WIP: Introduce class for sourcing block attributes from HTML

lib/experimental/html/class-wp-html-attribute-sourcer.php

@@ -0,0 +1,390 @@
+<?php
+
+/**
+ * Existing Core Selectors
+ *
+ *     .blocks-gallery-caption
+ *     .blocks-gallery-item
+ *     .blocks-gallery-item__caption
+ *     .book-author
+ *     .message
+ *     a
+ *     a[download]
+ *     audio
+ *     blockquote
+ *     cite
+ *     code
+ *     div
+ *     figcaption
+ *     figure > a
+ *     figure a
+ *     figure img
+ *     figure video,figure img
+ *     h1,h2,h3,h4,h5,h6
+ *     img
+ *     li
+ *     ol,ul
+ *     p
+ *     pre
+ *     tbody tr
+ *     td,th
+ *     tfoot tr
+ *     thead tr
+ *     video
+ */
+
+require_once __DIR__ . '/class-wp-html-naive-processor.php';
+
+/*
+ * @see PHP docs for array_is_list: user-contributed polyfill
+ */
+if ( ! function_exists( 'array_is_list' ) ) {
+	function array_is_list( $array ) {
+		$i = 0;
+
+		foreach ( $array as $k => $v ) {
+			if ( $k !== $i++ ) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+}
+
+
+class WP_HTML_Attribute_Sourcer {
+	/**
+	 * Attributes definitions, typically from `block.json`.
+	 *
+	 * @see WP_Block_Type_Registry
+	 *
+	 * @var mixed|null
+	 */
+	public $attribute_definitions;
+
+	/**
+	 * Source HTML containing embedded attributes.
+	 *
+	 * @var mixed|null
+	 */
+	private $html;
+
+	public function __construct( $attribute_definitions = null, $html = null ) {
+		$this->attribute_definitions = $attribute_definitions;
+		$this->html = $html;
+	}
+
+	public function source_attributes() {
+		$attributes = [];
+		$unparsed = [];
+
+		foreach ( $this->attribute_definitions as $name => $definition ) {
+			$sourcer = self::parse_definition( $definition );
+			switch ( $sourcer ) {
+				case null:
+				case 'not-sourced':
+				case 'unsupported':
+					$unparsed[] = $name;
+					continue 2;
+
+				case 'inner-html':
+					$attributes[ $name ] = $this->html;
+					continue 2;
+			}
+
+			$tags = self::select( $sourcer['selector'], $this->html );
+			if ( null === $tags ) {
+				$unparsed[] = $name;
+				continue;
+			}
+
+			switch ( $sourcer['type'] ) {
+				case 'html':
+					$attributes[ $name ] = self::get_inner_html( $tags );
+					continue 2;
+
+				case 'attribute':
+					$attributes[ $name ] = $tags->get_attribute( $sourcer['attribute'] );
+					continue 2;
+			}
+		}
+
+		return array(
+			'attributes' => $attributes,
+			'unparsed' => $unparsed
+		);
+	}
+
+	public static function select( $selector, $html ) {
+		$tags = new WP_HTML_Naive_Processor( $html );
+
+		if ( array_is_list( $selector ) ) {
+			while ( $tags->next_tag() ) {
+				foreach ( $selector as $s ) {
+					if ( 'element' === $s['type'] && $tags->get_tag() === strtoupper( $s['identifier'] ) ) {
+						return $tags;
+					}
+
+					// @TODO: $tags->has_class() would be _really_ handy here.
+					if ( 'class' === $s['type'] && preg_match( "~\b{$s['identifier']}\b~", $tags->get_attribute( 'class' ) ) ) {
+						return $tags;
+					}
+
+					if ( 'hash' === $s['type'] && $s['identifier'] === $tags->get_attribute( 'id' ) ) {
+						return $tags;
+					}
+				}
+			}
+
+			return null;
+		}
+
+		switch ( $selector['type'] ) {
+			case 'element':
+				$tags->next_tag( [ 'tag_name' => $selector['identifier'] ] );
+				return $tags;
+
+			case 'class':
+				$tags->next_tag( [ 'class_name' => $selector['identifier'] ] );
+				return $tags;
+
+			case 'hash':
+				while ( $tags->next_tag() ) {
+					if ( $selector['identifier'] === $tags->get_attribute( 'id' ) ) {
+						return $tags;
+					}
+				}
+		}
+
+		return null;
+	}
+
+	public static function get_inner_html( WP_HTML_Naive_Processor $tags ) {
+		$tags->set_bookmark( 'start' );
+		$tag_name = $tags->get_tag();
+		$depth = 1;
+
+		if ( self::is_void_element( $tag_name ) ) {
+			return '';
+		}
+
+		while ( $tags->next_tag( [ 'tag_closers' => 'visit' ] ) ) {
+			if ( $tags->get_tag() !== $tag_name ) {
+				continue;
+			}
+
+			if ( $tags->is_tag_closer() && $depth === 1 ) {
+				$tags->set_bookmark( 'end' );
+				break;
+			}
+
+			$depth += $tags->is_tag_closer() ? -1 : 1;
+		}
+
+		return $tags->inner_content( 'start', 'end' );
+	}
+
+	/**
+	 * @see https://html.spec.whatwg.org/#elements-2
+	 */
+	public static function is_void_element( $tag_name ) {
+		switch ( $tag_name ) {
+			case 'area':
+			case 'base':
+			case 'br':
+			case 'col':
+			case 'embed':
+			case 'hr':
+			case 'img':
+			case 'input':
+			case 'link':
+			case 'meta':
+			case 'source':
+			case 'track':
+			case 'wbr':
+				return true;
+
+			default:
+				return false;
+		}
+	}
+
+	public static function parse_definition( $definition ) {
+		if ( empty( $definition['source'] ) ) {
+			return 'not-sourced';
+		}
+
+		$source = $definition['source'];
+		if ( 'html' !== $source && 'attribute' !== $source ) {
+			return 'unsupported';
+		}
+
+		if ( 'attribute' === $source && empty( $definition['selector'] ) ) {
+			return null;
+		}
+
+		if ( 'html' === $source && empty( $definition['selector'] ) ) {
+			return 'inner-html';
+		}
+
+		$selector = self::parse_selector( $definition['selector'] );
+		if ( null === $selector ) {
+			return 'unsupported';
+		}
+
+		if ( 'html' === $source ) {
+			return array( 'type' => 'html', 'selector' => $selector );
+		}
+
+		$attribute = self::parse_attribute( $definition['attribute'] );
+		if ( null === $attribute ) {
+			return null;
+		}
+
+		return array( 'type' => 'attribute', 'selector' => $selector, 'attribute' => $attribute );
+	}
+
+	public static function parse_selector( $s, $at = 0 ) {
+		$selectors = explode( ',', $s );
+		if ( count( $selectors ) > 1 ) {
+			$parsed = [];
+
+			foreach ( $selectors as $selector ) {
+				$parsed[] = self::parse_selector( $selector, strspn( $selector, " \r\t\f\n" ) );
+			}
+
+			return $parsed;
+		}
+
+		$type = 'element';
+
+		switch ( $s[ $at ] ) {
+			case '+':
+				// no support for adjacent sibling combinator
+				return null;
+
+			case '>':
+				// no support for child combinator
+				return null;
+
+			case '~':
+				// no support for general sibling combinator
+				return null;
+
+			case ' ':
+				// no support for descendant combinator
+				return null;
+
+			case '[':
+				// no support for attribute
+				return null;
+
+			case ',':
+				// we shouldn't get here because we're exploding at the start
+				// of this function; this is a bug if we're here.
+				return null;
+
+			case ':':
+				// no support for pseudo-selectors
+				return null;
+
+			case '#':
+				$type = 'hash';
+				$at++;
+				break;
+
+			case '.':
+				$type = 'class';
+				$at++;
+				break;
+		}
+
+		// @TODO: Hashes don't have to start with `nmstart` so this might reject valid hash names.
+		$identifier = self::parse_css_identifier( $s, $at );
+		if ( null === $identifier ) {
+			return null;
+		}
+
+		if ( $at + strlen( $identifier ) < strlen( $s ) ) {
+			// no support for anything more complicated than a simple selector
+			return null;
+		}
+
+		return array( 'type' => $type, 'identifier' => $identifier );
+	}
+
+	/**
+	 * Parses CSS identifier; currently limited to ASCII identifiers.
+	 *
+	 * Example:
+	 * ```
+	 *     'div' === parse_css_identifier( 'div > img' );
+	 * ```
+	 *
+	 * Grammar:
+	 * ```
+	 *     ident        -?{nmstart}{nmchar}*
+	 *     nmstart      [_a-z]|{nonascii}|{escape}
+	 *     nmchar       [_a-z0-9-]|{nonascii}|{escape}
+	 *     nonascii     [\240-\377]
+	 *     escape       {unicode}|\\[^\r\n\f0-9a-f]
+	 *     unicode      \\{h}{1,6}(\r\n|[ \t\r\n\f])?
+	 *     h            [0-9a-f]
+	 * ```
+	 *
+	 * @TODO: Add support for the proper syntax
+	 *
+	 * @see https://www.w3.org/TR/CSS21/grammar.html
+	 *
+	 * @param $s
+	 * @return false|string|null
+	 */
+	public static function parse_css_identifier( $s, $at = 0 ) {
+		$budget = 1000;
+		$started_at = $at;
+
+		$starting_chars = strspn( $s, '_-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', $at );
+		if ( 0 === $starting_chars ) {
+			return null;
+		}
+		$at += $starting_chars;
+
+		while ( $at < strlen( $s ) && $budget-- > 0 ) {
+			$chars = strspn( $s, '_-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', $at );
+
+			if ( 0 === $chars ) {
+				break;
+			}
+
+			$at += $chars;
+		}
+
+		if ( $budget < 0 ) {
+			return null;
+		}
+
+		return substr( $s, $started_at, $at - $started_at );
+	}
+
+	public static function parse_attribute( $s ) {
+		$unallowed_characters_match = preg_match(
+			'~[' .
+			// Syntax-like characters.
+			'"\'>&</ =' .
+			// Control characters.
+			'\x{00}-\x{1F}' .
+			// HTML noncharacters.
+			'\x{FDD0}-\x{FDEF}' .
+			'\x{FFFE}\x{FFFF}\x{1FFFE}\x{1FFFF}\x{2FFFE}\x{2FFFF}\x{3FFFE}\x{3FFFF}' .
+			'\x{4FFFE}\x{4FFFF}\x{5FFFE}\x{5FFFF}\x{6FFFE}\x{6FFFF}\x{7FFFE}\x{7FFFF}' .
+			'\x{8FFFE}\x{8FFFF}\x{9FFFE}\x{9FFFF}\x{AFFFE}\x{AFFFF}\x{BFFFE}\x{BFFFF}' .
+			'\x{CFFFE}\x{CFFFF}\x{DFFFE}\x{DFFFF}\x{EFFFE}\x{EFFFF}\x{FFFFE}\x{FFFFF}' .
+			'\x{10FFFE}\x{10FFFF}' .
+			']~Ssu',
+			$s
+		);
+
+		return $unallowed_characters_match ? null : $s;
+	}
+}