<?php

declare( strict_types=1 );

namespace AcezSeo\Schema;

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

/**
 * Local structural validation of the generated @graph document: required
 * properties per type, duplicate @id detection, and JSON well-formedness.
 * A lightweight local substitute for Google's Rich Results Test — catches
 * obvious mistakes before a post is even published.
 */
final class SchemaValidator
{
	/**
	 * @var array<string, string[]>
	 */
	private const REQUIRED_PROPERTIES = array(
		'Article'        => array( 'headline' ),
		'WebPage'        => array( 'name' ),
		'WebSite'        => array( 'name', 'url' ),
		'Organization'   => array( 'name' ),
		'Person'         => array( 'name' ),
		'BreadcrumbList' => array( 'itemListElement' ),
		// M66 — user-forced main-node types (ForcedSchemaType).
		'BlogPosting'    => array( 'headline' ),
		'NewsArticle'    => array( 'headline' ),
		'Blog'           => array( 'name' ),
		'CollectionPage' => array( 'name' ),
		'AboutPage'      => array( 'name' ),
		'ContactPage'    => array( 'name' ),
	);

	/**
	 * @return array<string, string[]>
	 */
	private static function required_properties(): array
	{
		/**
		 * Filters the required-property map used by the local validator —
		 * the extension point premium schema types (Pro, M30) add their own
		 * Google Rich Results requirements through, without touching this class.
		 *
		 * @param array<string, string[]> $required_properties
		 */
		return (array) apply_filters( 'acez_seo_schema_required_properties', self::REQUIRED_PROPERTIES );
	}

	/**
	 * @param array<string, mixed> $graph_document The full {"@context":...,"@graph":[...]} array.
	 *
	 * @return string[] Human-readable issues; empty array means valid.
	 */
	public function validate( array $graph_document ): array
	{
		$issues = array();

		if ( ! isset( $graph_document['@graph'] ) || ! is_array( $graph_document['@graph'] ) )
		{
			$issues[] = __( 'Missing @graph node.', 'acez-seo' );

			return $issues;
		}

		$seen_ids           = array();
		$required_properties = self::required_properties();

		foreach ( $graph_document['@graph'] as $index => $node )
		{
			if ( ! is_array( $node ) )
			{
				$issues[] = sprintf(
					/* translators: %d: node index */
					__( 'Node #%d is not a valid object.', 'acez-seo' ),
					(int) $index
				);

				continue;
			}

			$type = isset( $node['@type'] ) ? (string) $node['@type'] : '';

			if ( '' === $type )
			{
				$issues[] = sprintf(
					/* translators: %d: node index */
					__( 'Node #%d has no @type field.', 'acez-seo' ),
					(int) $index
				);

				continue;
			}

			if ( isset( $node['@id'] ) )
			{
				$id = (string) $node['@id'];

				if ( isset( $seen_ids[ $id ] ) )
				{
					$issues[] = sprintf(
						/* translators: 1: @id value, 2: schema type */
						__( 'Duplicate @id: %1$s (type %2$s).', 'acez-seo' ),
						$id,
						$type
					);
				}

				$seen_ids[ $id ] = true;
			}

			foreach ( $required_properties[ $type ] ?? array() as $required_property )
			{
				if ( empty( $node[ $required_property ] ) )
				{
					$issues[] = sprintf(
						/* translators: 1: schema type, 2: missing property name */
						__( '%1$s: missing required property "%2$s".', 'acez-seo' ),
						$type,
						$required_property
					);
				}
			}
		}

		$json = wp_json_encode( $graph_document );

		if ( ! is_string( $json ) || null === json_decode( $json ) )
		{
			$issues[] = __( 'The generated JSON-LD has a syntax error.', 'acez-seo' );
		}

		return $issues;
	}
}