<?php
/**
 * Handles database migrations and data rescue during plugin updates.
 */

// SECURITY: Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

class TTDVR_Migration {

    /**
     * Run the migration check on admin init.
     */
    public function init() {
        add_action( 'admin_init', array( $this, 'check_for_upgrades' ) );
        add_action( 'admin_notices', array( $this, 'display_upgrade_notice' ) );
    }

    /**
     * Check if the database version matches the file version, and run specific patches.
     */
    public function check_for_upgrades() {
        $current_db_version = get_option( 'ttdvr_db_version', '1.0.0' );

        // 1. Core v2.0.0 Migration
        if ( version_compare( $current_db_version, TTDVR_VERSION, '<' ) ) {
            $this->run_v2_migration();
        }

        // 2. The Duplicate Cleaner (Runs exactly once, regardless of version number)
        if ( ! get_option( 'ttdvr_duplicates_cleaned' ) ) {
            $this->clean_existing_duplicates();
            update_option( 'ttdvr_duplicates_cleaned', true ); // Set flag so it never runs again
        }
    }

    /**
     * Phase 2: Scans the database for legacy duplicate Verification IDs and neutralizes them.
     */
    private function clean_existing_duplicates() {
        global $wpdb;

        // Find all duplicated verification IDs in the database
        $duplicates = $wpdb->get_results( "
            SELECT meta_value, COUNT(post_id) as count
            FROM {$wpdb->postmeta}
            WHERE meta_key = '_ttdvr_verification_id' AND meta_value != ''
            GROUP BY meta_value
            HAVING count > 1
        " );

        $total_neutralized = 0;

        if ( ! empty( $duplicates ) ) {
            foreach ( $duplicates as $dup ) {
                $meta_value = $dup->meta_value;
                
                // Get all post IDs sharing this exact Verification ID, ordered oldest to newest
                $posts = $wpdb->get_col( $wpdb->prepare( "
                    SELECT post_id FROM {$wpdb->postmeta} 
                    WHERE meta_key = '_ttdvr_verification_id' AND meta_value = %s 
                    ORDER BY post_id ASC
                ", $meta_value ) );

                // Remove the first/oldest document from the array (Keep the Original safe)
                array_shift( $posts ); 
                
                // Loop through the remaining fakes/duplicates and rename them permanently
                $counter = 1;
                foreach ( $posts as $duplicate_post_id ) {
                    // Example output: CERT-123-DUP-4829-1
                    $neutralized_id = $meta_value . '-DUP-' . wp_rand( 1000, 9999 ) . '-' . $counter;
                    update_post_meta( $duplicate_post_id, '_ttdvr_verification_id', $neutralized_id );
                    
                    $total_neutralized++;
                    $counter++;
                }
            }
        }

        // If we actually caught and fixed duplicates, save a message to show the admin!
        if ( $total_neutralized > 0 ) {
            set_transient( 'ttdvr_dup_clean_notice', $total_neutralized, 60 );
        }
    }

    /**
     * Execute the v2.0.0 data rescue and migration.
     */
    private function run_v2_migration() {
        global $wpdb;

        // 1. RESCUE OLD CUSTOM POST TYPES
        $wpdb->query( "
            UPDATE {$wpdb->posts} 
            SET post_type = 'ttdvr_document' 
            WHERE post_type IN ('24tt_document', 'tt_document')
        " );

        // 2. RESCUE OLD TAXONOMIES
        $wpdb->query( "
            UPDATE {$wpdb->term_taxonomy} 
            SET taxonomy = 'ttdvr_doc_category' 
            WHERE taxonomy IN ('24tt_doc_category', 'tt_doc_category')
        " );

        // 3. RESCUE OLD META KEYS (Data Fields)
        $wpdb->query( "
            UPDATE {$wpdb->postmeta} 
            SET meta_key = REPLACE(meta_key, '_24tt_', '_ttdvr_') 
            WHERE meta_key LIKE '_24tt_%'
        " );
        
        $wpdb->query( "
            UPDATE {$wpdb->postmeta} 
            SET meta_key = REPLACE(meta_key, '_tt_', '_ttdvr_') 
            WHERE meta_key LIKE '_tt_%'
        " );

        // 4. PREVENT BROKEN FRONTENDS (Configure the Kill Switch)
        $all_categories = get_terms( array( 'taxonomy' => 'ttdvr_doc_category', 'hide_empty' => false ) );
        if ( ! empty( $all_categories ) && ! is_wp_error( $all_categories ) ) {
            $cat_ids = wp_list_pluck( $all_categories, 'term_id' );
            update_option( 'ttdvr_public_categories', $cat_ids );
        }

        if ( false === get_option( 'ttdvr_show_pdf_link' ) ) {
            update_option( 'ttdvr_show_pdf_link', 'yes' );
        }

        // 5. FINALIZE MIGRATION
        flush_rewrite_rules();
        update_option( 'ttdvr_db_version', TTDVR_VERSION );
        set_transient( 'ttdvr_upgrade_complete', true, 60 );
    }

    /**
     * Show friendly notices after successful background tasks.
     */
    public function display_upgrade_notice() {
        // v2.0.0 Upgrade Notice
        if ( get_transient( 'ttdvr_upgrade_complete' ) ) {
            echo '<div class="notice ttdvr-notice notice-success is-dismissible" style="border-left-color: #28a745; padding: 10px;">
                <p><strong>🎉 ' . esc_html__( '24TT Document Verifier successfully upgraded to v2.0.0!', '24tt-document-verifier' ) . '</strong></p>
                <p>' . esc_html__( 'Your database and existing documents have been safely migrated to the new enterprise architecture. Please visit "Global Settings" to review your new security features.', '24tt-document-verifier' ) . '</p>
            </div>';
            delete_transient( 'ttdvr_upgrade_complete' );
        }

        // The New Duplicate Cleaner Notice
        $cleaned_count = get_transient( 'ttdvr_dup_clean_notice' );
        if ( $cleaned_count ) {
            echo '<div class="notice ttdvr-notice notice-warning is-dismissible" style="padding: 10px;">
                <p><strong>🛡️ ' . esc_html__( 'System Integrity Audit Complete', '24tt-document-verifier' ) . '</strong></p>
                <p>' . sprintf( esc_html__( 'We successfully scanned your database and neutralized %d legacy duplicate Document IDs. They have been given a "-DUP-" extension to protect your verification system.', '24tt-document-verifier' ), intval( $cleaned_count ) ) . '</p>
            </div>';
            delete_transient( 'ttdvr_dup_clean_notice' );
        }
    }
}