<?php
/**
 * The companion file to shortcodes.php
 *
 * This file contains the code that converts HTML embeds into shortcodes
 * for when the user copy/pastes in HTML.
 */

add_filter( 'pre_kses', array( 'Filter_Embedded_HTML_Objects', 'filter' ), 11 );
add_filter( 'pre_kses', array( 'Filter_Embedded_HTML_Objects', 'maybe_create_links' ), 100 ); // See WPCom_Embed_Stats::init()

/**
 * Helper class for identifying and parsing known HTML blocks
 *
 * @since 4.5.0
 *
 * @author mdawaffe
 *
 * Not completely done, but seems to work okay
 * Stolen from Mike's Seaside presentation:
 * @link http://mdawaffepresents.wordpress.com/?p=36
 */

class Filter_Embedded_HTML_Objects {
	static public $strpos_filters = array();
	static public $regexp_filters = array();
	static public $current_element = false;
	static public $html_strpos_filters = array();
	static public $html_regexp_filters = array();
	static public $failed_embeds = array();

	/**
	 * Store tokens found in Syntax Highlighter.
	 *
	 * @since 4.5.0
	 *
	 * @var array
	 */
	static private $sh_unfiltered_content_tokens;

	/**
	 * Capture tokens found in Syntax Highlighter and collect them in self::$sh_unfiltered_content_tokens.
	 *
	 * @since 4.5.0
	 *
	 * @param array $match
	 *
	 * @return string
	 */
	static public function sh_regexp_callback( $match ) {
		$token = '[prekses-filter-token-' . mt_rand() . '-' . md5( $match[0] ) . '-' . mt_rand() . ']';
		self::$sh_unfiltered_content_tokens[$token] = $match[0];
		return $token;
	}

	static public function filter( $html ) {
		if ( ! $html || ! is_string( $html ) ) {
			return $html;
		}

		$regexps = array(
			'object' => '%<object[^>]*+>(?>[^<]*+(?><(?!/object>)[^<]*+)*)</object>%i',
			'embed'  => '%<embed[^>]*+>(?:\s*</embed>)?%i',
			'iframe' => '%<iframe[^>]*+>(?>[^<]*+(?><(?!/iframe>)[^<]*+)*)</iframe>%i',
			'div'    => '%<div[^>]*+>(?>[^<]*+(?><(?!/div>)[^<]*+)*+)(?:</div>)+%i',
			'script' => '%<script[^>]*+>(?>[^<]*+(?><(?!/script>)[^<]*+)*)</script>%i',
		);

		$unfiltered_content_tokens = array();
		self::$sh_unfiltered_content_tokens = array();

		// Check here to make sure that SyntaxHighlighter is still used. (Just a little future proofing)
		if ( class_exists( 'SyntaxHighlighter' ) ) {
			// Replace any "code" shortcode blocks with a token that we'll later replace with its original text.
			// This will keep the contents of the shortcode from being filtered

			global $SyntaxHighlighter;

			// Check to see if the $SyntaxHighlighter object has been created and is ready for use
			if ( isset( $SyntaxHighlighter ) && is_array( $SyntaxHighlighter->shortcodes ) ) {
				$shortcode_regex = implode( '|', array_map( 'preg_quote', $SyntaxHighlighter->shortcodes ) );
				$html            = preg_replace_callback(
					'/\[(' . $shortcode_regex . ')(\s[^\]]*)?\][\s\S]*?\[\/\1\]/m', array( __CLASS__, 'sh_regexp_callback' ), $html
				);
				$unfiltered_content_tokens = self::$sh_unfiltered_content_tokens;
			}
		}

		foreach ( $regexps as $element => $regexp ) {
			self::$current_element = $element;

			if ( false !== stripos( $html, "<$element" ) ) {
				if ( $new_html = preg_replace_callback( $regexp, array( __CLASS__, 'dispatch' ), $html ) ) {
					$html = $new_html;
				}
			}

			if ( false !== stripos( $html, "&lt;$element" ) ) {
				$regexp_entities = self::regexp_entities( $regexp );
				if ( $new_html = preg_replace_callback( $regexp_entities, array( __CLASS__, 'dispatch_entities' ), $html ) ) {
					$html = $new_html;
				}
			}
		}

		if ( count( $unfiltered_content_tokens ) > 0 ) {
			// Replace any tokens generated earlier with their original unfiltered text
			$html = str_replace( array_keys( $unfiltered_content_tokens ), $unfiltered_content_tokens, $html );
		}

		return $html;
	}

	static public function regexp_entities( $regexp ) {
		return preg_replace(
			'/\[\^&([^\]]+)\]\*\+/',
			'(?>[^&]*+(?>&(?!\1)[^&])*+)*+',
			str_replace( '?&gt;', '?' . '>', htmlspecialchars( $regexp, ENT_NOQUOTES ) )
		);
	}

	static public function register( $match, $callback, $is_regexp = false, $is_html_filter = false ) {
		if ( $is_html_filter ) {
			if ( $is_regexp ) {
				self::$html_regexp_filters[$match] = $callback;
			} else {
				self::$html_strpos_filters[$match] = $callback;
			}
		} else {
			if ( $is_regexp ) {
				self::$regexp_filters[$match] = $callback;
			} else {
				self::$strpos_filters[$match] = $callback;
			}
		}
	}

	static public function unregister( $match ) {
		// Allow themes/plugins to remove registered embeds
		unset( self::$regexp_filters[$match] );
		unset( self::$strpos_filters[$match] );
		unset( self::$html_regexp_filters[$match] );
		unset( self::$html_strpos_filters[$match] );
	}

	static function dispatch_entities( $matches ) {
		$matches[0] = html_entity_decode( $matches[0] );

		return self::dispatch( $matches );
	}

	static function dispatch( $matches ) {
		$html  = preg_replace( '%&#0*58;//%', '://', $matches[0] );
		$attrs = self::get_attrs( $html );
		if ( isset( $attrs['src'] ) ) {
			$src = $attrs['src'];
		} else if ( isset( $attrs['movie'] ) ) {
			$src = $attrs['movie'];
		} else {
			// no src found, search html
			foreach ( self::$html_strpos_filters as $match => $callback ) {
				if ( false !== strpos( $html, $match ) ) {
					return call_user_func( $callback, $attrs );
				}
			}

			foreach ( self::$html_regexp_filters as $match => $callback ) {
				if ( preg_match( $match, $html ) ) {
					return call_user_func( $callback, $attrs );
				}
			}

			return $matches[0];
		}

		$src = trim( $src );

		// check source filter
		foreach ( self::$strpos_filters as $match => $callback ) {
			if ( false !== strpos( $src, $match ) ) {
				return call_user_func( $callback, $attrs );
			}
		}

		foreach ( self::$regexp_filters as $match => $callback ) {
			if ( preg_match( $match, $src ) ) {
				return call_user_func( $callback, $attrs );
			}
		}

		// check html filters
		foreach ( self::$html_strpos_filters as $match => $callback ) {
			if ( false !== strpos( $html, $match ) ) {
				return call_user_func( $callback, $attrs );
			}
		}

		foreach ( self::$html_regexp_filters as $match => $callback ) {
			if ( preg_match( $match, $html ) ) {
				return call_user_func( $callback, $attrs );
			}
		}

		// Log the strip
		if ( function_exists( 'wp_kses_reject' ) ) {
			wp_kses_reject( sprintf( __( '<code>%s</code> HTML tag removed as it is not allowed', 'jetpack' ), '&lt;' . self::$current_element . '&gt;' ), array( self::$current_element => $attrs ) );
		}

		// Keep the failed match so we can later replace it with a link,
		// but return the original content to give others a chance too.
		self::$failed_embeds[] = array(
			'match' => $matches[0],
			'src'   => esc_url( $src ),
		);

		return $matches[0];
	}

	/**
	 * Failed embeds are stripped, so let's convert them to links at least.
	 *
	 * @param string $string Failed embed string.
	 *
	 * @return string $string Linkified string.
	 */
	public static function maybe_create_links( $string ) {
		if ( empty( self::$failed_embeds ) ) {
			return $string;
		}

		foreach ( self::$failed_embeds as $entry ) {
			$html   = sprintf( '<a href="%s">%s</a>', esc_url( $entry['src'] ), esc_url( $entry['src'] ) );
			// Check if the string doesn't contain iframe, before replace.
			if ( ! preg_match( '/<iframe /', $string ) ) {
				$string = str_replace( $entry['match'], $html, $string );
			}
		}

		self::$failed_embeds = array();

		return $string;
	}

	static function get_attrs( $html ) {
		if ( ! ( class_exists( 'DOMDocument' ) && function_exists( 'libxml_use_internal_errors' ) && function_exists( 'simplexml_load_string' ) ) ) {
			trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
			return array();
		}
		// We have to go through DOM, since it can load non-well-formed XML (i.e. HTML).  SimpleXML cannot.
		$dom = new DOMDocument;
		// The @ is not enough to suppress errors when dealing with libxml,
		// we have to tell it directly how we want to handle errors.
		libxml_use_internal_errors( TRUE );
		@$dom->loadHTML( $html ); // suppress parser warnings
		libxml_use_internal_errors( FALSE );
		$xml = false;
		foreach ( $dom->childNodes as $node ) {
			// find the root node (html)
			if ( XML_ELEMENT_NODE == $node->nodeType ) {
				// Use simplexml_load_string rather than simplexml_import_dom as the later doesn't cope well if the XML is malformmed in the DOM See #1688-wpcom
				libxml_use_internal_errors( true );
				$xml = simplexml_load_string( $dom->saveXML( $node->firstChild->firstChild ) ); // html->body->object
				libxml_clear_errors();
				break;
			}
		}
		if ( ! $xml ) {
			return array();
		}

		$attrs              = array();
		$attrs['_raw_html'] = $html;

		// <param> elements
		foreach ( $xml->param as $param ) {
			$attrs[(string) $param['name']] = (string) $param['value'];
		}

		// <object> attributes
		foreach ( $xml->attributes() as $name => $attr ) {
			$attrs[$name] = (string) $attr;
		}

		// <embed> attributes
		if ( $xml->embed ) {
			foreach ( $xml->embed->attributes() as $name => $attr ) {
				$attrs[$name] = (string) $attr;
			}
		}

		return $attrs;
	}
}
