<?php
if (!defined('ABSPATH')) exit;

/** Persisted queue; WP-Cron continues work after the admin tab closes. */
class Linkbraid_Jobs {
    const OPTION = 'lbraid_job';
    public function __construct() {
        add_action('lbraid_job_tick', [__CLASS__, 'tick']);
        add_action('wp_ajax_lbraid_job', [$this, 'ajax']);
    }
    public static function lock($key) {
        global $wpdb;
        $name = 'lbraid_' . md5($wpdb->prefix . $key);
        $suppressed = $wpdb->suppress_errors();
        $result = $wpdb->get_var($wpdb->prepare('SELECT GET_LOCK(%s, 0)', $name));
        $wpdb->suppress_errors($suppressed);
        if ((string) $result === '1') return $name;
        if ((string) $result === '0') return false; // Real contention, never bypass it.
        // Some managed databases do not implement named locks. Use the unique
        // option_name index as an atomic mutex, not get_option()/update_option().
        $name = '_lbraid_lock_' . md5($wpdb->prefix . $key);
        $value = (time() + 1800) . ':' . wp_generate_uuid4();
        $old = $wpdb->get_var($wpdb->prepare("SELECT option_value FROM {$wpdb->options} WHERE option_name=%s", $name));
        if ($old && (int) $old < time()) {
            $wpdb->query($wpdb->prepare("DELETE FROM {$wpdb->options} WHERE option_name=%s AND option_value=%s", $name, $old));
        }
        $inserted = $wpdb->query($wpdb->prepare("INSERT IGNORE INTO {$wpdb->options} (option_name, option_value, autoload) VALUES (%s, %s, 'no')", $name, $value));
        return $inserted === 1 ? ['name' => $name, 'value' => $value] : false;
    }
    public static function owns_lock($token) {
        global $wpdb;
        if (!is_array($token)) return (bool) $token;
        return (int) $token['value'] >= time() && $wpdb->get_var($wpdb->prepare("SELECT option_value FROM {$wpdb->options} WHERE option_name=%s", $token['name'])) === $token['value'];
    }
    public static function unlock($key, $token) {
        global $wpdb;
        if (is_array($token)) $wpdb->query($wpdb->prepare("DELETE FROM {$wpdb->options} WHERE option_name=%s AND option_value=%s", $token['name'], $token['value']));
        elseif ($token) $wpdb->get_var($wpdb->prepare('SELECT RELEASE_LOCK(%s)', $token));
    }
    private static function schedule($delay = 5) {
        if (!wp_next_scheduled('lbraid_job_tick')) wp_schedule_single_event(time() + $delay, 'lbraid_job_tick');
    }
    public function ajax() {
        check_ajax_referer('lbraid_nonce', 'nonce');
        if (!current_user_can('manage_options')) wp_send_json_error(__( 'Insufficient permissions.', 'linkbraid' ), 403);
        $action = sanitize_key($_POST['operation'] ?? 'status');
        if ($action === 'status') {
            $job = get_option(self::OPTION, null);
            if ($job && $job['status'] === 'running') { self::schedule(); spawn_cron(); }
            wp_send_json_success($job);
        }
        // Browser-driven fallback: when WP-Cron never fires (loopback blocked,
        // DISABLE_WP_CRON, firewall), the open admin tab advances the queue by
        // one item per request. tick() takes the queue lock itself, so a live
        // cron and the fallback can never process the same item twice.
        if ($action === 'tick') {
            $job = get_option(self::OPTION, null);
            if ($job && $job['status'] === 'running') {
                self::tick();
                $job = get_option(self::OPTION, null);
            }
            wp_send_json_success($job);
        }
        $lock = self::lock('queue');
        if (!$lock) wp_send_json_error(__( 'A post is being processed. Try again in a moment.', 'linkbraid' ));
        $error = null;
        try {
            $job = get_option(self::OPTION, null);
            if ($action === 'start') {
                if ($job && $job['status'] === 'running') $error = __( 'A job is already running.', 'linkbraid' );
                else {
                    $type = sanitize_key($_POST['type'] ?? 'analyze');
                    $allowed = lbraid_has_pro_code() ? ['analyze', 'index', 'gsc', 'scan', 'broken', 'autobraid'] : ['scan', 'broken', 'autobraid'];
                    if (!in_array($type, $allowed, true)) $error = __( 'Invalid job type.', 'linkbraid' );
                    elseif (in_array($type, ['analyze', 'index', 'gsc'], true) && !lbraid_premium()) $error = __( 'This job type requires an active Linkbraid license. Activate it under Linkbraid → Account.', 'linkbraid' );
                    elseif ($type === 'broken' && !($ids = Linkbraid_Broken::prepare_queue())) $error = __( 'No URLs to check. Run a link scan first, or wait a day after the previous check.', 'linkbraid' );
                    else {
                        if ($type !== 'broken') $ids = get_posts(['post_type' => lbraid_post_types(), 'post_status' => 'publish', 'posts_per_page' => -1, 'fields' => 'ids', 'orderby' => 'ID', 'order' => 'ASC']);
                        $job = ['id' => wp_generate_uuid4(), 'type' => $type, 'owner' => get_current_user_id(), 'status' => 'running', 'ids' => $ids, 'total' => count($ids), 'cursor' => 0, 'ok' => 0, 'empty' => 0, 'failed' => 0, 'attempt' => 0, 'errors' => [], 'current' => '', 'updated' => current_time('mysql')];
                    }
                }
            } elseif ($job && $action === 'pause') $job['status'] = 'paused';
            elseif ($job && $action === 'resume') { $job['status'] = 'running'; $job['owner'] = get_current_user_id(); }
            elseif ($job && $action === 'retry' && $job['status'] !== 'running') {
                $ids = array_map('intval', array_keys($job['errors']));
                $job = array_merge($job, ['ids' => $ids, 'total' => count($ids), 'cursor' => 0, 'ok' => 0, 'empty' => 0, 'failed' => 0, 'errors' => [], 'attempt' => 0, 'status' => 'running', 'owner' => get_current_user_id()]);
            } else $error = __( 'Invalid operation.', 'linkbraid' );
            if (!$error) { update_option(self::OPTION, $job, false); if ($job['status'] === 'running') self::schedule(); }
        } finally { self::unlock('queue', $lock); }
        if ($error) wp_send_json_error($error);
        spawn_cron();
        wp_send_json_success($job);
    }
    public static function tick() {
        $lock = self::lock('queue');
        if (!$lock) { self::schedule(30); return; }
        $previous_user = get_current_user_id();
        try {
            $job = get_option(self::OPTION, null);
            if (!$job || $job['status'] !== 'running') return;
            wp_set_current_user($job['owner']);
            if (!current_user_can('manage_options')) { $job['status'] = 'paused'; update_option(self::OPTION, $job, false); return; }
            if ($job['cursor'] >= $job['total']) { $job['status'] = 'complete'; update_option(self::OPTION, $job, false); return; }
            // Schedule recovery before external I/O. Fatal errors/timeouts cannot lose the job.
            self::schedule(60);
            $id = (int) $job['ids'][$job['cursor']];
            $job['current'] = $job['type'] === 'broken' ? Linkbraid_Broken::label($id) : get_the_title($id);
            $job['attempt']++;
            update_option(self::OPTION, $job, false);
            try {
                if ($job['attempt'] > 2) $result = ['error' => __( 'Retry limit exceeded (timeout or interrupted request).', 'linkbraid' )];
                elseif ($job['type'] === 'broken') $result = Linkbraid_Broken::check($id);
                elseif (!current_user_can('edit_post', $id) || get_post_status($id) !== 'publish') $result = ['error' => __( 'Post deleted, unpublished or unavailable.', 'linkbraid' )];
                // Ignored content is skipped silently for suggestion jobs — that is intent, not an error.
                elseif (in_array($job['type'], ['analyze', 'autobraid'], true) && in_array((int) $id, lbraid_ignored_posts(), true)) $result = ['success' => true, 'count' => 0];
                elseif ($job['type'] === 'scan') $result = Linkbraid_Database::refresh_existing_links($id) ? ['success' => true, 'count' => 1] : ['error' => __( 'The link scan could not be saved.', 'linkbraid' )];
                elseif ($job['type'] === 'autobraid') $result = Linkbraid_Autobraid::scan_post($id);
                elseif ($job['type'] === 'index') $result = Linkbraid_Embeddings::index_post($id) ? ['success' => true, 'count' => 1] : ['error' => Linkbraid_Embeddings::$last_error ?: __( 'No embedding was created. Check the AI provider key and the content support.', 'linkbraid' )];
                elseif ($job['type'] === 'gsc') {
                    $gsc = new Linkbraid_GSC(); $queries = $gsc->get_page_queries(get_permalink($id), 90, 20);
                    if ($gsc->last_error) $result = ['error' => $gsc->last_error];
                    else { Linkbraid_Database::save_gsc_queries($id, $queries); $result = ['success' => true, 'count' => count($queries)]; }
                } else $result = Linkbraid_LLM_Analyzer::analyze_post($id);
            /* translators: %s: dynamic value inserted at runtime. */
            } catch (Throwable $e) { $result = ['error' => sprintf( __( 'Processing error: %s', 'linkbraid' ), $e->getMessage() )]; }
            if (isset($result['error']) && $job['attempt'] < 2) {
                /* translators: %s: dynamic value inserted at runtime. */
                $job['current'] = sprintf( __( '%s — retrying after an error', 'linkbraid' ), $job['current'] );
            } else {
                if (isset($result['error'])) { $job['failed']++; $job['errors'][$id] = mb_substr($result['error'], 0, 500); }
                elseif (empty($result['count'])) $job['empty']++;
                else $job['ok']++;
                $job['cursor']++; $job['attempt'] = 0;
            }
            if (!self::owns_lock($lock)) return;
            $job['updated'] = current_time('mysql');
            if ($job['cursor'] >= $job['total']) {
                $job['status'] = 'complete';
                if ($job['type'] === 'gsc' && !$job['failed']) update_option('lbraid_gsc_last_sync', current_time('mysql'));
            }
            update_option(self::OPTION, $job, false);
            wp_clear_scheduled_hook('lbraid_job_tick');
            if ($job['status'] === 'running') self::schedule($job['attempt'] ? 30 : 5);
        } finally { wp_set_current_user($previous_user); self::unlock('queue', $lock); }
    }
}