<?php
/**
 * Escaping of the template markup.
 *
 * @package HeadFoot
 */

namespace HeadFoot;

defined( 'ABSPATH' ) || exit;

/**
 * Passes the template markup through wp_kses() before WordPress prints it.
 *
 * The shortcode and the block theme integration return markup to WordPress
 * instead of printing it. This class escapes that markup. The list of
 * permitted elements is the list for post content plus the elements that
 * Elementor widgets print: inline SVG icons, iframes, forms, and pictures.
 *
 * Script elements do not pass. The CSS of a style element goes to
 * wp_add_inline_style() when the CSS holds no "<" character, and WordPress
 * prints it with the other styles. The returned markup holds no style element.
 */
class Kses {

	/**
	 * Attributes that every element can carry.
	 *
	 * @var array
	 */
	const GLOBAL_ATTRIBUTES = [
		'aria-atomic',
		'aria-busy',
		'aria-checked',
		'aria-controls',
		'aria-current',
		'aria-describedby',
		'aria-details',
		'aria-disabled',
		'aria-expanded',
		'aria-haspopup',
		'aria-hidden',
		'aria-invalid',
		'aria-label',
		'aria-labelledby',
		'aria-level',
		'aria-live',
		'aria-modal',
		'aria-orientation',
		'aria-owns',
		'aria-posinset',
		'aria-pressed',
		'aria-required',
		'aria-roledescription',
		'aria-selected',
		'aria-setsize',
		'aria-valuemax',
		'aria-valuemin',
		'aria-valuenow',
		'aria-valuetext',
		'class',
		'content',
		'data-*',
		'dir',
		'hidden',
		'id',
		'itemprop',
		'itemscope',
		'itemtype',
		'lang',
		'role',
		'style',
		'tabindex',
		'title',
	];

	/**
	 * Presentation attributes of the SVG shape elements.
	 *
	 * @var array
	 */
	const SVG_ATTRIBUTES = [
		'clip-path',
		'clip-rule',
		'fill',
		'fill-opacity',
		'fill-rule',
		'mask',
		'opacity',
		'stroke',
		'stroke-dasharray',
		'stroke-dashoffset',
		'stroke-linecap',
		'stroke-linejoin',
		'stroke-miterlimit',
		'stroke-opacity',
		'stroke-width',
		'transform',
	];

	/**
	 * Elements that the list for post content does not have, or has with fewer attributes.
	 *
	 * The names are in lowercase, because wp_kses() compares them in lowercase.
	 * The attribute viewBox is viewbox here.
	 *
	 * @var array
	 */
	const ELEMENTS = [
		'img'            => [ 'srcset', 'sizes', 'decoding', 'fetchpriority' ],
		'video'          => [ 'controlslist', 'disablepictureinpicture' ],
		'meta'           => [],
		'picture'        => [],
		'source'         => [ 'src', 'srcset', 'sizes', 'type', 'media', 'width', 'height' ],
		'noscript'       => [],
		'canvas'         => [ 'width', 'height' ],
		'iframe'         => [ 'src', 'width', 'height', 'name', 'frameborder', 'allow', 'allowfullscreen', 'loading', 'referrerpolicy', 'sandbox' ],
		'form'           => [ 'action', 'method', 'name', 'target', 'novalidate', 'autocomplete', 'enctype', 'accept-charset' ],
		'input'          => [ 'type', 'name', 'value', 'placeholder', 'required', 'checked', 'disabled', 'readonly', 'min', 'max', 'step', 'pattern', 'autocomplete', 'size', 'maxlength', 'minlength', 'multiple', 'accept', 'inputmode', 'list' ],
		'select'         => [ 'name', 'required', 'disabled', 'multiple', 'size', 'autocomplete' ],
		'option'         => [ 'value', 'selected', 'disabled', 'label' ],
		'optgroup'       => [ 'label', 'disabled' ],
		'textarea'       => [ 'name', 'rows', 'cols', 'placeholder', 'required', 'disabled', 'readonly', 'maxlength', 'minlength', 'autocomplete' ],
		'datalist'       => [],
		'output'         => [ 'for', 'name' ],
		'svg'            => [ 'xmlns', 'xmlns:xlink', 'viewbox', 'width', 'height', 'x', 'y', 'version', 'preserveaspectratio', 'focusable', 'xml:space' ],
		'g'              => [],
		'path'           => [ 'd' ],
		'circle'         => [ 'cx', 'cy', 'r' ],
		'ellipse'        => [ 'cx', 'cy', 'rx', 'ry' ],
		'rect'           => [ 'x', 'y', 'width', 'height', 'rx', 'ry' ],
		'line'           => [ 'x1', 'y1', 'x2', 'y2' ],
		'polyline'       => [ 'points' ],
		'polygon'        => [ 'points' ],
		'defs'           => [],
		'symbol'         => [ 'viewbox', 'preserveaspectratio' ],
		'use'            => [ 'href', 'xlink:href', 'x', 'y', 'width', 'height' ],
		'title'          => [],
		'desc'           => [],
		'lineargradient' => [ 'x1', 'y1', 'x2', 'y2', 'gradientunits', 'gradienttransform' ],
		'radialgradient' => [ 'cx', 'cy', 'r', 'fx', 'fy', 'gradientunits', 'gradienttransform' ],
		'stop'           => [ 'offset', 'stop-color', 'stop-opacity' ],
		'clippath'       => [ 'clippathunits' ],
		'text'           => [ 'x', 'y', 'dx', 'dy', 'text-anchor', 'font-family', 'font-size', 'font-weight' ],
		'tspan'          => [ 'x', 'y', 'dx', 'dy' ],
		'textpath'       => [ 'href', 'xlink:href', 'startoffset' ],
	];

	/**
	 * SVG elements that take the presentation attributes.
	 *
	 * @var array
	 */
	const SVG_SHAPES = [ 'svg', 'g', 'path', 'circle', 'ellipse', 'rect', 'line', 'polyline', 'polygon', 'use', 'text', 'tspan', 'textpath' ];

	/**
	 * Handle of the registered style that carries the CSS of the style elements.
	 *
	 * @var string
	 */
	const STYLE_HANDLE = 'headfoot-inline';

	/**
	 * The list of permitted elements, built once per request.
	 *
	 * @var array|null
	 */
	private static $allowed = null;

	/**
	 * Returns the elements and attributes that pass.
	 *
	 * @return array element => [ attribute => true ]
	 */
	public static function allowed_html() {
		if ( null !== self::$allowed ) {
			return self::$allowed;
		}

		$allowed = wp_kses_allowed_html( 'post' );

		foreach ( self::ELEMENTS as $element => $attributes ) {
			$current             = isset( $allowed[ $element ] ) && is_array( $allowed[ $element ] ) ? $allowed[ $element ] : [];
			$allowed[ $element ] = $current + array_fill_keys( $attributes, true );
		}

		foreach ( self::SVG_SHAPES as $element ) {
			$allowed[ $element ] += array_fill_keys( self::SVG_ATTRIBUTES, true );
		}

		$global = array_fill_keys( self::GLOBAL_ATTRIBUTES, true );

		foreach ( $allowed as $element => $attributes ) {
			$allowed[ $element ] = ( is_array( $attributes ) ? $attributes : [] ) + $global;
		}

		/**
		 * Filters the elements and attributes that pass in template markup.
		 *
		 * @param array $allowed element => [ attribute => true ], with all names in lowercase.
		 */
		$allowed = apply_filters( 'headfoot_kses_allowed_html', $allowed );

		self::$allowed = is_array( $allowed ) ? $allowed : [];

		return self::$allowed;
	}

	/**
	 * Escapes template markup.
	 *
	 * The CSS of each style element goes to wp_add_inline_style(). The return
	 * value holds no style element.
	 *
	 * @param string $html Markup from Elementor.
	 * @return string
	 */
	public static function filter( $html ) {
		$html = (string) $html;

		if ( '' === $html ) {
			return '';
		}

		// wp_kses() removes a tag but keeps the text inside it, so a script
		// element goes away together with its source.
		$without_scripts = preg_replace( '#<script\b[^>]*>.*?</script\s*>#is', '', $html );

		if ( is_string( $without_scripts ) ) {
			$html = $without_scripts;
		}

		// wp_kses() changes ">" and "&" in text, and that breaks CSS. The parts
		// around each style element go through wp_kses() on their own.
		$parts = preg_split( '#<style\b[^>]*>(.*?)</style\s*>#is', $html, -1, PREG_SPLIT_DELIM_CAPTURE );

		if ( ! is_array( $parts ) ) {
			return wp_kses( $html, self::allowed_html() );
		}

		$allowed = self::allowed_html();
		$output  = '';

		foreach ( $parts as $index => $part ) {
			if ( 0 === $index % 2 ) {
				$output .= wp_kses( $part, $allowed );
				continue;
			}

			// CSS without "<" cannot close the style element or open another one.
			if ( '' !== trim( $part ) && false === strpos( $part, '<' ) ) {
				self::add_inline_style( $part );
			}
		}

		return $output;
	}

	/**
	 * Hands the CSS of a style element to WordPress.
	 *
	 * WordPress prints the CSS in the head when the call comes before wp_head(),
	 * and with the late styles in the footer after that. A handle that WordPress
	 * printed already takes no more CSS, so the next handle gets a number.
	 *
	 * @param string $css CSS without "<".
	 * @return void
	 */
	private static function add_inline_style( $css ) {
		$handle = self::STYLE_HANDLE;
		$count  = 1;

		while ( wp_style_is( $handle, 'done' ) ) {
			++$count;
			$handle = self::STYLE_HANDLE . '-' . $count;
		}

		if ( ! wp_style_is( $handle, 'registered' ) ) {
			wp_register_style( $handle, false, [], HEADFOOT_VERSION );
		}

		wp_enqueue_style( $handle );
		wp_add_inline_style( $handle, $css );
	}

	/**
	 * Clears the cached list. Tests use this.
	 *
	 * @return void
	 */
	public static function reset() {
		self::$allowed = null;
	}
}