<?php
/**
 * Approved fixes, change log and undo.
 *
 * @package FlareOps
 */

namespace FlareOps;

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

final class Changes {

	public const FIELDS  = array( 'brand', 'gtin', 'mpn', 'title', 'short_description', 'description', 'faq' );
	public const SOURCES = array( 'ai_suggestion', 'merchant', 'feed' );

	/** v0.3 content lever: treatment products only (unless content_any_product), sources ai_suggestion | merchant. */
	public const CONTENT_FIELDS  = array( 'description', 'faq' );
	public const CONTENT_SOURCES = array( 'ai_suggestion', 'merchant' );

	public const DESCRIPTION_MAX = 20000;
	public const FAQ_MIN         = 1;
	public const FAQ_MAX         = 8;
	public const FAQ_Q_MAX       = 200;
	public const FAQ_A_MAX       = 800;

	/** wp_kses allowlist for the description (architecture v0.3). Only table-cell spans as attributes. */
	public static function description_allowed_html(): array {
		$cell = array(
			'colspan' => true,
			'rowspan' => true,
		);
		return array(
			'p'      => array(),
			'ul'     => array(),
			'ol'     => array(),
			'li'     => array(),
			'strong' => array(),
			'em'     => array(),
			'h3'     => array(),
			'h4'     => array(),
			'table'  => array(),
			'thead'  => array(),
			'tbody'  => array(),
			'tr'     => array(),
			'th'     => $cell + array( 'scope' => true ),
			'td'     => $cell,
			'br'     => array(),
		);
	}

	/** Sanitize description HTML: drop dangerous elements with their content, then wp_kses to the allowlist. */
	public static function sanitize_description( string $html ): string {
		// Elements whose content must never survive as text (wp_kses would keep the inner text).
		$html = (string) preg_replace( '#<(script|style|iframe|noscript|template|object|embed|svg|math|textarea|select|head|title)\b[^>]*>.*?</\1\s*>#is', '', $html );
		$html = (string) preg_replace( '#<(script|style|iframe|noscript|template|object|embed|svg|math)\b[^>]*/?>#i', '', $html );
		$html = wp_kses( $html, self::description_allowed_html(), array() );
		$html = force_balance_tags( $html );
		return trim( $html );
	}

	/** JSON form of a FAQ list, used for the change log before/after and for comparisons. */
	public static function faq_json( array $faq ): string {
		return (string) wp_json_encode( array_values( $faq ), JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES );
	}

	/**
	 * Validate a FAQ: [] (removes) or 1-8 items {q, a}, plain text, q <= 200, a <= 800 chars.
	 *
	 * @param mixed $value Input.
	 * @return array|\WP_Error
	 */
	public static function sanitize_faq( $value ) {
		if ( ! is_array( $value ) || ( $value && array_keys( $value ) !== range( 0, count( $value ) - 1 ) ) ) {
			return self::err( 'faq must be an array of {q, a} objects ([] removes the FAQ)' );
		}
		if ( count( $value ) > self::FAQ_MAX ) {
			return self::err( 'faq has more than ' . self::FAQ_MAX . ' items' );
		}
		$out = array();
		foreach ( $value as $i => $item ) {
			if ( ! is_array( $item ) || array_diff( array_keys( $item ), array( 'q', 'a' ) ) || ! isset( $item['q'], $item['a'] ) || ! is_string( $item['q'] ) || ! is_string( $item['a'] ) ) {
				return self::err( 'faq[' . $i . '] must be an object {q: string, a: string}' );
			}
			$q = trim( sanitize_text_field( $item['q'] ) );
			$a = trim( sanitize_textarea_field( $item['a'] ) );
			if ( '' === $q || '' === $a ) {
				return self::err( 'faq[' . $i . ']: q and a must not be empty' );
			}
			if ( mb_strlen( $q ) > self::FAQ_Q_MAX ) {
				return self::err( 'faq[' . $i . '].q is longer than ' . self::FAQ_Q_MAX . ' characters' );
			}
			if ( mb_strlen( $a ) > self::FAQ_A_MAX ) {
				return self::err( 'faq[' . $i . '].a is longer than ' . self::FAQ_A_MAX . ' characters' );
			}
			$out[] = array(
				'q' => $q,
				'a' => $a,
			);
		}
		return $out;
	}

	/** Fields that must never come from AI (data rule: never invent identifiers). */
	public const NO_AI_FIELDS = array( 'gtin', 'mpn' );

	private static function err( string $msg, int $status = 400, string $code = 'flareops_invalid' ): \WP_Error {
		return new \WP_Error( $code, $msg, array( 'status' => $status ) );
	}

	/** Current display value of a field. */
	public static function current_value( \WC_Product $p, string $field ): string {
		switch ( $field ) {
			case 'brand':
				return implode( ', ', Products::brand_names( $p->get_id() ) );
			case 'gtin':
				return Products::gtin( $p );
			case 'mpn':
				return Products::mpn( $p );
			case 'title':
				return html_entity_decode( (string) $p->get_name( 'edit' ), ENT_QUOTES, 'UTF-8' );
			case 'short_description':
				return (string) $p->get_short_description( 'edit' );
			case 'description':
				return (string) $p->get_description( 'edit' );
			case 'faq':
				return self::faq_json( Products::faq( $p ) );
		}
		return '';
	}

	/** Data needed to restore the field exactly. */
	private static function restore_data( \WC_Product $p, string $field ): array {
		if ( 'brand' === $field ) {
			if ( Products::brand_uses_taxonomy() ) {
				$ids = wp_get_object_terms( $p->get_id(), Products::BRAND_TAX, array( 'fields' => 'ids' ) );
				return array(
					'mode'     => 'tax',
					'term_ids' => is_array( $ids ) ? array_map( 'intval', $ids ) : array(),
				);
			}
			return array(
				'mode'  => 'meta',
				'value' => (string) get_post_meta( $p->get_id(), Products::BRAND_META, true ),
			);
		}
		return array( 'value' => self::current_value( $p, $field ) );
	}

	/**
	 * Validate + normalize a requested value.
	 *
	 * @return string|\WP_Error
	 */
	private static function normalize_value( \WC_Product $p, string $field, $value ) {
		if ( 'faq' === $field ) {
			$faq = self::sanitize_faq( $value );
			return is_wp_error( $faq ) ? $faq : self::faq_json( $faq );
		}
		if ( ! is_string( $value ) && ! is_numeric( $value ) ) {
			return self::err( $field . ' must be a string' );
		}
		$value = (string) $value;
		switch ( $field ) {
			case 'brand':
				$v = trim( sanitize_text_field( $value ) );
				if ( mb_strlen( $v ) > 70 ) {
					return self::err( 'brand is longer than 70 characters' );
				}
				return $v;
			case 'gtin':
				$v = Util::normalize_gtin( $value );
				if ( '' === $v ) {
					return '';
				}
				if ( ! Util::is_valid_gtin( $v ) ) {
					return self::err( 'invalid GTIN: must be 8, 12, 13 or 14 digits with a valid GS1 check digit', 400, 'flareops_invalid_gtin' );
				}
				if ( function_exists( 'wc_get_product_id_by_global_unique_id' ) ) {
					$other = (int) wc_get_product_id_by_global_unique_id( $v );
					if ( $other && $other !== $p->get_id() ) {
						return self::err( 'GTIN already used by product ' . $other, 409, 'flareops_duplicate_gtin' );
					}
				}
				return $v;
			case 'mpn':
				$v = trim( sanitize_text_field( $value ) );
				if ( mb_strlen( $v ) > 70 ) {
					return self::err( 'mpn is longer than 70 characters' );
				}
				return $v;
			case 'title':
				$v = trim( sanitize_text_field( $value ) );
				if ( '' === $v ) {
					return self::err( 'title cannot be empty' );
				}
				if ( mb_strlen( $v ) > 150 ) {
					return self::err( 'title is longer than 150 characters' );
				}
				return $v;
			case 'short_description':
				return trim( wp_kses_post( $value ) );
			case 'description':
				if ( mb_strlen( $value ) > self::DESCRIPTION_MAX ) {
					return self::err( 'description is longer than ' . self::DESCRIPTION_MAX . ' characters' );
				}
				$v = self::sanitize_description( $value );
				if ( '' === trim( wp_strip_all_tags( $v ) ) ) {
					return self::err( 'description is empty after sanitizing (allowed tags: ' . implode( ', ', array_keys( self::description_allowed_html() ) ) . ')' );
				}
				if ( mb_strlen( $v ) > self::DESCRIPTION_MAX ) {
					return self::err( 'description is longer than ' . self::DESCRIPTION_MAX . ' characters' );
				}
				return $v;
		}
		return self::err( 'unknown field ' . $field );
	}

	/** Write one field on a product (does not save the product for non-taxonomy fields). */
	private static function write_field( \WC_Product $p, string $field, string $value ): void {
		switch ( $field ) {
			case 'brand':
				$target = $p->get_id();
				if ( Products::brand_uses_taxonomy() ) {
					$r = wp_set_object_terms( $target, '' === $value ? array() : array( $value ), Products::BRAND_TAX, false );
					if ( is_wp_error( $r ) ) {
						throw new \RuntimeException( esc_html( $r->get_error_message() ) );
					}
				} elseif ( '' === $value ) {
					delete_post_meta( $target, Products::BRAND_META );
				} else {
					update_post_meta( $target, Products::BRAND_META, $value );
				}
				break;
			case 'gtin':
				if ( ! method_exists( $p, 'set_global_unique_id' ) ) {
					throw new \RuntimeException( 'WooCommerce 9.2+ is required for GTIN' );
				}
				$p->set_global_unique_id( $value );
				break;
			case 'mpn':
				if ( '' === $value ) {
					$p->delete_meta_data( Products::MPN_META );
				} else {
					$p->update_meta_data( Products::MPN_META, $value );
				}
				break;
			case 'title':
				$p->set_name( $value );
				break;
			case 'short_description':
				$p->set_short_description( $value );
				break;
			case 'description':
				$p->set_description( $value );
				break;
			case 'faq':
				$faq = json_decode( $value, true );
				if ( ! is_array( $faq ) || ! $faq ) {
					$p->delete_meta_data( Products::FAQ_META );
				} else {
					$p->update_meta_data( Products::FAQ_META, array_values( $faq ) );
				}
				break;
		}
	}

	/**
	 * WooCommerce saves post_content through wp_update_post(), which unslashes it (and runs kses for users without
	 * unfiltered_html). The change log promises the exact stored HTML, so check after save() and correct if needed.
	 */
	private static function ensure_description( int $product_id, string $want ): void {
		global $wpdb;
		$stored = (string) $wpdb->get_var( $wpdb->prepare( "SELECT post_content FROM {$wpdb->posts} WHERE ID = %d", $product_id ) ); // phpcs:ignore WordPress.DB
		if ( $stored === $want ) {
			return;
		}
		$wpdb->update( $wpdb->posts, array( 'post_content' => $want ), array( 'ID' => $product_id ) ); // phpcs:ignore WordPress.DB
		clean_post_cache( $product_id );
		if ( function_exists( 'wc_delete_product_transients' ) ) {
			wc_delete_product_transients( $product_id );
		}
	}

	/**
	 * Save a product without WordPress' kses filters. API requests run as no user (no unfiltered_html), so
	 * wp_update_post() would otherwise run kses over EVERY post field WooCommerce re-saves, e.g. turn a title's
	 * "&" into "&amp;" and drop "<X>", even when only the description changed. Values written here are either
	 * sanitized by flareOps (normalize_value) or the product's existing / previously stored values.
	 */
	private static function save_product( \WC_Product $p ): void {
		$kses = false !== has_filter( 'content_save_pre', 'wp_filter_post_kses' ) || false !== has_filter( 'title_save_pre', 'wp_filter_kses' );
		if ( $kses ) {
			kses_remove_filters();
		}
		try {
			$p->save();
		} finally {
			if ( $kses ) {
				kses_init_filters();
			}
		}
	}

	/** After a content change: the feed is rebuilt, and IndexNow queues the URL (IndexNow checks consent itself). */
	private static function after_content_change( int $product_id ): void {
		Feed::invalidate();
		IndexNow::on_product_change( $product_id );
	}

	/**
	 * Apply approved fixes.
	 *
	 * @return array|\WP_Error
	 */
	public static function apply( int $product_id, array $body ) {
		$p = wc_get_product( $product_id );
		if ( ! $p ) {
			return self::err( 'product not found', 404, 'flareops_not_found' );
		}
		$fields = $body['fields'] ?? null;
		if ( ! is_array( $fields ) || ! $fields ) {
			return self::err( 'fields must be a non-empty object' );
		}
		$source = $body['source'] ?? '';
		if ( ! is_string( $source ) || ! in_array( $source, self::SOURCES, true ) ) {
			return self::err( 'source must be one of: ' . implode( ', ', self::SOURCES ) );
		}
		$approved_by = $body['approved_by'] ?? '';
		if ( ! is_string( $approved_by ) || '' === trim( $approved_by ) ) {
			return self::err( 'approved_by is required' );
		}
		$approved_by = mb_substr( sanitize_text_field( $approved_by ), 0, 190 );
		$dry_run     = ! empty( $body['dry_run'] ) && 'false' !== $body['dry_run'];

		$planned = array();
		foreach ( $fields as $field => $value ) {
			if ( ! in_array( $field, self::FIELDS, true ) ) {
				return self::err( 'unknown field: ' . sanitize_key( (string) $field ) );
			}
			if ( 'ai_suggestion' === $source && in_array( $field, self::NO_AI_FIELDS, true ) ) {
				return self::err( $field . ' cannot come from an AI suggestion (identifiers are never invented)', 400, 'flareops_forbidden_source' );
			}
			if ( in_array( $field, self::CONTENT_FIELDS, true ) ) {
				if ( ! in_array( $source, self::CONTENT_SOURCES, true ) ) {
					return self::err( $field . ' accepts source ' . implode( ' or ', self::CONTENT_SOURCES ) . ' only' );
				}
				if ( $p->is_type( 'variation' ) ) {
					return self::err( $field . ' must be set on the parent product, not a variation' );
				}
				if ( ! Settings::content_allowed( $product_id ) ) {
					return self::err( 'product ' . $product_id . ' is not a treatment product; description and faq are refused so the experiment is not contaminated (setting content_any_product lifts this)', 409, 'flareops_not_treatment' );
				}
			}
			if ( $p->is_type( 'variation' ) && in_array( $field, array( 'brand', 'title', 'short_description' ), true ) ) {
				return self::err( $field . ' must be set on the parent product, not a variation' );
			}
			$v = self::normalize_value( $p, $field, $value );
			if ( is_wp_error( $v ) ) {
				return $v;
			}
			$before            = self::current_value( $p, $field );
			$planned[ $field ] = array(
				'before'  => $before,
				'after'   => $v,
				'changed' => $before !== $v,
				'restore' => self::restore_data( $p, $field ),
			);
		}

		$results = array();
		foreach ( $planned as $field => $pl ) {
			$results[] = array(
				'field'   => $field,
				'before'  => $pl['before'],
				'after'   => $pl['after'],
				'changed' => $pl['changed'],
			);
		}

		$to_change = array_filter( $planned, static fn( $pl ) => $pl['changed'] );
		if ( $dry_run || ! $to_change ) {
			return array(
				'id'        => $product_id,
				'dry_run'   => $dry_run,
				'results'   => $results,
				'change_id' => null,
			);
		}

		try {
			$needs_save = false;
			foreach ( $to_change as $field => $pl ) {
				self::write_field( $p, $field, $pl['after'] );
				if ( 'brand' !== $field ) {
					$needs_save = true;
				}
			}
			if ( $needs_save || isset( $to_change['brand'] ) ) {
				// Brand lives outside the product object; still save to bump modified + fire update hooks.
				self::save_product( $p );
			}
			if ( isset( $to_change['description'] ) ) {
				self::ensure_description( $product_id, $to_change['description']['after'] );
			}
		} catch ( \Throwable $e ) {
			return self::err( 'could not apply: ' . $e->getMessage(), 400, 'flareops_apply_failed' );
		}
		if ( array_intersect( array_keys( $to_change ), self::CONTENT_FIELDS ) ) {
			self::after_content_change( $product_id );
		}

		$change_id = wp_generate_uuid4();
		self::log_rows( $change_id, $product_id, $to_change, $source, $approved_by );

		// Re-read actual stored values for the response.
		$fresh = wc_get_product( $product_id );
		foreach ( $results as &$r ) {
			if ( $r['changed'] && $fresh ) {
				$r['after'] = self::current_value( $fresh, $r['field'] );
			}
		}
		unset( $r );

		return array(
			'id'        => $product_id,
			'dry_run'   => false,
			'results'   => $results,
			'change_id' => $change_id,
		);
	}

	private static function log_rows( string $change_id, int $product_id, array $rows, string $source, string $approved_by ): void {
		global $wpdb;
		$now = gmdate( 'Y-m-d H:i:s' );
		foreach ( $rows as $field => $pl ) {
			$wpdb->insert( // phpcs:ignore WordPress.DB
				Install::table( 'changes' ),
				array(
					'change_id'    => $change_id,
					'product_id'   => $product_id,
					'field'        => $field,
					'before_value' => $pl['before'],
					'after_value'  => $pl['after'],
					'restore_data' => wp_json_encode( $pl['restore'] ),
					'at'           => $now,
					'source'       => $source,
					'approved_by'  => $approved_by,
				)
			);
		}
	}

	/**
	 * Undo a change.
	 *
	 * @return array|\WP_Error
	 */
	public static function undo( string $change_id, string $by = '' ) {
		global $wpdb;
		$t    = Install::table( 'changes' );
		$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT * FROM %i WHERE change_id = %s', $t, $change_id ), ARRAY_A ); // phpcs:ignore WordPress.DB
		if ( ! $rows ) {
			return self::err( 'change not found', 404, 'flareops_not_found' );
		}
		$pending = array_filter( $rows, static fn( $r ) => empty( $r['undone_at'] ) );
		if ( ! $pending ) {
			return self::err( 'change already undone', 409, 'flareops_already_undone' );
		}
		$product_id = (int) $rows[0]['product_id'];
		$p          = wc_get_product( $product_id );
		if ( ! $p ) {
			return self::err( 'product no longer exists', 410, 'flareops_gone' );
		}

		$restored   = array();
		$restore_dc = null;
		try {
			$needs_save = false;
			foreach ( $pending as $r ) {
				$field = (string) $r['field'];
				$data  = json_decode( (string) $r['restore_data'], true );
				$data  = is_array( $data ) ? $data : array( 'value' => (string) $r['before_value'] );
				if ( 'brand' === $field ) {
					if ( 'tax' === ( $data['mode'] ?? '' ) && Products::brand_uses_taxonomy() ) {
						$res = wp_set_object_terms( $product_id, array_map( 'intval', (array) ( $data['term_ids'] ?? array() ) ), Products::BRAND_TAX, false );
						if ( is_wp_error( $res ) ) {
							throw new \RuntimeException( $res->get_error_message() );
						}
					} else {
						self::write_field( $p, 'brand', (string) ( $data['value'] ?? '' ) );
					}
				} else {
					self::write_field( $p, $field, (string) ( $data['value'] ?? '' ) );
				}
				if ( 'description' === $field ) {
					$restore_dc = (string) ( $data['value'] ?? '' );
				}
				$needs_save = true;
			}
			if ( $needs_save ) {
				// Undo restores the merchant's own earlier values exactly; kses must not alter them.
				self::save_product( $p );
			}
			if ( null !== $restore_dc ) {
				self::ensure_description( $product_id, $restore_dc );
			}
		} catch ( \Throwable $e ) {
			return self::err( 'undo failed: ' . $e->getMessage(), 409, 'flareops_undo_failed' );
		}
		if ( array_intersect( array_map( static fn( $r ) => (string) $r['field'], $pending ), self::CONTENT_FIELDS ) ) {
			self::after_content_change( $product_id );
		}

		$fresh = wc_get_product( $product_id );
		foreach ( $pending as $r ) {
			$restored[ $r['field'] ] = $fresh ? self::current_value( $fresh, (string) $r['field'] ) : (string) $r['before_value'];
		}
		$wpdb->query( $wpdb->prepare( 'UPDATE %i SET undone_at = %s WHERE change_id = %s AND undone_at IS NULL', $t, gmdate( 'Y-m-d H:i:s' ), $change_id ) ); // phpcs:ignore WordPress.DB

		return array(
			'ok'         => true,
			'change_id'  => $change_id,
			'product_id' => $product_id,
			'restored'   => (object) $restored,
		);
	}

	public static function list_since( ?string $since, int $limit = 500 ): array {
		global $wpdb;
		$t = Install::table( 'changes' );
		// phpcs:disable WordPress.DB
		if ( $since ) {
			$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT * FROM %i WHERE at >= %s ORDER BY id DESC LIMIT %d', $t, $since, $limit ), ARRAY_A );
		} else {
			$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT * FROM %i ORDER BY id DESC LIMIT %d', $t, $limit ), ARRAY_A );
		}
		// phpcs:enable
		return array_map(
			static fn( $r ) => array(
				'change_id'   => $r['change_id'],
				'product_id'  => (int) $r['product_id'],
				'field'       => $r['field'],
				'before'      => (string) $r['before_value'],
				'after'       => (string) $r['after_value'],
				'at'          => Util::mysql_to_iso( $r['at'] ),
				'source'      => $r['source'],
				'approved_by' => $r['approved_by'],
				'undone_at'   => Util::mysql_to_iso( $r['undone_at'] ?? null ),
			),
			(array) $rows
		);
	}
}