<?php

namespace Give\Framework\WordPressLibraries;


/**
 * This is a fork of WP_Background_Process that  adds GiveWP namespaces to prevent conflicts with other plugins.
 *
 * IMPORTANT: Developers, please be aware that the usage of WPAsyncRequest and WPBackgroundProcess is discouraged as they are included only for legacy purposes.
 * Instead, it is strongly recommended to use Action Scheduler for any asynchronous processing needs.
 * Action Scheduler is available, provides a more efficient solution, and is the preferred choice for new development.
 *
 * @since 2.32.0
 */
abstract class WPBackgroundProcess extends WPAsyncRequest
{
    /**
     * Action
     *
     * (default value: 'background_process')
     *
     * @var string
     * @access protected
     */
    protected $action = 'background_process';

    /**
     * Start time of current process.
     *
     * (default value: 0)
     *
     * @var int
     * @access protected
     */
    protected $start_time = 0;

    /**
     * Cron_hook_identifier
     *
     * @var mixed
     * @access protected
     */
    protected $cron_hook_identifier;

    /**
     * Cron_interval_identifier
     *
     * @var mixed
     * @access protected
     */
    protected $cron_interval_identifier;

    /**
     * Initiate new background process
     */
    public function __construct()
    {
        parent::__construct();

        $this->cron_hook_identifier = $this->identifier . '_cron';
        $this->cron_interval_identifier = $this->identifier . '_cron_interval';

        add_action($this->cron_hook_identifier, [$this, 'handle_cron_healthcheck']);
        add_filter('cron_schedules', [$this, 'schedule_cron_healthcheck']);
    }

    /**
     * Dispatch
     *
     * @access public
     * @return void
     */
    public function dispatch()
    {
        // Schedule the cron healthcheck.
        $this->schedule_event();

        // Perform remote post.
        return parent::dispatch();
    }

    /**
     * Push to queue
     *
     * @param mixed $data Data.
     *
     * @return $this
     */
    public function push_to_queue($data)
    {
        $this->data[] = $data;

        return $this;
    }

    /**
     * Save queue
     *
     * @return $this
     */
    public function save()
    {
        $key = $this->generate_key();

        if ( ! empty($this->data)) {
            update_site_option($key, $this->data);
        }

        return $this;
    }

    /**
     * Update queue
     *
     * @param string $key  Key.
     * @param array  $data Data.
     *
     * @return $this
     */
    public function update($key, $data)
    {
        if ( ! empty($data)) {
            update_site_option($key, $data);
        }

        return $this;
    }

    /**
     * Delete queue
     *
     * @param string $key Key.
     *
     * @return $this
     */
    public function delete($key)
    {
        delete_site_option($key);

        return $this;
    }

    /**
     * Generate key
     *
     * Generates a unique key based on microtime. Queue items are
     * given a unique key so that they can be merged upon save.
     *
     * @param int $length Length.
     *
     * @return string
     */
    protected function generate_key($length = 64)
    {
        $unique = md5(microtime() . rand());
        $prepend = $this->identifier . '_batch_';

        return substr($prepend . $unique, 0, $length);
    }

    /**
     * Maybe process queue
     *
     * Checks whether data exists within the queue and that
     * the process is not already running.
     */
    public function maybe_handle()
    {
        // Don't lock up other requests while processing
        session_write_close();

        if ($this->is_process_running()) {
            // Background process already running.
            wp_die();
        }

        if ($this->is_queue_empty()) {
            // No data to process.
            wp_die();
        }

        check_ajax_referer($this->identifier, 'nonce');

        $this->handle();

        wp_die();
    }

    /**
     * Is queue empty
     *
     * @return bool
     */
    protected function is_queue_empty()
    {
        global $wpdb;

        $table = $wpdb->options;
        $column = 'option_name';

        if (is_multisite()) {
            $table = $wpdb->sitemeta;
            $column = 'meta_key';
        }

        $key = $this->identifier . '_batch_%';

        $count = $wpdb->get_var(
            $wpdb->prepare(
                "
			SELECT COUNT(*)
			FROM {$table}
			WHERE {$column} LIKE %s
		",
                $key
            )
        );

        return ($count > 0) ? false : true;
    }

    /**
     * Is process running
     *
     * Check whether the current process is already running
     * in a background process.
     */
    public function is_process_running()
    {
        if (get_site_transient($this->identifier . '_process_lock')) {
            // Process already running.
            return true;
        }

        return false;
    }

    /**
     * Lock process
     *
     * Lock the process so that multiple instances can't run simultaneously.
     * Override if applicable, but the duration should be greater than that
     * defined in the time_exceeded() method.
     */
    protected function lock_process()
    {
        $this->start_time = time(); // Set start time of current process.

        $lock_duration = (property_exists($this, 'queue_lock_time')) ? $this->queue_lock_time : 60; // 1 minute
        $lock_duration = apply_filters($this->identifier . '_queue_lock_time', $lock_duration);

        set_site_transient($this->identifier . '_process_lock', microtime(), $lock_duration);
    }

    /**
     * Unlock process
     *
     * Unlock the process so that other instances can spawn.
     *
     * @return $this
     */
    protected function unlock_process()
    {
        delete_site_transient($this->identifier . '_process_lock');

        return $this;
    }

    /**
     * Get batch
     *
     * @return stdClass Return the first batch from the queue
     */
    protected function get_batch()
    {
        global $wpdb;

        $table = $wpdb->options;
        $column = 'option_name';
        $key_column = 'option_id';
        $value_column = 'option_value';

        if (is_multisite()) {
            $table = $wpdb->sitemeta;
            $column = 'meta_key';
            $key_column = 'meta_id';
            $value_column = 'meta_value';
        }

        $key = $this->identifier . '_batch_%';

        $query = $wpdb->get_row(
            $wpdb->prepare(
                "
			SELECT *
			FROM {$table}
			WHERE {$column} LIKE %s
			ORDER BY {$key_column} ASC
			LIMIT 1
		",
                $key
            )
        );

        $batch = new \stdClass();
        $batch->key = $query->$column;
        $batch->data = maybe_unserialize($query->$value_column);

        return $batch;
    }

    /**
     * Handle
     *
     * Pass each queue item to the task handler, while remaining
     * within server memory and time limit constraints.
     */
    protected function handle()
    {
        $this->lock_process();

        do {
            $batch = $this->get_batch();

            foreach ($batch->data as $key => $value) {
                $task = $this->task($value);

                if (false !== $task) {
                    $batch->data[$key] = $task;
                } else {
                    unset($batch->data[$key]);
                }

                if ($this->time_exceeded() || $this->memory_exceeded()) {
                    // Batch limits reached.
                    break;
                }
            }

            // Update or delete current batch.
            if ( ! empty($batch->data)) {
                $this->update($batch->key, $batch->data);
            } else {
                $this->delete($batch->key);
            }
        } while ( ! $this->time_exceeded() && ! $this->memory_exceeded() && ! $this->is_queue_empty());

        $this->unlock_process();

        // Start next batch or complete process.
        if ( ! $this->is_queue_empty()) {
            $this->dispatch();
        } else {
            $this->complete();
        }

        wp_die();
    }

    /**
     * Memory exceeded
     *
     * Ensures the batch process never exceeds 90%
     * of the maximum WordPress memory.
     *
     * @return bool
     */
    protected function memory_exceeded()
    {
        $memory_limit = $this->get_memory_limit() * 0.9; // 90% of max memory
        $current_memory = memory_get_usage(true);
        $return = false;

        if ($current_memory >= $memory_limit) {
            $return = true;
        }

        return apply_filters($this->identifier . '_memory_exceeded', $return);
    }

    /**
     * Get memory limit
     *
     * @return int
     */
    protected function get_memory_limit()
    {
        if (function_exists('ini_get')) {
            $memory_limit = ini_get('memory_limit');
        } else {
            // Sensible default.
            $memory_limit = '128M';
        }

        if ( ! $memory_limit || -1 === $memory_limit) {
            // Unlimited, set to 32GB.
            $memory_limit = '32000M';
        }

        return intval($memory_limit) * 1024 * 1024;
    }

    /**
     * Time exceeded.
     *
     * Ensures the batch never exceeds a sensible time limit.
     * A timeout limit of 30s is common on shared hosting.
     *
     * @return bool
     */
    protected function time_exceeded()
    {
        $finish = $this->start_time + apply_filters($this->identifier . '_default_time_limit', 20); // 20 seconds
        $return = false;

        if (time() >= $finish) {
            $return = true;
        }

        return apply_filters($this->identifier . '_time_exceeded', $return);
    }

    /**
     * Complete.
     *
     * Override if applicable, but ensure that the below actions are
     * performed, or, call parent::complete().
     */
    protected function complete()
    {
        // Unschedule the cron healthcheck.
        $this->clear_scheduled_event();
    }

    /**
     * Schedule cron healthcheck
     *
     * @access public
     *
     * @param mixed $schedules Schedules.
     *
     * @return mixed
     */
    public function schedule_cron_healthcheck($schedules)
    {
        $interval = apply_filters($this->identifier . '_cron_interval', 5);

        if (property_exists($this, 'cron_interval')) {
            $interval = apply_filters($this->identifier . '_cron_interval', $this->cron_interval_identifier);
        }

        // Adds every 5 minutes to the existing schedules.
        $schedules[$this->identifier . '_cron_interval'] = [
            'interval' => MINUTE_IN_SECONDS * $interval,
            'display' => sprintf(__('Every %d Minutes', 'give'), $interval),
        ];

        return $schedules;
    }

    /**
     * Handle cron healthcheck
     *
     * Restart the background process if not already running
     * and data exists in the queue.
     */
    public function handle_cron_healthcheck()
    {
        if ($this->is_process_running()) {
            // Background process already running.
            exit;
        }

        if ($this->is_queue_empty()) {
            // No data to process.
            $this->clear_scheduled_event();
            exit;
        }

        $this->handle();

        exit;
    }

    /**
     * Schedule event
     */
    protected function schedule_event()
    {
        if ( ! wp_next_scheduled($this->cron_hook_identifier)) {
            wp_schedule_event(time(), $this->cron_interval_identifier, $this->cron_hook_identifier);
        }
    }

    /**
     * Clear scheduled event
     */
    protected function clear_scheduled_event()
    {
        $timestamp = wp_next_scheduled($this->cron_hook_identifier);

        if ($timestamp) {
            wp_unschedule_event($timestamp, $this->cron_hook_identifier);
        }
    }

    /**
     * Cancel Process
     *
     * Stop processing queue items, clear cronjob and delete batch.
     *
     */
    public function cancel_process()
    {
        if ( ! $this->is_queue_empty()) {
            $batch = $this->get_batch();

            $this->delete($batch->key);

            wp_clear_scheduled_hook($this->cron_hook_identifier);
        }
    }

    /**
     * Task
     *
     * Override this method to perform any actions required on each
     * queue item. Return the modified item for further processing
     * in the next pass through. Or, return false to remove the
     * item from the queue.
     *
     * @param mixed $item Queue item to iterate over.
     *
     * @return mixed
     */
    abstract protected function task($item);
}