<?php
/**
 * Data migrator for AILinkMaster v1 → v2 architecture transition.
 *
 * Migrates data from the legacy scattered storage:
 * - _ailm_frozen_map (postmeta) → wp_ailm_link_rules
 * - wp_ailm_link_monitor (Scout DB) → wp_ailm_links
 *
 * Runs once on first load after update. Safe to re-run.
 *
 * @since 2.0
 * @package AILinkMaster
 */

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

class AILM_Migrator
{

    const MIGRATION_VERSION_KEY = 'ailm_db_version';
    const CURRENT_DB_VERSION = '2.1';

    /**
     * Check if migration is needed and run it.
     *
     * Called on `plugins_loaded` hook. Safe to call multiple times.
     *
     * @return void
     */
    public static function maybe_migrate()
    {
        $current = get_option(self::MIGRATION_VERSION_KEY, '1.0');

        if (version_compare($current, self::CURRENT_DB_VERSION, '>=')) {
            return; // Already migrated.
        }

        // Ensure tables exist before migration.
        if (!AILM_Link_DB::tables_exist()) {
            AILM_Link_DB::create_tables();
        }

        // v1 → v2: migrate legacy scattered storage into unified tables.
        if (version_compare($current, '2.0', '<')) {
            self::migrate_frozen_maps_to_rules();
            self::migrate_link_monitor_to_links();
        }

        // v2.0 → v2.1: re-run create_tables() so dbDelta + ensure_in_html_column()
        // add the new `in_html` column to existing installs. This is additive and
        // non-breaking: existing rules get in_html=0 (treated as "needs injection",
        // i.e. the previous behaviour).
        if (version_compare($current, '2.1', '<')) {
            AILM_Link_DB::create_tables();
        }

        update_option(self::MIGRATION_VERSION_KEY, self::CURRENT_DB_VERSION);
    }

    /**
     * Migrate _ailm_frozen_map postmeta entries to wp_ailm_link_rules.
     *
     * Each frozen map item becomes an individual rule row.
     * Maps old origins to new `source` values:
     * - 'rule-*' origin → 'ki_manual'
     * - Everything else → 'ai'
     *
     * @return int Number of rules migrated.
     */
    private static function migrate_frozen_maps_to_rules()
    {
        global $wpdb;

        $rules_table = AILM_Link_DB::get_rules_table();

        // Skip if rules already exist (re-run safety).
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $existing = (int) $wpdb->get_var("SELECT COUNT(*) FROM {$rules_table}");
        if ($existing > 0) {
            return 0;
        }

        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
        $frozen_results = $wpdb->get_results(
            "SELECT post_id, meta_value FROM {$wpdb->postmeta} WHERE meta_key = '_ailm_frozen_map'"
        );

        if (empty($frozen_results)) {
            return 0;
        }

        $count = 0;
        foreach ($frozen_results as $result) {
            $map = maybe_unserialize($result->meta_value);
            if (!is_array($map) || empty($map)) {
                continue;
            }

            foreach ($map as $item) {
                if (empty($item['url']) || empty($item['word'])) {
                    continue;
                }

                $origin = isset($item['origin']) ? $item['origin'] : 'ai';
                $occurrence = isset($item['occurrence']) ? (int) $item['occurrence'] : 1;
                $target_id = url_to_postid($item['url']);

                // Map old origin format to new source values.
                if (strpos($origin, 'rule-') === 0) {
                    $source = 'ki_manual';
                } elseif ('dashboard' === $origin) {
                    $source = 'dashboard';
                } else {
                    $source = 'ai';
                }

                // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery
                $wpdb->insert(
                    $rules_table,
                    array(
                        'donor_id' => (int) $result->post_id,
                        'target_id' => $target_id ? $target_id : 0,
                        'target_url' => esc_url_raw($item['url']),
                        'anchor' => sanitize_text_field($item['word']),
                        'occurrence' => $occurrence,
                        'source' => $source,
                        'status' => 'active',
                    ),
                    array('%d', '%d', '%s', '%s', '%d', '%s', '%s')
                );
                $count++;
            }
        }

        return $count;
    }

    /**
     * Migrate wp_ailm_link_monitor entries to wp_ailm_links.
     *
     * Maps old `link_origin` values to simplified `origin`:
     * - 'ai', 'ailm' → 'plugin'
     * - 'manual'      → 'manual'
     *
     * Resolves target_id via url_to_postid for internal links.
     *
     * @return int Number of links migrated.
     */
    private static function migrate_link_monitor_to_links()
    {
        global $wpdb;

        $links_table = AILM_Link_DB::get_links_table();
        $old_table = $wpdb->prefix . 'ailm_link_monitor';

        // Check if old table exists.
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
        $old_exists = $wpdb->get_var(
            $wpdb->prepare('SHOW TABLES LIKE %s', $old_table)
        );
        if ($old_exists !== $old_table) {
            return 0;
        }

        // Skip if links already exist (re-run safety).
        // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
        $existing = (int) $wpdb->get_var("SELECT COUNT(*) FROM {$links_table}");
        if ($existing > 0) {
            return 0;
        }

        // Process in batches of 200 to avoid memory issues.
        $batch_size = 200;
        $offset = 0;
        $total = 0;

        do {
            // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
            $rows = $wpdb->get_results(
                $wpdb->prepare(
                    "SELECT * FROM {$old_table} ORDER BY id ASC LIMIT %d OFFSET %d", // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
                    $batch_size,
                    $offset
                )
            );

            if (empty($rows)) {
                break;
            }

            foreach ($rows as $row) {
                // Map old link_origin to new simplified origin.
                $origin = 'manual';
                if (in_array($row->link_origin, array('ai', 'ailm'), true)) {
                    $origin = 'plugin';
                }

                // Resolve target_id for internal links.
                $target_id = 0;
                if ('internal' === $row->link_type && !empty($row->url)) {
                    $target_id = url_to_postid($row->url);
                }

                // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery
                $wpdb->insert(
                    $links_table,
                    array(
                        'donor_id' => (int) $row->post_id,
                        'target_id' => $target_id,
                        'url' => $row->url,
                        'anchor' => $row->anchor,
                        'origin' => $origin,
                        'link_type' => $row->link_type,
                        'position' => 0.5, // Default; will be recalculated on next scan.
                        'status_code' => (int) $row->status_code,
                        'last_checked' => $row->last_checked,
                        'rule_id' => null,
                    ),
                    array('%d', '%d', '%s', '%s', '%s', '%s', '%f', '%d', '%s', '%d')
                );
                $total++;
            }

            $offset += $batch_size;
        } while (count($rows) === $batch_size);

        return $total;
    }
}