<?php
/**
 * Works out the SEO values for a request, post or term.
 *
 * @package OrbitstemSEO
 */

namespace Orbitstem\SEO\Frontend;

use Orbitstem\SEO\Content\MetaRepository;
use Orbitstem\SEO\Content\TemplateEngine;
use Orbitstem\SEO\Content\TypeRegistry;
use Orbitstem\SEO\Core\Settings;
use WP_Post;
use WP_Term;

defined( 'ABSPATH' ) || exit;

/**
 * Produces one normalized array of SEO values. Every output (head tags, admin
 * previews, later audits) reads from here, so they cannot disagree.
 *
 * Result keys: title, description, canonical, noindex, nofollow, og_type,
 * image, published, modified, object_type (post|term|front|archive|author|
 * date|search|404), object_id, url (the page's own address), schema.
 * Values are plain text, not escaped.
 */
class Resolver {

	/**
	 * Settings service.
	 *
	 * @var Settings
	 */
	private $settings;

	/**
	 * Content type registry.
	 *
	 * @var TypeRegistry
	 */
	private $types;

	/**
	 * SEO field storage.
	 *
	 * @var MetaRepository
	 */
	private $meta;

	/**
	 * Template engine.
	 *
	 * @var TemplateEngine
	 */
	private $templates;

	/**
	 * Cached result for the current request (false = not computed yet).
	 *
	 * @var array|null|false
	 */
	private $current = false;

	/**
	 * Constructor.
	 *
	 * @param Settings       $settings  Settings.
	 * @param TypeRegistry   $types     Type registry.
	 * @param MetaRepository $meta      Meta repository.
	 * @param TemplateEngine $templates Template engine.
	 */
	public function __construct( Settings $settings, TypeRegistry $types, MetaRepository $meta, TemplateEngine $templates ) {
		$this->settings  = $settings;
		$this->types     = $types;
		$this->meta      = $meta;
		$this->templates = $templates;
	}

	/**
	 * Clears the per-request cache (used by tests and after query changes).
	 */
	public function reset() {
		$this->current = false;
	}

	/**
	 * Values for the main query, or null for views Orbitstem does not manage.
	 *
	 * @return array|null
	 */
	public function for_request() {
		if ( false === $this->current ) {
			$data = $this->resolve_request();

			/**
			 * Filters the resolved SEO values for the current request.
			 *
			 * @param array|null $data Resolved values, or null when unmanaged.
			 */
			$this->current = apply_filters( 'orbitstem_seo_resolved', $data );
		}
		return $this->current;
	}

	/**
	 * Dispatches on the WordPress conditional tags.
	 *
	 * @return array|null
	 */
	private function resolve_request() {
		$paged = max( 1, (int) get_query_var( 'paged' ) );

		if ( is_front_page() ) {
			return $this->for_front_page( max( $paged, (int) get_query_var( 'page' ) ) );
		}
		if ( is_home() ) {
			$posts_page = (int) get_option( 'page_for_posts' );
			$post       = $posts_page ? get_post( $posts_page ) : null;
			return $post ? $this->for_post( $post, $paged, true ) : null;
		}
		if ( is_singular() ) {
			$post = get_queried_object();
			return $post instanceof WP_Post ? $this->for_post( $post ) : null;
		}
		if ( is_category() || is_tag() || is_tax() ) {
			$term = get_queried_object();
			return $term instanceof WP_Term ? $this->for_term( $term, $paged ) : null;
		}
		if ( is_post_type_archive() ) {
			$type = get_query_var( 'post_type' );
			$type = is_array( $type ) ? reset( $type ) : $type;
			return $this->for_post_type_archive( (string) $type, $paged );
		}
		if ( is_author() ) {
			return $this->for_author( (int) get_queried_object_id(), $paged );
		}
		if ( is_date() ) {
			return $this->for_date_archive( $paged );
		}
		if ( is_search() ) {
			$data = $this->simple(
				$this->settings->get( 'search_title' ),
				array(
					'search' => TemplateEngine::plain( get_search_query( false ) ),
					'page'   => $this->page_label( $paged ),
				),
				true
			);

			$data['object_type'] = 'search';
			$data['url']         = get_search_link();
			return $data;
		}
		if ( is_404() ) {
			$data = $this->simple(
				$this->settings->get( 'not_found_title' ),
				array( 'not_found' => __( 'Page not found', 'orbitstem-seo' ) ),
				true
			);

			$data['object_type'] = '404';
			return $data;
		}
		return null;
	}

	/**
	 * Values for a post of a managed type.
	 *
	 * @param WP_Post $post       Post.
	 * @param int     $paged      Archive page (posts page only).
	 * @param bool    $posts_page Whether the post is the "Posts page" listing.
	 * @return array|null
	 */
	public function for_post( WP_Post $post, $paged = 1, $posts_page = false ) {
		if ( ! $this->types->supports_post_type( $post->post_type ) ) {
			return null;
		}
		$type_object = get_post_type_object( $post->post_type );
		if ( ! $posts_page && is_singular() && (int) get_queried_object_id() === (int) $post->ID ) {
			$paged = max( 1, (int) get_query_var( 'page' ) ); // Split posts (<!--nextpage-->): page 2 and later.
		}
		$vars = array(
			'title'   => TemplateEngine::plain( $post->post_title ),
			'excerpt' => $this->post_excerpt( $post ),
			'type'    => $type_object ? TemplateEngine::plain( $type_object->labels->name ) : '',
			'page'    => $this->page_label( $paged ),
		);

		$custom_title  = $this->meta->get_post( $post->ID, 'title' );
		$custom_desc   = $this->meta->get_post( $post->ID, 'description' );
		$custom_canon  = $this->meta->get_post( $post->ID, 'canonical' );
		$custom_schema = $this->meta->get_post( $post->ID, 'schema' );

		if ( $posts_page ) {
			$canonical = $this->paged_url( get_permalink( $post ), $paged );
			$own_url   = $canonical;
		} else {
			$canonical = wp_get_canonical_url( $post );
			$own_url   = $canonical ? $canonical : get_permalink( $post );
		}

		$image        = get_the_post_thumbnail_url( $post, 'large' );
		$social_image = $this->meta->get_post( $post->ID, 'social_image' );
		$social_title = $this->meta->get_post( $post->ID, 'social_title' );
		$social_desc  = $this->meta->get_post( $post->ID, 'social_description' );

		return array(
			'title'       => $this->templates->render( '' !== $custom_title ? $custom_title : $this->settings->post_type( $post->post_type, 'title' ), $vars ),
			'description' => $this->templates->render( '' !== $custom_desc ? $custom_desc : $this->settings->post_type( $post->post_type, 'description' ), $vars ),
			// Share previews: their own text when set, otherwise the SEO title and description.
			'og_title'    => '' !== $social_title ? $this->templates->render( $social_title, $vars ) : '',
			'og_desc'     => '' !== $social_desc ? $this->templates->render( $social_desc, $vars ) : '',
			'canonical'   => '' !== $custom_canon ? $custom_canon : (string) $canonical,
			// The posts page lists posts; it does not inherit the "Pages" noindex setting.
			'noindex'     => $this->meta->get_post( $post->ID, 'noindex' ) || ( ! $posts_page && (bool) $this->settings->post_type( $post->post_type, 'noindex' ) ),
			'nofollow'    => (bool) $this->meta->get_post( $post->ID, 'nofollow' ),
			'og_type'     => 'post' === $post->post_type && ! $posts_page ? 'article' : 'website',
			'image'       => '' !== $social_image ? $social_image : ( $image ? $image : (string) $this->settings->get( 'og_default_image' ) ),
			'published'   => 'post' === $post->post_type ? get_post_time( 'c', true, $post ) : '',
			'modified'    => 'post' === $post->post_type ? get_post_modified_time( 'c', true, $post ) : '',
			'object_type' => 'post',
			'object_id'   => $post->ID,
			'url'         => (string) $own_url,
			'schema'      => $posts_page ? 'WebPage' : ( '' !== $custom_schema ? $custom_schema : (string) $this->settings->post_type( $post->post_type, 'schema' ) ),
		);
	}

	/**
	 * Only the indexing signals of a post: noindex, canonical and its own URL.
	 * Much cheaper than for_post() (no excerpt, templates or images), for scans.
	 *
	 * @param WP_Post $post Post.
	 * @return array{noindex:bool,canonical:string,url:string}|null Null for unmanaged types.
	 */
	public function indexing_for_post( WP_Post $post ) {
		if ( ! $this->types->supports_post_type( $post->post_type ) ) {
			return null;
		}
		$own     = (string) get_permalink( $post );
		$custom  = $this->meta->get_post( $post->ID, 'canonical' );
		$special = 'page' === get_option( 'show_on_front' ) && in_array( (int) $post->ID, array( (int) get_option( 'page_on_front' ), (int) get_option( 'page_for_posts' ) ), true );
		return array(
			'noindex'   => $this->meta->get_post( $post->ID, 'noindex' ) || ( ! $special && (bool) $this->settings->post_type( $post->post_type, 'noindex' ) ),
			'canonical' => '' !== $custom ? $custom : $own,
			'url'       => $own,
		);
	}

	/**
	 * Values for a term of a managed taxonomy.
	 *
	 * @param WP_Term $term  Term.
	 * @param int     $paged Archive page.
	 * @return array|null
	 */
	public function for_term( WP_Term $term, $paged = 1 ) {
		if ( ! $this->types->supports_taxonomy( $term->taxonomy ) ) {
			return null;
		}
		$vars = array(
			'term'             => TemplateEngine::plain( $term->name ),
			'term_description' => TemplateEngine::truncate( strip_shortcodes( $term->description ) ),
			'page'             => $this->page_label( $paged ),
		);

		$custom_title = $this->meta->get_term( $term->term_id, 'title' );
		$custom_desc  = $this->meta->get_term( $term->term_id, 'description' );
		$custom_canon = $this->meta->get_term( $term->term_id, 'canonical' );
		$link         = get_term_link( $term );
		$own_url      = is_wp_error( $link ) ? '' : $this->paged_url( $link, $paged );

		return array(
			'title'       => $this->templates->render( '' !== $custom_title ? $custom_title : $this->settings->taxonomy( $term->taxonomy, 'title' ), $vars ),
			'description' => $this->templates->render( '' !== $custom_desc ? $custom_desc : $this->settings->taxonomy( $term->taxonomy, 'description' ), $vars ),
			'canonical'   => '' !== $custom_canon ? $custom_canon : $own_url,
			// An empty archive ("thin page") is noindex when Settings says so.
			'noindex'     => $this->meta->get_term( $term->term_id, 'noindex' ) || (bool) $this->settings->taxonomy( $term->taxonomy, 'noindex' ) || ( 0 === (int) $term->count && $this->settings->get( 'noindex_empty_terms' ) ),
			'nofollow'    => (bool) $this->meta->get_term( $term->term_id, 'nofollow' ),
			'og_type'     => 'website',
			'image'       => (string) $this->settings->get( 'og_default_image' ),
			'published'   => '',
			'modified'    => '',
			'object_type' => 'term',
			'object_id'   => $term->term_id,
			'url'         => $own_url,
			'schema'      => 'CollectionPage',
		);
	}

	/**
	 * Values for the front page (static page or latest posts).
	 *
	 * @param int $paged Page number.
	 * @return array
	 */
	private function for_front_page( $paged ) {
		$paged = max( 1, (int) $paged );
		$vars  = array( 'page' => $this->page_label( $paged ) );
		$title = $this->templates->render( $this->settings->get( 'home_title' ), $vars );
		$desc  = $this->templates->render( $this->settings->get( 'home_description' ), $vars );
		$data  = null;

		$front_id = 'page' === get_option( 'show_on_front' ) ? (int) get_option( 'page_on_front' ) : 0;
		$front    = $front_id ? get_post( $front_id ) : null;
		if ( $front instanceof WP_Post ) {
			$data = $this->for_post( $front );
		}
		if ( null === $data ) {
			$data = $this->simple( '', array(), false );
		}

		// The page's own fields win; otherwise the homepage templates apply.
		if ( ! $front || '' === $this->meta->get_post( $front->ID, 'title' ) ) {
			$data['title'] = $title;
		}
		// An empty homepage template (e.g. no tagline) falls back to the front page's own text.
		if ( ( ! $front || '' === $this->meta->get_post( $front->ID, 'description' ) ) && '' !== $desc ) {
			$data['description'] = $desc;
		}
		$home_url = $this->paged_url( home_url( '/' ), $paged );
		if ( ! $front || '' === $this->meta->get_post( $front->ID, 'canonical' ) ) {
			$data['canonical'] = $home_url;
		}
		// The homepage never inherits the "Pages" noindex setting; only its own field counts.
		$data['noindex']     = $front ? $this->meta->get_post( $front->ID, 'noindex' ) : false;
		$data['og_type']     = 'website';
		$data['published']   = '';
		$data['modified']    = '';
		$data['object_type'] = 'front';
		$data['object_id']   = $front ? $front->ID : 0;
		$data['url']         = $home_url;
		$data['schema']      = $front ? 'WebPage' : 'CollectionPage';
		return $data;
	}

	/**
	 * Values for a post type archive, e.g. /products/.
	 *
	 * @param string $post_type Post type name.
	 * @param int    $paged     Page number.
	 * @return array|null
	 */
	private function for_post_type_archive( $post_type, $paged ) {
		if ( ! $this->types->supports_post_type( $post_type ) ) {
			return null;
		}
		$object = get_post_type_object( $post_type );
		$vars   = array(
			'type' => $object ? TemplateEngine::plain( $object->labels->name ) : '',
			'page' => $this->page_label( $paged ),
		);
		$link   = get_post_type_archive_link( $post_type );
		$data   = $this->simple( $this->settings->post_type( $post_type, 'archive_title' ), $vars, false );

		$data['description'] = $this->templates->render( $this->settings->post_type( $post_type, 'archive_description' ), $vars );
		$data['canonical']   = $link ? $this->paged_url( $link, $paged ) : '';
		$data['object_type'] = 'archive';
		$data['url']         = $data['canonical'];
		$data['schema']      = 'CollectionPage';
		return $data;
	}

	/**
	 * Values for an author archive.
	 *
	 * @param int $user_id Author ID.
	 * @param int $paged   Page number.
	 * @return array
	 */
	private function for_author( $user_id, $paged ) {
		$group = (array) $this->settings->get( 'author_archive' );
		$vars  = array(
			'author'             => TemplateEngine::plain( get_the_author_meta( 'display_name', $user_id ) ),
			'author_description' => TemplateEngine::truncate( strip_shortcodes( get_the_author_meta( 'description', $user_id ) ) ),
			'page'               => $this->page_label( $paged ),
		);
		$data  = $this->simple( isset( $group['title'] ) ? $group['title'] : '', $vars, ! empty( $group['noindex'] ) );

		$data['description'] = $this->templates->render( isset( $group['description'] ) ? $group['description'] : '', $vars );
		$data['url']         = $this->paged_url( get_author_posts_url( $user_id ), $paged );
		$data['canonical']   = $data['noindex'] ? '' : $data['url'];
		$data['object_type'] = 'author';
		$data['object_id']   = $user_id;
		$data['schema']      = 'ProfilePage';
		return $data;
	}

	/**
	 * Values for a year, month or day archive.
	 *
	 * @param int $paged Page number.
	 * @return array
	 */
	private function for_date_archive( $paged ) {
		$group = (array) $this->settings->get( 'date_archive' );
		$year  = (int) get_query_var( 'year' );
		$month = (int) get_query_var( 'monthnum' );
		$day   = (int) get_query_var( 'day' );

		if ( is_day() ) {
			$label = date_i18n( get_option( 'date_format' ), mktime( 0, 0, 0, $month, $day, $year ) );
			$link  = get_day_link( $year, $month, $day );
		} elseif ( is_month() ) {
			$label = date_i18n( 'F Y', mktime( 0, 0, 0, $month, 1, $year ) );
			$link  = get_month_link( $year, $month );
		} else {
			$label = (string) $year;
			$link  = get_year_link( $year );
		}

		$vars = array(
			'date' => $label,
			'page' => $this->page_label( $paged ),
		);
		$data = $this->simple( isset( $group['title'] ) ? $group['title'] : '', $vars, ! empty( $group['noindex'] ) );

		$data['description'] = $this->templates->render( isset( $group['description'] ) ? $group['description'] : '', $vars );
		$data['url']         = $this->paged_url( $link, $paged );
		$data['canonical']   = $data['noindex'] ? '' : $data['url'];
		$data['object_type'] = 'date';
		$data['schema']      = 'CollectionPage';
		return $data;
	}

	/**
	 * A result with only a title and robots value.
	 *
	 * @param string $template Title template.
	 * @param array  $vars     Template values.
	 * @param bool   $noindex  Whether to noindex.
	 * @return array
	 */
	private function simple( $template, array $vars, $noindex ) {
		return array(
			'title'       => '' === (string) $template ? '' : $this->templates->render( $template, $vars ),
			'description' => '',
			'canonical'   => '',
			'noindex'     => (bool) $noindex,
			'nofollow'    => false,
			'og_type'     => 'website',
			'image'       => (string) $this->settings->get( 'og_default_image' ),
			'published'   => '',
			'modified'    => '',
			'object_type' => '',
			'object_id'   => 0,
			'url'         => '',
			'schema'      => 'WebPage',
		);
	}

	/**
	 * Generated description for a post: excerpt, else the start of the content.
	 *
	 * @param WP_Post $post Post.
	 * @return string
	 */
	private function post_excerpt( WP_Post $post ) {
		if ( '' !== $post->post_password ) {
			return '';
		}
		$text = '' !== trim( $post->post_excerpt ) ? $post->post_excerpt : $post->post_content;
		$text = strip_shortcodes( excerpt_remove_blocks( $text ) );
		return TemplateEngine::truncate( $text );
	}

	/**
	 * "Page 2" label for paginated views, empty on page 1.
	 *
	 * @param int $paged Page number.
	 * @return string
	 */
	private function page_label( $paged ) {
		/* translators: %d: page number */
		return $paged > 1 ? sprintf( __( 'Page %d', 'orbitstem-seo' ), $paged ) : '';
	}

	/**
	 * Adds pagination to an archive URL.
	 *
	 * @param string $base  Page-1 URL.
	 * @param int    $paged Page number.
	 * @return string
	 */
	private function paged_url( $base, $paged ) {
		global $wp_rewrite;
		$base = (string) $base;
		if ( '' === $base || $paged < 2 ) {
			return $base;
		}
		if ( $wp_rewrite->using_permalinks() && false === strpos( $base, '?' ) ) {
			return user_trailingslashit( trailingslashit( $base ) . $wp_rewrite->pagination_base . '/' . $paged, 'paged' );
		}
		return add_query_arg( 'paged', $paged, $base );
	}
}