.
```elixir
client = GitHub.get_token!(code: code)
```
Use the access token to access desired resources.
```elixir
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
```
## Examples
- [Authenticate with Github (OAuth2/Phoenix)](https://github.com/scrogson/oauth2_example)
## License
The MIT License (MIT)
Copyright (c) 2015 Sonny Scroggin
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.