<?php
/**
 * JSON-LD structured data.
 *
 * @package ACSSEO
 */

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

/**
 * Prints schema.org JSON-LD for the front page and for opted in entries.
 */
class ACSSEO_Schema {

	/**
	 * Singleton instance.
	 *
	 * @var ACSSEO_Schema|null
	 */
	private static $instance = null;

	/**
	 * Return the shared instance.
	 *
	 * @return ACSSEO_Schema
	 */
	public static function instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Hook the output.
	 */
	private function __construct() {
		add_action( 'wp_head', array( $this, 'output' ), 6 );
	}

	/**
	 * Decide which graph to print, then print it.
	 *
	 * @return void
	 */
	public function output() {
		if ( ! ACSSEO_Settings::get( 'output_schema' ) ) {
			return;
		}

		if ( is_front_page() || is_home() ) {
			$this->print_graph( $this->website_graph() );

			return;
		}

		if ( ! is_singular() ) {
			return;
		}

		$post_id = get_queried_object_id();
		if ( ! $post_id || ! self::is_enabled_for( $post_id ) ) {
			return;
		}

		$this->print_graph( $this->entry_graph( $post_id ) );
	}

	/**
	 * Whether JSON-LD is printed for an entry.
	 *
	 * Entries opt in one by one, or every post does when the site wide
	 * setting is on.
	 *
	 * @param int $post_id Post ID.
	 * @return bool
	 */
	public static function is_enabled_for( $post_id ) {
		if ( '1' === (string) get_post_meta( $post_id, '_acsseo_schema', true ) ) {
			return true;
		}

		return ACSSEO_Settings::get( 'schema_all_posts' ) && 'post' === get_post_type( $post_id );
	}

	/**
	 * Graph used on the site front page.
	 *
	 * @return array<string,mixed>
	 */
	private function website_graph() {
		$graph = array(
			'@context' => 'https://schema.org',
			'@type'    => 'WebSite',
			'name'     => get_bloginfo( 'name', 'display' ),
			'url'      => home_url( '/' ),
		);

		$tagline = ACSSEO_Settings::home_description();
		if ( '' !== $tagline ) {
			$graph['description'] = $tagline;
		}

		$graph['potentialAction'] = array(
			'@type'       => 'SearchAction',
			'target'      => array(
				'@type'       => 'EntryPoint',
				'urlTemplate' => home_url( '/?s={search_term_string}' ),
			),
			'query-input' => 'required name=search_term_string',
		);

		return $graph;
	}

	/**
	 * Graph used on a single entry.
	 *
	 * @param int $post_id Post ID.
	 * @return array<string,mixed>
	 */
	private function entry_graph( $post_id ) {
		$is_post = ( 'post' === get_post_type( $post_id ) );

		$graph = array(
			'@context'      => 'https://schema.org',
			'@type'         => $is_post ? 'BlogPosting' : 'WebPage',
			'headline'      => get_the_title( $post_id ),
			'url'           => get_permalink( $post_id ),
			'datePublished' => get_the_date( DATE_W3C, $post_id ),
			'dateModified'  => get_the_modified_date( DATE_W3C, $post_id ),
			'mainEntityOfPage' => array(
				'@type' => 'WebPage',
				'@id'   => get_permalink( $post_id ),
			),
		);

		$description = ACSSEO_Meta::resolve_description( $post_id );
		if ( '' !== $description ) {
			$graph['description'] = $description;
		}

		if ( $is_post ) {
			$author_id = (int) get_post_field( 'post_author', $post_id );
			$author    = get_the_author_meta( 'display_name', $author_id );

			if ( $author ) {
				$graph['author'] = array(
					'@type' => 'Person',
					'name'  => $author,
				);
			}
		}

		$image = ACSSEO_Social::resolve_image( $post_id );
		if ( '' !== $image ) {
			$graph['image'] = $image;
		}

		$publisher = array(
			'@type' => 'Organization',
			'name'  => get_bloginfo( 'name', 'display' ),
		);

		$logo = get_site_icon_url();
		if ( $logo ) {
			$publisher['logo'] = array(
				'@type' => 'ImageObject',
				'url'   => $logo,
			);
		}

		$graph['publisher'] = $publisher;

		return $graph;
	}

	/**
	 * Print one JSON-LD block.
	 *
	 * @param array<string,mixed> $graph Graph to encode.
	 * @return void
	 */
	private function print_graph( array $graph ) {
		$json = wp_json_encode( $graph, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );

		if ( false === $json ) {
			return;
		}

		// A closing tag can only appear inside a string value, so neutralising the
		// angle brackets keeps the block from being broken out of.
		$json = str_replace( array( '<', '>' ), array( '\u003c', '\u003e' ), $json );

		wp_print_inline_script_tag(
			$json,
			array(
				'type' => 'application/ld+json',
			)
		);
	}
}