<?php
/**
 * Async replication queue for AILinkMaster (Phase 5).
 *
 * Enqueues rule-change events (upsert / delete) into wp_ailm_sync_queue and
 * pushes them to the SaaS server via a WP-Cron worker. The queue is strictly
 * fire-and-forget: if the SaaS server is down, events accumulate and are
 * retried later. The main plugin flow is NEVER blocked by network calls.
 *
 * Design principles:
 *  - enqueue() is called from register_link(), mark_in_html(), delete_rule(),
 *    update_rule_status() — all local DB writes, no network.
 *  - process_batch() runs on wp_cron every 5 minutes, pushes up to 100 events
 *    in a single HTTP request to the SaaS server.
 *  - Failed batches are retried up to 3 times, then marked 'failed' (visible
 *    in admin for manual review).
 *  - If the SaaS server URL or license key is not configured, enqueue is a
 *    no-op (graceful degradation — plugin works fully without SaaS).
 *
 * @since 2.1
 * @package AILinkMaster
 */

if (!defined('ABSPATH')) {
    exit;
}

class AILM_Sync_Queue
{

    const MAX_ATTEMPTS = 3;
    const BATCH_SIZE   = 100;

    /**
     * Hook the cron worker.
     *
     * Called from AILM_Core::define_public_hooks().
     *
     * @return void
     */
    public static function init()
    {
        // Register custom cron schedule (every 5 minutes).
        add_filter('cron_schedules', array(__CLASS__, 'add_cron_schedule'));

        // Schedule the event if not already scheduled.
        if (!wp_next_scheduled('ailm_sync_queue_cron')) {
            wp_schedule_event(time(), 'ailm_every_5_minutes', 'ailm_sync_queue_cron');
        }
        add_action('ailm_sync_queue_cron', array(__CLASS__, 'process_batch'));
    }

    /**
     * Add a custom cron schedule: every 5 minutes.
     *
     * @param array $schedules Existing schedules.
     * @return array
     */
    public static function add_cron_schedule($schedules)
    {
        $schedules['ailm_every_5_minutes'] = array(
            'interval' => 300,
            'display'  => __('Every 5 Minutes', 'ailinkmaster-internal-auto-manager'),
        );
        return $schedules;
    }

    /**
     * Enqueue a rule-change event for async replication to SaaS.
     *
     * This method is intentionally lightweight (single INSERT) and never
     * touches the network. It is safe to call from any code path, including
     * save_post hooks and AJAX handlers.
     *
     * If the SaaS server is not configured (no license key / server URL),
     * this is a silent no-op — the plugin works fully in standalone mode.
     *
     * @param string $action  'upsert' or 'delete'.
     * @param int    $rule_id Rule ID (0 for bulk operations).
     * @param array  $payload Optional. Rule data to replicate (donor_id,
     *                        target_id, target_url, anchor, occurrence,
     *                        source, status, in_html). Required for 'upsert'.
     * @return void
     */
    public static function enqueue($action, $rule_id = 0, $payload = array())
    {
        // Graceful degradation: if SaaS is not configured, skip enqueue.
        $license_key = get_option('ailm_saas_license_key', '');
        $server_url  = get_option('ailm_saas_server_url', '');
        if (empty($license_key) || empty($server_url)) {
            return;
        }

        // Allow third-party code to disable replication entirely.
        if (apply_filters('ailm_disable_saas_replication', false)) {
            return;
        }

        global $wpdb;
        $table = AILM_Link_DB::get_sync_queue_table();

        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery
        $wpdb->insert(
            $table,
            array(
                'action'  => sanitize_key($action),
                'rule_id' => (int) $rule_id,
                'payload' => empty($payload) ? '' : wp_json_encode($payload),
                'status'  => 'pending',
            ),
            array('%s', '%d', '%s', '%s')
        );
    }

    /**
     * Process one batch of pending events.
     *
     * Called by wp_cron. Reads up to BATCH_SIZE pending events, sends them
     * to the SaaS server in a single HTTP request, and marks them
     * 'synced' (success) or increments 'attempts' (failure).
     *
     * @return array {
     *     @type int $synced   Number of events successfully synced.
     *     @type int $failed   Number of events that failed (retry pending).
     *     @type int $dropped  Number of events dropped (max attempts reached).
     * }
     */
    public static function process_batch()
    {
        $result = array('synced' => 0, 'failed' => 0, 'dropped' => 0);

        $license_key = get_option('ailm_saas_license_key', '');
        $server_url  = get_option('ailm_saas_server_url', '');
        if (empty($license_key) || empty($server_url)) {
            return $result; // SaaS not configured — nothing to do.
        }

        global $wpdb;
        $table = AILM_Link_DB::get_sync_queue_table();

        // Fetch a batch of pending events.
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $events = $wpdb->get_results(
            $wpdb->prepare(
                "SELECT id, action, rule_id, payload, attempts FROM {$table} WHERE status = 'pending' ORDER BY id ASC LIMIT %d", // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                self::BATCH_SIZE
            )
        );

        if (empty($events)) {
            return $result;
        }

        // Build the batch payload for the SaaS server.
        $batch = array();
        $event_ids = array();
        foreach ($events as $ev) {
            $batch[] = array(
                'queue_id' => (int) $ev->id,
                'action'   => $ev->action,
                'rule_id'  => (int) $ev->rule_id,
                'data'     => $ev->payload ? json_decode($ev->payload, true) : null,
            );
            $event_ids[] = (int) $ev->id;
        }

        // Send to SaaS.
        $success = self::send_to_saas($batch);

        if ($success) {
            // Mark all as synced.
            // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
            $wpdb->query(
                $wpdb->prepare(
                    "UPDATE {$table} SET status = 'synced', updated_at = NOW() WHERE id IN (" . implode(',', array_fill(0, count($event_ids), '%d')) . ")", // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                    $event_ids
                )
            );
            $result['synced'] = count($event_ids);
        } else {
            // Increment attempts; drop if max reached.
            foreach ($events as $ev) {
                $new_attempts = (int) $ev->attempts + 1;
                if ($new_attempts >= self::MAX_ATTEMPTS) {
                    // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
                    $wpdb->update(
                        $table,
                        array('status' => 'failed', 'attempts' => $new_attempts, 'updated_at' => current_time('mysql')),
                        array('id' => (int) $ev->id),
                        array('%s', '%d', '%s'),
                        array('%d')
                    );
                    $result['dropped']++;
                } else {
                    // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
                    $wpdb->update(
                        $table,
                        array('status' => 'pending', 'attempts' => $new_attempts, 'updated_at' => current_time('mysql')),
                        array('id' => (int) $ev->id),
                        array('%s', '%d', '%s'),
                        array('%d')
                    );
                    $result['failed']++;
                }
            }
        }

        return $result;
    }

    /**
     * Send a batch of events to the SaaS server.
     *
     * Uses the same HMAC-SHA256 signing as AILM_OpenAI_Provider::request_saas().
     *
     * @param array $batch Array of event payloads.
     * @return bool True on success, false on failure.
     */
    private static function send_to_saas($batch)
    {
        $license_key = get_option('ailm_saas_license_key', '');
        $server_url  = rtrim(get_option('ailm_saas_server_url', ''), '/');
        $site_url    = get_site_url();

        $endpoint = '/api/v1/sites/0/rules/sync';
        $url      = $server_url . $endpoint;
        $body     = wp_json_encode(array('events' => $batch));

        $signature = hash_hmac('sha256', $body, $license_key);

        $args = array(
            'method'  => 'POST',
            'timeout' => 30,
            'headers' => array(
                'Content-Type'  => 'application/json',
                'X-Site-URL'    => $site_url,
                'X-Signature'   => $signature,
            ),
            'body'    => $body,
        );

        $response = wp_remote_request($url, $args);

        if (is_wp_error($response)) {
            if (defined('WP_DEBUG') && WP_DEBUG && defined('WP_DEBUG_LOG') && WP_DEBUG_LOG) {
                // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
                error_log('AILM Sync Queue: SaaS request failed — ' . $response->get_error_message());
            }
            return false;
        }

        $status_code = wp_remote_retrieve_response_code($response);

        if ($status_code >= 200 && $status_code < 300) {
            return true;
        }

        if (defined('WP_DEBUG') && WP_DEBUG && defined('WP_DEBUG_LOG') && WP_DEBUG_LOG) {
            // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
            error_log('AILM Sync Queue: SaaS returned status ' . $status_code);
        }
        return false;
    }

    /**
     * Get queue statistics for the admin UI.
     *
     * @return array {
     *     @type int $pending  Number of pending events.
     *     @type int $synced   Number of synced events (all time).
     *     @type int $failed   Number of failed events.
     * }
     */
    public static function get_stats()
    {
        global $wpdb;
        $table = AILM_Link_DB::get_sync_queue_table();

        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $pending = (int) $wpdb->get_var("SELECT COUNT(*) FROM {$table} WHERE status = 'pending'");
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $synced  = (int) $wpdb->get_var("SELECT COUNT(*) FROM {$table} WHERE status = 'synced'");
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $failed  = (int) $wpdb->get_var("SELECT COUNT(*) FROM {$table} WHERE status = 'failed'");

        return array(
            'pending' => $pending,
            'synced'  => $synced,
            'failed'  => $failed,
        );
    }

    /**
     * Clear synced events older than N days (housekeeping).
     *
     * @param int $days Number of days to keep synced events. Default 7.
     * @return int Number of rows deleted.
     */
    public static function cleanup_old_synced($days = 7)
    {
        global $wpdb;
        $table = AILM_Link_DB::get_sync_queue_table();

        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        return (int) $wpdb->query(
            $wpdb->prepare(
                "DELETE FROM {$table} WHERE status = 'synced' AND updated_at < DATE_SUB(NOW(), INTERVAL %d DAY)", // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                $days
            )
        );
    }
}