Document authentication, closes #32, closes php-http/authentication#1

Author: sagikazarmark

docs/components/authentication.md

@@ -0,0 +1,164 @@
+# Authentication
+
+The Authentication component allows you to to implement authentication methods which can simply update the request
+with authentication detail (for example by adding an `Authorization` header).
+This is useful when you have to send multiple requests to the same endpoint. Using an authentication implementation,
+these details can be separated from the actual requests.
+
+
+## Installation
+
+```
+$ composer require php-http/authentication
+```
+
+
+## Authentication methods
+
+General usage looks like the following:
+
+``` php
+$authentication = new AuthenticationMethod();
+
+/** @var Psr\Http\Message\RequestInterface */
+$authentication->authenticate($request);
+```
+
+
+### Basic Auth
+
+This authentication method accepts two parameters: username and password. Getters/Setters are provided by
+`Http\Authentication\UserPasswordPair` trait.
+
+``` php
+use Http\Authentication\BasicAuth;
+
+$authentication = new BasicAuth('username', 'password');
+
+// These details can be set later as well
+// There are also getters with the appropriate method names
+$authentication->setUsername('username');
+$authentication->setPassword('password');
+```
+
+
+### Bearer
+
+This authentication method accepts one parameter: a token.
+
+``` php
+use Http\Authentication\Bearer;
+
+$authentication = new Bearer('token');
+
+// Token can be set later as well
+$authentication->setToken('token');
+```
+
+
+### Chain
+
+This authentication method accepts one parameter: an array of other authentication methods.
+
+The idea behind this authentication method is that in some cases you might need to
+authenticate the request with multiple methods.
+
+For example it's a common practice to protect development APIs with Basic Auth and the regular token auth as well
+to protect the API from unnecessary processing.
+
+
+``` php
+use Http\Authentication\Chain;
+
+$authenticationChain = [
+    new AuthenticationMethod1(),
+    new AuthenticationMethod2(),
+];
+
+$authentication = new Chain($authenticationChain);
+
+// Authentication chain can be modified later
+$authenticationChain = $authentication->getAuthenticationChain();
+
+array_pop($authenticationChain);
+
+$authentication->setAuthenticationChain($authenticationChain);
+
+$authentication->clearAuthenticationChain();
+
+$authentication->addAuthentication(new AuthenticationMethod3());
+```
+
+
+### Matching
+
+With this authentication method you can conditionally add authentication details to your request by passing a callable
+to it. When a request is passed, the callable is called and used as a boolean value in order to decide whether
+the request should be authenticated or not.
+It also accepts an authentication method instance which does the actual authentication when the condition is
+fulfilled.
+
+For example a common use case is to authenticate requests sent to certain paths.
+
+
+``` php
+use Http\Authentication\Mathing;
+
+$authentication = new Mathing(new AuthenticationMethod1(), function () { return true; });
+
+// There are also getters with the appropriate method names
+$authentication->setAuthentication(new AuthenticationMethod2());
+$authentication->setMatcher(function () { return false; });
+```
+
+
+In order to ease creating matchers for URLs/paths, there is a static factory method for this purpose.
+The first argument is an authentication method, the second is a regexp to match against the URL.
+
+
+``` php
+use Http\Authentication\Mathing;
+
+$authentication = Matching::createUrlMatcher(new AuthenticationMethod(), '\/api');
+```
+
+### WSSE
+
+This method implements [WSSE Authentication](http://www.xml.com/pub/a/2003/12/17/dive.html).
+Just like Basic Auth, it also accepts a username-password pair and exposes the same methods as well.
+
+
+``` php
+use Http\Authentication\Wsse;
+
+$authentication = new Wsse('username', 'password');
+```
+
+
+## Implement your own
+
+Implementing an authentication method is easy: only one method needs to be implemented.
+
+``` php
+use Http\Authentication\Authentication;
+use Psr\Http\Message\RequestInterface;
+
+class MyAuth implements Authentication
+{
+    public function authenticate(RequestInterface $request)
+    {
+        // do something with the request
+
+        // keep in mind that the request is immutable!
+        return $request;
+    }
+}
+```
+
+
+## Integration with HTTPlug
+
+Normally requests must be authenticated "by hand" which is not really convenient.
+
+If you use HTTPlug, you can integrate this component into the client using the
+[authentication plugin](/httplug/plugins/authentication).

docs/httplug/plugins/authentication.md

@@ -1,3 +1,16 @@
 # Authentication Plugin
 
-TODO: explain the authentication plugin
+This plugin uses the [authentication component](/components/authentication) to authenticate all requests sent through
+the client.
+
+
+## Usage
+
+``` php
+use Http\Plugins\PluginClient;
+use Http\Plugins\AuthenticationPlugin;
+
+$pluginClient = new PluginClient(new HttpClient(), [new AuthenticationPlugin(new AuthenticationMethod()]);
+```
+
+Check the [component documentation](/components/authentication) for the list of available authentication methods.