<?php
/**
 * Builds the JSON-LD graph of a page.
 *
 * @package ElevenRank
 * @since   1.0.0
 */

namespace ElevenRank\Modules\Schema;

use ElevenRank\Modules\Breadcrumbs\Breadcrumb_Trail;
use ElevenRank\Modules\Meta\Context;
use ElevenRank\Modules\Meta\Resolver;
use ElevenRank\Settings;
use WP_Post;

defined( 'ABSPATH' ) || exit;

/**
 * Always: the organization or person, the website, the page and (with two or more items) the
 * breadcrumb. For a post whose type is chosen: an Article, Product, Recipe, Event, VideoObject or
 * Review. Every piece can be changed with `elevenrank_schema_{type}` and the whole graph with
 * `elevenrank_schema_graph`.
 *
 * @since 1.0.0
 */
final class Graph_Builder {

	/**
	 * Settings store.
	 *
	 * @since 1.0.0
	 *
	 * @var Settings
	 */
	private $settings;

	/**
	 * Resolver of titles, descriptions and addresses.
	 *
	 * @since 1.0.0
	 *
	 * @var Resolver
	 */
	private $resolver;

	/**
	 * Breadcrumb trail.
	 *
	 * @since 1.0.0
	 *
	 * @var Breadcrumb_Trail
	 */
	private $trail;

	/**
	 * Constructor.
	 *
	 * @since 1.0.0
	 *
	 * @param Settings         $settings Settings store.
	 * @param Resolver         $resolver Resolver.
	 * @param Breadcrumb_Trail $trail    Breadcrumb trail.
	 */
	public function __construct( Settings $settings, Resolver $resolver, Breadcrumb_Trail $trail ) {
		$this->settings = $settings;
		$this->resolver = $resolver;
		$this->trail    = $trail;
	}

	/**
	 * The JSON-LD document of a page.
	 *
	 * @since 1.0.0
	 *
	 * @param Context $context Page context.
	 * @return array<string, mixed> Empty when the page gets no markup.
	 */
	public function build( Context $context ): array {
		if ( in_array( $context->type(), array( Context::NOT_FOUND, Context::OTHER ), true ) ) {
			return array();
		}

		$post = $context->post();

		if ( null !== $post ) {
			/**
			 * Filters whether a post gets structured data at all.
			 *
			 * @since 1.0.0
			 *
			 * @param bool $enabled Whether markup is printed. Default true.
			 * @param int  $post_id Post id.
			 */
			if ( ! apply_filters( 'elevenrank_schema_enabled_for_post', true, $post->ID ) ) {
				return array();
			}
		}

		$c     = new Node_Context( $context, $this->settings, $this->resolver );
		$graph = new Graph();

		$this->emit( $graph, Entity_Node::build( $c ), $c );
		$this->emit( $graph, Entity_Node::logo( $c ), $c );
		$this->emit( $graph, Website_Node::build( $c ), $c );

		$image      = $this->primary_image( $c );
		$breadcrumb = $this->settings->value( 'schema', 'include_breadcrumbs' )
			? Breadcrumb_Node::build( $c, $this->trail->items( $context ) )
			: null;

		$this->emit( $graph, Webpage_Node::build( $c, null !== $breadcrumb, null !== $image ), $c );
		$this->emit( $graph, $image, $c );
		$this->emit( $graph, $breadcrumb, $c );

		if ( null !== $context->user() ) {
			$this->emit( $graph, Author_Node::build( $context->user()->ID ), $c );
		}

		if ( null !== $post && Context::SINGULAR === $context->type() ) {
			$this->add_content( $graph, $post, $c );
		}

		$document = array(
			'@context' => 'https://schema.org',
			'@graph'   => $graph->nodes(),
		);

		/**
		 * Filters the whole graph before it is printed.
		 *
		 * @since 1.0.0
		 *
		 * @param array<string, mixed> $document The document: `@context` and `@graph`.
		 * @param Context              $context  Page context.
		 */
		$filtered = apply_filters( 'elevenrank_schema_graph', $document, $context );

		return is_array( $filtered ) && ! empty( $filtered['@graph'] ) ? $filtered : array();
	}

	/**
	 * Adds the node of the post's chosen type.
	 *
	 * @since 1.0.0
	 *
	 * @param Graph        $graph Graph.
	 * @param WP_Post      $post  Post.
	 * @param Node_Context $c     Page information.
	 * @return void
	 */
	private function add_content( Graph $graph, WP_Post $post, Node_Context $c ): void {
		$type = Schema_Fields::type_for( $post, $this->settings );

		if ( ! Type_Definitions::is_type( $type ) ) {
			return;
		}

		$builder = $this->content_builder( $type );
		$node    = $builder->build( $type, Schema_Fields::for_post( $post->ID )['fields'], $post, $c, $graph );

		$this->emit( $graph, $node, $c );
	}

	/**
	 * The class that builds a content type.
	 *
	 * @since 1.0.0
	 *
	 * @param string $type One of {@see Type_Definitions::TYPES}.
	 * @return Content_Node
	 */
	private function content_builder( string $type ): Content_Node {
		switch ( $type ) {
			case 'Product':
				return new Product_Node();

			case 'Recipe':
				return new Recipe_Node();

			case 'Event':
				return new Event_Node();

			case 'VideoObject':
				return new Video_Node();

			case 'Review':
				return new Review_Node();
		}

		return new Article_Node();
	}

	/**
	 * The primary image of a post: its featured image, or the image itself for an attachment page.
	 *
	 * @since 1.0.0
	 *
	 * @param Node_Context $c Page information.
	 * @return array<string, mixed>|null
	 */
	private function primary_image( Node_Context $c ): ?array {
		$post = $c->post();

		if ( null === $post ) {
			return null;
		}

		$id = Context::ATTACHMENT === $c->context->type() ? $post->ID : (int) get_post_thumbnail_id( $post );

		return Image_Node::build( $id, $c->id( 'primaryimage' ) );
	}

	/**
	 * Lets the filter for the node's type change it, then adds it to the graph.
	 *
	 * @since 1.0.0
	 *
	 * @param Graph                     $graph Graph.
	 * @param array<string, mixed>|null $node  Node.
	 * @param Node_Context              $c     Page information.
	 * @return void
	 */
	private function emit( Graph $graph, ?array $node, Node_Context $c ): void {
		if ( null === $node ) {
			return;
		}

		$type = strtolower( preg_replace( '/[^A-Za-z]/', '', (string) ( $node['@type'] ?? '' ) ) ?? '' );

		if ( '' !== $type ) {
			/**
			 * Filters one node of the graph. The part after `elevenrank_schema_` is the node's `@type` in
			 * lower case: `article`, `product`, `webpage`, `breadcrumblist`, `organization` and so on. Return
			 * null to leave the node out.
			 *
			 * @since 1.0.0
			 *
			 * @param array<string, mixed>|null $node    The node.
			 * @param Context                   $context Page context.
			 */
			$node = apply_filters( "elevenrank_schema_{$type}", $node, $c->context );
		}

		$graph->add( is_array( $node ) ? $node : null );
	}
}