<?php
/**
 * Outputs <title> and <meta name="description"> tags in the <head>.
 *
 * @package S1_SEO_Meta
 */

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

class S1_SEO_Meta_Output {

	public function __construct() {
		// Output meta tags as early as possible in wp_head.
		add_action( 'wp_head', array( $this, 'output_meta_tags' ), 1 );

		// Override the document <title> tag via wp_title (classic themes).
		add_filter( 'wp_title', array( $this, 'filter_wp_title' ), 20, 1 );

		// Override the document <title> tag via document_title_parts (block / modern themes).
		add_filter( 'document_title_parts', array( $this, 'filter_document_title_parts' ), 20 );
	}

	/**
	 * Determine the SEO title and description for the current page and echo them.
	 */
	public function output_meta_tags() {
		$seo_title = $this->get_current_title();
		$seo_desc  = $this->get_current_description();

		if ( $seo_desc ) {
			echo '<meta name="description" content="' . esc_attr( $seo_desc ) . '" />' . "\n";
		}
	}

	/**
	 * Filter wp_title() for classic themes that use it.
	 *
	 * @param string $title Current title string.
	 * @return string
	 */
	public function filter_wp_title( $title ) {
		$seo_title = $this->get_current_title();
		return $seo_title ? $seo_title : $title;
	}

	/**
	 * Filter document_title_parts for modern themes that use add_theme_support('title-tag').
	 *
	 * @param array $parts Title parts array.
	 * @return array
	 */
	public function filter_document_title_parts( $parts ) {
		$seo_title = $this->get_current_title();

		if ( $seo_title ) {
			// Replace the 'title' part; remove 'site' to avoid duplication.
			$parts['title'] = $seo_title;
			unset( $parts['tagline'], $parts['site'] );
		}

		return $parts;
	}

	// -------------------------------------------------------------------------
	// Helpers
	// -------------------------------------------------------------------------

	/**
	 * Return the SEO title for whatever is currently being displayed.
	 *
	 * @return string Empty string when no custom title is set.
	 */
	private function get_current_title() {
		if ( is_singular() ) {
			return S1_SEO_Meta_Post::get_title( get_the_ID() );
		}

		if ( is_category() || is_tag() || is_tax() ) {
			$term = get_queried_object();
			if ( $term instanceof WP_Term ) {
				return S1_SEO_Meta_Term::get_title( $term->term_id );
			}
		}

		return '';
	}

	/**
	 * Return the SEO description for whatever is currently being displayed.
	 *
	 * @return string Empty string when no custom description is set.
	 */
	private function get_current_description() {
		if ( is_singular() ) {
			return S1_SEO_Meta_Post::get_description( get_the_ID() );
		}

		if ( is_category() || is_tag() || is_tax() ) {
			$term = get_queried_object();
			if ( $term instanceof WP_Term ) {
				return S1_SEO_Meta_Term::get_description( $term->term_id );
			}
		}

		return '';
	}
}