<?php
/**
 * Front-end repairs.
 *
 * This is what separates the plugin from an overlay: wherever a fix can be made
 * in PHP it is made in the real markup before the page is sent, not patched in
 * the visitor's browser afterwards. Only the repairs that genuinely require the
 * rendered DOM (measuring overflow, finding orphaned inputs) run as JavaScript,
 * and those are additive — they add missing labels, they never restructure the
 * page.
 *
 * Every repair is opt-in and independently reversible. Turning one off restores
 * the original output exactly, because nothing here writes to the database or
 * modifies stored content.
 *
 * @package AccessVane
 */

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

/**
 * Applies the enabled repairs to the front end.
 */
class AccessVane_Fixes {

	/**
	 * Hook registration.
	 *
	 * @return void
	 */
	public function register() {
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue_assets' ) );
		add_action( 'wp_body_open', array( $this, 'print_skip_link' ), 1 );

		if ( AccessVane_Settings::enabled( 'fix_image_alt' ) ) {
			add_filter( 'wp_get_attachment_image_attributes', array( $this, 'fill_attachment_alt' ), 10, 2 );
		}

		if ( AccessVane_Settings::enabled( 'fix_iframe_titles' ) ) {
			add_filter( 'embed_oembed_html', array( $this, 'title_oembed' ), 10, 2 );
			add_filter( 'video_embed_html', array( $this, 'title_generic_embed' ) );
		}

		if ( AccessVane_Settings::enabled( 'fix_lang_attribute' ) ) {
			add_filter( 'language_attributes', array( $this, 'ensure_language_attribute' ) );
		}
	}

	/**
	 * Whether any repair needing the browser is switched on.
	 *
	 * @return bool
	 */
	private function needs_script() {
		// fix_skip_link is in this list because the link's target has to be
		// resolved against the rendered page: a guessed id that does not exist
		// produces a skip link that goes nowhere, which is worse than none.
		foreach ( array( 'fix_skip_link', 'fix_scrollable_focus', 'fix_landmark_labels', 'fix_form_labels', 'fix_iframe_titles', 'fix_viewport_zoom' ) as $key ) {
			if ( AccessVane_Settings::enabled( $key ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Whether any repair needs a stylesheet.
	 *
	 * @return bool
	 */
	private function needs_style() {
		foreach ( array( 'fix_skip_link', 'fix_focus_visible', 'fix_link_underline' ) as $key ) {
			if ( AccessVane_Settings::enabled( $key ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Load the front-end script only when something actually needs it.
	 *
	 * @return void
	 */
	public function enqueue_assets() {
		$css = $this->build_css();

		if ( '' !== $css ) {
			// There is no stylesheet to ship: every rule is generated from the
			// site owner's repair settings. Registering the handle with no
			// source gives wp_add_inline_style() something to attach to without
			// adding a request.
			wp_register_style( 'accessvane-fixes', false, array(), ACCESSVANE_VERSION );
			wp_enqueue_style( 'accessvane-fixes' );
			wp_add_inline_style( 'accessvane-fixes', $css );
		}

		if ( ! $this->needs_script() ) {
			return;
		}

		wp_enqueue_script(
			'accessvane-fixes',
			ACCESSVANE_URL . 'assets/js/fixes.js',
			array(),
			ACCESSVANE_VERSION,
			true
		);

		wp_localize_script(
			'accessvane-fixes',
			'accessVaneFixes',
			array(
				'skipLink'        => AccessVane_Settings::enabled( 'fix_skip_link' ),
				'scrollableFocus' => AccessVane_Settings::enabled( 'fix_scrollable_focus' ),
				'landmarkLabels'  => AccessVane_Settings::enabled( 'fix_landmark_labels' ),
				'formLabels'      => AccessVane_Settings::enabled( 'fix_form_labels' ),
				'iframeTitles'    => AccessVane_Settings::enabled( 'fix_iframe_titles' ),
				'strings'         => array(
					'scrollableRegion' => __( 'Scrollable content', 'accessvane' ),
					'embeddedContent'  => __( 'Embedded content', 'accessvane' ),
					'primaryNav'       => __( 'Primary', 'accessvane' ),
					'secondaryNav'     => __( 'Secondary', 'accessvane' ),
					// A screen reader announces these to the visitor, so leaving
					// them in English gave half-translated names like
					// "Footer navigasjon" on a translated site.
					'footerNav'        => __( 'Footer', 'accessvane' ),
					'headerNav'        => __( 'Header', 'accessvane' ),
					'sidebarNav'       => __( 'Sidebar', 'accessvane' ),
					'navSuffix'        => __( 'navigation', 'accessvane' ),
				),
			)
		);

		if ( AccessVane_Settings::enabled( 'fix_viewport_zoom' ) ) {
			// Attached to the footer script rather than printed into the head.
			// That is also the more correct moment: the theme's own viewport tag
			// exists in the DOM by then, so it can actually be rewritten instead
			// of being printed after us and winning.
			wp_add_inline_script( 'accessvane-fixes', $this->viewport_unlock_js() );
		}
	}

	/**
	 * Build the small stylesheet the CSS-only repairs need.
	 *
	 * Added inline rather than shipped as a file: it is well under a kilobyte,
	 * and a separate request for that would be a worse trade than the extra
	 * bytes in the document.
	 *
	 * @return string
	 */
	private function build_css() {
		if ( ! $this->needs_style() ) {
			return '';
		}

		$css = '';

		if ( AccessVane_Settings::enabled( 'fix_skip_link' ) ) {
			// Positioned off-screen rather than display:none — a hidden element
			// cannot receive keyboard focus, which would defeat the entire point
			// of a skip link.
			$css .= '.accessvane-skip-link{position:absolute;left:-9999px;top:0;z-index:100000;padding:12px 20px;background:#000;color:#fff;font:600 16px/1.2 system-ui,sans-serif;text-decoration:underline;border-radius:0 0 6px 0}';
			$css .= '.accessvane-skip-link:focus,.accessvane-skip-link:focus-visible{left:0}';
		}

		if ( AccessVane_Settings::enabled( 'fix_focus_visible' ) ) {
			$color = AccessVane_Settings::get( 'focus_ring_color', '#0b63ce' );
			$width = (int) AccessVane_Settings::get( 'focus_ring_width', 3 );

			// :focus-visible only, so the ring appears for keyboard users and
			// not on every mouse click — which is the reason themes strip focus
			// styles in the first place.
			$css .= sprintf(
				'a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible,summary:focus-visible,[tabindex]:focus-visible{outline:%1$dpx solid %2$s !important;outline-offset:2px !important;box-shadow:0 0 0 %3$dpx #fff !important}',
				$width,
				$color,
				max( 1, $width - 1 )
			);
		}

		if ( AccessVane_Settings::enabled( 'fix_link_underline' ) ) {
			// Scoped to body copy only. Underlining every link on the site would
			// wreck menus, buttons and image links.
			$css .= '.entry-content a:not([class]),.post-content a:not([class]),.page-content a:not([class]),.wp-block-post-content a:not([class]){text-decoration:underline;text-underline-offset:2px}';
		}

		// Settings are sanitised on save; this is belt-and-braces against a
		// stored value that somehow carries markup.
		return wp_strip_all_tags( $css );
	}

	/**
	 * Print the skip link as the first thing inside <body>.
	 *
	 * @return void
	 */
	public function print_skip_link() {
		if ( ! AccessVane_Settings::enabled( 'fix_skip_link' ) ) {
			return;
		}

		$target = AccessVane_Settings::sanitize_fragment( AccessVane_Settings::get( 'skip_link_target', '#content' ) );
		$text   = trim( (string) AccessVane_Settings::get( 'skip_link_text', '' ) );

		if ( '' === $text ) {
			$text = __( 'Skip to main content', 'accessvane' );
		}

		printf(
			'<a class="accessvane-skip-link" href="%1$s">%2$s</a>',
			esc_attr( $target ),
			esc_html( $text )
		);
	}

	/**
	 * Allow pinch-zoom regardless of what the theme asked for.
	 *
	 * The theme's own viewport tag is left in place and overridden from
	 * JavaScript, because rewriting another plugin's wp_head output would mean
	 * buffering the whole head — far more intrusive than this.
	 *
	 * @return string
	 */
	private function viewport_unlock_js() {
		return <<<'JS'
(function(){
var tag=document.querySelector('meta[name="viewport"]');
if(!tag){tag=document.createElement('meta');tag.setAttribute('name','viewport');document.head.appendChild(tag);}
var content=tag.getAttribute('content')||'';
content=content.replace(/,?\s*user-scalable\s*=\s*(no|0)/gi,'').replace(/,?\s*maximum-scale\s*=\s*[0-9.]+/gi,'');
if(!/width\s*=/i.test(content)){content='width=device-width'+(content?', '+content:'');}
tag.setAttribute('content',content.replace(/^\s*,\s*/,'').trim()+', maximum-scale=5, user-scalable=yes');
})();
JS;
	}

	/**
	 * Guarantee the html element carries a language.
	 *
	 * @param string $output Existing attributes.
	 * @return string
	 */
	public function ensure_language_attribute( $output ) {
		if ( false !== stripos( (string) $output, 'lang=' ) ) {
			return $output;
		}

		$locale = get_bloginfo( 'language' );

		if ( ! $locale ) {
			$locale = 'en';
		}

		return trim( $output . ' lang="' . esc_attr( $locale ) . '"' );
	}

	/**
	 * Supply alt text for attachments that have none.
	 *
	 * Falls back to the image's own caption, then its title — never the file
	 * name, which is noise rather than a description. If nothing usable exists
	 * the alt is set to empty, which marks the image decorative; that is a
	 * defensible default and is far better than a missing attribute, but the
	 * Alt Text screen exists because a real description is better still.
	 *
	 * @param array   $attr       Image attributes.
	 * @param WP_Post $attachment Attachment post.
	 * @return array
	 */
	public function fill_attachment_alt( $attr, $attachment ) {
		if ( isset( $attr['alt'] ) && '' !== trim( $attr['alt'] ) ) {
			return $attr;
		}

		if ( ! $attachment instanceof WP_Post ) {
			$attr['alt'] = '';

			return $attr;
		}

		$caption = trim( (string) $attachment->post_excerpt );
		$title   = trim( (string) $attachment->post_title );

		if ( '' !== $caption ) {
			$attr['alt'] = $caption;

			return $attr;
		}

		// A title that is just the uploaded file name describes nothing.
		if ( '' !== $title && ! $this->looks_like_filename( $title ) ) {
			$attr['alt'] = $title;

			return $attr;
		}

		$attr['alt'] = '';

		return $attr;
	}

	/**
	 * Detect titles WordPress generated from a file name.
	 *
	 * @param string $title Attachment title.
	 * @return bool
	 */
	private function looks_like_filename( $title ) {
		if ( preg_match( '/\.(jpe?g|png|gif|webp|avif|svg|bmp|tiff?)$/i', $title ) ) {
			return true;
		}

		// IMG_1234, DSC00042, screenshot-2026-08-24-at-10-04-11, 20260824123456.
		if ( preg_match( '/^(img|dsc|dscn|pxl|photo|image|screenshot|screen[ _-]?shot|untitled)[ _-]?\d*/i', $title ) ) {
			return true;
		}

		if ( preg_match( '/^\d{6,}$/', $title ) ) {
			return true;
		}

		return false;
	}

	/**
	 * Give oEmbed iframes a title naming what they contain.
	 *
	 * @param string $html Embed markup.
	 * @param string $url  Embedded URL.
	 * @return string
	 */
	public function title_oembed( $html, $url ) {
		if ( ! is_string( $html ) || false === stripos( $html, '<iframe' ) ) {
			return $html;
		}

		if ( preg_match( '/<iframe[^>]*\stitle\s*=\s*["\'][^"\']+["\']/i', $html ) ) {
			return $html;
		}

		$host  = wp_parse_url( (string) $url, PHP_URL_HOST );
		$host  = $host ? preg_replace( '/^www\./i', '', $host ) : '';
		$label = $host
			/* translators: %s: the website an embed comes from, for example youtube.com. */
			? sprintf( __( 'Embedded content from %s', 'accessvane' ), $host )
			: __( 'Embedded content', 'accessvane' );

		return preg_replace(
			'/<iframe/i',
			'<iframe title="' . esc_attr( $label ) . '"',
			$html,
			1
		);
	}

	/**
	 * Give any other embedded iframe a generic title.
	 *
	 * @param string $html Embed markup.
	 * @return string
	 */
	public function title_generic_embed( $html ) {
		return $this->title_oembed( $html, '' );
	}
}