<?php

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

class Twokcs_Variations_Exporter
{
    /**
     * Export variants filtered by product_ids or ids query param.
     *
     * @param WP_REST_Request $request Request object.
     * @return WP_REST_Response|WP_Error
     */
    public function export(WP_REST_Request $request)
    {
        $product_ids = $this->get_id_list_param($request, 'product_ids');
        $ids         = $this->get_id_list_param($request, 'ids');

        $has_product_ids = !empty($product_ids);
        $has_ids         = !empty($ids);

        if ($has_product_ids && $has_ids) {
            return new WP_Error(
                'twokcs_ambiguous_variants_request',
                __('Provide either product_ids or ids, not both.', '2khat-catalog-sync'),
                ['status' => 400]
            );
        }

        if (!$has_product_ids && !$has_ids) {
            return new WP_Error(
                'twokcs_missing_variants_filter',
                __('Provide product_ids or ids query parameter.', '2khat-catalog-sync'),
                ['status' => 400]
            );
        }

        if ($has_product_ids) {
            return $this->export_by_product_ids($request, $product_ids);
        }

        return $this->export_by_ids($request, $ids);
    }

    /**
     * Export a single variant by ID.
     *
     * @param WP_REST_Request $request Request object.
     * @return WP_REST_Response|WP_Error
     */
    public function export_by_id(WP_REST_Request $request)
    {
        $id = (int) $request->get_param('id');

        if ($id < 1) {
            return new WP_Error(
                'twokcs_missing_variation_id',
                __('Variation ID is required.', '2khat-catalog-sync'),
                ['status' => 400]
            );
        }

        $this->register_export_hooks();

        $variation = wc_get_product($id);

        if (!$variation || !$variation->is_type('variation') || $variation->get_status() !== 'publish') {
            return new WP_Error(
                'twokcs_variation_not_found',
                __('Variation not found.', '2khat-catalog-sync'),
                ['status' => 404]
            );
        }

        $this->warm_meta_cache([$variation]);

        $data = $this->prepare_compact_variation($variation, $request);

        return new WP_REST_Response($data, 200);
    }

    /**
     * Export variants grouped by parent product IDs.
     *
     * @param WP_REST_Request $request     Request object.
     * @param int[]           $product_ids Parent product IDs.
     * @return WP_REST_Response
     */
    private function export_by_product_ids(WP_REST_Request $request, array $product_ids)
    {
        $this->register_export_hooks();

        $products_by_id  = $this->load_products_by_ids($product_ids);
        $variation_posts = get_posts([
            'posts_per_page'  => -1,
            'post_status'     => 'publish',
            'orderby'         => 'menu_order',
            'order'           => 'ASC',
            'post_type'       => 'product_variation',
            'post_parent__in' => $product_ids,
        ]);

        $variations_by_parent = array_fill_keys($product_ids, []);

        if (!empty($variation_posts)) {
            $variations = $this->load_variations_from_posts($variation_posts);

            foreach ($variations as $variation) {
                $parent_id = (int) $variation->get_parent_id();

                if (isset($variations_by_parent[$parent_id])) {
                    $variations_by_parent[$parent_id][] = $this->prepare_compact_variation($variation, $request);
                }
            }
        }

        $results = [];

        foreach ($product_ids as $product_id) {
            if (isset($products_by_id[$product_id])) {
                $item = $this->prepare_compact_product($products_by_id[$product_id], $request);
            } else {
                $item = $this->empty_compact_product($product_id);
            }

            $item['variants'] = $variations_by_parent[$product_id];
            $results[]        = $item;
        }

        $data = [
            'count'   => count($results),
            'results' => $results,
        ];

        if ($this->is_debug_enabled($request)) {
            $this->append_debug_data($data);
        }

        return new WP_REST_Response($data, 200);
    }

    /**
     * Export variants by variation IDs.
     *
     * @param WP_REST_Request $request Request object.
     * @param int[]           $ids     Variation IDs.
     * @return WP_REST_Response
     */
    private function export_by_ids(WP_REST_Request $request, array $ids)
    {
        $this->register_export_hooks();

        $variation_posts = get_posts([
            'posts_per_page' => -1,
            'post_status'    => 'publish',
            'post_type'      => 'product_variation',
            'post__in'       => $ids,
            'orderby'        => 'post__in',
        ]);

        $variations_by_id = [];

        if (!empty($variation_posts)) {
            $variations = $this->load_variations_from_posts($variation_posts);

            foreach ($variations as $variation) {
                $variations_by_id[$variation->get_id()] = $variation;
            }
        }

        $results = [];

        foreach ($ids as $id) {
            if (!isset($variations_by_id[$id])) {
                continue;
            }

            $results[] = $this->prepare_compact_variation($variations_by_id[$id], $request);
        }

        $data = [
            'count'   => count($results),
            'results' => $results,
        ];

        if ($this->is_debug_enabled($request)) {
            $this->append_debug_data($data);
        }

        return new WP_REST_Response($data, 200);
    }

    /**
     * Load parent products keyed by ID and warm caches.
     *
     * @param int[] $product_ids Product IDs.
     * @return array<int, WC_Product>
     */
    private function load_products_by_ids(array $product_ids)
    {
        $product_posts = get_posts([
            'posts_per_page' => -1,
            'post_status'    => 'any',
            'post_type'      => 'product',
            'post__in'       => $product_ids,
            'orderby'        => 'post__in',
        ]);

        if (empty($product_posts)) {
            return [];
        }

        $loaded_ids = wp_list_pluck($product_posts, 'ID');

        update_post_caches($product_posts, 'product', true, false);
        update_meta_cache('post', $loaded_ids);

        $products_by_id = [];

        foreach ($product_posts as $post) {
            $product = wc_get_product($post);

            if ($product && !$product->is_type('variation')) {
                $products_by_id[$product->get_id()] = $product;
            }
        }

        $this->warm_meta_cache(array_values($products_by_id));

        return $products_by_id;
    }

    /**
     * Load variation objects from posts and warm caches.
     *
     * @param WP_Post[] $variation_posts Variation posts.
     * @return WC_Product_Variation[]
     */
    private function load_variations_from_posts(array $variation_posts)
    {
        $variation_ids = wp_list_pluck($variation_posts, 'ID');

        update_post_caches($variation_posts, 'product_variation', true, false);
        update_meta_cache('post', $variation_ids);

        $variations = [];

        foreach ($variation_posts as $post) {
            $variation = wc_get_product($post);

            if ($variation && $variation->is_type('variation')) {
                $variations[] = $variation;
            }
        }

        $this->warm_meta_cache($variations);

        return $variations;
    }

    /**
     * Build compact parent-product payload with discount-rule pricing applied.
     *
     * @param WC_Product      $product Product object.
     * @param WP_REST_Request $request Request object.
     * @return array
     */
    private function prepare_compact_product($product, WP_REST_Request $request)
    {
        $data = [
            'product_id'     => $product->get_id(),
            'type'           => $product->get_type(),
            'manage_stock'   => $product->managing_stock(),
            'price'          => $product->get_price(),
            'regular_price'  => $product->get_regular_price(),
            'sale_price'     => $product->get_sale_price(),
            'stock_quantity' => $product->get_stock_quantity(),
            'stock_status'   => $product->get_stock_status(),
        ];

        $response = rest_ensure_response($data);
        $response = apply_filters(
            // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedHooknameFound -- WooCommerce core filter.
            'woocommerce_rest_prepare_product_object',
            $response,
            $product,
            $request
        );

        return $response->get_data();
    }

    /**
     * Placeholder group when a requested product ID is missing.
     *
     * @param int $product_id Product ID.
     * @return array
     */
    private function empty_compact_product($product_id)
    {
        return [
            'product_id'     => $product_id,
            'type'           => null,
            'manage_stock'   => null,
            'price'          => '',
            'regular_price'  => '',
            'sale_price'     => '',
            'stock_quantity' => null,
            'stock_status'   => '',
        ];
    }

    /**
     * Build compact variation payload with discount-rule pricing applied.
     *
     * @param WC_Product_Variation $variation Variation object.
     * @param WP_REST_Request      $request   Request object.
     * @return array
     */
    private function prepare_compact_variation($variation, WP_REST_Request $request)
    {
        $data = [
            'id'              => $variation->get_id(),
            'on_sale'         => $variation->is_on_sale(),
            'status'          => $variation->get_status(),
            'price'           => $variation->get_price(),
            'regular_price'   => $variation->get_regular_price(),
            'sale_price'      => $variation->get_sale_price(),
            'stock_quantity'  => $variation->get_stock_quantity(),
            'stock_status'    => $variation->get_stock_status(),
        ];

        $response = rest_ensure_response($data);
        $response = apply_filters(
            // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedHooknameFound -- WooCommerce core filter.
            'woocommerce_rest_prepare_product_variation_object',
            $response,
            $variation,
            $request
        );

        return $response->get_data();
    }

    /**
     * Register temporary hooks for export performance and compatibility.
     */
    private function register_export_hooks()
    {
        add_filter('woocommerce_data_stores', function ($stores) {
            $stores['product']           = 'Twokcs_Product_Data_Store';
            $stores['product-variation'] = 'Twokcs_Variation_Data_Store';

            return $stores;
        });

        add_action('pre_get_posts', function ($query) {
            if (!empty($query->query_vars['woodmart_single_variations_filter'])) {
                unset($query->query_vars['woodmart_single_variations_filter']);
                $query->set('post_type', 'product');
            }
        }, PHP_INT_MAX);
    }

    /**
     * Parse a comma-separated or array request param into a list of positive integers.
     *
     * @param WP_REST_Request $request Request object.
     * @param string          $name    Parameter name.
     * @return int[]
     */
    private function get_id_list_param(WP_REST_Request $request, $name)
    {
        $value = $request->get_param($name);

        if (empty($value)) {
            return [];
        }

        if (!is_array($value)) {
            $value = explode(',', (string) $value);
        }

        $ids = array_map('intval', $value);

        return array_values(array_filter($ids, function ($id) {
            return $id > 0;
        }));
    }

    /**
     * Batch-load and cache variation meta.
     *
     * @param WC_Product[] $instances Product or variation objects.
     */
    private function warm_meta_cache(array $instances)
    {
        if (empty($instances)) {
            return;
        }

        $data_store = new Twokcs_Data_Store();
        $metas      = $data_store->read_metas($instances);

        foreach ($instances as $i => $instance) {
            wp_cache_set($instance->get_meta_cache_key(), $metas[$i], 'products');
        }
    }

    /**
     * @param WP_REST_Request $request Request object.
     * @return bool
     */
    private function is_debug_enabled(WP_REST_Request $request)
    {
        if (!(bool) $request->get_param('debug')) {
            return false;
        }

        if (apply_filters('twokcs_allow_debug', false)) {
            return true;
        }

        return defined('WP_DEBUG') && WP_DEBUG && defined('TWOKCS_DEBUG') && TWOKCS_DEBUG;
    }

    /**
     * Append read-only SQL debug stats when debug mode is enabled.
     *
     * @param array $data Response data array.
     */
    private function append_debug_data(array &$data)
    {
        global $wpdb;

        $data['debug'] = ['num_queries' => $wpdb->num_queries];

        if (defined('SAVEQUERIES') && SAVEQUERIES && !empty($wpdb->queries)) {
            $data['debug']['queries'] = $wpdb->queries;
        }
    }
}