<?php
/** Durable identity log; ordinary saves never perform external HTTP requests. */
if (!defined('ABSPATH')) { exit; }

final class Chat4U_Changes {
    public static function table(): string { global $wpdb; return $wpdb->prefix . 'chat4u_changes'; }

    public static function activate(): void {
        global $wpdb;
        require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        $table = self::table();
        dbDelta("CREATE TABLE {$table} (
            sequence bigint unsigned NOT NULL AUTO_INCREMENT,
            object_id bigint unsigned NOT NULL,
            post_type varchar(32) NOT NULL,
            locale varchar(32) NOT NULL,
            removed tinyint NOT NULL DEFAULT 0,
            happened_at datetime NOT NULL,
            PRIMARY KEY  (sequence),
            KEY happened_at (happened_at)
        ) " . $wpdb->get_charset_collate() . ';');
        if (!wp_next_scheduled('chat4u_cleanup')) { wp_schedule_event(time() + 60, 'hourly', 'chat4u_cleanup'); }
        $state = Chat4U_Protocol::connection();
        if (($state['state'] ?? '') === 'connected') {
            update_option('chat4u_pending_control', 'reactivated', false);
            update_option('chat4u_control_delivery', wp_generate_uuid4(), false);
            wp_schedule_single_event(time() + 2, 'chat4u_deliver');
        }
    }

    public static function head(): int {
        global $wpdb;
        return (int) $wpdb->get_var($wpdb->prepare('SELECT COALESCE(MAX(sequence),0) FROM %i', self::table()));
    }

    public static function changed(int $id): void {
        $post = get_post($id);
        if (!$post || wp_is_post_revision($id) || !in_array($post->post_type, Chat4U_Content::types(), true)) { return; }
        self::append($id, $post->post_type, Chat4U_Content::locale($id), !Chat4U_Content::public_post($post));
    }

    public static function metadata($meta_id, int $id): void { self::changed($id); }

    public static function render_changed(): void {
        foreach (Chat4U_Content::languages() as $language) {
            self::append(0, 'home', $language['code'], false);
        }
    }

    public static function deleted(int $id, $post): void {
        if ($post instanceof WP_Post && in_array($post->post_type, Chat4U_Content::types(), true)) {
            self::append($id, $post->post_type, Chat4U_Content::locale($id), true);
        }
    }

    public static function commerce(int $id, bool $removed): void {
        self::append($id, 'woo_product', Chat4U_Content::locale($id), $removed);
    }

    private static function append(int $id, string $type, string $locale, bool $removed): void {
        global $wpdb;
        $wpdb->insert(self::table(), ['object_id' => $id, 'post_type' => $type, 'locale' => $locale,
            'removed' => (int) $removed, 'happened_at' => gmdate('Y-m-d H:i:s')], ['%d', '%s', '%s', '%d', '%s']);
        if (!wp_next_scheduled('chat4u_deliver')) { wp_schedule_single_event(time() + 2, 'chat4u_deliver'); }
    }

    public static function page(int $after, int $limit = 25): array {
        global $wpdb;
        $table = self::table();
        $floor = (int) $wpdb->get_var($wpdb->prepare('SELECT COALESCE(MIN(sequence),0) FROM %i', $table));
        $head = self::head();
        if ($after > $head || ($floor && $after < $floor - 1)) {
            return ['cursor_expired' => true, 'head' => $head, 'high_water' => Chat4U_Content::high_water()];
        }
        $limit = min(100, max(1, $limit));
        $rows = $wpdb->get_results($wpdb->prepare('SELECT * FROM %i WHERE sequence > %d ORDER BY sequence LIMIT %d', $table, $after, $limit + 1));
        $items = [];
        foreach (array_slice($rows, 0, $limit) as $row) {
            if ($row->post_type === 'woo_product') {
                $value = ['type' => 'woo_product', 'id' => (int) $row->object_id, 'locale' => $row->locale,
                    'removed' => (bool) $row->removed, 'version' => Chat4U_Commerce_Catalog::family_version((int) $row->object_id)];
                $items[] = $value; continue;
            }
            $value = $row->removed ? ['removed' => true, 'id' => (int) $row->object_id, 'type' => $row->post_type, 'locale' => $row->locale] : Chat4U_Content::record((int) $row->object_id, $row->post_type, $row->locale);
            $value = Chat4U_Protocol::discovery_record($value);
            if ($items && !Chat4U_Protocol::fits(['items' => [...$items, $value], 'cursor' => (int) $row->sequence, 'head' => $head, 'complete' => false])) { break; }
            $items[] = $value;
            $after = (int) $row->sequence;
        }
        return ['items' => $items, 'cursor' => $after, 'head' => $head, 'complete' => count($items) === count($rows)];
    }

    public static function deliver(): void {
        $state = Chat4U_Protocol::connection();
        if (($state['state'] ?? '') !== 'connected') { return; }
        $control = get_option('chat4u_pending_control', '');
        if ($control === 'reactivated') {
            $result = Chat4U_Protocol::remote('events', ['installation_id' => $state['scope'],
                'delivery_id' => get_option('chat4u_control_delivery'), 'topic' => $control], $state);
            if (is_wp_error($result)) { wp_schedule_single_event(time() + 60, 'chat4u_deliver'); return; }
            delete_option('chat4u_pending_control');
            delete_option('chat4u_control_delivery');
        }
        $delivery = get_option('chat4u_pending_delivery', []);
        if (!$delivery) {
            $after = (int) get_option('chat4u_delivered_cursor', 0);
            $page = self::page($after, 100);
            if (!empty($page['cursor_expired'])) { $page = ['head' => self::head(), 'cursor' => self::head(), 'items' => [], 'complete' => true]; }
            $removed = [];
            foreach ($page['items'] as $item) {
                if (!empty($item['removed']) && !empty(Chat4U_Content::record((int) $item['id'], $item['type'], $item['locale'])['removed'])) {
                    $removed[] = $item['type'] . ':' . $item['id'] . ':' . $item['locale'];
                }
            }
            $delivery = ['delivery_id' => wp_generate_uuid4(), 'head' => $page['head'], 'removed' => $removed,
                'cursor' => $page['cursor'], 'complete' => $page['complete']];
            update_option('chat4u_pending_delivery', $delivery, false);
        }
        $result = Chat4U_Protocol::remote('events', ['installation_id' => $state['scope'],
            'topic' => 'changes', 'head' => $delivery['head'], 'removed' => $delivery['removed'],
            'delivery_id' => $delivery['delivery_id']], $state);
        if (is_wp_error($result)) {
            $attempts = min(6, (int) get_option('chat4u_delivery_attempts', 0) + 1);
            update_option('chat4u_delivery_attempts', $attempts, false);
            wp_schedule_single_event(time() + min(900, 15 * (2 ** $attempts)), 'chat4u_deliver');
            return;
        }
        update_option('chat4u_delivery_attempts', 0, false);
        update_option('chat4u_delivered_cursor', $delivery['cursor'], false);
        delete_option('chat4u_pending_delivery');
        if (!$delivery['complete']) { wp_schedule_single_event(time() + 2, 'chat4u_deliver'); }
    }

    public static function cleanup(): void {
        global $wpdb;
        $table = self::table();
        $wpdb->query($wpdb->prepare('DELETE FROM %i WHERE happened_at < %s LIMIT 10000', $table, gmdate('Y-m-d H:i:s', time() - 7 * DAY_IN_SECONDS)));
        $cutoff = (int) $wpdb->get_var($wpdb->prepare('SELECT sequence FROM %i ORDER BY sequence DESC LIMIT 1 OFFSET 99999', $table));
        if ($cutoff) { $wpdb->query($wpdb->prepare('DELETE FROM %i WHERE sequence < %d LIMIT 10000', $table, $cutoff)); }
        $pattern = $wpdb->esc_like('chat4u_req_') . '%';
        $wpdb->query($wpdb->prepare('DELETE FROM %i WHERE option_name LIKE %s AND CAST(option_value AS UNSIGNED) < %d LIMIT 10000', $wpdb->options, $pattern, time()));
    }

    public static function deactivate(): void {
        $state = Chat4U_Protocol::connection();
        if (($state['state'] ?? '') === 'connected') {
            Chat4U_Protocol::remote('events', ['installation_id' => $state['scope'], 'delivery_id' => wp_generate_uuid4(), 'topic' => 'deactivated'], $state);
        }
        wp_clear_scheduled_hook('chat4u_deliver');
        wp_clear_scheduled_hook('chat4u_cleanup');
    }
}