<?php
/**
 * Hash-based change detection for incremental feed generation.
 *
 * Tracks per-feed-type dirty state so each feed format can independently
 * detect which products need re-export. Uses transients for fast dirty
 * lookups and the product_cache table for hash storage.
 *
 * @package AICommerce\Feed
 */

declare(strict_types=1);

namespace AICommerce\Feed;

/**
 * Detects product data changes using per-feed-type hash comparison.
 */
class ChangeDetector {

	/**
	 * WordPress database abstraction.
	 *
	 * @var \wpdb
	 */
	private \wpdb $wpdb;

	/**
	 * Cache table name.
	 *
	 * @var string
	 */
	private string $table;

	/**
	 * Transient prefix for dirty product sets.
	 *
	 * @var string
	 */
	private const DIRTY_TRANSIENT_PREFIX = 'aicommerce_dirty_';

	/**
	 * Constructor.
	 *
	 * @param \wpdb $wpdb WordPress database instance.
	 */
	public function __construct( \wpdb $wpdb ) {
		$this->wpdb  = $wpdb;
		$this->table = $wpdb->prefix . 'aicommerce_product_cache';
	}

	/**
	 * Compute a hash representing the current state of a product.
	 *
	 * @param \WC_Product $product The WooCommerce product.
	 *
	 * @return string SHA-256 hash.
	 */
	public function compute_hash( \WC_Product $product ): string {
		$data = array(
			'name'              => $product->get_name(),
			'description'       => $product->get_description(),
			'short_description' => $product->get_short_description(),
			'sku'               => $product->get_sku(),
			'price'             => $product->get_price(),
			'regular_price'     => $product->get_regular_price(),
			'sale_price'        => $product->get_sale_price(),
			'stock_status'      => $product->get_stock_status(),
			'stock_quantity'    => $product->get_stock_quantity(),
			'weight'            => $product->get_weight(),
			'image_id'          => $product->get_image_id(),
			'gallery_ids'       => $product->get_gallery_image_ids(),
			'category_ids'      => $product->get_category_ids(),
			'tag_ids'           => $product->get_tag_ids(),
			'brand'             => $product->get_meta( '_aicommerce_brand' ),
			'gtin'              => $product->get_meta( '_aicommerce_gtin' ),
			'mpn'               => $product->get_meta( '_aicommerce_mpn' ),
			'date_modified'     => $product->get_date_modified() ? $product->get_date_modified()->getTimestamp() : 0,
		);

		return hash( 'sha256', wp_json_encode( $data ) );
	}

	/**
	 * Get the stored hash for a product and feed type.
	 *
	 * @param int    $product_id The product ID.
	 * @param string $feed_type  The feed type slug.
	 *
	 * @return string|null Stored hash or null if not cached.
	 */
	public function get_stored_hash( int $product_id, string $feed_type = '' ): ?string {
		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$row = $this->wpdb->get_row(
			$this->wpdb->prepare(
				"SELECT data_hash FROM {$this->table} WHERE product_id = %d AND feed_type = %s",
				$product_id,
				$feed_type
			)
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

		return $row ? $row->data_hash : null;
	}

	/**
	 * Check if a product is dirty for a given feed type.
	 *
	 * @param int    $product_id The product ID.
	 * @param string $feed_type  The feed type slug.
	 *
	 * @return bool True if the product needs re-export.
	 */
	public function is_dirty( int $product_id, string $feed_type ): bool {
		$dirty_set = $this->get_dirty_transient( $feed_type );

		if ( is_array( $dirty_set ) && in_array( $product_id, $dirty_set, true ) ) {
			return true;
		}

		// No stored hash means never exported — dirty.
		$stored = $this->get_stored_hash( $product_id, $feed_type );
		return null === $stored;
	}

	/**
	 * Mark a product as dirty for specified (or all) feed types.
	 *
	 * @param int   $product_id The product ID.
	 * @param array $feed_types Feed type slugs. Empty = all registered types.
	 *
	 * @return void
	 */
	public function mark_dirty( int $product_id, array $feed_types = array() ): void {
		if ( empty( $feed_types ) ) {
			$feed_types = $this->get_registered_feed_types();
		}

		foreach ( $feed_types as $feed_type ) {
			$dirty_set = $this->get_dirty_transient( $feed_type );
			if ( ! is_array( $dirty_set ) ) {
				$dirty_set = array();
			}

			if ( ! in_array( $product_id, $dirty_set, true ) ) {
				$dirty_set[] = $product_id;
				set_transient( self::DIRTY_TRANSIENT_PREFIX . $feed_type, $dirty_set, DAY_IN_SECONDS );
			}
		}
	}

	/**
	 * Mark a product as clean for a specific feed type.
	 *
	 * @param int    $product_id The product ID.
	 * @param string $feed_type  The feed type slug.
	 * @param string $hash       The computed data hash.
	 *
	 * @return void
	 */
	public function mark_clean( int $product_id, string $feed_type, string $hash ): void {
		// Remove from dirty transient.
		$dirty_set = $this->get_dirty_transient( $feed_type );
		if ( is_array( $dirty_set ) ) {
			$dirty_set = array_values( array_diff( $dirty_set, array( $product_id ) ) );
			set_transient( self::DIRTY_TRANSIENT_PREFIX . $feed_type, $dirty_set, DAY_IN_SECONDS );
		}

		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$this->wpdb->replace(
			$this->table,
			array(
				'product_id'     => $product_id,
				'feed_type'      => $feed_type,
				'data_hash'      => $hash,
				'last_synced_at' => current_time( 'mysql' ),
			),
			array( '%d', '%s', '%s', '%s' )
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
	}

	/**
	 * Get all dirty product IDs for a feed type.
	 *
	 * @param string $feed_type The feed type slug.
	 * @param int    $limit     Max IDs to return. 0 = unlimited.
	 *
	 * @return array Array of product IDs needing re-export.
	 */
	public function get_dirty_products( string $feed_type, int $limit = 0 ): array {
		$dirty_set = $this->get_dirty_transient( $feed_type );
		$dirty_ids = is_array( $dirty_set ) ? $dirty_set : array();

		if ( $limit > 0 && count( $dirty_ids ) >= $limit ) {
			return array_slice( $dirty_ids, 0, $limit );
		}

		return $dirty_ids;
	}

	/**
	 * Update the stored hash and feed data for a product.
	 *
	 * @param int    $product_id The product ID.
	 * @param string $hash       The computed data hash.
	 * @param array  $feed_data  The normalized feed data to cache.
	 * @param string $feed_type  The feed type slug.
	 *
	 * @return void
	 */
	public function update_cache( int $product_id, string $hash, array $feed_data, string $feed_type = '' ): void {
		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$this->wpdb->replace(
			$this->table,
			array(
				'product_id'     => $product_id,
				'feed_type'      => $feed_type,
				'data_hash'      => $hash,
				'feed_data'      => wp_json_encode( $feed_data ),
				'last_synced_at' => current_time( 'mysql' ),
			),
			array( '%d', '%s', '%s', '%s', '%s' )
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
	}

	/**
	 * Batch update cache for multiple products.
	 *
	 * @param array  $entries   Array of ['product_id' => int, 'hash' => string, 'feed_data' => array].
	 * @param string $feed_type The feed type slug.
	 *
	 * @return void
	 */
	public function update_cache_batch( array $entries, string $feed_type = '' ): void {
		if ( empty( $entries ) ) {
			return;
		}

		$now    = current_time( 'mysql' );
		$values = array();

		foreach ( $entries as $entry ) {
			$values[] = $this->wpdb->prepare(
				'(%d, %s, %s, %s, %s)',
				$entry['product_id'],
				$feed_type,
				$entry['hash'],
				wp_json_encode( $entry['feed_data'] ),
				$now
			);
		}

		$values_sql = implode( ', ', $values );

		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$this->wpdb->query(
			"INSERT INTO {$this->table} (product_id, feed_type, data_hash, feed_data, last_synced_at)
			 VALUES {$values_sql}
			 ON DUPLICATE KEY UPDATE data_hash = VALUES(data_hash), feed_data = VALUES(feed_data), last_synced_at = VALUES(last_synced_at)"
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
	}

	/**
	 * Get cached feed data for a product.
	 *
	 * @param int    $product_id The product ID.
	 * @param string $feed_type  The feed type slug.
	 *
	 * @return array|null Cached feed data or null.
	 */
	public function get_cached_data( int $product_id, string $feed_type = '' ): ?array {
		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$row = $this->wpdb->get_row(
			$this->wpdb->prepare(
				"SELECT feed_data FROM {$this->table} WHERE product_id = %d AND feed_type = %s",
				$product_id,
				$feed_type
			)
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

		if ( ! $row || empty( $row->feed_data ) ) {
			return null;
		}

		$data = json_decode( $row->feed_data, true );
		return is_array( $data ) ? $data : null;
	}

	/**
	 * Remove cache entries for a product across all feed types.
	 *
	 * @param int $product_id The product ID.
	 *
	 * @return void
	 */
	public function invalidate( int $product_id ): void {
		// Safe: internal $wpdb->prefix table names; user values use placeholders.
		// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter
		$this->wpdb->delete(
			$this->table,
			array( 'product_id' => $product_id ),
			array( '%d' )
		);
		// phpcs:enable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

		$this->mark_dirty( $product_id );
	}

	/**
	 * Clear all dirty transients for a feed type.
	 *
	 * @param string $feed_type The feed type slug.
	 *
	 * @return void
	 */
	public function clear_dirty( string $feed_type ): void {
		delete_transient( self::DIRTY_TRANSIENT_PREFIX . $feed_type );
	}

	/**
	 * Get the dirty transient value for a feed type.
	 *
	 * @param string $feed_type The feed type slug.
	 *
	 * @return array|false Array of dirty product IDs or false.
	 */
	private function get_dirty_transient( string $feed_type ) {
		return get_transient( self::DIRTY_TRANSIENT_PREFIX . $feed_type );
	}

	/**
	 * Get registered feed types from options.
	 *
	 * @return array Feed type slugs.
	 */
	private function get_registered_feed_types(): array {
		$types = get_option( 'aicommerce_registered_feed_types', array() );
		return is_array( $types ) ? $types : array();
	}
}