<?php
/**
 * Page structure rules.
 *
 * @package A11yMate
 */

namespace A11yMate\Rules\Server;

use A11yMate\Support\Html;

defined( 'ABSPATH' ) || exit;

/**
 * Language, title, headings, landmarks, tables, frames.
 */
class Structure {

	/**
	 * Run the checks.
	 *
	 * @param Context $c Context.
	 * @return void
	 */
	public function run( Context $c ) {
		$html = $c->q( '/html' );
		$body = $c->q( '//body' );
		$root = $html ? $html[0] : null;
		$bod  = $body ? $body[0] : null;

		if ( $root ) {
			$lang = trim( $root->getAttribute( 'lang' ) );
			if ( '' === $lang ) {
				$lang = trim( $root->getAttribute( 'xml:lang' ) );
			}
			if ( '' === $lang ) {
				$c->add( 'html-lang-missing', $root );
			} elseif ( ! preg_match( '/^([a-z]{2,3}|x|i)(-[A-Za-z0-9]{1,8})*$/', $lang ) ) {
				$c->add( 'html-lang-invalid', $root, array( 'lang' => $lang ) );
			}
		}

		$titles = $c->q( '/html/head/title' );
		if ( ! $titles || '' === Html::clean( $titles[0]->textContent ) ) {
			if ( $root ) {
				$head = $c->q( '/html/head' );
				$c->add( 'title-missing', $head ? $head[0] : $root );
			}
		}

		if ( $bod ) {
			$this->headings( $c, $bod );
			if ( ! $c->q( "//main | //*[@role='main']" ) ) {
				$c->add( 'landmark-main-missing', $bod );
			}
			$this->skip_link( $c, $bod );
		}

		$navs = $c->q( "//nav | //*[@role='navigation']" );
		if ( count( $navs ) > 1 ) {
			foreach ( $navs as $nav ) {
				if ( '' === trim( $nav->getAttribute( 'aria-label' ) ) && '' === trim( $nav->getAttribute( 'aria-labelledby' ) ) && ! Html::is_hidden( $nav ) ) {
					$c->add( 'landmark-nav-unlabelled', $nav );
				}
			}
		}

		foreach ( $c->q( "//li[not(ancestor::ul or ancestor::ol or ancestor::menu or ancestor::*[@role='list' or @role='menu' or @role='listbox' or @role='tablist' or @role='tree' or @role='group'])]" ) as $li ) {
			if ( ! Html::is_hidden( $li ) ) {
				$c->add( 'list-orphan-li', $li );
			}
		}

		foreach ( $c->q( '//table' ) as $table ) {
			$role = strtolower( $table->getAttribute( 'role' ) );
			if ( 'presentation' === $role || 'none' === $role || Html::is_hidden( $table ) ) {
				continue;
			}
			$rows = $c->q( './/tr', $table );
			$ths  = $c->q( './/th', $table );
			$tds  = $c->q( './/td', $table );
			if ( ! $ths && count( $rows ) >= 2 && count( $tds ) >= 2 && ! $c->q( ".//*[@role='columnheader' or @role='rowheader']", $table ) ) {
				$c->add( 'table-no-headers', $table );
			}
		}

		foreach ( $c->q( '//iframe' ) as $frame ) {
			if ( '' !== trim( $frame->getAttribute( 'title' ) ) || '' !== trim( $frame->getAttribute( 'aria-label' ) ) || '' !== trim( $frame->getAttribute( 'aria-labelledby' ) ) ) {
				continue;
			}
			if ( 'true' === $frame->getAttribute( 'aria-hidden' ) || '-1' === $frame->getAttribute( 'tabindex' ) || Html::is_hidden( $frame ) ) {
				continue;
			}
			$c->add( 'iframe-title-missing', $frame );
		}

		foreach ( $c->q( "//meta[@name='viewport']" ) as $meta ) {
			$content = strtolower( $meta->getAttribute( 'content' ) );
			$bad     = false;
			if ( preg_match( '/user-scalable\s*=\s*(no|0)/', $content ) ) {
				$bad = true;
			}
			if ( preg_match( '/maximum-scale\s*=\s*([0-9.]+)/', $content, $m ) && (float) $m[1] < 2 ) {
				$bad = true;
			}
			if ( $bad ) {
				$c->add( 'viewport-zoom-disabled', $meta );
			}
		}

		foreach ( $c->q( "//meta[translate(@http-equiv,'REFSH','refsh')='refresh']" ) as $meta ) {
			if ( preg_match( '/^\s*(\d+)/', $meta->getAttribute( 'content' ), $m ) && (int) $m[1] > 0 ) {
				$c->add( 'meta-refresh', $meta, array( 'seconds' => (int) $m[1] ) );
			}
		}

		$this->references( $c );
	}

	/**
	 * Headings.
	 *
	 * @param Context     $c   Context.
	 * @param \DOMElement $bod Body.
	 * @return void
	 */
	private function headings( Context $c, \DOMElement $bod ) {
		$heads = $c->q( '//*[self::h1 or self::h2 or self::h3 or self::h4 or self::h5 or self::h6 or @role="heading"]' );
		$h1s   = 0;
		$prev  = 0;
		foreach ( $heads as $h ) {
			if ( Html::is_hidden( $h ) || 'true' === $h->getAttribute( 'aria-hidden' ) ) {
				continue;
			}
			$tag   = strtolower( $h->tagName );
			$level = (int) substr( $tag, 1 );
			if ( 'h' !== $tag[0] || strlen( $tag ) !== 2 ) {
				$level = (int) $h->getAttribute( 'aria-level' );
				if ( $level < 1 ) {
					$level = 2;
				}
			}
			if ( 1 === $level ) {
				++$h1s;
			}
			if ( '' === trim( Html::clean( Html::text_of( $h ) ) ) && '' === trim( $h->getAttribute( 'aria-label' ) ) ) {
				$c->add( 'heading-empty', $h );
				continue;
			}
			if ( $prev > 0 && $level > $prev + 1 ) {
				$c->add(
					'heading-skipped',
					$h,
					array(
						'from' => $prev,
						'to'   => $level,
					)
				);
			}
			$prev = $level;
		}
		if ( 0 === $h1s ) {
			$c->add( 'h1-missing', $bod );
		}
	}

	/**
	 * Skip link.
	 *
	 * @param Context     $c   Context.
	 * @param \DOMElement $bod Body.
	 * @return void
	 */
	private function skip_link( Context $c, \DOMElement $bod ) {
		// WordPress 6.4+ adds its own skip link with JavaScript, so look for its script.
		if ( $c->xp->query( "//script[contains(@id,'skip-link')]" )->length ) {
			return;
		}
		$links = $c->q( "//body//a[starts-with(@href,'#') and string-length(@href) > 1]" );
		$n     = 0;
		foreach ( $links as $a ) {
			++$n;
			if ( $n > 12 ) {
				break;
			}
			$text = strtolower( Html::clean( Html::text_of( $a ) ) . ' ' . $a->getAttribute( 'aria-label' ) );
			if ( preg_match( '/skip|jump to|go to (the )?(main|content)|main content/', $text ) ) {
				return;
			}
		}
		$c->add( 'skip-link-missing', $bod );
	}

	/**
	 * ARIA and label references.
	 *
	 * @param Context $c Context.
	 * @return void
	 */
	private function references( Context $c ) {
		$ids    = array();
		$counts = array();
		foreach ( $c->q( '//*[@id]' ) as $el ) {
			$id            = $el->getAttribute( 'id' );
			$ids[ $id ]    = true;
			$counts[ $id ] = isset( $counts[ $id ] ) ? $counts[ $id ] + 1 : 1;
		}
		$referenced = array();
		foreach ( $c->q( '//*[@aria-labelledby or @aria-describedby]' ) as $el ) {
			foreach ( array( 'aria-labelledby', 'aria-describedby' ) as $attr ) {
				if ( ! $el->hasAttribute( $attr ) ) {
					continue;
				}
				foreach ( preg_split( '/\s+/', trim( $el->getAttribute( $attr ) ) ) as $id ) {
					if ( '' === $id ) {
						continue;
					}
					$referenced[ $id ] = true;
					if ( ! isset( $ids[ $id ] ) && ! Html::is_hidden( $el ) ) {
						$c->add(
							'aria-ref-missing-id',
							$el,
							array(
								'attribute' => $attr,
								'id'        => $id,
							)
						);
					}
				}
			}
		}
		foreach ( $c->q( '//label[@for]' ) as $label ) {
			$for = $label->getAttribute( 'for' );
			if ( '' !== $for ) {
				$referenced[ $for ] = true;
				if ( ! isset( $ids[ $for ] ) && ! Html::is_hidden( $label ) ) {
					$c->add(
						'aria-ref-missing-id',
						$label,
						array(
							'attribute' => 'for',
							'id'        => $for,
						)
					);
				}
			}
		}
		foreach ( $referenced as $id => $_ ) {
			if ( isset( $counts[ $id ] ) && $counts[ $id ] > 1 ) {
				$dups = $c->q( '//*[@id=' . Html::xpath_literal( $id ) . ']' );
				if ( count( $dups ) > 1 ) {
					$c->add( 'id-duplicate-referenced', $dups[1], array( 'id' => $id ) );
				}
			}
		}
	}
}