<?php
/**
 * Optional speed and SEO helpers (front end only).
 *
 * Every switch is off by default and only changes what is sent to visitors;
 * nothing is written to posts, media or settings, so switching an option off
 * restores the default output immediately.
 *
 * Speed:
 * - remove the emoji detection script and styles;
 * - remove the oEmbed discovery links and the wp-embed script;
 * - drop jQuery Migrate from jQuery on the front end;
 * - load Dashicons only for logged-in users;
 * - load scripts with "defer" using WordPress's script loading strategies
 *   (WordPress keeps a script blocking when deferring it would be unsafe).
 *
 * SEO / accessibility:
 * - add alt text to images that have none (from the media title or file name);
 * - add a meta description when no SEO plugin provides one.
 *
 * @package SiteAuditHub
 */

namespace SiteAuditHub;

defined( 'ABSPATH' ) || exit;

/**
 * Speed and SEO switches.
 */
class Speed {

	/**
	 * Scripts that are never deferred (many inline scripts expect jQuery).
	 */
	const NO_DEFER = array( 'jquery', 'jquery-core', 'jquery-migrate' );

	/**
	 * Register hooks for the enabled switches.
	 */
	public static function init() {
		if ( self::on( 'speed_emoji' ) ) {
			self::remove_emoji();
		}
		if ( self::on( 'speed_embeds' ) ) {
			remove_action( 'wp_head', 'wp_oembed_add_discovery_links' );
			remove_action( 'wp_head', 'wp_oembed_add_host_js' );
			add_action( 'wp_footer', array( __CLASS__, 'remove_embed_script' ), 1 );
		}
		if ( self::on( 'speed_jquery_migrate' ) ) {
			add_action( 'wp_default_scripts', array( __CLASS__, 'remove_jquery_migrate' ) );
		}
		if ( self::on( 'speed_dashicons' ) ) {
			add_action( 'wp_enqueue_scripts', array( __CLASS__, 'dashicons_logged_in_only' ), 100 );
		}
		if ( self::on( 'speed_defer_js' ) ) {
			add_action( 'wp_print_scripts', array( __CLASS__, 'defer_scripts' ), 1 );
		}
		if ( self::on( 'fix_alt_text' ) ) {
			add_filter( 'wp_get_attachment_image_attributes', array( __CLASS__, 'attachment_alt' ), 20, 2 );
			add_filter( 'wp_content_img_tag', array( __CLASS__, 'content_img_alt' ), 20, 3 );
		}
		if ( self::on( 'fix_meta_description' ) ) {
			add_action( 'wp_head', array( __CLASS__, 'meta_description' ), 1 );
		}
	}

	/**
	 * Is a switch on?
	 *
	 * @param string $key Setting key.
	 * @return bool
	 */
	private static function on( $key ) {
		return (bool) (int) Settings::get( $key );
	}

	/* ------------------------------------------------------------------ */
	/* Speed                                                               */
	/* ------------------------------------------------------------------ */

	/**
	 * Remove WordPress's emoji script and styles.
	 */
	private static function remove_emoji() {
		remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
		remove_action( 'wp_print_styles', 'print_emoji_styles' );
		remove_action( 'wp_enqueue_scripts', 'wp_enqueue_emoji_styles' );
		remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
		remove_filter( 'comment_text_rss', 'wp_staticize_emoji' );
		remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );
		add_filter( 'emoji_svg_url', '__return_false' ); // Also stops the emoji dns-prefetch hint.
	}


	/**
	 * Remove the wp-embed script.
	 */
	public static function remove_embed_script() {
		wp_dequeue_script( 'wp-embed' );
	}

	/**
	 * Load jQuery without jQuery Migrate on the front end.
	 *
	 * @param \WP_Scripts $scripts Scripts.
	 */
	public static function remove_jquery_migrate( $scripts ) {
		if ( is_admin() || ! is_object( $scripts ) || empty( $scripts->registered['jquery'] ) ) {
			return;
		}
		$scripts->registered['jquery']->deps = array_values( array_diff( (array) $scripts->registered['jquery']->deps, array( 'jquery-migrate' ) ) );
	}

	/**
	 * Remove Dashicons for visitors who are not logged in.
	 */
	public static function dashicons_logged_in_only() {
		if ( ! is_user_logged_in() ) {
			wp_dequeue_style( 'dashicons' );
		}
	}

	/**
	 * Ask WordPress to load queued scripts (and what they depend on) with
	 * "defer". WordPress checks every script and keeps it blocking when an
	 * inline script or a blocking script depends on it.
	 */
	public static function defer_scripts() {
		global $wp_version;
		if ( is_admin() || version_compare( $wp_version, '6.3', '<' ) ) {
			return;
		}
		$scripts = wp_scripts();
		$todo    = (array) $scripts->queue;
		$seen    = array();
		while ( $todo ) {
			$handle = array_shift( $todo );
			if ( isset( $seen[ $handle ] ) || empty( $scripts->registered[ $handle ] ) ) {
				continue;
			}
			$seen[ $handle ] = true;
			$todo            = array_merge( $todo, (array) $scripts->registered[ $handle ]->deps );
			if ( in_array( $handle, self::NO_DEFER, true ) || ! $scripts->registered[ $handle ]->src || $scripts->get_data( $handle, 'strategy' ) ) {
				continue;
			}
			$scripts->add_data( $handle, 'strategy', 'defer' );
		}
	}

	/* ------------------------------------------------------------------ */
	/* SEO / accessibility                                                 */
	/* ------------------------------------------------------------------ */

	/**
	 * Readable text from a media title or file name.
	 *
	 * @param int    $attachment_id Attachment.
	 * @param string $src           Image URL (fallback).
	 * @return string
	 */
	private static function alt_for( $attachment_id, $src = '' ) {
		$text = $attachment_id ? get_the_title( $attachment_id ) : '';
		if ( '' === trim( (string) $text ) && $src ) {
			$file = pathinfo( (string) wp_parse_url( $src, PHP_URL_PATH ), PATHINFO_FILENAME );
			$file = preg_replace( '/-\d+x\d+$|-scaled$|-e\d{10,}$/', '', (string) $file );
			$text = ucfirst( trim( preg_replace( '/[\-_.]+/', ' ', (string) $file ) ) );
		}
		return trim( wp_strip_all_tags( (string) $text ) );
	}

	/**
	 * Images added with WordPress image functions.
	 *
	 * @param array    $attr       Attributes.
	 * @param \WP_Post $attachment Attachment.
	 * @return array
	 */
	public static function attachment_alt( $attr, $attachment ) {
		if ( is_array( $attr ) && ! isset( $attr['alt'] ) && is_object( $attachment ) ) {
			$attr['alt'] = self::alt_for( (int) $attachment->ID, isset( $attr['src'] ) ? $attr['src'] : '' );
		}
		return $attr;
	}

	/**
	 * Images inside post content. Only images without any alt attribute are
	 * changed; alt="" (a decorative image) is respected.
	 *
	 * @param string $tag           Image tag.
	 * @param string $context       Context.
	 * @param int    $attachment_id Attachment.
	 * @return string
	 */
	public static function content_img_alt( $tag, $context, $attachment_id ) {
		if ( ! is_string( $tag ) || preg_match( '/\salt\s*=/i', $tag ) ) {
			return $tag;
		}
		$src = preg_match( '/\ssrc\s*=\s*["\']([^"\']+)["\']/i', $tag, $m ) ? $m[1] : '';
		$alt = self::alt_for( (int) $attachment_id, $src );
		return '' === $alt ? $tag : preg_replace( '/^<img\b/i', '<img alt="' . esc_attr( $alt ) . '"', $tag, 1 );
	}

	/**
	 * Whether an SEO plugin already prints meta descriptions.
	 *
	 * @return string Plugin name, or ''.
	 */
	public static function seo_plugin() {
		$known = array(
			'WPSEO_VERSION'              => 'Yoast SEO',
			'RANK_MATH_VERSION'          => 'Rank Math',
			'AIOSEO_VERSION'             => 'All in One SEO',
			'SEOPRESS_VERSION'           => 'SEOPress',
			'THE_SEO_FRAMEWORK_VERSION'  => 'The SEO Framework',
			'SQUIRRLY_VERSION'           => 'Squirrly SEO',
		);
		foreach ( $known as $constant => $name ) {
			if ( defined( $constant ) ) {
				return $name;
			}
		}
		return '';
	}

	/**
	 * Print a meta description from the excerpt, term description or tagline.
	 */
	public static function meta_description() {
		if ( '' !== self::seo_plugin() ) {
			return;
		}
		$text = '';
		if ( is_singular() ) {
			$post = get_queried_object();
			if ( $post instanceof \WP_Post && ! post_password_required( $post ) ) {
				$text = has_excerpt( $post ) ? $post->post_excerpt : strip_shortcodes( $post->post_content );
			}
		} elseif ( is_front_page() || is_home() ) {
			$text = get_bloginfo( 'description', 'display' );
		} elseif ( is_category() || is_tag() || is_tax() ) {
			$text = term_description();
		} elseif ( is_author() ) {
			$text = get_the_author_meta( 'description', (int) get_query_var( 'author' ) );
		}
		$text = trim( preg_replace( '/\s+/', ' ', wp_strip_all_tags( excerpt_remove_blocks( (string) $text ) ) ) );
		if ( '' === $text ) {
			return;
		}
		if ( function_exists( 'mb_strlen' ) && mb_strlen( $text ) > 155 ) {
			$text = rtrim( mb_substr( $text, 0, 152 ), " ,.;:-" ) . '…';
		}
		echo '<meta name="description" content="' . esc_attr( $text ) . '">' . "\n";
	}
}