<?php
/**
 * Google Merchant Center product feed (RSS 2.0 + g: namespace).
 *
 * @package FlareOps
 */

namespace FlareOps;

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

final class Feed {

	public const QUERY_VAR       = 'flareops_feed';
	public const TRANSIENT       = 'flareops_feed_google';
	public const TTL             = 15 * MINUTE_IN_SECONDS;
	public const REWRITE_VERSION = '1';
	public const MAX_ITEMS       = 5000;

	public static function add_rewrite(): void {
		add_rewrite_rule( '^flareops-feed/google\.xml$', 'index.php?' . self::QUERY_VAR . '=google', 'top' );
	}

	public static function query_vars( $vars ) {
		$vars[] = self::QUERY_VAR;
		return $vars;
	}

	public static function url(): string {
		return get_option( 'permalink_structure' ) ? home_url( '/flareops-feed/google.xml' ) : add_query_arg( self::QUERY_VAR, 'google', home_url( '/' ) );
	}

	public static function invalidate(): void {
		delete_transient( self::TRANSIENT );
	}

	/** parse_request handler. */
	public static function maybe_serve( $wp ): void {
		$which = '';
		if ( is_object( $wp ) && ! empty( $wp->query_vars[ self::QUERY_VAR ] ) ) {
			$which = (string) $wp->query_vars[ self::QUERY_VAR ];
		} elseif ( isset( $_GET[ self::QUERY_VAR ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$which = sanitize_key( wp_unslash( $_GET[ self::QUERY_VAR ] ) ); // phpcs:ignore WordPress.Security.NonceVerification
		}
		if ( 'google' !== $which ) {
			return;
		}
		if ( ! Settings::feature( 'feed_google' ) || ! Util::woo_active() ) {
			status_header( 404 );
			nocache_headers();
			header( 'Content-Type: text/plain; charset=UTF-8' );
			echo 'Feed disabled';
			exit;
		}
		$xml = get_transient( self::TRANSIENT );
		if ( ! is_string( $xml ) || '' === $xml ) {
			$xml = self::build();
			set_transient( self::TRANSIENT, $xml, self::TTL );
		}
		status_header( 200 );
		header( 'Content-Type: application/xml; charset=UTF-8' );
		header( 'X-Robots-Tag: noindex' );
		header( 'Cache-Control: public, max-age=900' );
		echo $xml; // phpcs:ignore WordPress.Security.EscapeOutput -- built with self::x().
		exit;
	}

	/** Escape text for XML 1.0 (removes characters that are invalid in XML). */
	public static function x( $s ): string {
		$s = (string) $s;
		if ( ! mb_check_encoding( $s, 'UTF-8' ) ) {
			$s = mb_convert_encoding( $s, 'UTF-8', 'UTF-8' );
		}
		$s = (string) preg_replace( '/[^\x{9}\x{A}\x{D}\x{20}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]/u', '', $s );
		return htmlspecialchars( $s, ENT_XML1 | ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8' );
	}

	private static function money( $amount, string $currency ): string {
		return number_format( (float) $amount, 2, '.', '' ) . ' ' . $currency;
	}

	/** Shopper-facing price: tax-exclusive for US/CA, tax-inclusive elsewhere (Google spec). */
	private static function display_price( \WC_Product $p, $raw ): string {
		if ( '' === (string) $raw ) {
			return '';
		}
		$country = function_exists( 'WC' ) && WC()->countries ? WC()->countries->get_base_country() : 'US';
		if ( in_array( $country, array( 'US', 'CA' ), true ) || ! wc_tax_enabled() ) {
			return (string) wc_get_price_excluding_tax( $p, array( 'price' => $raw ) );
		}
		return (string) wc_get_price_including_tax( $p, array( 'price' => $raw ) );
	}

	public static function availability( string $stock_status ): string {
		switch ( $stock_status ) {
			case 'instock':
				return 'in_stock';
			case 'onbackorder':
				return 'backorder';
			case 'preorder':
			case 'pre-order':
				return 'preorder';
			default:
				return 'out_of_stock';
		}
	}

	private static function truncate( string $s, int $max ): string {
		return mb_strlen( $s ) > $max ? rtrim( mb_substr( $s, 0, $max - 1 ) ) . '…' : $s;
	}

	/** Products in scope (feed_scope "treatment" = only treatment_ids). */
	public static function scope_products(): array {
		$settings = Settings::all();
		$args     = array(
			'status'  => 'publish',
			'limit'   => self::MAX_ITEMS,
			'orderby' => 'ID',
			'order'   => 'ASC',
			'type'    => array( 'simple', 'variable', 'external' ),
		);
		if ( 'treatment' === $settings['feed_scope'] ) {
			if ( ! $settings['treatment_ids'] ) {
				return array();
			}
			$args['include'] = $settings['treatment_ids'];
		}
		return (array) wc_get_products( $args );
	}

	/**
	 * g:availability_date (ISO 8601) for backorder / preorder items, only when the merchant has recorded one:
	 * product (or parent) meta `_flareops_availability_date`, or the `flareops_availability_date` filter (for
	 * pre-order plugins). Only future dates are used. Otherwise '' (Merchant Center may then warn; never guessed).
	 */
	public static function availability_date( \WC_Product $p, ?\WC_Product $parent ): string {
		$raw = (string) $p->get_meta( '_flareops_availability_date', true );
		if ( '' === $raw && $parent ) {
			$raw = (string) $parent->get_meta( '_flareops_availability_date', true );
		}
		$raw = (string) apply_filters( 'flareops_availability_date', $raw, $p, $parent );
		if ( '' === trim( $raw ) ) {
			return '';
		}
		try {
			$tz = function_exists( 'wp_timezone' ) ? wp_timezone() : new \DateTimeZone( 'UTC' );
			$dt = new \DateTimeImmutable( trim( $raw ), $tz );
		} catch ( \Throwable $e ) {
			return '';
		}
		if ( $dt->getTimestamp() <= time() ) {
			return '';
		}
		return $dt->format( 'c' );
	}

	/** Image URLs: [main, additional...]. Variations use their own image first, then the parent's image and gallery. */
	public static function images( \WC_Product $p, ?\WC_Product $parent ): array {
		$main = Products::image_url( $p );
		$ids  = array();
		if ( $parent && $parent->get_image_id() ) {
			$ids[] = (int) $parent->get_image_id();
		}
		$base = $parent ? $parent : $p;
		foreach ( (array) $base->get_gallery_image_ids() as $gid ) {
			$ids[] = (int) $gid;
		}
		$extra = array();
		foreach ( array_unique( $ids ) as $gid ) {
			$u = $gid ? wp_get_attachment_image_url( $gid, 'full' ) : '';
			if ( $u && $u !== $main && ! in_array( $u, $extra, true ) ) {
				$extra[] = (string) $u;
			}
			if ( count( $extra ) >= 10 ) {
				break; // Google accepts up to 10 additional_image_link values.
			}
		}
		return array( $main, $extra );
	}

	/** Description: own description, parent's (variations), short description, then title. Plain text, ≤ 5000 chars. */
	public static function description( \WC_Product $p, ?\WC_Product $parent, string $title ): string {
		foreach ( array(
			static fn() => $p->get_description(),
			static fn() => $parent ? $parent->get_description() : '',
			static fn() => $p->get_short_description(),
			static fn() => $parent ? $parent->get_short_description() : '',
		) as $get ) {
			$d = Util::plain_text( $get() );
			if ( '' !== $d ) {
				return self::truncate( $d, 5000 );
			}
		}
		return self::truncate( $title, 5000 );
	}

	/** One <item> for a sellable product or variation; '' when it cannot be listed. */
	private static function item( \WC_Product $p, ?\WC_Product $parent, string $currency ): string {
		$base = $parent ? $parent : $p;
		if ( 'hidden' === $base->get_catalog_visibility() || post_password_required( $base->get_id() ) ) {
			return '';
		}
		$regular = $p->get_regular_price();
		$active  = $p->get_price();
		if ( '' === (string) $regular ) {
			$regular = $active;
		}
		if ( '' === (string) $active || '' === (string) $regular || (float) $regular <= 0 ) {
			return ''; // Google requires a price; never invent one. Products without a price are left out.
		}

		$title = html_entity_decode( (string) $p->get_name(), ENT_QUOTES, 'UTF-8' );
		$desc  = self::description( $p, $parent, $title );

		$gtin  = Products::gtin( $p );
		$mpn   = Products::mpn( $p );
		$brand = Products::effective_brand( $p );
		$type  = Products::category_path( $base->get_id() );
		$gcat  = Products::google_category( $base->get_id() );
		[ $img, $extra ] = self::images( $p, $parent );
		$avail = self::availability( (string) $p->get_stock_status() );

		$f   = array();
		$f[] = '<g:id>' . self::x( (string) $p->get_id() ) . '</g:id>';
		if ( $parent ) {
			$f[] = '<g:item_group_id>' . self::x( (string) $parent->get_id() ) . '</g:item_group_id>';
		}
		$f[] = '<title>' . self::x( self::truncate( $title, 150 ) ) . '</title>';
		$f[] = '<description>' . self::x( $desc ) . '</description>';
		$f[] = '<link>' . self::x( (string) $p->get_permalink() ) . '</link>';
		if ( '' !== $img ) {
			$f[] = '<g:image_link>' . self::x( $img ) . '</g:image_link>';
		}
		foreach ( $extra as $u ) {
			$f[] = '<g:additional_image_link>' . self::x( $u ) . '</g:additional_image_link>';
		}
		$f[] = '<g:availability>' . $avail . '</g:availability>';
		if ( 'backorder' === $avail || 'preorder' === $avail ) {
			$ad = self::availability_date( $p, $parent );
			if ( '' !== $ad ) {
				$f[] = '<g:availability_date>' . self::x( $ad ) . '</g:availability_date>';
			}
		}
		$f[] = '<g:price>' . self::x( self::money( self::display_price( $p, $regular ), $currency ) ) . '</g:price>';
		if ( $p->is_on_sale( 'edit' ) && '' !== (string) $p->get_sale_price() && (float) $p->get_sale_price() < (float) $regular ) {
			$f[] = '<g:sale_price>' . self::x( self::money( self::display_price( $p, $p->get_sale_price() ), $currency ) ) . '</g:sale_price>';
			$from = $p->get_date_on_sale_from();
			$to   = $p->get_date_on_sale_to();
			if ( $from && $to ) {
				$f[] = '<g:sale_price_effective_date>' . self::x( $from->date( 'c' ) . '/' . $to->date( 'c' ) ) . '</g:sale_price_effective_date>';
			}
		}
		if ( '' !== $brand ) {
			$f[] = '<g:brand>' . self::x( $brand ) . '</g:brand>';
		}
		if ( '' !== $gtin ) {
			$f[] = '<g:gtin>' . self::x( $gtin ) . '</g:gtin>';
		}
		if ( '' !== $mpn ) {
			$f[] = '<g:mpn>' . self::x( $mpn ) . '</g:mpn>';
		}
		if ( '' === $gtin && '' === $mpn ) {
			$f[] = '<g:identifier_exists>no</g:identifier_exists>';
		}
		$f[] = '<g:condition>' . self::x( Products::condition( $p ) ) . '</g:condition>';
		if ( '' !== $gcat ) {
			$f[] = '<g:google_product_category>' . self::x( $gcat ) . '</g:google_product_category>';
		}
		if ( '' !== $type ) {
			$f[] = '<g:product_type>' . self::x( $type ) . '</g:product_type>';
		}
		if ( $parent ) {
			foreach ( Products::attributes( $p ) as $label => $vals ) {
				$l = strtolower( (string) $label );
				if ( in_array( $l, array( 'color', 'colour' ), true ) ) {
					$f[] = '<g:color>' . self::x( implode( '/', $vals ) ) . '</g:color>';
				} elseif ( 'size' === $l ) {
					$f[] = '<g:size>' . self::x( implode( '/', $vals ) ) . '</g:size>';
				}
			}
		}
		$ship = Settings::all()['feed_shipping'];
		if ( is_array( $ship ) ) {
			$sh = '<g:country>' . self::x( $ship['country'] ) . '</g:country>';
			if ( '' !== $ship['service'] ) {
				$sh .= '<g:service>' . self::x( $ship['service'] ) . '</g:service>';
			}
			$sh .= '<g:price>' . self::x( self::money( $ship['price'], $currency ) ) . '</g:price>';
			$f[] = '<g:shipping>' . $sh . '</g:shipping>';
		}
		$w = $p->get_weight();
		if ( '' !== (string) $w && (float) $w > 0 ) {
			$f[] = '<g:shipping_weight>' . self::x( wc_format_decimal( $w ) . ' ' . get_option( 'woocommerce_weight_unit', 'kg' ) ) . '</g:shipping_weight>';
		}
		return "  <item>\n    " . implode( "\n    ", $f ) . "\n  </item>\n";
	}

	/**
	 * Variable products: only the variations are listed, each with g:item_group_id = parent ID. Google wants one item
	 * per purchasable variant (own price, availability, colour/size, GTIN); the parent has no single price or stock,
	 * so listing it too would duplicate the product and fail validation.
	 */
	public static function build(): string {
		$settings  = Settings::all();
		$treatment = 'treatment' === $settings['feed_scope'];
		$currency  = get_woocommerce_currency();
		$items     = '';
		$count     = 0;
		foreach ( self::scope_products() as $p ) {
			if ( $count >= self::MAX_ITEMS ) {
				break;
			}
			// Belt and braces: in treatment scope a control product can never reach the feed.
			if ( $treatment && ! Settings::is_treatment( (int) $p->get_id() ) ) {
				continue;
			}
			try {
				if ( $p->is_type( 'variable' ) ) {
					foreach ( $p->get_children() as $vid ) {
						$v = wc_get_product( $vid );
						if ( $v && 'publish' === $v->get_status() ) {
							$s = self::item( $v, $p, $currency );
							if ( '' !== $s ) {
								$items .= $s;
								++$count;
							}
						}
					}
					continue;
				}
				$s = self::item( $p, null, $currency );
				if ( '' !== $s ) {
					$items .= $s;
					++$count;
				}
			} catch ( \Throwable $e ) {
				Util::log( 'feed item ' . $p->get_id() . ': ' . $e->getMessage() );
			}
		}
		$name = html_entity_decode( (string) get_bloginfo( 'name' ), ENT_QUOTES, 'UTF-8' );
		$desc = html_entity_decode( (string) get_bloginfo( 'description' ), ENT_QUOTES, 'UTF-8' );
		$name = '' !== trim( $name ) ? $name : (string) wp_parse_url( home_url( '/' ), PHP_URL_HOST );

		return '<?xml version="1.0" encoding="UTF-8"?>' . "\n"
			. '<rss version="2.0" xmlns:g="http://base.google.com/ns/1.0">' . "\n"
			. "<channel>\n"
			. '  <title>' . self::x( $name ) . "</title>\n"
			. '  <link>' . self::x( home_url( '/' ) ) . "</link>\n"
			. '  <description>' . self::x( '' !== trim( $desc ) ? $desc : $name . ' products' ) . "</description>\n"
			. '  <!-- flareOps ' . self::x( FLAREOPS_VERSION ) . ' | scope=' . self::x( $settings['feed_scope'] ) . ' | items=' . $count . ' | generated ' . Util::iso() . " -->\n"
			. $items
			. "</channel>\n</rss>\n";
	}
}