<?php
/**
 * @author Robin J. Rogge <rrogge@bigpoint.net>
 * @link http://www.pradosoft.com/
 * @copyright 2010 Bigpoint GmbH
 * @license http://www.pradosoft.com/license/
 * @since 3.2
 * @package Prado\Web\Services
 */

namespace Prado\Web\Services;

/**
 * TRpcService class
 *
 * The TRpcService class is a generic class that can be extended and used to implement
 * rpc services using different servers and protocols.
 * 
 * A server is a {@link TModule} that must subclass {@link TRpcServer}: its role is
 * to be an intermediate, moving data between the service and the provider. The base
 * {@link TRpcServer} class should suit the most common needs, but can be sublassed for
 * logging and debugging purposes, or to filter and modify the request/response on the fly.
 * 
 * A protocol is a {@link TModule} that must subclass {@link TRpcProtocol}: its role is
 * to implement the protocol that exposes the rpc api. Prado already implements two
 * protocols: {@link TXmlRpcProtocol} for Xml-Rpc request and {@link TJsonRpcProtocol} for
 * JSON-Rpc requests.
 *
 * A provider is a {@link TModule} that must subclass {@link TRpcApiProvider}: its role is
 * to implement the methods that are available through the api. Each defined api must be
 * a sublass of the abstract class {@link TRpcApiProvider} and implement its methods.
 *
 * The flow of requests and reponses is the following:
 * Request <-> TRpcService <-> TRpcServer <-> TRpcProtocol <-> TRpcApiProvider <-> Response
 *
 * To define an rpc service, add the proper application configuration:
 *
 * <code>
 * <service id="rpc" class="System.Web.Services.TRpcService">
 * 	 <rpcapi id="customers" class="Application.Api.CustomersApi" />
 *   <modules>
 *     <!--  register any module needed by the service here -->
 *   </modules>
 * </service>
 * </code>
 *
 * An api can be registered adding a proper <rpcapi ..> definition inside the service
 * configuration. Each api definition must contain an id property and a class name
 * expressed in namespace format. When the service receives a request for that api,
 * the specified class will be instanciated in order to satisfy the request.
 *
 * @author Robin J. Rogge <rrogge@bigpoint.net>
 * @package Prado\Web\Services
 * @since 3.2
 **/
class TRpcService extends TService
{
	/**
	 * const string base api provider class which every API must extend
	 */
	const BASE_API_PROVIDER = 'TRpcApiProvider';

	/**
	 * const string base RPC server implementation
	 */
	const BASE_RPC_SERVER = 'TRpcServer';

	/**
	 * @var array containing mimetype to protocol handler mappings
	 */
	protected $protocolHandlers = array(
		'application/json' => 'TJsonRpcProtocol',
		'text/xml' => 'TXmlRpcProtocol'
	);

	/**
	 * @var array containing API provider and their configured properties
	 */
	protected $apiProviders = array();

	// methods

	/**
	 * Creates the API provider instance for the current request
	 * @param TRpcProtocol $protocolHandler instance
	 * @param string $providerId
	 */
	public function createApiProvider(TRpcProtocol $protocolHandler, $providerId)
	{
		$_properties = $this->apiProviders[$providerId];

		if(($_providerClass = $_properties->remove('class')) === null)
			throw new TConfigurationException('rpcservice_apiprovider_required');

		Prado::using($_providerClass);

		$_providerClassName = ($_pos = strrpos($_providerClass, '.')) !== false ? substr($_providerClass, $_pos + 1) : $_providerClass;
		if(!is_subclass_of($_providerClassName, self::BASE_API_PROVIDER))
			throw new TConfigurationException('rpcservice_apiprovider_invalid');

		if(($_rpcServerClass = $_properties->remove('server')) === null)
			$_rpcServerClass = self::BASE_RPC_SERVER;

		Prado::using($_rpcServerClass);

		$_rpcServerClassName = ($_pos = strrpos($_rpcServerClass, '.')) !== false ? substr($_rpcServerClass, $_pos + 1) : $_rpcServerClass;
		if($_rpcServerClassName!==self::BASE_RPC_SERVER && !is_subclass_of($_rpcServerClassName, self::BASE_RPC_SERVER))
			throw new TConfigurationException('rpcservice_rpcserver_invalid');

		$_apiProvider = new $_providerClassName(new $_rpcServerClassName($protocolHandler));
		$_apiProvider->setId($providerId);

		foreach($_properties as $_key => $_value)
			$_apiProvider->setSubProperty($_key, $_value);

		return $_apiProvider;
	}

	/**
	 * Initializes the service
	 * @param TXmlElement $config containing the module configuration
	 */
	public function init($config)
	{
		$this->loadConfig($config);
	}

	/**
	 * Loads the service configuration
	 * @param TXmlElement $xml configuration
	 */
	public function loadConfig(TXmlElement $xml)
	{
		foreach($xml->getElementsByTagName('rpcapi') as $_apiProviderXml)
		{
			$_properties = $_apiProviderXml->getAttributes();

			if(($_id = $_properties->remove('id')) === null || $_id == "")
				throw new TConfigurationException('rpcservice_apiproviderid_required');

			if(isset($this->apiProviders[$_id]))
				throw new TConfigurationException('rpcservice_apiproviderid_duplicated');

			$this->apiProviders[$_id] = $_properties;
		}
	}

	/**
	 * Runs the service
	 */
	public function run()
	{
		$_request = $this->getRequest();

		if(($_providerId = $_request->getServiceParameter()) == "")
			throw new THttpException(400, 'RPC API-Provider id required');
		
		if(($_method = $_request->getRequestType()) != 'POST')
			throw new THttpException(405, 'Invalid request method "'.$_method.'"!'); // TODO Exception muss "Allow POST" Header setzen

		if(($_mimeType = $_request->getContentType()) === null)
			throw new THttpException(406, 'Content-Type is missing!'); // TODO Exception muss gültige Content-Type werte zurück geben

		if(!in_array($_mimeType, array_keys($this->protocolHandlers)))
			throw new THttpException(406, 'Unsupported Content-Type!'); // TODO see previous

		$_protocolHandlerClass = $this->protocolHandlers[$_mimeType];
		$_protocolHandler = new $_protocolHandlerClass;

		if(($_result = $this->createApiProvider($_protocolHandler, $_providerId)->processRequest()) !== null)
		{
			$_response = $this->getResponse();
			$_protocolHandler->createResponseHeaders($_response);
			$_response->write($_result);
		}
	}
}