<?php
/**
 * A Task handler
 *
 * @author		Roland Haeder <webmaster@shipsimu.org>
 * @version		0.0.0
 * @copyright	Copyright (c) 2007, 2008 Roland Haeder, 2009 - 2015 Core Developer Team
 * @license		GNU GPL 3.0 or any newer version
 * @link		http://www.shipsimu.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
class TaskHandler extends BaseHandler implements Registerable, HandleableTask {
	// Exception constants
	const EXCEPTION_TASK_IS_INVALID = 0xb00;

	/**
	 * Protected constructor
	 *
	 * @return	void
	 */
	protected function __construct () {
		// Call parent constructor
		parent::__construct(__CLASS__);

		// Set handler name
		$this->setHandlerName('task');
	}

	/**
	 * Creates an instance of this class
	 *
	 * @return	$handlerInstance	An instance of a HandleableTask class
	 */
	public static final function createTaskHandler () {
		// Get new instance
		$handlerInstance = new TaskHandler();

		// Output debug message
		self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Initializing task handler.');

		// Init the task list
		$handlerInstance->setListInstance(ObjectFactory::createObjectByConfiguredName('task_list_class'));

		// Get default instance
		$handlerInstance->setIteratorInstance($handlerInstance->getListInstance()->getIterator());

		// Init visitor instance for faster loop
		$handlerInstance->setVisitorInstance(ObjectFactory::createObjectByConfiguredName('active_task_visitor_class'));

		// Register the first (and generic) idle-loop task
		$taskInstance = ObjectFactory::createObjectByConfiguredName('idle_task_class');
		$handlerInstance->registerTask('idle_loop', $taskInstance);

		// Output debug message
		self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Task handler initialized.');

		// Return the prepared instance
		return $handlerInstance;
	}

	/**
	 * Tries to execute the given task. If as task should not be started (yet)
	 * or the interval time (see task_interval_delay) is not yet reached the
	 * task is quietly skipped.
	 *
	 * @return	void
	 * @throws	InvalidTaskException	If the current task is invalid
	 */
	private function executeCurrentTask () {
		// Update no task by default
		$updateTask = FALSE;

		// Is the current task valid?
		if (!$this->getListInstance()->getIterator()->valid()) {
			// Not valid!
			throw new InvalidTaskException($this, self::EXCEPTION_TASK_IS_INVALID);
		} // END - if

		// Get current task
		$currentTask = $this->getListInstance()->getIterator()->current();

		// Is the task not yet started?
		if ($currentTask['task_started'] === FALSE) {
			// Determine difference between current time and registration
			$diff = ($this->getMilliTime() - $currentTask['task_registered']) * 1000;

			// Should we start now?
			if ($diff < $currentTask['task_startup_delay']) {
				// Skip this silently
				//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Task ' . $currentTask['id'] . ' not started: diff=' . $diff . ',task_startup_delay=' . $currentTask['task_startup_delay']);
				return;
			} // END - if

			// Launch the task and mark it as updated
			$currentTask['task_started'] = TRUE;
			$updateTask = TRUE;

			// Debug message
			self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Task ' . $currentTask['id'] . ' started with startup_delay=' . $currentTask['task_startup_delay'] . 'ms');
		} // END - if

		// Get time difference from interval delay
		$diff = ($this->getMilliTime() - $currentTask['task_last_activity']) * 1000;

		// Debug message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Task ' . $currentTask['id'] . ' diff=' . $diff . ',task_interval_delay=' . $currentTask['task_interval_delay'] . ',task_max_runs=' . $currentTask['task_max_runs'] . ',task_total_runs=' . $currentTask['task_total_runs']);

		// Is the interval delay reached?
		if ((($diff < $currentTask['task_interval_delay']) && ($currentTask['task_max_runs'] == 0)) || (($currentTask['task_max_runs'] > 0) && ($currentTask['task_total_runs'] == $currentTask['task_max_runs']))) {
			// Should we update the task from startup?
			if ($updateTask === TRUE) {
				// Update the task before leaving
				$this->updateTask($currentTask);
			} // END - if

			// Skip this silently
			return;
		} // END - if

		// Set last activity
		$currentTask['task_last_activity'] = $this->getMilliTime();

		// Count this run
		$currentTask['task_total_runs']++;

		// Update the task
		$this->updateTask($currentTask);

		// And visit/run it
		// @TODO Messurement can be added around this call
		$currentTask['task_instance']->accept($this->getVisitorInstance());
	}

	/**
	 * Updates given task by updating the underlaying list
	 *
	 * @param	$taskEntry	An array with a task
	 * @return	void
	 */
	private function updateTask (array $taskEntry) {
		// Get the key from current iteration
		$key = $this->getListInstance()->getIterator()->key();

		// Get the hash from key
		$hash = $this->getListInstance()->getHash($key);

		// Update the entry
		$this->getListInstance()->updateCurrentEntryByHash($hash, $taskEntry);
	}

	/**
	 * Unregisters the given task
	 *
	 * @param	$taskData	Data of the task
	 * @return	void
	 */
	private function unregisterTask (array $taskData) {
		// Debug output
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Removing task ' . $taskData['id'] . ' from queue - CALLED!');

		// Remove the entry
		$this->getListInstance()->removeEntry('tasks', $taskData);

		// Debug output
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Removing task ' . $taskData['id'] . ' from queue - EXIT!');
	 }

	/**
	 * Searches a task by given instance
	 *
	 * @param	$taskInstanc	An instanceof a Taskable class
	 * @return	$taskName		Name of the task as used while registration
	 */
	public function searchTask (Taskable $taskInstance) {
		// Default is an empty (not found) task name
		$taskName = '';

		// Get whole list
		$taskList = $this->getListInstance()->getArrayFromList('tasks');

		// Search all instances
		foreach ($taskList as $currentTask) {
			// Does it match given task instance?
			if ($currentTask['task_instance']->equals($taskInstance)) {
				// Found it
				$taskName = $currentTask['id'];

				// Abort here
				break;
			} // END - if
		} // END - foreach

		// Return found name
		return $taskName;
	}

	/**
	 * Registers a task with a task handler.
	 *
	 * @param	$taskName		A task name to register the task on
	 * @param	$taskInstance	The instance we should register as a task
	 * @return	void
	 */
	public function registerTask ($taskName, Visitable $taskInstance) {
		// Get interval delay
		$intervalDelay = $this->getConfigInstance()->getConfigEntry('task_' . $taskName . '_interval_delay');
		$startupDelay  = $this->getConfigInstance()->getConfigEntry('task_' . $taskName . '_startup_delay');

		// If the task is 'idle_loop', a deplay of zero seconds is fine
		assert($intervalDelay >= 0);
		assert(($taskName != 'idle_loop') && ($intervalDelay > 0));
		assert(($taskName != 'idle_loop') && ($startupDelay > 0));

		// Create the entry
		$taskEntry = array(
			// Identifier for the generateHash() method
			'id'                  => $taskName,
			// Whether the task is started
			'task_started'        => FALSE,
			// Whether the task is paused (not yet implemented)
			'task_paused'         => FALSE,
			// Whether the task can be paused (not yet implemented)
			'task_pauseable'      => TRUE,
			// Timestamp of registration
			'task_registered'     => $this->getMilliTime(),
			// Last activity timestamp
			'task_last_activity'  => 0,
			// Total runs of this task
			'task_total_runs'     => 0,
			// Task instance itself
			'task_instance'       => $taskInstance,
			// Startup delay in milliseconds
			'task_startup_delay'  => $startupDelay,
			// Interval time (delay) in milliseconds before this task is executed again
			'task_interval_delay' => $intervalDelay,
			// How often should this task run?
			'task_max_runs'       => $this->getConfigInstance()->getConfigEntry('task_' . $taskName . '_max_runs'),
		);

		// Add the entry
		$this->getListInstance()->addEntry('tasks', $taskEntry);

		// Debug message
		self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Task registered: taskName=' . $taskName .
			' (taskInstance=' . $taskInstance->__toString() . ')' .
			', startupDelay=' . $taskEntry['task_startup_delay'] . 'ms' .
			', intervalDelay=' . $taskEntry['task_interval_delay'] . 'ms' .
			', maxRuns=' . $taskEntry['task_max_runs'] . ' ...'
		);
	}

	/**
	 * Checks whether tasks are left including idle task
	 *
	 * @return	$tasksLeft	Whether there are tasks left to handle
	 */
	public function hasTasksLeft () {
		// Do we have tasks there?
		$tasksLeft = (($this->getListInstance() instanceof Listable) && ($this->getListInstance()->count() > 0));

		// Return result
		return $tasksLeft;
	}

	/**
	 * Handles all tasks by checking if they should startup or if it is their
	 * turn to run. You should use this method in a while() loop in conjuntion
	 * with hasTasksLeft() so you can e.g. shutdown by adding a ShutdownTask
	 * which will attempt to remove all tasks from the task handler.
	 *
	 * @return	void
	 */
	public function handleTasks () {
		// Should we rewind?
		if (!$this->getListInstance()->getIterator()->valid()) {
			// Rewind to the beginning for next loop
			$this->getListInstance()->getIterator()->rewind();
		} // END - if

		// Try to execute the task
		$this->executeCurrentTask();

		// Go to next entry
		$this->getListInstance()->getIterator()->next();
	}

	/**
	 * Shuts down all tasks and the task handler itself. This method should be
	 * called from a corresponding filter class.
	 * 
	 * @return	void
	 */
	public function doShutdown () {
		// Always rewind to the beginning for next loop
		$this->getListInstance()->getIterator()->rewind();

		// Debug message
		self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Shutting down all ' . $this->getListInstance()->count() . ' tasks...');

		// Remember all tasks that has been shutdown for removal
		$tasks = array();

		// Instance a visitor
		$this->setVisitorInstance(ObjectFactory::createObjectByConfiguredName('shutdown_task_visitor_class'));

		// Shutdown all tasks in once go
		while ($this->getListInstance()->getIterator()->valid()) {
			// Get current entry
			$currentTask = $this->getListInstance()->getIterator()->current();

			// Output debug message
			self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Shutting down task ' . $currentTask['id'] . ' (taskInstance=' . $currentTask['task_instance']->__toString() . ') ...');

			// Shutdown the task
			$currentTask['task_instance']->accept($this->getVisitorInstance());

			// Remember this task
			array_push($tasks, $currentTask);

			// Advance to next one
			$this->getListInstance()->getIterator()->next();
		} // END - while

		// Debug message
		self::createDebugInstance(__CLASS__)->debugOutput('TASK-HANDLER[' . __METHOD__ . ':' . __LINE__ . ']: Shutdown of all tasks completed.');

		// Remove all tasks
		foreach ($tasks as $entry) {
			$this->unregisterTask($entry);
		} // END - foreach
	}
}

// [EOF]
?>