<?php

/**
 * This class is the base class of any SilverStripe object that can be used to handle HTTP requests.
 * 
 * Any RequestHandler object can be made responsible for handling its own segment of the URL namespace.
 * The {@link Director} begins the URL parsing process; it will parse the beginning of the URL to identify which
 * controller is being used.  It will then call {@link handleRequest()} on that Controller, passing it the parameters
 * that it parsed from the URL, and the {@link SS_HTTPRequest} that contains the remainder of the URL to be parsed.
 *
 * You can use ?debug_request=1 to view information about the different components and rule matches for a specific URL.
 *
 * In SilverStripe, URL parsing is distributed throughout the object graph.  For example, suppose that we have a
 * search form that contains a {@link TreeMultiSelectField} named "Groups".  We want to use ajax to load segments of
 * this tree as they are needed rather than downloading the tree right at the beginning.  We could use this URL to get
 * the tree segment that appears underneath
 * 
 * Group #36: "admin/crm/SearchForm/field/Groups/treesegment/36"
 *  - Director will determine that admin/crm is controlled by a new ModelAdmin object, and pass control to that.
 *    Matching Director Rule: "admin/crm" => "ModelAdmin" (defined in mysite/_config.php)
 *  - ModelAdmin will determine that SearchForm is controlled by a Form object returned by $this->SearchForm(), and
 *    pass control to that.
 *    Matching $url_handlers: "$Action" => "$Action" (defined in RequestHandler class)
 *  - Form will determine that field/Groups is controlled by the Groups field, a TreeMultiselectField, and pass
 *    control to that.
 *    Matching $url_handlers: 'field/$FieldName!' => 'handleField' (defined in Form class)
 *  - TreeMultiselectField will determine that treesegment/36 is handled by its treesegment() method.  This method
 *    will return an HTML fragment that is output to the screen.
 *    Matching $url_handlers: "$Action/$ID" => "handleItem" (defined in TreeMultiSelectField class)
 *
 * {@link RequestHandler::handleRequest()} is where this behaviour is implemented.
 * 
 * @package framework
 * @subpackage control
 */
class RequestHandler extends ViewableData {
	
	/**
	 * @var SS_HTTPRequest $request The request object that the controller was called with.
	 * Set in {@link handleRequest()}. Useful to generate the {}
	 */
	protected $request = null;
	
	/**
	 * The DataModel for this request
	 */
	protected $model = null;
	
	/**
	 * This variable records whether RequestHandler::__construct()
	 * was called or not. Useful for checking if subclasses have
	 * called parent::__construct()
	 *
	 * @var boolean
	 */
	protected $brokenOnConstruct = true;
	
	/**
	 * The default URL handling rules.  This specifies that the next component of the URL corresponds to a method to
	 * be called on this RequestHandlingData object.
	 *
	 * The keys of this array are parse rules.  See {@link SS_HTTPRequest::match()} for a description of the rules
	 * available.
	 * 
	 * The values of the array are the method to be called if the rule matches.  If this value starts with a '$', then
	 * the named parameter of the parsed URL wil be used to determine the method name.
	 * @config
	 */
	private static $url_handlers = array(
		'$Action' => '$Action',
	);

	
	/**
	 * Define a list of action handling methods that are allowed to be called directly by URLs.
	 * The variable should be an array of action names. This sample shows the different values that it can contain:
	 *
	 * <code>
	 * array(
	 * 		// someaction can be accessed by anyone, any time
	 *		'someaction', 
	 *		// So can otheraction
	 *		'otheraction' => true, 
	 *		// restrictedaction can only be people with ADMIN privilege
	 *		'restrictedaction' => 'ADMIN', 
	 *		// complexaction can only be accessed if $this->canComplexAction() returns true
	 *		'complexaction' '->canComplexAction' 
	 *	);
	 * </code>
	 * 
	 * Form getters count as URL actions as well, and should be included in allowed_actions.
	 * Form actions on the other handed (first argument to {@link FormAction()} should NOT be included,
	 * these are handled separately through {@link Form->httpSubmission}. You can control access on form actions
	 * either by conditionally removing {@link FormAction} in the form construction,
	 * or by defining $allowed_actions in your {@link Form} class.
	 * @config
	 */
	private static $allowed_actions = null;
	
	public function __construct() {
		$this->brokenOnConstruct = false;

		// Check necessary to avoid class conflicts before manifest is rebuilt
		if(class_exists('NullHTTPRequest')) $this->request = new NullHTTPRequest();
		
		// This will prevent bugs if setDataModel() isn't called.
		$this->model = DataModel::inst();
		
		parent::__construct();
	}
	
	/**
	 * Set the DataModel for this request.
	 */
	public function setDataModel($model) {
		$this->model = $model;
	}
	
	/**
	 * Handles URL requests.
	 *
	 *  - ViewableData::handleRequest() iterates through each rule in {@link self::$url_handlers}.
	 *  - If the rule matches, the named method will be called.
	 *  - If there is still more URL to be processed, then handleRequest() 
	 *    is called on the object that that method returns.
	 *
	 * Once all of the URL has been processed, the final result is returned.  
	 * However, if the final result is an array, this
	 * array is interpreted as being additional template data to customise the 
	 * 2nd to last result with, rather than an object
	 * in its own right.  This is most frequently used when a Controller's 
	 * action will return an array of data with which to
	 * customise the controller.
	 * 
	 * @param $request The {@link SS_HTTPRequest} object that is reponsible for distributing URL parsing
	 * @uses SS_HTTPRequest
	 * @uses SS_HTTPRequest->match()
	 * @return SS_HTTPResponse|RequestHandler|string|array
	 */
	public function handleRequest(SS_HTTPRequest $request, DataModel $model) {
		// $handlerClass is used to step up the class hierarchy to implement url_handlers inheritance
		$handlerClass = ($this->class) ? $this->class : get_class($this);
	
		if($this->brokenOnConstruct) {
			user_error("parent::__construct() needs to be called on {$handlerClass}::__construct()", E_USER_WARNING);
		}
	
		$this->request = $request;
		$this->setDataModel($model);

		$match = $this->findAction($request);

		// If nothing matches, return this object
		if (!$match) return $this;

		// Start to find what action to call. Start by using what findAction returned
		$action = $match['action'];

		// We used to put "handleAction" as the action on controllers, but (a) this could only be called when
		// you had $Action in your rule, and (b) RequestHandler didn't have one. $Action is better
		if ($action == 'handleAction') {
			// TODO Fix LeftAndMain usage
			// Deprecation::notice('3.2.0', 'Calling handleAction directly is deprecated - use $Action instead');
			$action = '$Action';
		}

		// Actions can reference URL parameters, eg, '$Action/$ID/$OtherID' => '$Action',
		if($action[0] == '$') {
			$action = str_replace("-", "_", $request->latestParam(substr($action,1)));
		}

		if(!$action) {
			if(isset($_REQUEST['debug_request'])) {
				Debug::message("Action not set; using default action method name 'index'");
			}
			$action = "index";
		} else if(!is_string($action)) {
			user_error("Non-string method name: " . var_export($action, true), E_USER_ERROR);
		}

		$className = get_class($this);

		try {
			if(!$this->hasAction($action)) {
				return $this->httpError(404, "Action '$action' isn't available on class $className.");
			}
			if(!$this->checkAccessAction($action) || in_array(strtolower($action), array('run', 'init'))) {
				return $this->httpError(403, "Action '$action' isn't allowed on class $className.");
			}
			$result = $this->handleAction($request, $action);
		}
		catch (SS_HTTPResponse_Exception $e) {
			return $e->getResponse();
		}
		catch(PermissionFailureException $e) {
			$result = Security::permissionFailure(null, $e->getMessage());
		}

		if($result instanceof SS_HTTPResponse && $result->isError()) {
			if(isset($_REQUEST['debug_request'])) Debug::message("Rule resulted in HTTP error; breaking");
			return $result;
		}

		// If we return a RequestHandler, call handleRequest() on that, even if there is no more URL to
		// parse. It might have its own handler. However, we only do this if we haven't just parsed an
		// empty rule ourselves, to prevent infinite loops. Also prevent further handling of controller
		// actions which return themselves to avoid infinite loops.
		$matchedRuleWasEmpty = $request->isEmptyPattern($match['rule']);
		$resultIsRequestHandler = is_object($result) && $result instanceof RequestHandler;
		
		if($this !== $result && !$matchedRuleWasEmpty && $resultIsRequestHandler) {
			$returnValue = $result->handleRequest($request, $model);

			// Array results can be used to handle
			if(is_array($returnValue)) $returnValue = $this->customise($returnValue);

			return $returnValue;

		// If we return some other data, and all the URL is parsed, then return that
		} else if($request->allParsed()) {
			return $result;

		// But if we have more content on the URL and we don't know what to do with it, return an error.
		} else {
			return $this->httpError(404, "I can't handle sub-URLs of a $this->class object.");
		}

		return $this;
	}

	protected function findAction($request) {
		$handlerClass = ($this->class) ? $this->class : get_class($this);

		// We stop after RequestHandler; in other words, at ViewableData
		while($handlerClass && $handlerClass != 'ViewableData') {
			$urlHandlers = Config::inst()->get($handlerClass, 'url_handlers', Config::UNINHERITED);

			if($urlHandlers) foreach($urlHandlers as $rule => $action) {
				if(isset($_REQUEST['debug_request'])) {
					Debug::message("Testing '$rule' with '" . $request->remaining() . "' on $this->class");
				}

				if($request->match($rule, true)) {
					if(isset($_REQUEST['debug_request'])) {
						Debug::message(
							"Rule '$rule' matched to action '$action' on $this->class. ".
							"Latest request params: " . var_export($request->latestParams(), true)
						);
					}

					return array('rule' => $rule, 'action' => $action);
				}
			}

			$handlerClass = get_parent_class($handlerClass);
		}
	}

	/**
	 * Given a request, and an action name, call that action name on this RequestHandler
	 *
	 * Must not raise SS_HTTPResponse_Exceptions - instead it should return
	 *
	 * @param $request
	 * @param $action
	 * @return SS_HTTPResponse
	 */
	protected function handleAction($request, $action) {
		$className = get_class($this);

		if(!$this->hasMethod($action)) {
			return new SS_HTTPResponse("Action '$action' isn't available on class $className.", 404);
		}

		$res = $this->extend('beforeCallActionHandler', $request, $action);
		if ($res) return reset($res);

		$actionRes = $this->$action($request);

		$res = $this->extend('afterCallActionHandler', $request, $action);
		if ($res) return reset($res);

		return $actionRes;
	}
	
	/**
	 * Get a array of allowed actions defined on this controller,
	 * any parent classes or extensions.
	 * 
	 * Caution: Since 3.1, allowed_actions definitions only apply
	 * to methods on the controller they're defined on,
	 * so it is recommended to use the $class argument
	 * when invoking this method.
	 *
	 * @param String $limitToClass
	 * @return array|null
	 */
	public function allowedActions($limitToClass = null) {
		if($limitToClass) {
			$actions = Config::inst()->get(
				$limitToClass, 
				'allowed_actions', 
				Config::UNINHERITED | Config::EXCLUDE_EXTRA_SOURCES
			);
		} else {
			$actions = Config::inst()->get(get_class($this), 'allowed_actions');
		}

		if(is_array($actions)) {
			if(array_key_exists('*', $actions)) {
				Deprecation::notice(
					'3.0', 
					'Wildcards (*) are no longer valid in $allowed_actions due their ambiguous '
					. ' and potentially insecure behaviour. Please define all methods explicitly instead.'
				);
			}

			// convert all keys and values to lowercase to 
			// allow for easier comparison, unless it is a permission code
			$actions = array_change_key_case($actions, CASE_LOWER);
			
			foreach($actions as $key => $value) {
				if(is_numeric($key)) $actions[$key] = strtolower($value);
			}

			return $actions;
		} else {
			return null;
		}
	}
	
	/**
	 * Checks if this request handler has a specific action, 
	 * even if the current user cannot access it.
	 * Includes class ancestry and extensions in the checks.
	 *
	 * @param string $action
	 * @return bool
	 */
	public function hasAction($action) {
		if($action == 'index') return true;

		// Don't allow access to any non-public methods (inspect instance plus all extensions)
		$insts = array_merge(array($this), (array)$this->getExtensionInstances());
		foreach($insts as $inst) {
			if(!method_exists($inst, $action)) continue;
			$r = new ReflectionClass(get_class($inst));
			$m = $r->getMethod($action);
			if(!$m || !$m->isPublic()) return false;
		}
		
		$action  = strtolower($action);
		$actions = $this->allowedActions();

		// Check if the action is defined in the allowed actions of any ancestry class
		// as either a key or value. Note that if the action is numeric, then keys are not
		// searched for actions to prevent actual array keys being recognised as actions.
		if(is_array($actions)) {
			$isKey   = !is_numeric($action) && array_key_exists($action, $actions);
			$isValue = in_array($action, $actions, true);
			if($isKey || $isValue) return true;
		}

		$actionsWithoutExtra = $this->config()->get(
			'allowed_actions',
			Config::UNINHERITED | Config::EXCLUDE_EXTRA_SOURCES
		);
		if(!is_array($actions) || !$actionsWithoutExtra) {
			if($action != 'init' && $action != 'run' && method_exists($this, $action)) return true;
		}
		
		return false;
	}

	/**
	 * Return the class that defines the given action, so that we know where to check allowed_actions.
	 */
	protected function definingClassForAction($actionOrigCasing) {
		$action = strtolower($actionOrigCasing);

		$definingClass = null;
		$insts = array_merge(array($this), (array)$this->getExtensionInstances());
		foreach($insts as $inst) {
			if(!method_exists($inst, $action)) continue;
			$r = new ReflectionClass(get_class($inst));
			$m = $r->getMethod($actionOrigCasing);
			return $m->getDeclaringClass()->getName();	
		}
	}
	
	/**
	 * Check that the given action is allowed to be called from a URL.
	 * It will interrogate {@link self::$allowed_actions} to determine this.
	 */
	public function checkAccessAction($action) {
		$actionOrigCasing = $action;
		$action = strtolower($action);

		$isAllowed = false;
		$isDefined = false;
		
		// Get actions for this specific class (without inheritance)
		$definingClass = $this->definingClassForAction($actionOrigCasing);
		$allowedActions = $this->allowedActions($definingClass);	

		// check if specific action is set
		if(isset($allowedActions[$action])) {
			$isDefined = true;
			$test = $allowedActions[$action];
			if($test === true || $test === 1 || $test === '1') {
				// TRUE should always allow access
				$isAllowed = true;
			} elseif(substr($test, 0, 2) == '->') {
				// Determined by custom method with "->" prefix
				list($method, $arguments) = Object::parse_class_spec(substr($test, 2));
				$isAllowed = call_user_func_array(array($this, $method), $arguments);
			} else {
				// Value is a permission code to check the current member against
				$isAllowed = Permission::check($test);
			}
		} elseif(
			is_array($allowedActions) 
			&& (($key = array_search($action, $allowedActions, true)) !== false) 
			&& is_numeric($key)
		) {
			// Allow numeric array notation (search for array value as action instead of key)
			$isDefined = true;
			$isAllowed = true;
		} elseif(is_array($allowedActions) && !count($allowedActions)) {
			// If defined as empty array, deny action
			$isAllowed = false;
		} elseif($allowedActions === null) {
			// If undefined, allow action
			$isAllowed = true;
		}

		// If we don't have a match in allowed_actions,
		// whitelist the 'index' action as well as undefined actions.
		if(!$isDefined && ($action == 'index' || empty($action))) {
			$isAllowed = true;
		}

		return $isAllowed;
	}
	
	/**
	 * Throws a HTTP error response encased in a {@link SS_HTTPResponse_Exception}, which is later caught in
	 * {@link RequestHandler::handleAction()} and returned to the user.
	 *
	 * @param int $errorCode
	 * @param string $errorMessage Plaintext error message
	 * @uses SS_HTTPResponse_Exception
	 */
	public function httpError($errorCode, $errorMessage = null) {
		// Call a handler method such as onBeforeHTTPError404
		$this->extend('onBeforeHTTPError' . $errorCode, $this->request);

		// Call a handler method such as onBeforeHTTPError, passing 404 as the first arg
		$this->extend('onBeforeHTTPError', $errorCode, $this->request);

		// Throw a new exception
		throw new SS_HTTPResponse_Exception($errorMessage, $errorCode);
	}

	/**
	 * Returns the SS_HTTPRequest object that this controller is using.
	 * Returns a placeholder {@link NullHTTPRequest} object unless 
	 * {@link handleAction()} or {@link handleRequest()} have been called,
	 * which adds a reference to an actual {@link SS_HTTPRequest} object.
	 *
	 * @return SS_HTTPRequest|NullHTTPRequest
	 */
	public function getRequest() {
		return $this->request;
	}
	
	/**
	 * Typically the request is set through {@link handleAction()}
	 * or {@link handleRequest()}, but in some based we want to set it manually.
	 * 
	 * @param SS_HTTPRequest
	 */
	public function setRequest($request) {
		$this->request = $request;
	}
}