<?php
/**
 * Plugin Name: AI Search
 * Description: Replaces the default search with an intelligent search system.
 * Version: 1.18.0
 * Author: Samuel Silva
 * Author URI: https://samuelsilva.pt
 * Plugin URI: https://wp-search.ai
 * License: GPL2
 * Text Domain: ai-search
 * Domain Path: /languages
 */

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

// Define plugin constants
define( 'AI_SEARCH_VERSION', '1.18.0' );
define( 'AI_SEARCH_PATH', plugin_dir_path( __FILE__ ) );
define( 'AI_SEARCH_URL', plugin_dir_url( __FILE__ ) );
define( 'AI_SEARCH_TEXT_DOMAIN', 'ai-search' );

// Load dependencies
require_once AI_SEARCH_PATH . 'includes/class-ai-search-service.php';
require_once AI_SEARCH_PATH . 'includes/class-rest-api.php';
require_once AI_SEARCH_PATH . 'admin/class-admin-manager.php';


class AI_Search {

    /**
     * Singleton instance.
     *
     * @var AI_Search|null
     */
    private static $instance = null;

    /**
     * Plugin version.
     */
    const VERSION = '1.18.0';

    /**
     * OpenAI API Key.
     */
    private $api_key;

    /**
     * Threshold for similarity score.
     */
    private $similarity_threshold;

    /**
     * Admin manager instance.
     */
    private $admin_manager;

    /**
     * AI provider (ai_service or openai).
     */
    private $provider;

    /**
     * AI Search Service token.
     */
    private $service_token;

    /**
     * AI Search Service client.
     */
    private $service_client;

    /**
     * Similarity scores for current search results.
     *
     * @var array
     */
    private static $similarity_scores = [];

    /**
     * Whether hybrid search is enabled.
     */
    private $hybrid_enabled;

    /**
     * Hybrid search balance (0-100, where 0 = 100% semantic, 100 = 100% keyword).
     */
    private $hybrid_balance;

    /**
     * Initialize the plugin.
     */
    private function __construct() {
        $this->api_key = get_option( 'ai_search_api_key', '' );
        $this->similarity_threshold = get_option( 'ai_search_similarity_threshold', 0.65 );
        $this->provider = get_option( 'ai_search_provider', 'ai_service' );
        $this->service_token = get_option( 'ai_search_service_token', '' );
        $this->service_client = new AI_Search_Service();
        $this->hybrid_enabled = get_option( 'ai_search_hybrid_enabled', false );
        $this->hybrid_balance = get_option( 'ai_search_hybrid_balance', 30 );

        $this->register_hooks();

        // Initialize REST API
        new AI_Search_REST_API();

        // Initialize admin interface if in admin area
        if ( is_admin() ) {
            $this->admin_manager = new AI_Search_Admin_Manager();
        }

    }

    /**
     * Get the singleton instance.
     *
     * @return AI_Search
     */
    public static function get_instance() {
        if ( null === self::$instance ) {
            self::$instance = new self();
        }

        return self::$instance;
    }
    
    /**
     * Get admin manager instance
     */
    public function get_admin_manager() {
        return $this->admin_manager;
    }

    /**
     * Register hooks.
     */
    private function register_hooks() {
        // Load text domain for translations
        add_action( 'init', [ $this, 'load_textdomain' ] );

        // Core functionality hooks
        // Generate embedding automatically when post is published
        add_action( 'transition_post_status', [ $this, 'generate_embedding_on_publish' ], 10, 3 );
        add_filter( 'posts_results', [ $this, 'filter_search_results' ], 10, 2 );

        // Add similarity class to search results
        add_filter( 'post_class', [ $this, 'add_similarity_class' ], 10, 3 );

        // Add AI Search badge to results
        add_filter( 'the_title', [ $this, 'add_ai_search_badge' ], 10, 2 );
        add_action( 'wp_head', [ $this, 'add_ai_search_badge_styles' ] );

        // Frontend threshold slider for admins
        add_action( 'wp_footer', [ $this, 'add_frontend_threshold_slider' ] );

        // AJAX handlers
        add_action( 'wp_ajax_ai_search_clear_feedback', [ $this, 'clear_search_feedback' ] );
        add_action( 'wp_ajax_nopriv_ai_search_clear_feedback', [ $this, 'clear_search_feedback' ] );
        add_action( 'wp_ajax_ai_search_update_threshold', [ $this, 'ajax_update_threshold' ] );

        // Admin hooks are now handled by AI_Search_Admin_Manager
    }

    /**
     * Load plugin text domain for translations.
     */
    public function load_textdomain() {
        load_plugin_textdomain(
            'ai-search',
            false,
            dirname( plugin_basename( __FILE__ ) ) . '/languages'
        );
    }

    /**
     * Generate embedding when post transitions to publish status
     *
     * @param string $new_status New post status.
     * @param string $old_status Old post status.
     * @param WP_Post $post Post object.
     */
    public function generate_embedding_on_publish( $new_status, $old_status, $post ) {
        // Only generate when transitioning TO publish status
        if ( 'publish' !== $new_status ) {
            return;
        }

        // Don't generate for revisions or auto-saves
        if ( wp_is_post_revision( $post->ID ) || wp_is_post_autosave( $post->ID ) ) {
            return;
        }

        // Generate the embedding
        $this->generate_embedding( $post->ID );
    }

    /**
     * Generate embedding for a post and save it to post meta.
     *
     * @param int $post_id Post ID.
     */
    public function generate_embedding( $post_id ) {
        if ( wp_is_post_revision( $post_id ) ) {
            return;
        }

        $post = get_post( $post_id );
        if ( ! $post || 'publish' !== $post->post_status ) {
            return;
        }

        // Sanitize post title and content
        $post_title = sanitize_text_field( $post->post_title );

        // Extract plain text from content (remove HTML, shortcodes, etc.)
        $post_content = wp_strip_all_tags( strip_shortcodes( $post->post_content ) );
        // Remove extra whitespace and normalize
        $post_content = preg_replace( '/\s+/', ' ', trim( $post_content ) );

        // Get custom fields for this post type
        $custom_fields_content = $this->get_custom_fields_content( $post_id, $post->post_type );

        // Combine context with content for embedding and convert to lowercase for case-insensitive search
        $content = $post_title . ' ' . $post_content . ' ' . $custom_fields_content;
        $content = strtolower( $content );
        $embedding = $this->get_embedding( $content );

        if ( $embedding ) {
            update_post_meta( $post_id, '_ai_search_embedding', wp_json_encode( $embedding ) );
        }
    }

    /**
     * Get custom fields content for a post.
     *
     * @param int $post_id Post ID.
     * @param string $post_type Post type.
     *
     * @return string Custom fields content.
     */
    private function get_custom_fields_content( $post_id, $post_type ) {
        $content = '';

        // Get selected custom fields for this post type
        $selected_fields = get_option( 'ai_search_custom_fields_' . $post_type, [] );

        if ( empty( $selected_fields ) || ! is_array( $selected_fields ) ) {
            return $content;
        }

        // Get custom field values
        foreach ( $selected_fields as $field_key ) {
            $field_value = get_post_meta( $post_id, $field_key, true );

            if ( ! empty( $field_value ) ) {
                // Get field label (support ACF if available)
                $field_label = $field_key;

                // Try to get ACF field label
                if ( function_exists( 'get_field_object' ) ) {
                    $field_object = get_field_object( $field_key, $post_id );
                    if ( $field_object && isset( $field_object['label'] ) ) {
                        $field_label = $field_object['label'];
                    }
                }

                // Handle different field value types
                if ( is_array( $field_value ) ) {
                    // Handle ACF relationship, post object, or other array fields
                    $processed_values = [];
                    foreach ( $field_value as $item ) {
                        if ( is_object( $item ) && isset( $item->post_title ) ) {
                            // ACF Post Object or Relationship field
                            $processed_values[] = $item->post_title;
                        } elseif ( is_string( $item ) ) {
                            $processed_values[] = $item;
                        } elseif ( is_array( $item ) && isset( $item['label'] ) ) {
                            // ACF select/checkbox with labels
                            $processed_values[] = $item['label'];
                        } elseif ( is_array( $item ) && isset( $item['title'] ) ) {
                            // ACF image/file field
                            $processed_values[] = $item['title'];
                        }
                    }
                    if ( ! empty( $processed_values ) ) {
                        $field_value = implode( ' ', $processed_values );
                    } else {
                        continue; // Skip if we couldn't extract meaningful data
                    }
                } elseif ( is_object( $field_value ) ) {
                    // Handle ACF User field or other object types
                    if ( isset( $field_value->display_name ) ) {
                        $field_value = $field_value->display_name;
                    } elseif ( isset( $field_value->post_title ) ) {
                        $field_value = $field_value->post_title;
                    } else {
                        continue; // Skip objects we can't process
                    }
                }

                // Sanitize and add to content (without field label)
                if ( is_string( $field_value ) ) {
                    // Strip HTML and shortcodes from field value
                    $clean_value = wp_strip_all_tags( strip_shortcodes( $field_value ) );
                    $clean_value = preg_replace( '/\s+/', ' ', trim( $clean_value ) );

                    if ( ! empty( $clean_value ) ) {
                        $content .= ' ' . $clean_value;
                    }
                }
            }
        }

        // Handle WooCommerce products if applicable
        if ( $post_type === 'product' && class_exists( 'WooCommerce' ) ) {
            $woo_fields = get_option( 'ai_search_woocommerce_fields', [] );

            if ( ! empty( $woo_fields ) && is_array( $woo_fields ) ) {
                $product = wc_get_product( $post_id );

                if ( $product ) {
                    foreach ( $woo_fields as $woo_field ) {
                        switch ( $woo_field ) {
                            case 'product_description':
                                $desc = $product->get_description();
                                if ( ! empty( $desc ) ) {
                                    // Strip HTML and shortcodes from description
                                    $desc = wp_strip_all_tags( strip_shortcodes( $desc ) );
                                    $desc = preg_replace( '/\s+/', ' ', trim( $desc ) );
                                    if ( ! empty( $desc ) ) {
                                        $content .= ' ' . $desc;
                                    }
                                }
                                break;
                            case 'product_short_description':
                                $short_desc = $product->get_short_description();
                                if ( ! empty( $short_desc ) ) {
                                    // Strip HTML and shortcodes from short description
                                    $short_desc = wp_strip_all_tags( strip_shortcodes( $short_desc ) );
                                    $short_desc = preg_replace( '/\s+/', ' ', trim( $short_desc ) );
                                    if ( ! empty( $short_desc ) ) {
                                        $content .= ' ' . $short_desc;
                                    }
                                }
                                break;
                            case 'product_sku':
                                $sku = $product->get_sku();
                                if ( ! empty( $sku ) ) {
                                    $content .= ' ' . sanitize_text_field( $sku );
                                }
                                break;
                            case 'product_categories':
                                $categories = wp_get_post_terms( $post_id, 'product_cat', [ 'fields' => 'names' ] );
                                if ( ! is_wp_error( $categories ) && ! empty( $categories ) ) {
                                    $content .= ' ' . implode( ' ', array_map( 'sanitize_text_field', $categories ) );
                                }
                                break;
                            case 'product_tags':
                                $tags = wp_get_post_terms( $post_id, 'product_tag', [ 'fields' => 'names' ] );
                                if ( ! is_wp_error( $tags ) && ! empty( $tags ) ) {
                                    $content .= ' ' . implode( ' ', array_map( 'sanitize_text_field', $tags ) );
                                }
                                break;
                        }
                    }

                    // Handle product attributes
                    $attributes = $product->get_attributes();
                    foreach ( $attributes as $attribute ) {
                        $attribute_key = 'attribute_' . $attribute->get_name();
                        if ( in_array( $attribute_key, $woo_fields ) ) {
                            $values = $attribute->get_options();
                            if ( ! empty( $values ) ) {
                                $attribute_values = [];

                                if ( is_array( $values ) ) {
                                    foreach ( $values as $value ) {
                                        $term = get_term( $value );
                                        if ( $term && ! is_wp_error( $term ) ) {
                                            $attribute_values[] = sanitize_text_field( $term->name );
                                        }
                                    }
                                } else {
                                    $attribute_values[] = sanitize_text_field( $values );
                                }

                                if ( ! empty( $attribute_values ) ) {
                                    $content .= ' ' . implode( ' ', $attribute_values );
                                }
                            }
                        }
                    }
                }
            }
        }

        return trim( $content );
    }

    /**
     * Get embedding from OpenAI.
     *
     * @param string $content Content to embed.
     *
     * @return array|false Embedding data or false on failure.
     */
    private function get_embedding( $content ) {
        $content = sanitize_textarea_field( $content );

        // Check for Cached Embedding
        $cached_embedding = get_transient( 'ai_search_embedding_' . md5( $content ) );
        if ( $cached_embedding ) {
            return $cached_embedding;
        }

        if ( $this->provider === 'ai_service' ) {
            // Check if we have a service token first
            $service_token = get_option( 'ai_search_service_token', '' );
            if ( empty( $service_token ) ) {
                return false; // No token available, service not registered
            }

            $embedding = $this->service_client->get_embedding( $content );
            if ( $embedding && ! empty( $embedding['embedding'] ) ) {
                // Cache the embedding
                set_transient( 'ai_search_embedding_' . md5( $content ), $embedding['embedding'], MONTH_IN_SECONDS );
                return $embedding['embedding'];
            }
            return false; // Service failed, don't fallback to OpenAI without user consent
        }

        $response = wp_remote_post( 'https://api.openai.com/v1/embeddings', [
            'headers' => [
                'Authorization' => 'Bearer ' . $this->api_key,
                'Content-Type'  => 'application/json',
            ],
            'body'    => wp_json_encode([
                'input' => $content,
                'model' => get_option( 'ai_search_openai_model', 'text-embedding-3-small' ),
            ]),
        ]);

        if ( is_wp_error( $response ) ) {
            return false;
        }

        $body = json_decode( wp_remote_retrieve_body( $response ), true );

        if ( ! isset( $body['data'][0]['embedding'] ) ) {
            return false;
        }

        // Cache the embedding for 1 day
        set_transient( 'ai_search_embedding_' . md5( $content ), $body['data'][0]['embedding'], MONTH_IN_SECONDS );
        return $body['data'][0]['embedding'];
    }

    /**
     * Customize the search query.
     *
     * @param string $sql Original SQL query.
     * @param WP_Query $query WP_Query object.
     *
     * @return string Modified SQL query.
     */
    public function filter_search_results( $posts, $query ) {
        if ( ! $query->is_search() || is_admin() ) {
            return $posts;
        }

        $post_type = $query->get( 'post_type' );

        // If no post type is specified, search all public post types
        if ( empty( $post_type ) ) {
            $post_type = get_post_types( [ 'public' => true ], 'names' );
            // Remove attachments from the list
            unset( $post_type['attachment'] );
        }

        /**
         * Filter the post types that AI Search will search through.
         *
         * @since 1.9.2
         *
         * @param string|array $post_type The post type(s) to search. Default is all public post types.
         * @param WP_Query     $query     The current WP_Query object.
         */
        $post_type = apply_filters( 'ai_search_searchable_post_types', $post_type, $query );

        $search_query = get_search_query();
        $search_query = sanitize_text_field( $search_query );
        $search_query = strtolower( $search_query );
        $query_embedding = $this->get_embedding( $search_query );

        if ( ! $query_embedding ) {
            return $posts;
        }

        // Allow admins to temporarily override threshold for testing
        $threshold = $this->similarity_threshold;
        if ( current_user_can( 'manage_options' ) && isset( $_GET['ai_threshold'] ) ) {
            $threshold = floatval( $_GET['ai_threshold'] );
            $threshold = max( 0.1, min( 1.0, $threshold ) ); // Clamp between 0.5 and 1.0
        }

        $similarities = [];

        $all_posts = get_posts([
            'numberposts' => -1,
            'post_type'   => $post_type,
            'post_status' => 'publish',
            'meta_key'    => '_ai_search_embedding',
        ]);


        foreach ( $all_posts as $post ) {

            $embedding_json = get_post_meta( $post->ID, '_ai_search_embedding', true );
            if ( empty( $embedding_json ) ) {
                continue;
            }

            $embedding = json_decode( $embedding_json, true );
            if ( ! empty( $embedding['embedding'] ) ) {
                $embedding = $embedding['embedding'];
            }
            $semantic_score = $this->calculate_similarity( $query_embedding, $embedding );

            // Calculate hybrid score if enabled
            if ( $this->hybrid_enabled ) {
                $keyword_score = $this->calculate_keyword_score( $post, $search_query );
                $final_score = $this->calculate_hybrid_score( $semantic_score, $keyword_score );
            } else {
                $final_score = $semantic_score;
            }

            if ( $final_score >= $threshold ) {
                $similarities[ $post->ID ] = $final_score;
            }
        }

        if ( empty( $similarities ) ) {
            // AI Search found no results, try enhanced fallback search
            return $this->enhanced_fallback_search( $search_query, $post_type, $posts );
        }

        arsort( $similarities );
        $ordered_ids = array_keys( $similarities );

        // Store similarity scores for post_class filter
        self::$similarity_scores = $similarities;

        $posts = get_posts([
            'post_type'      => $post_type,
            'post_status'    => 'publish',
            'post__in'       => $ordered_ids,
            'orderby'        => 'post__in',
            'posts_per_page' => -1,
        ]);

        return $posts;
    }

    /**
     * Calculate cosine similarity.
     *
     * @param array $a First vector.
     * @param array $b Second vector.
     *
     * @return float Cosine similarity.
     */
   private function calculate_similarity( $a, $b ) {

        if ( ! is_array( $a ) || ! is_array( $b ) || count( $a ) !== count( $b ) ) {
            return 0;
        }

        $dot_product = array_sum( array_map( function ( $x, $y ) {
            return $x * $y;
        }, $a, $b ) );

        $magnitude_a = sqrt( array_sum( array_map( function ( $x ) {
            return $x ** 2;
        }, $a ) ) );

        $magnitude_b = sqrt( array_sum( array_map( function ( $x ) {
            return $x ** 2;
        }, $b ) ) );

        if ( $magnitude_a === 0 || $magnitude_b === 0 ) {
            return 0;
        }

        return $dot_product / ( $magnitude_a * $magnitude_b );
    }

    /**
     * Calculate keyword match score for a post.
     *
     * @param WP_Post $post The post to score.
     * @param string $search_query The search query (already lowercase).
     * @return float Keyword match score (0-1).
     */
    private function calculate_keyword_score( $post, $search_query ) {
        $score = 0.0;
        $search_words = array_filter( explode( ' ', $search_query ) );

        if ( empty( $search_words ) ) {
            return 0.0;
        }

        $title = strtolower( $post->post_title );
        $content = strtolower( wp_strip_all_tags( $post->post_content ) );

        // Check each search word
        $title_matches = 0;
        $content_matches = 0;
        $custom_field_matches = 0;

        foreach ( $search_words as $word ) {
            if ( strlen( $word ) < 2 ) {
                continue; // Skip very short words
            }

            // Exact word match in title (highest priority)
            if ( preg_match( '/\b' . preg_quote( $word, '/' ) . '\b/i', $title ) ) {
                $title_matches++;
            }

            // Word match in content
            if ( preg_match( '/\b' . preg_quote( $word, '/' ) . '\b/i', $content ) ) {
                $content_matches++;
            }
        }

        $total_words = count( array_filter( $search_words, function( $w ) { return strlen( $w ) >= 2; } ) );

        if ( $total_words === 0 ) {
            return 0.0;
        }

        // Calculate title score (0-1)
        $title_score = $title_matches / $total_words;

        // Calculate content score (0-1)
        $content_score = $content_matches / $total_words;

        // Check categories and tags
        $taxonomy_score = 0.0;
        $taxonomies = get_object_taxonomies( $post->post_type, 'names' );

        foreach ( $taxonomies as $taxonomy ) {
            $terms = wp_get_post_terms( $post->ID, $taxonomy, [ 'fields' => 'names' ] );
            if ( ! is_wp_error( $terms ) && ! empty( $terms ) ) {
                $terms_string = strtolower( implode( ' ', $terms ) );
                foreach ( $search_words as $word ) {
                    if ( strlen( $word ) >= 2 && strpos( $terms_string, $word ) !== false ) {
                        $taxonomy_score = max( $taxonomy_score, 0.4 );
                        break 2;
                    }
                }
            }
        }

        // Check custom fields configured in settings
        $custom_fields = get_option( 'ai_search_custom_fields_' . $post->post_type, [] );
        $custom_field_content = '';

        if ( ! empty( $custom_fields ) ) {
            foreach ( $custom_fields as $field_key ) {
                $field_value = get_post_meta( $post->ID, $field_key, true );
                if ( ! empty( $field_value ) ) {
                    if ( is_array( $field_value ) ) {
                        $custom_field_content .= ' ' . implode( ' ', array_map( 'strval', $field_value ) );
                    } else {
                        $custom_field_content .= ' ' . strval( $field_value );
                    }
                }
            }
        }

        // Check WooCommerce fields for products
        if ( $post->post_type === 'product' && class_exists( 'WooCommerce' ) ) {
            $woo_fields = get_option( 'ai_search_woocommerce_fields', [] );
            $product = wc_get_product( $post->ID );

            if ( $product ) {
                // SKU
                if ( in_array( 'sku', $woo_fields, true ) ) {
                    $sku = $product->get_sku();
                    if ( ! empty( $sku ) ) {
                        $custom_field_content .= ' ' . $sku;
                    }
                }

                // Short description
                if ( in_array( 'short_description', $woo_fields, true ) ) {
                    $short_desc = $product->get_short_description();
                    if ( ! empty( $short_desc ) ) {
                        $custom_field_content .= ' ' . wp_strip_all_tags( $short_desc );
                    }
                }

                // Product attributes
                if ( in_array( 'attributes', $woo_fields, true ) ) {
                    $attributes = $product->get_attributes();
                    if ( ! empty( $attributes ) ) {
                        foreach ( $attributes as $attribute ) {
                            if ( is_object( $attribute ) && method_exists( $attribute, 'get_options' ) ) {
                                $options = $attribute->get_options();
                                if ( ! empty( $options ) ) {
                                    $custom_field_content .= ' ' . implode( ' ', $options );
                                }
                            }
                        }
                    }
                }
            }
        }

        // Calculate custom field score
        $custom_field_score = 0.0;
        if ( ! empty( $custom_field_content ) ) {
            $custom_field_content = strtolower( $custom_field_content );
            foreach ( $search_words as $word ) {
                if ( strlen( $word ) >= 2 && preg_match( '/\b' . preg_quote( $word, '/' ) . '\b/i', $custom_field_content ) ) {
                    $custom_field_matches++;
                }
            }
            $custom_field_score = $custom_field_matches / $total_words;
        }

        // Weighted combination: title (1.0), content (0.5), taxonomy (0.4), custom fields (0.6)
        $score = ( $title_score * 1.0 ) + ( $content_score * 0.5 ) + $taxonomy_score + ( $custom_field_score * 0.6 );

        // Normalize to 0-1 range (max possible is now 2.5: 1.0 + 0.5 + 0.4 + 0.6)
        $score = min( 1.0, $score / 2.5 );

        return $score;
    }

    /**
     * Calculate hybrid score combining semantic and keyword scores.
     *
     * @param float $semantic_score Cosine similarity score (0-1).
     * @param float $keyword_score Keyword match score (0-1).
     * @return float Combined hybrid score (0-1).
     */
    private function calculate_hybrid_score( $semantic_score, $keyword_score ) {
        if ( ! $this->hybrid_enabled ) {
            return $semantic_score;
        }

        // Balance: 0 = 100% semantic, 100 = 100% keyword
        $keyword_weight = $this->hybrid_balance / 100;
        $semantic_weight = 1 - $keyword_weight;

        return ( $semantic_score * $semantic_weight ) + ( $keyword_score * $keyword_weight );
    }

    /**
     * Enhanced fallback search when AI search finds no results.
     *
     * @param string $search_query The original search query.
     * @param string $post_type The post type being searched.
     * @param array $original_posts Original WordPress search results.
     * @return array Enhanced search results or informative fallback.
     */
    private function enhanced_fallback_search( $search_query, $post_type, $original_posts ) {
        // Get query embedding for similarity calculation
        $query_embedding = $this->get_embedding( $search_query );

        // Get current threshold (with admin override support)
        $threshold = $this->similarity_threshold;
        if ( current_user_can( 'manage_options' ) && isset( $_GET['ai_threshold'] ) ) {
            $threshold = floatval( $_GET['ai_threshold'] );
            $threshold = max( 0.1, min( 1.0, $threshold ) );
        }

        // Strategy 1: If original WordPress search found results, use them
        if ( ! empty( $original_posts ) ) {
            $filtered_posts = [];

            // Calculate similarity scores for fallback results that have embeddings
            if ( $query_embedding ) {
                foreach ( $original_posts as $post ) {
                    $embedding_json = get_post_meta( $post->ID, '_ai_search_embedding', true );
                    if ( ! empty( $embedding_json ) ) {
                        $embedding = json_decode( $embedding_json, true );
                        if ( ! empty( $embedding['embedding'] ) ) {
                            $embedding = $embedding['embedding'];
                        }
                        $semantic_score = $this->calculate_similarity( $query_embedding, $embedding );

                        // Calculate hybrid score if enabled
                        if ( $this->hybrid_enabled ) {
                            $keyword_score = $this->calculate_keyword_score( $post, $search_query );
                            $final_score = $this->calculate_hybrid_score( $semantic_score, $keyword_score );
                        } else {
                            $final_score = $semantic_score;
                        }

                        self::$similarity_scores[ $post->ID ] = $final_score;

                        // Only include posts that meet the threshold
                        if ( $final_score >= $threshold ) {
                            $filtered_posts[] = $post;
                        }
                    } else {
                        // Post has no embedding, include it anyway (WordPress default behavior)
                        $filtered_posts[] = $post;
                    }
                }
            } else {
                $filtered_posts = $original_posts;
            }

            // If we have filtered results, return them
            if ( ! empty( $filtered_posts ) ) {
                // Add a transient to indicate fallback was used
                set_transient( 'ai_search_used_fallback', [
                    'query' => $search_query,
                    'type' => 'wordpress_default',
                    'count' => count( $filtered_posts )
                ], 300 ); // 5 minutes

                return $filtered_posts;
            }
        }
        
        // Strategy 2: Try broader WordPress search with partial matching
        $broader_results = $this->perform_broader_search( $search_query, $post_type );
        if ( ! empty( $broader_results ) ) {
            $filtered_broader = [];

            // Calculate similarity scores for broader results that have embeddings
            if ( $query_embedding ) {
                foreach ( $broader_results as $post ) {
                    $embedding_json = get_post_meta( $post->ID, '_ai_search_embedding', true );
                    if ( ! empty( $embedding_json ) ) {
                        $embedding = json_decode( $embedding_json, true );
                        if ( ! empty( $embedding['embedding'] ) ) {
                            $embedding = $embedding['embedding'];
                        }
                        $semantic_score = $this->calculate_similarity( $query_embedding, $embedding );

                        // Calculate hybrid score if enabled
                        if ( $this->hybrid_enabled ) {
                            $keyword_score = $this->calculate_keyword_score( $post, $search_query );
                            $final_score = $this->calculate_hybrid_score( $semantic_score, $keyword_score );
                        } else {
                            $final_score = $semantic_score;
                        }

                        self::$similarity_scores[ $post->ID ] = $final_score;

                        // Only include posts that meet the threshold
                        if ( $final_score >= $threshold ) {
                            $filtered_broader[] = $post;
                        }
                    } else {
                        // Post has no embedding, include it anyway
                        $filtered_broader[] = $post;
                    }
                }
            } else {
                $filtered_broader = $broader_results;
            }

            // If we have filtered results, return them
            if ( ! empty( $filtered_broader ) ) {
                set_transient( 'ai_search_used_fallback', [
                    'query' => $search_query,
                    'type' => 'broader_search',
                    'count' => count( $filtered_broader )
                ], 300 );

                return $filtered_broader;
            }
        }

        // Strategy 3: Try searching posts without embeddings (not yet processed)
        $unprocessed_results = $this->search_unprocessed_posts( $search_query, $post_type );
        if ( ! empty( $unprocessed_results ) ) {
            $filtered_unprocessed = [];

            // Calculate similarity scores for unprocessed results that have embeddings
            if ( $query_embedding ) {
                foreach ( $unprocessed_results as $post ) {
                    $embedding_json = get_post_meta( $post->ID, '_ai_search_embedding', true );
                    if ( ! empty( $embedding_json ) ) {
                        $embedding = json_decode( $embedding_json, true );
                        if ( ! empty( $embedding['embedding'] ) ) {
                            $embedding = $embedding['embedding'];
                        }
                        $semantic_score = $this->calculate_similarity( $query_embedding, $embedding );

                        // Calculate hybrid score if enabled
                        if ( $this->hybrid_enabled ) {
                            $keyword_score = $this->calculate_keyword_score( $post, $search_query );
                            $final_score = $this->calculate_hybrid_score( $semantic_score, $keyword_score );
                        } else {
                            $final_score = $semantic_score;
                        }

                        self::$similarity_scores[ $post->ID ] = $final_score;

                        // Only include posts that meet the threshold
                        if ( $final_score >= $threshold ) {
                            $filtered_unprocessed[] = $post;
                        }
                    } else {
                        // Post has no embedding, include it anyway
                        $filtered_unprocessed[] = $post;
                    }
                }
            } else {
                $filtered_unprocessed = $unprocessed_results;
            }

            // If we have filtered results, return them
            if ( ! empty( $filtered_unprocessed ) ) {
                set_transient( 'ai_search_used_fallback', [
                    'query' => $search_query,
                    'type' => 'unprocessed_posts',
                    'count' => count( $filtered_unprocessed )
                ], 300 );

                return $filtered_unprocessed;
            }
        }
        
        // Strategy 4: No results found anywhere, store info for user feedback
        set_transient( 'ai_search_no_results', [
            'query' => $search_query,
            'suggestions' => $this->generate_search_suggestions( $search_query ),
            'timestamp' => time()
        ], 300 );
        
        // Return empty array - WordPress will show its "no results" page
        return [];
    }
    
    /**
     * Perform broader search with more flexible matching.
     *
     * @param string $search_query Search query.
     * @param string $post_type Post type to search.
     * @return array Found posts.
     */
    private function perform_broader_search( $search_query, $post_type ) {
        // Split search query into individual words
        $search_words = explode( ' ', $search_query );
        $search_words = array_filter( array_map( 'trim', $search_words ) );
        
        if ( empty( $search_words ) ) {
            return [];
        }
        
        // Try searching for individual words (OR logic instead of AND)
        $args = [
            'post_type' => $post_type ?: 'any',
            'post_status' => 'publish',
            'posts_per_page' => 20,
            's' => '', // We'll use meta_query for more flexible searching
            'meta_query' => [
                'relation' => 'OR',
            ]
        ];
        
        // Add word-based searches in title and content
        foreach ( $search_words as $word ) {
            if ( strlen( $word ) >= 3 ) { // Only search words with 3+ characters
                $word_results = get_posts([
                    'post_type' => $post_type ?: 'any',
                    'post_status' => 'publish',
                    'posts_per_page' => 10,
                    's' => $word,
                ]);
                
                if ( ! empty( $word_results ) ) {
                    return $word_results;
                }
            }
        }
        
        return [];
    }
    
    /**
     * Search posts that haven't been processed for AI embeddings yet.
     *
     * @param string $search_query Search query.
     * @param string $post_type Post type to search.
     * @return array Found posts.
     */
    private function search_unprocessed_posts( $search_query, $post_type ) {
        $args = [
            'post_type' => $post_type ?: 'any',
            'post_status' => 'publish',
            'posts_per_page' => 15,
            's' => $search_query,
            'meta_query' => [
                [
                    'key' => '_ai_search_embedding',
                    'compare' => 'NOT EXISTS'
                ]
            ]
        ];
        
        return get_posts( $args );
    }
    
    /**
     * Generate search suggestions when no results are found.
     *
     * @param string $search_query Original search query.
     * @return array Suggested search terms.
     */
    private function generate_search_suggestions( $search_query ) {
        $suggestions = [];
        
        // Get common terms from existing posts
        $recent_posts = get_posts([
            'posts_per_page' => 50,
            'post_status' => 'publish'
        ]);
        
        $common_words = [];
        foreach ( $recent_posts as $post ) {
            $title_words = explode( ' ', strtolower( $post->post_title ) );
            foreach ( $title_words as $word ) {
                $word = trim( $word, '.,!?;:"()[]' );
                if ( strlen( $word ) >= 4 ) {
                    $common_words[] = $word;
                }
            }
        }
        
        // Get most frequent words
        $word_counts = array_count_values( $common_words );
        arsort( $word_counts );
        
        $suggestions = array_slice( array_keys( $word_counts ), 0, 5 );
        
        return $suggestions;
    }

    /**
     * Handle AJAX request to clear search feedback transients.
     */
    public function clear_search_feedback() {
        // Verify nonce for security
        if ( ! wp_verify_nonce( $_POST['nonce'] ?? '', 'ai_search_clear_feedback' ) ) {
            wp_die( 'Security check failed' );
        }

        // Clear the transients
        delete_transient( 'ai_search_used_fallback' );
        delete_transient( 'ai_search_no_results' );

        wp_die( 'success' );
    }

    /**
     * Add similarity score as CSS class to search result posts.
     *
     * @param array $classes Existing post classes.
     * @param array $class Additional classes.
     * @param int   $post_id Post ID.
     * @return array Modified classes.
     */
    public function add_similarity_class( $classes, $class, $post_id ) {
        if ( ! is_search() || is_admin() ) {
            return $classes;
        }

        if ( isset( self::$similarity_scores[ $post_id ] ) ) {
            $score = self::$similarity_scores[ $post_id ];
            // Convert to percentage (0-100) for CSS class, clamped to 0-100 range
            $score_percent = max( 0, min( 100, round( $score * 100 ) ) );
            $classes[] = 'ai-search-result';
            $classes[] = 'ai-search-similarity-' . $score_percent;

            // Add class based on threshold comparison
            if ( $score >= $this->similarity_threshold ) {
                $classes[] = 'ai-search-match';
            } else {
                $classes[] = 'ai-search-below-threshold';
            }
        } else {
            // Not an AI search result (fallback or no embedding)
            $classes[] = 'ai-search-fallback';
            $classes[] = 'ai-search-similarity-0';
        }

        return $classes;
    }

    /**
     * Add AI Search badge to post titles in search results.
     *
     * @param string $title The post title.
     * @param int    $post_id The post ID.
     * @return string Modified title with badge.
     */
    public function add_ai_search_badge( $title, $post_id = 0 ) {
        // Only on search pages, in the loop, on frontend
        if ( ! is_search() || is_admin() || ! in_the_loop() ) {
            return $title;
        }

        // Check visibility permission
        $badge_public = get_option( 'ai_search_badge_public', false );
        if ( ! $badge_public && ! current_user_can( 'edit_posts' ) ) {
            return $title;
        }

        $icon_url = AI_SEARCH_URL . 'assets/icon.svg';
        $is_ai_result = isset( self::$similarity_scores[ $post_id ] );

        if ( $is_ai_result ) {
            // AI Search result with similarity score
            $score = self::$similarity_scores[ $post_id ];
            // Clamp score percentage to 0-100 range
            $score_percent = max( 0, min( 100, round( $score * 100 ) ) );

            // Show different tooltip based on visibility setting
            if ( $badge_public ) {
                $tooltip = __( 'This result was found using AI-powered semantic search.', 'ai-search' );
            } else {
                $tooltip = __( 'This badge is only visible to editors and administrators.', 'ai-search' );
            }

            $badge = sprintf(
                '<span class="ai-search-badge" title="%s"><img src="%s" alt="%s" class="ai-search-badge-icon" />%s <span class="ai-search-badge-score">%d%%</span></span>',
                esc_attr( $tooltip ),
                esc_url( $icon_url ),
                esc_attr__( 'AI Search', 'ai-search' ),
                esc_html__( 'AI Search Result', 'ai-search' ),
                $score_percent
            );
        } else {
            // Fallback result (no AI similarity score)
            if ( $badge_public ) {
                $tooltip = __( 'This result was found using fallback search (no AI embedding available).', 'ai-search' );
            } else {
                $tooltip = __( 'Fallback result - This badge is only visible to editors and administrators.', 'ai-search' );
            }

            $badge = sprintf(
                '<span class="ai-search-badge ai-search-badge-fallback" title="%s"><img src="%s" alt="%s" class="ai-search-badge-icon" />%s</span>',
                esc_attr( $tooltip ),
                esc_url( $icon_url ),
                esc_attr__( 'AI Search', 'ai-search' ),
                esc_html__( 'Fallback Result', 'ai-search' )
            );
        }

        return $badge . '<br>' . $title;
    }

    /**
     * Add CSS styles for AI Search badge.
     */
    public function add_ai_search_badge_styles() {
        if ( ! is_search() ) {
            return;
        }

        // Check visibility permission
        $badge_public = get_option( 'ai_search_badge_public', false );
        if ( ! $badge_public && ! current_user_can( 'edit_posts' ) ) {
            return;
        }
        ?>
        <style id="ai-search-badge-styles">
            .ai-search-badge {
                display: inline-flex;
                align-items: center;
                gap: 4px;
                background: #3a3a3a;
                color: #fff;
                font-size: 10px;
                font-weight: 600;
                padding: 6px 12px;
                border-radius: 4px;
                margin-bottom: 4px;
                text-transform: uppercase;
                letter-spacing: 0.5px;
            }
            .ai-search-badge-icon {
                width: 14px;
                height: 14px;
            }
            .ai-search-badge-score {
                margin-left: 4px;
                font-size: 11px;
                font-weight: 700;
                background: rgba(255,255,255,0.2);
                padding: 2px 6px;
                border-radius: 3px;
            }
            .ai-search-badge-fallback {
                background: #dc3545;
                opacity: 0.85;
            }
        </style>
        <?php
    }

    /**
     * Add frontend threshold slider for admins on search results pages.
     */
    public function add_frontend_threshold_slider() {
        // Only show on search results pages for admins
        if ( ! is_search() || ! current_user_can( 'manage_options' ) ) {
            return;
        }

        $current_threshold = $this->similarity_threshold;

        // Use override value if set
        if ( isset( $_GET['ai_threshold'] ) ) {
            $current_threshold = floatval( $_GET['ai_threshold'] );
            $current_threshold = max( 0.1, min( 1.0, $current_threshold ) );
        }

        $current_percent = round( $current_threshold * 100 );
        $search_query = get_search_query();
        ?>
        <div id="ai-search-frontend-slider" style="position: fixed; bottom: 20px; right: 20px; background: white; padding: 20px; border-radius: 8px; box-shadow: 0 4px 12px rgba(0,0,0,0.15); z-index: 9999; width: 320px; max-width: calc(100vw - 40px);">
            <div style="display: flex; justify-content: space-between; align-items: center; margin-bottom: 15px;">
                <strong style="font-size: 14px;">AI Search Threshold</strong>
                <button id="ai-search-close-slider" style="background: none; border: none; font-size: 20px; cursor: pointer; padding: 0; line-height: 1;">&times;</button>
            </div>

            <div style="margin-bottom: 10px;">
                <div style="display: flex; justify-content: space-between; align-items: center; margin-bottom: 5px;">
                    <span style="font-size: 12px; color: #666;">Current Value:</span>
                    <output id="ai-search-frontend-output" style="font-size: 16px; font-weight: 600; color: #2271b1;"><?php echo $current_percent; ?>%</output>
                </div>
                <input type="range"
                       id="ai-search-frontend-threshold"
                       min="10"
                       max="100"
                       step="1"
                       value="<?php echo esc_attr( $current_percent ); ?>"
                       style="width: 100%; margin: 10px 0;">
                <div style="display: flex; justify-content: space-between; font-size: 10px; color: #666; margin-bottom: 10px;">
                    <span>10% - Very Broad</span>
                    <span>100% - Exact</span>
                </div>
            </div>

            <div id="ai-search-frontend-indicator" style="padding: 12px; border-left: 3px solid #2271b1; background: #f0f6fc; border-radius: 4px; margin-bottom: 15px;">
                <div style="font-size: 11px; font-weight: 600; color: #2271b1; margin-bottom: 3px;">Balanced Search</div>
                <div style="font-size: 11px; color: #495057;">Good balance between precision and coverage.</div>
            </div>

            <div style="display: flex; gap: 8px;">
                <button id="ai-search-test-threshold" class="ai-search-btn-test" style="flex: 1; background: #2271b1; color: white; border: none; padding: 8px 12px; border-radius: 4px; cursor: pointer; font-size: 12px; font-weight: 600;">Test</button>
                <button id="ai-search-save-threshold" class="ai-search-btn-save" style="flex: 1; background: #00a32a; color: white; border: none; padding: 8px 12px; border-radius: 4px; cursor: pointer; font-size: 12px; font-weight: 600;">Save</button>
            </div>

            <div id="ai-search-message" style="margin-top: 10px; padding: 8px; border-radius: 4px; font-size: 11px; display: none;"></div>
        </div>

        <script>
        (function() {
            var slider = document.getElementById('ai-search-frontend-threshold');
            var output = document.getElementById('ai-search-frontend-output');
            var indicator = document.getElementById('ai-search-frontend-indicator');
            var testBtn = document.getElementById('ai-search-test-threshold');
            var saveBtn = document.getElementById('ai-search-save-threshold');
            var closeBtn = document.getElementById('ai-search-close-slider');
            var message = document.getElementById('ai-search-message');
            var container = document.getElementById('ai-search-frontend-slider');

            slider.oninput = function() {
                var percent = this.value;
                var decimal = (percent / 100).toFixed(2);
                output.textContent = percent + '%';
                updateIndicator(parseFloat(decimal));
            };

            function updateIndicator(threshold) {
                var label, description, color, bg;

                if (threshold < 0.30) {
                    label = 'Very Broad Search';
                    description = 'Returns almost everything, even loosely related content.';
                    color = '#8B0000';
                    bg = '#fff0f0';
                } else if (threshold < 0.60) {
                    label = 'Broad Search';
                    description = 'Many results including loosely related content.';
                    color = '#d63638';
                    bg = '#fff5f5';
                } else if (threshold < 0.70) {
                    label = 'Balanced Search';
                    description = 'Good balance between precision and coverage.';
                    color = '#2271b1';
                    bg = '#f0f6fc';
                } else if (threshold < 0.80) {
                    label = 'Precise Search';
                    description = 'More targeted results with higher relevance.';
                    color = '#dba617';
                    bg = '#fffbf0';
                } else {
                    label = 'Very Strict Matching';
                    description = 'Only highly similar results.';
                    color = '#00a32a';
                    bg = '#f0fdf4';
                }

                indicator.style.borderLeftColor = color;
                indicator.style.background = bg;
                indicator.innerHTML = '<div style="font-size: 11px; font-weight: 600; color: ' + color + '; margin-bottom: 3px;">' + label + '</div>' +
                                    '<div style="font-size: 11px; color: #495057;">' + description + '</div>';
            }

            testBtn.onclick = function() {
                var percent = slider.value;
                var decimal = (percent / 100).toFixed(2);
                var url = new URL(window.location.href);
                url.searchParams.set('ai_threshold', decimal);
                window.location.href = url.toString();
            };

            saveBtn.onclick = function() {
                var percent = slider.value;
                var decimal = (percent / 100).toFixed(2);

                saveBtn.textContent = 'Saving...';
                saveBtn.disabled = true;

                var formData = new FormData();
                formData.append('action', 'ai_search_update_threshold');
                formData.append('nonce', '<?php echo wp_create_nonce( "ai_search_update_threshold" ); ?>');
                formData.append('threshold', decimal);

                fetch('<?php echo admin_url( "admin-ajax.php" ); ?>', {
                    method: 'POST',
                    body: formData
                })
                .then(response => response.json())
                .then(data => {
                    if (data.success) {
                        showMessage('Threshold saved successfully!', 'success');
                        saveBtn.textContent = 'Save';
                        saveBtn.disabled = false;

                        // Remove override parameter and reload
                        setTimeout(function() {
                            var url = new URL(window.location.href);
                            url.searchParams.delete('ai_threshold');
                            window.location.href = url.toString();
                        }, 1000);
                    } else {
                        showMessage('Failed to save threshold.', 'error');
                        saveBtn.textContent = 'Save';
                        saveBtn.disabled = false;
                    }
                })
                .catch(error => {
                    showMessage('Error: ' + error.message, 'error');
                    saveBtn.textContent = 'Save';
                    saveBtn.disabled = false;
                });
            };

            closeBtn.onclick = function() {
                container.style.display = 'none';
            };

            function showMessage(text, type) {
                message.textContent = text;
                message.style.display = 'block';
                message.style.background = type === 'success' ? '#d4edda' : '#f8d7da';
                message.style.color = type === 'success' ? '#155724' : '#721c24';
                message.style.border = '1px solid ' + (type === 'success' ? '#c3e6cb' : '#f5c6cb');

                setTimeout(function() {
                    message.style.display = 'none';
                }, 3000);
            }

            // Initialize indicator
            updateIndicator(<?php echo $current_threshold; ?>);
        })();
        </script>
        <?php
    }

    /**
     * AJAX handler to update threshold setting.
     */
    public function ajax_update_threshold() {
        check_ajax_referer( 'ai_search_update_threshold', 'nonce' );

        if ( ! current_user_can( 'manage_options' ) ) {
            wp_send_json_error( [ 'message' => 'Unauthorized' ] );
        }

        $threshold = isset( $_POST['threshold'] ) ? floatval( $_POST['threshold'] ) : 0.65;
        $threshold = max( 0.1, min( 1.0, $threshold ) );

        update_option( 'ai_search_similarity_threshold', $threshold );

        wp_send_json_success( [ 'threshold' => $threshold ] );
    }

}

// Plugin activation hook
register_activation_hook( __FILE__, 'ai_search_activate_plugin' );

/**
 * Plugin activation handler.
 */
function ai_search_activate_plugin() {
    // Set default settings
    add_option( 'ai_search_provider', 'ai_service' );
    add_option( 'ai_search_similarity_threshold', 0.65 );

    // Set flag to show setup wizard
    update_option( 'ai_search_show_setup_wizard', true );

    // Register origin with AI Search Service immediately
    require_once plugin_dir_path( __FILE__ ) . 'includes/class-ai-search-service.php';
    $service_client = new AI_Search_Service();
    $service_token = $service_client->register_origin();
    if ( $service_token ) {
        update_option( 'ai_search_service_token', $service_token );
    }

    // Set activation redirect flag
    set_transient( 'ai_search_activation_redirect', true, 30 );
}

// Handle activation redirect
add_action( 'admin_init', 'ai_search_activation_redirect' );

/**
 * Redirect to setup wizard after plugin activation.
 */
function ai_search_activation_redirect() {
    // Check if we should redirect
    if ( ! get_transient( 'ai_search_activation_redirect' ) ) {
        return;
    }

    // Delete the transient so we don't redirect again
    delete_transient( 'ai_search_activation_redirect' );

    // Don't redirect if activating multiple plugins or doing bulk action
    if ( isset( $_GET['activate-multi'] ) || ! current_user_can( 'manage_options' ) ) {
        return;
    }

    // Don't redirect if setup was already completed
    if ( get_option( 'ai_search_setup_completed', false ) ) {
        return;
    }

    // Redirect to setup wizard
    wp_safe_redirect( admin_url( 'options-general.php?page=ai-search&setup=wizard' ) );
    exit;
}

// Initialize the plugin.
AI_Search::get_instance();