<?php

/**

 * Semaphore Lock Management

 *

 * @package Social

 */

final class Social_Semaphore {

	/**

	 * Initializes the semaphore object.

	 *

	 * @static

	 * @return Social_Semaphore

	 */

	public static function factory() {

		return new self;

	}

	/**

	 * @var bool

	 */

	protected $lock_broke = false;

	/**

	 * Attempts to start the lock. If the rename works, the lock is started.

	 *

	 * @return bool

	 */

	public function lock() {

		global $wpdb;

		// Attempt to set the lock

		$affected = $wpdb->query("

			UPDATE $wpdb->options

			   SET option_name = 'social_locked'

			 WHERE option_name = 'social_unlocked'

		");

		if ($affected == '0' and !$this->stuck_check()) {

			Social::log('Semaphore lock failed. (Line '.__LINE__.')');

			return false;

		}

		// Check to see if all processes are complete

		$affected = $wpdb->query("

			UPDATE $wpdb->options

			   SET option_value = CAST(option_value AS UNSIGNED) + 1

			 WHERE option_name = 'social_semaphore'

			   AND option_value = '0'

		");

		if ($affected != '1') {

			if (!$this->stuck_check()) {

				Social::log('Semaphore lock failed. (Line '.__LINE__.')');

				return false;

			}

			// Reset the semaphore to 1

			$wpdb->query("

				UPDATE $wpdb->options

				   SET option_value = '1'

				 WHERE option_name = 'social_semaphore'

			");

			Social::log('Semaphore reset to 1.');

		}

		// Set the lock time

		$wpdb->query($wpdb->prepare("

			UPDATE $wpdb->options

			   SET option_value = %s

			 WHERE option_name = 'social_last_lock_time'

		", current_time('mysql', 1)));

		Social::log('Set semaphore last lock time to '.current_time('mysql', 1));

		Social::log('Semaphore lock complete.');

		return true;

	}

	/**

	 * Increment the semaphore.

	 *

	 * @param  array  $filters

	 * @return Social_Semaphore

	 */

	public function increment(array $filters = array()) {

		global $wpdb;

		if (count($filters)) {

			// Loop through all of the filters and increment the semaphore

			foreach ($filters as $priority) {

				for ($i = 0, $j = count($priority); $i < $j; ++$i) {

					$this->increment();

				}

			}

		}

		else {

			$wpdb->query("

				UPDATE $wpdb->options

				   SET option_value = CAST(option_value AS UNSIGNED) + 1

				 WHERE option_name = 'social_semaphore'

			");

			Social::log('Incremented the semaphore by 1.');

		}

		return $this;

	}

	/**

	 * Decrements the semaphore.

	 *

	 * @return void

	 */

	public function decrement() {

		global $wpdb;

		$wpdb->query("

			UPDATE $wpdb->options

			   SET option_value = CAST(option_value AS UNSIGNED) - 1

			 WHERE option_name = 'social_semaphore'

			   AND CAST(option_value AS UNSIGNED) > 0

		");

		Social::log('Decremented the semaphore by 1.');

	}

	/**

	 * Unlocks the process.

	 *

	 * @return bool

	 */

	public function unlock() {

		global $wpdb;

		// Decrement for the master process.

		$this->decrement();

		$result = $wpdb->query("

			UPDATE $wpdb->options

			   SET option_name = 'social_unlocked'

			 WHERE option_name = 'social_locked'

		");

		if ($result == '1') {

			Social::log('Semaphore unlocked.');

			return true;

		}

		Social::log('Semaphore still locked.');

		return false;

	}

	/**

	 * Attempts to jiggle the stuck lock loose.

	 *

	 * @return bool

	 */

	private function stuck_check() {

		global $wpdb;

		// Check to see if we already broke the lock.

		if ($this->lock_broke) {

			return true;

		}

		$current_time = current_time('mysql', 1);

		$affected = $wpdb->query($wpdb->prepare("

			UPDATE $wpdb->options

			   SET option_value = %s

			 WHERE option_name = 'social_last_lock_time'

			   AND option_value <= DATE_SUB(%s, INTERVAL 30 MINUTE)

		", $current_time, $current_time));

		if ($affected == '1') {

			Social::log('Semaphore was stuck, set lock time to '.$current_time);

			$this->lock_broke = true;

			return true;

		}

		return false;

	}

} // End Social_Semaphore