<?php
// Own namespace
namespace Org\Mxchange\CoreFramework\Handler\Task;

// Import framework stuff
use Org\Mxchange\CoreFramework\Bootstrap\FrameworkBootstrap;
use Org\Mxchange\CoreFramework\Factory\Object\ObjectFactory;
use Org\Mxchange\CoreFramework\Generic\FrameworkInterface;
use Org\Mxchange\CoreFramework\Handler\BaseHandler;
use Org\Mxchange\CoreFramework\Registry\Registerable;
use Org\Mxchange\CoreFramework\Task\Taskable;
use Org\Mxchange\CoreFramework\Traits\Iterator\IteratorTrait;
use Org\Mxchange\CoreFramework\Traits\Lists\ListableTrait;
use Org\Mxchange\CoreFramework\Traits\Visitor\VisitorTrait;
use Org\Mxchange\CoreFramework\Visitor\Visitable;

// Import SPL stuff
use \InvalidArgumentException;
use \UnexpectedValueException;

/**
 * A Task handler
 *
 * @author		Roland Haeder <webmaster@shipsimu.org>
 * @version		0.0.0
 * @copyright	Copyright (c) 2007, 2008 Roland Haeder, 2009 - 2023 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 {
	// Load traits
	use IteratorTrait;
	use ListableTrait;
	use VisitorTrait;

	// Exception constants
	const EXCEPTION_TASK_IS_INVALID = 0xb00;

	/**
	 * Protected constructor
	 *
	 * @return	void
	 */
	private function __construct () {
		// Call parent constructor
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: CONSTRUCTWD!');
		parent::__construct(__CLASS__);

		// Set handler name
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('TASK-HANDLER: Setting handlerName=task ...');
		$this->setHandlerName('task');

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

	/**
	 * Creates an instance of this class
	 *
	 * @return	$handlerInstance	An instance of a HandleableTask class
	 */
	public static final function createTaskHandler () {
		// Get new instance
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: CALLED!');
		$handlerInstance = new TaskHandler();

		// Output debug message
		self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('TASK-HANDLER: 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__, __LINE__)->debugMessage('TASK-HANDLER: Task handler initialized.');

		// Return the prepared instance
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER:handlerInstance=%s - EXIT!', $handlerInstance->__toString()));
		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
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: CALLED!');
		$updateTask = false;

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

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

		// Is the task not yet started?
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: currentTask()=%d', count($currentTask)));
		if ($currentTask['task_started'] === false) {
			// Determine difference between current time and registration
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: currentTask[id]=%s has not started yet, checking ...', $currentTask['id']));
			$diff = ($this->getMilliTime() - $currentTask['task_registered']) * 1000;

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

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

			// Debug message
			self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Task %s started with startup_delay=%dms', $currentTask['id'], $currentTask['task_startup_delay']));
		}

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

		// Is the interval delay reached?
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('TASK-HANDLER: Task ' . $currentTask['id'] . ' diff=' . $diff . ',task_interval_delay=' . $currentTask['task_interval_delay'] . ',task_max_runs=' . $currentTask['task_max_runs'] . ',task_total_runs=' . $currentTask['task_total_runs']);
		if ((($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?
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: currentTask[id]=%s has reached interval ... updateTask=%d', $currentTask['id'], intval($updateTask)));
			if ($updateTask === true) {
				// Update the task before leaving
				//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Updating task %s ...', $currentTask['id']));
				$this->updateTask($currentTask);
			}

			// Skip this silently
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Task %s has been updated - EXIT!', $currentTask['id']));
			return;
		}

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

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

		// Update the task
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Updating task %s ...', $currentTask['id']));
		$this->updateTask($currentTask);

		// And visit/run it
		// @TODO Messurement can be added around this call
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Invoking currentTask[task_instance]->accept(%s), task_instance=%s ...', $this->getVisitorInstance()->__toString(), $currentTask['task_instance']->__toString()));
		$currentTask['task_instance']->accept($this->getVisitorInstance());

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

	/**
	 * Updates given task by updating the underlaying list
	 *
	 * @param	$taskEntry	An array with a task
	 * @return	void
	 */
	private function updateTask (array $taskEntry) {
		// Get the key from current iteration
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: taskEntry()=%d - CALLED!', count($taskEntry)));
		$key = $this->getListInstance()->getIterator()->key();

		// Get the hash from key
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: key=%s', $key));
		$hash = $this->getListInstance()->getHashByIndex($key);

		// Update the entry
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Invoking this->listInstance->updateCurrentEntryByHash(%s,taskEntry()=%d) ...', $hash, count($taskEntry)));
		$this->getListInstance()->updateCurrentEntryByHash($hash, $taskEntry);

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

	/**
	 * Unregisters the given task
	 *
	 * @param	$taskData	Data of the task
	 * @return	void
	 */
	private function unregisterTask (array $taskData) {
		// Remove the entry
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Removing task %s from queue - CALLED!', $taskData['id']));
		$this->getListInstance()->removeEntry('tasks', $taskData);

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Removing task %s from queue - EXIT!', $taskData['id']));
	 }

	/**
	 * 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
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: taskInstance=%s - CALLED!', $taskInstance->__toString()));
		$taskName = '';

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

		// Search all instances
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: taskList()=%d', count($taskList)));
		foreach ($taskList as $currentTask) {
			// Does it match given task instance?
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: currentTask[id=%s', $currentTask['id']));
			if ($currentTask['task_instance']->equals($taskInstance)) {
				// Found it
				$taskName = $currentTask['id'];

				// Abort here
				//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: taskName=%s - BREAK!', $taskName));
				break;
			}
		}

		// Return found name
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: taskName=%s - EXIT!', $taskName));
		return $taskName;
	}

	/**
	 * Registers a task with a task handler.
	 *
	 * @param	$taskName		A task name to register the task on
	 * @param	$taskInstance	An instance of a Taskable class
	 * @return	void
	 * @throws	InvalidArgumentException	If a parameter is not valid
	 * @throws	UnexpectedValueException	If an unexpected value has been configured
	 */
	public function registerTask (string $taskName, Taskable $taskInstance) {
		// Is the parameter valid
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: taskName=%s,taskInstance - CALLED!', $taskName, $taskInstance->__toString()));
		if (empty($taskName)) {
			// Task name cannot be empty
			throw new InvalidArgumentException('Parameter "taskName" is empty', FrameworkInterface::EXCEPTION_INVALID_ARGUMENT);
		}

		// Get interval delay, startup delay and max runs
		$intervalDelay = FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('task_' . $taskName . '_interval_delay');
		$startupDelay = FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('task_' . $taskName . '_startup_delay');
		$maxRuns = FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('task_' . $taskName . '_max_runs');

		// If the task is 'idle_loop', a deplay of zero seconds is fine
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: intervalDelay=%d,startupDelay=%d,maxRuns=%d', $intervalDelay, $startupDelay, $maxRuns));
		if ($intervalDelay < 0) {
			// Invalid configuration value
			throw new UnexpectedValueException(sprintf('taskName=%s has intervalDelay=%d below zero', $taskName, $intervalDelay), FrameworkInterface::EXCEPTION_UNEXPECTED_VALUE);
		} elseif ($startupDelay < 0) {
			// Invalid configuration value
			throw new UnexpectedValueException(sprintf('taskName=%s has startupDelay=%d below zero', $taskName, $startupDelay), FrameworkInterface::EXCEPTION_UNEXPECTED_VALUE);
		} elseif ($maxRuns < 0) {
			// Invalid configuration value
			throw new UnexpectedValueException(sprintf('taskName=%s has maxRuns=%d below zero', $taskName, $maxRuns), FrameworkInterface::EXCEPTION_UNEXPECTED_VALUE);
		} elseif ($taskName != 'idle_loop' && $intervalDelay == 0) {
			// Only idle_loop can have a zero interval delay
			throw new UnexpectedValueException(sprintf('taskName=%s has zero interval delay which is only valid for "idle_loop" task', $taskName), FrameworkInterface::EXCEPTION_UNEXPECTED_VALUE);
		} elseif ($taskName != 'idle_loop' && $startupDelay == 0) {
			// Only idle_loop can have a zero interval delay
			throw new UnexpectedValueException(sprintf('taskName=%s has zero startup delay which is only valid for "idle_loop" task', $taskName), FrameworkInterface::EXCEPTION_UNEXPECTED_VALUE);
		}

		// Create the entry
		$taskEntry = [
			// 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'       => $maxRuns,
		];

		// Add the entry
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Invoking this->listInstance->addEntry(tasks,taskEntry()=%d) ...', count($taskEntry)));
		$this->getListInstance()->addEntry('tasks', $taskEntry);

		// Debug message
		self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Task registered: taskName=%s (taskInstance=%s), startupDelay=%dms, intervalDelay=%dms, maxRuns=%d ...',
			$taskName,
			$taskInstance->__toString(),
			$taskEntry['task_startup_delay'],
			$taskEntry['task_interval_delay'],
			$taskEntry['task_max_runs'],
		));

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

	/**
	 * 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?
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: CALLED!');
		$tasksLeft = ($this->getListInstance()->count() > 0);

		// Return result
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: tasksLeft=%d - EXIT!', intval($tasksLeft)));
		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?
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: CALLED!');
		if (!$this->getListInstance()->getIterator()->valid()) {
			// Rewind to the beginning for next loop
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: Invoking this->listInstance->iterator->rewind() ...');
			$this->getListInstance()->getIterator()->rewind();
		}

		// Try to execute the task
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: Invoking this->executeCurrentTask() ...');
		$this->executeCurrentTask();

		// Go to next entry
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: Invoking this->listInstance->iterator->next() ...');
		$this->getListInstance()->getIterator()->next();

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

	/**
	 * 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
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: Invoking this->listInstance->iterator->rewind() - CALLED!');
		$this->getListInstance()->getIterator()->rewind();

		// Remember all tasks that has been shutdown for removal
		self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Shutting down all %d tasks...', $this->getListInstance()->count()));
		$tasks = [];

		// Instance a visitor
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('TASK-HANDLER: Setting visitorInstance=shutdown_task_visitor_class from configuration ...');
		$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();

			// Shutdown the task
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('TASK-HANDLER: Shutting down task ' . $currentTask['id'] . ' (taskInstance=' . $currentTask['task_instance']->__toString() . ') ...');
			$currentTask['task_instance']->accept($this->getVisitorInstance());

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

			// Advance to next one
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: Invoking this->listInstance->iterator->next() ...');
			$this->getListInstance()->getIterator()->next();
		}

		// Remove all tasks
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage(sprintf('TASK-HANDLER: Shutdown of all tasks completed. tasks()=%d', count($tasks)));
		foreach ($tasks as $taskEntry) {
			// Unregister this task
			//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('TASK-HANDLER: Invokint this->unregisterTask(taskEntry()=%d) ...', count($taskEntry)));
			$this->unregisterTask($taskEntry);
		}

		// Trace message
		//* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('TASK-HANDLER: EXIT!');
	}

}