<?php

namespace PluginMagnet\AIStockPredictor\Admin\Pages;

use PluginMagnet\AIStockPredictor\Api\API;

defined( 'ABSPATH' ) || exit;

/**
 * Admin Dashboard Page.
 *
 * @since 1.0.0
 * @package PluginMagnet\AIStockPredictor\Admin\Pages
 */
class Dashboard {
	/**
	 * API instance.
	 *
	 * @var API
	 */
	private $api;

	/**
	 * Default items per page.
	 *
	 * @var int
	 */
	private $default_per_page = 20;

	/**
	 * Constructor.
	 *
	 * @since 1.0.0
	 */
	public function __construct() {
		$this->api = new API();
		add_action( 'admin_init', array( $this, 'handle_actions' ) );
	}

	/**
	 * Handle all admin actions
	 *
	 * @return void
	 */
	public function handle_actions() {
		// Handle per page update.
		if ( isset( $_POST['aistpr_per_page_nonce'] ) && wp_verify_nonce( sanitize_text_field( wp_unslash( $_POST['aistpr_per_page_nonce'] ) ), 'aistpr_update_per_page' ) ) {
			if ( current_user_can( 'manage_woocommerce' ) && isset( $_POST['aistpr_per_page'] ) ) {
				$per_page = absint( $_POST['aistpr_per_page'] );
				if ( $per_page > 0 ) {
					update_user_meta( get_current_user_id(), 'aistpr_predictions_per_page', $per_page );
				}
				wp_safe_redirect(
					add_query_arg(
						array(
							'page'    => 'ai-stock-predictor',
							'updated' => '1',
						),
						admin_url( 'admin.php' )
					)
				);
				exit;
			}
		}

		// Handle refresh actions.
		if ( isset( $_GET['aistpr_refresh'], $_GET['_wpnonce'] ) && wp_verify_nonce( sanitize_text_field( wp_unslash( $_GET['_wpnonce'] ) ), 'aistpr_refresh_dashboard' ) ) {
			if ( ! current_user_can( 'manage_woocommerce' ) ) {
				wp_die( esc_html__( 'You do not have sufficient permissions to access this page.', 'ai-stock-predictor' ) );
			}

			// Handle individual product refresh.
			if ( isset( $_GET['product_id'] ) ) {
				$product_id = absint( $_GET['product_id'] );
				delete_transient( 'aistpr_prediction_' . $product_id );
				wp_safe_redirect(
					add_query_arg(
						array(
							'page'      => 'ai-stock-predictor',
							'refreshed' => $product_id,
						),
						admin_url( 'admin.php' )
					)
				);
				exit;
			}

			// Handle bulk refresh.
			$this->clear_all_cache();
			wp_safe_redirect(
				add_query_arg(
					array(
						'page'      => 'ai-stock-predictor',
						'refreshed' => 'all',
					),
					admin_url( 'admin.php' )
				)
			);
			exit;
		}
	}

	/**
	 * Clear all plugin cache
	 *
	 * @return void
	 */
	private function clear_all_cache() {
		global $wpdb;

		// Clear transients.
		delete_transient( 'aistpr_recent_predictions' );
		delete_transient( 'aistpr_stock_statistics' );
		delete_transient( 'aistpr_total_products' );

		// Clear all prediction transients - direct query needed for bulk deletion pattern matching.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$wpdb->query( "DELETE FROM {$wpdb->options} WHERE option_name LIKE '_transient_aistpr_prediction_%'" );
		$wpdb->query( "DELETE FROM {$wpdb->options} WHERE option_name LIKE '_transient_timeout_aistpr_prediction_%'" );
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
	}

	/**
	 * Get items per page setting.
	 *
	 * @return int
	 */
	private function get_items_per_page() {
		$saved_value = get_user_meta( get_current_user_id(), 'aistpr_predictions_per_page', true );
		return $saved_value ? absint( $saved_value ) : $this->default_per_page;
	}

	/**
	 * Render dashboard page.
	 *
	 * @since 1.0.0
	 * @return void
	 */
	public function render() {
		$current_page = isset( $_GET['paged'] ) ? max( 1, absint( $_GET['paged'] ) ) : 1;
		$per_page     = $this->get_items_per_page();
		$offset       = ( $current_page - 1 ) * $per_page;

		$recent_predictions = $this->get_recent_predictions( $per_page, $offset );
		$total_items        = $this->get_total_products();
		$total_pages        = ceil( $total_items / $per_page );
		$stock_stats        = $this->get_stock_statistics();

		$refresh_url = wp_nonce_url(
			add_query_arg(
				array(
					'page'           => 'ai-stock-predictor',
					'aistpr_refresh' => '1',
				),
				admin_url( 'admin.php' )
			),
			'aistpr_refresh_dashboard'
		);

		require_once AISTPR_TEMPLATE_PATH_MAIN . 'admin/dashboard.php';
	}

	/**
	 * Get total number of products.
	 *
	 * @return int
	 */
	private function get_total_products() {
		$total = get_transient( 'aistpr_total_products' );
		if ( false !== $total ) {
			return (int) $total;
		}

		global $wpdb;
		// Direct query with JOIN is more efficient than WP_Query for this count operation.
		// Result is cached in transient for 1 hour.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$total = $wpdb->get_var(
			"SELECT COUNT(*)
			FROM {$wpdb->prefix}posts p
			LEFT JOIN {$wpdb->prefix}postmeta pm ON p.ID = pm.post_id AND pm.meta_key = '_stock'
			WHERE p.post_type = 'product'
			AND p.post_status = 'publish'
			AND pm.meta_value IS NOT NULL
			AND pm.meta_value > 0"
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching

		set_transient( 'aistpr_total_products', $total, HOUR_IN_SECONDS );
		return (int) $total;
	}

	/**
	 * Get stock statistics.
	 *
	 * @return array
	 */
	private function get_stock_statistics() {
		$cached_stats = get_transient( 'aistpr_stock_statistics' );
		if ( false !== $cached_stats ) {
			return $cached_stats;
		}

		$stats = array(
			'total_products'    => 0,
			'low_stock'         => 0,
			'out_of_stock'      => 0,
			'total_stock_value' => 0,
		);

		$products = wc_get_products(
			array(
				'limit'  => -1,
				'status' => 'publish',
				'type'   => array( 'simple', 'variable' ),
			)
		);

		foreach ( $products as $product ) {
			if ( ! $product || ! is_object( $product ) ) {
				continue;
			}

			++$stats['total_products'];

			if ( $product->managing_stock() ) {
				$stock            = $product->get_stock_quantity();
				$low_stock_amount = get_option( 'woocommerce_notify_low_stock_amount' );

				if ( 0 === $stock || '' === $stock ) {
					++$stats['out_of_stock'];
				} elseif ( $stock <= $low_stock_amount ) {
					++$stats['low_stock'];
				}

				$regular_price = (float) $product->get_regular_price();
				if ( $stock > 0 && $regular_price > 0 ) {
					$stats['total_stock_value'] += $stock * $regular_price;
				}
			}
		}

		set_transient( 'aistpr_stock_statistics', $stats, HOUR_IN_SECONDS );
		return $stats;
	}

	/**
	 * Get recent stock predictions.
	 *
	 * @param int $limit Number of predictions to fetch.
	 * @param int $offset Offset for pagination.
	 * @return array
	 */
	private function get_recent_predictions( $limit = 20, $offset = 0 ) {
		global $wpdb;

		// Direct query with multiple JOINs and custom fields is more efficient than WP_Query.
		// Results vary by pagination, so not suitable for object caching.
		// Individual predictions are cached via transients in get_product_prediction().
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$predictions = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT p.*, pm.meta_value as current_stock, pm2.meta_value as regular_price
				FROM {$wpdb->prefix}posts p
				LEFT JOIN {$wpdb->prefix}postmeta pm ON p.ID = pm.post_id AND pm.meta_key = '_stock'
				LEFT JOIN {$wpdb->prefix}postmeta pm2 ON p.ID = pm2.post_id AND pm2.meta_key = '_regular_price'
				WHERE p.post_type = 'product'
				AND p.post_status = 'publish'
				AND pm.meta_value IS NOT NULL
				AND pm.meta_value > 0
				ORDER BY p.post_modified DESC
				LIMIT %d OFFSET %d",
				$limit,
				$offset
			),
			ARRAY_A
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching

		if ( empty( $predictions ) ) {
			return array();
		}

		$formatted_predictions = array();
		foreach ( $predictions as $product ) {
			$product_id = $product['ID'];
			$wc_product = wc_get_product( $product_id );

			if ( ! $wc_product ) {
				continue;
			}

			// Get cached or new prediction.
			$prediction = $this->get_product_prediction( $product_id );
			if ( ! $prediction ) {
				continue;
			}

			$current_stock = (int) $product['current_stock'];
			$regular_price = (float) $product['regular_price'];

			$formatted_predictions[] = array(
				'id'                => $product_id,
				'name'              => $product['post_title'],
				'current_stock'     => $current_stock,
				'regular_price'     => $regular_price,
				'stock_value'       => $current_stock * $regular_price,
				'stockout_date'     => $prediction['stockout_date'],
				'risk_level'        => $prediction['risk_level'],
				'sales_velocity'    => $this->get_sales_velocity( $product_id ),
				'lead_time'         => $this->get_lead_time( $product_id ),
				'edit_url'          => get_edit_post_link( $product_id ),
				'view_url'          => get_permalink( $product_id ),
				'sku'               => $wc_product->get_sku(),
				'categories'        => wp_strip_all_tags( wc_get_product_category_list( $product_id ) ),
				'prediction_source' => isset( $prediction['source'] ) ? $prediction['source'] : 'api',
			);
		}

		return $formatted_predictions;
	}

	/**
	 * Get product prediction
	 *
	 * @param int $product_id Product ID.
	 * @return array|false
	 */
	private function get_product_prediction( $product_id ) {
		$cached_prediction = get_transient( 'aistpr_prediction_' . $product_id );
		if ( false !== $cached_prediction ) {
			$cached_prediction['source'] = 'cache';
			return $cached_prediction;
		}

		$product_data = $this->prepare_product_data( $product_id );
		$prediction   = $this->api->generate_prediction( $product_data );

		if ( is_wp_error( $prediction ) ) {
			$prediction = $this->api->generate_fallback_prediction( $product_data );
		}

		if ( $prediction ) {
			$prediction['source'] = 'api';
			set_transient( 'aistpr_prediction_' . $product_id, $prediction, HOUR_IN_SECONDS );
		}

		return $prediction;
	}

	/**
	 * Get sales velocity for a product
	 *
	 * @param int $product_id Product ID.
	 * @return array
	 */
	private function get_sales_velocity( $product_id ) {
		return array(
			'30' => round( $this->get_sales_count( $product_id, 30 ) / 30, 2 ),
			'60' => round( $this->get_sales_count( $product_id, 60 ) / 60, 2 ),
			'90' => round( $this->get_sales_count( $product_id, 90 ) / 90, 2 ),
		);
	}

	/**
	 * Get lead time for a product
	 *
	 * @param int $product_id Product ID.
	 * @return int
	 */
	private function get_lead_time( $product_id ) {
		return (int) get_post_meta( $product_id, '_aistpr_lead_time', true ) ?: get_option( 'aistpr_default_lead_time', 7 );
	}

	/**
	 * Prepare product data for prediction
	 *
	 * @param int $product_id Product ID.
	 * @return array
	 */
	private function prepare_product_data( $product_id ) {
		$product = wc_get_product( $product_id );
		if ( ! $product ) {
			return array();
		}

		return array(
			'sales_velocity' => $this->get_sales_velocity( $product_id ),
			'current_stock'  => $product->get_stock_quantity(),
			'lead_time'      => $this->get_lead_time( $product_id ),
		);
	}

	/**
	 * Get sales count for a product in a given period
	 *
	 * @param int $product_id Product ID.
	 * @param int $days Number of days to look back.
	 * @return int
	 */
	private function get_sales_count( $product_id, $days ) {
		global $wpdb;

		$date = gmdate( 'Y-m-d', strtotime( "-{$days} days" ) );

		// Direct query needed to access WooCommerce order tables with complex JOINs.
		// No WordPress API exists for this specific aggregate query.
		// Results are cached within get_sales_velocity() via prediction transients.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		return (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COALESCE(SUM(order_item_meta.meta_value), 0)
				FROM {$wpdb->prefix}woocommerce_order_items as order_items
				LEFT JOIN {$wpdb->prefix}woocommerce_order_itemmeta as order_item_meta ON order_items.order_item_id = order_item_meta.order_item_id
				LEFT JOIN {$wpdb->prefix}woocommerce_order_itemmeta as product_id_meta ON order_items.order_item_id = product_id_meta.order_item_id
				LEFT JOIN {$wpdb->posts} as orders ON order_items.order_id = orders.ID
				WHERE orders.post_type = 'shop_order'
				AND orders.post_status IN ('wc-completed', 'wc-processing')
				AND order_item_meta.meta_key = '_qty'
				AND product_id_meta.meta_key = '_product_id'
				AND product_id_meta.meta_value = %d
				AND orders.post_date >= %s",
				$product_id,
				$date
			)
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
	}
}