WP_Rewrite::generate_rewrite_rules( string $permalink_structure, int $ep_mask = EP_NONE, bool $paged = true, bool $feed = true, bool $forcomments = false, bool $walk_dirs = true, bool $endpoints = true )

	public function generate_rewrite_rules($permalink_structure, $ep_mask = EP_NONE, $paged = true, $feed = true, $forcomments = false, $walk_dirs = true, $endpoints = true) {
		// Build a regex to match the feed section of URLs, something like (feed|atom|rss|rss2)/?
		$feedregex2 = '';
		foreach ( (array) $this->feeds as $feed_name)
			$feedregex2 .= $feed_name . '|';
		$feedregex2 = '(' . trim($feedregex2, '|') . ')/?$';

		/*
		 * $feedregex is identical but with /feed/ added on as well, so URLs like <permalink>/feed/atom
		 * and <permalink>/atom are both possible
		 */
		$feedregex = $this->feed_base . '/' . $feedregex2;

		// Build a regex to match the trackback and page/xx parts of URLs.
		$trackbackregex = 'trackback/?$';
		$pageregex = $this->pagination_base . '/?([0-9]{1,})/?$';
		$commentregex = $this->comments_pagination_base . '-([0-9]{1,})/?$';
		$embedregex = 'embed/?$';

		// Build up an array of endpoint regexes to append => queries to append.
		if ( $endpoints ) {
			$ep_query_append = array ();
			foreach ( (array) $this->endpoints as $endpoint) {
				// Match everything after the endpoint name, but allow for nothing to appear there.
				$epmatch = $endpoint[1] . '(/(.*))?/?$';

				// This will be appended on to the rest of the query for each dir.
				$epquery = '&' . $endpoint[2] . '=';
				$ep_query_append[$epmatch] = array ( $endpoint[0], $epquery );
			}
		}

		// Get everything up to the first rewrite tag.
		$front = substr($permalink_structure, 0, strpos($permalink_structure, '%'));

		// Build an array of the tags (note that said array ends up being in $tokens[0]).
		preg_match_all('/%.+?%/', $permalink_structure, $tokens);

		$num_tokens = count($tokens[0]);

		$index = $this->index; //probably 'index.php'
		$feedindex = $index;
		$trackbackindex = $index;
		$embedindex = $index;

		/*
		 * Build a list from the rewritecode and queryreplace arrays, that will look something
		 * like tagname=$matches[i] where i is the current $i.
		 */
		$queries = array();
		for ( $i = 0; $i < $num_tokens; ++$i ) {
			if ( 0 < $i )
				$queries[$i] = $queries[$i - 1] . '&';
			else
				$queries[$i] = '';

			$query_token = str_replace($this->rewritecode, $this->queryreplace, $tokens[0][$i]) . $this->preg_index($i+1);
			$queries[$i] .= $query_token;
		}

		// Get the structure, minus any cruft (stuff that isn't tags) at the front.
		$structure = $permalink_structure;
		if ( $front != '/' )
			$structure = str_replace($front, '', $structure);

		/*
		 * Create a list of dirs to walk over, making rewrite rules for each level
		 * so for example, a $structure of /%year%/%monthnum%/%postname% would create
		 * rewrite rules for /%year%/, /%year%/%monthnum%/ and /%year%/%monthnum%/%postname%
		 */
		$structure = trim($structure, '/');
		$dirs = $walk_dirs ? explode('/', $structure) : array( $structure );
		$num_dirs = count($dirs);

		// Strip slashes from the front of $front.
		$front = preg_replace('|^/+|', '', $front);

		// The main workhorse loop.
		$post_rewrite = array();
		$struct = $front;
		for ( $j = 0; $j < $num_dirs; ++$j ) {
			// Get the struct for this dir, and trim slashes off the front.
			$struct .= $dirs[$j] . '/'; // Accumulate. see comment near explode('/', $structure) above.
			$struct = ltrim($struct, '/');

			// Replace tags with regexes.
			$match = str_replace($this->rewritecode, $this->rewritereplace, $struct);

			// Make a list of tags, and store how many there are in $num_toks.
			$num_toks = preg_match_all('/%.+?%/', $struct, $toks);

			// Get the 'tagname=$matches[i]'.
			$query = ( ! empty( $num_toks ) && isset( $queries[$num_toks - 1] ) ) ? $queries[$num_toks - 1] : '';

			// Set up $ep_mask_specific which is used to match more specific URL types.
			switch ( $dirs[$j] ) {
				case '%year%':
					$ep_mask_specific = EP_YEAR;
					break;
				case '%monthnum%':
					$ep_mask_specific = EP_MONTH;
					break;
				case '%day%':
					$ep_mask_specific = EP_DAY;
					break;
				default:
					$ep_mask_specific = EP_NONE;
			}

			// Create query for /page/xx.
			$pagematch = $match . $pageregex;
			$pagequery = $index . '?' . $query . '&paged=' . $this->preg_index($num_toks + 1);

			// Create query for /comment-page-xx.
			$commentmatch = $match . $commentregex;
			$commentquery = $index . '?' . $query . '&cpage=' . $this->preg_index($num_toks + 1);

			if ( get_option('page_on_front') ) {
				// Create query for Root /comment-page-xx.
				$rootcommentmatch = $match . $commentregex;
				$rootcommentquery = $index . '?' . $query . '&page_id=' . get_option('page_on_front') . '&cpage=' . $this->preg_index($num_toks + 1);
			}

			// Create query for /feed/(feed|atom|rss|rss2|rdf).
			$feedmatch = $match . $feedregex;
			$feedquery = $feedindex . '?' . $query . '&feed=' . $this->preg_index($num_toks + 1);

			// Create query for /(feed|atom|rss|rss2|rdf) (see comment near creation of $feedregex).
			$feedmatch2 = $match . $feedregex2;
			$feedquery2 = $feedindex . '?' . $query . '&feed=' . $this->preg_index($num_toks + 1);

			// Create query and regex for embeds.
			$embedmatch = $match . $embedregex;
			$embedquery = $embedindex . '?' . $query . '&embed=true';

			// If asked to, turn the feed queries into comment feed ones.
			if ( $forcomments ) {
				$feedquery .= '&withcomments=1';
				$feedquery2 .= '&withcomments=1';
			}

			// Start creating the array of rewrites for this dir.
			$rewrite = array();

			// ...adding on /feed/ regexes => queries
			if ( $feed ) {
				$rewrite = array( $feedmatch => $feedquery, $feedmatch2 => $feedquery2, $embedmatch => $embedquery );
			}

			//...and /page/xx ones
			if ( $paged ) {
				$rewrite = array_merge( $rewrite, array( $pagematch => $pagequery ) );
			}

			// Only on pages with comments add ../comment-page-xx/.
			if ( EP_PAGES & $ep_mask || EP_PERMALINK & $ep_mask ) {
				$rewrite = array_merge($rewrite, array($commentmatch => $commentquery));
			} elseif ( EP_ROOT & $ep_mask && get_option('page_on_front') ) {
				$rewrite = array_merge($rewrite, array($rootcommentmatch => $rootcommentquery));
			}

			// Do endpoints.
			if ( $endpoints ) {
				foreach ( (array) $ep_query_append as $regex => $ep) {
					// Add the endpoints on if the mask fits.
					if ( $ep[0] & $ep_mask || $ep[0] & $ep_mask_specific )
						$rewrite[$match . $regex] = $index . '?' . $query . $ep[1] . $this->preg_index($num_toks + 2);
				}
			}

			// If we've got some tags in this dir.
			if ( $num_toks ) {
				$post = false;
				$page = false;

				/*
				 * Check to see if this dir is permalink-level: i.e. the structure specifies an
				 * individual post. Do this by checking it contains at least one of 1) post name,
				 * 2) post ID, 3) page name, 4) timestamp (year, month, day, hour, second and
				 * minute all present). Set these flags now as we need them for the endpoints.
				 */
				if ( strpos($struct, '%postname%') !== false
						|| strpos($struct, '%post_id%') !== false
						|| strpos($struct, '%pagename%') !== false
						|| (strpos($struct, '%year%') !== false && strpos($struct, '%monthnum%') !== false && strpos($struct, '%day%') !== false && strpos($struct, '%hour%') !== false && strpos($struct, '%minute%') !== false && strpos($struct, '%second%') !== false)
						) {
					$post = true;
					if ( strpos($struct, '%pagename%') !== false )
						$page = true;
				}

				if ( ! $post ) {
					// For custom post types, we need to add on endpoints as well.
					foreach ( get_post_types( array('_builtin' => false ) ) as $ptype ) {
						if ( strpos($struct, "%$ptype%") !== false ) {
							$post = true;

							// This is for page style attachment URLs.
							$page = is_post_type_hierarchical( $ptype );
							break;
						}
					}
				}

				// If creating rules for a permalink, do all the endpoints like attachments etc.
				if ( $post ) {
					// Create query and regex for trackback.
					$trackbackmatch = $match . $trackbackregex;
					$trackbackquery = $trackbackindex . '?' . $query . '&tb=1';

					// Create query and regex for embeds.
					$embedmatch = $match . $embedregex;
					$embedquery = $embedindex . '?' . $query . '&embed=true';

					// Trim slashes from the end of the regex for this dir.
					$match = rtrim($match, '/');

					// Get rid of brackets.
					$submatchbase = str_replace( array('(', ')'), '', $match);

					// Add a rule for at attachments, which take the form of <permalink>/some-text.
					$sub1 = $submatchbase . '/([^/]+)/';

					// Add trackback regex <permalink>/trackback/...
					$sub1tb = $sub1 . $trackbackregex;

					// And <permalink>/feed/(atom|...)
					$sub1feed = $sub1 . $feedregex;

					// And <permalink>/(feed|atom...)
					$sub1feed2 = $sub1 . $feedregex2;

					// And <permalink>/comment-page-xx
					$sub1comment = $sub1 . $commentregex;

					// And <permalink>/embed/...
					$sub1embed = $sub1 . $embedregex;

					/*
					 * Add another rule to match attachments in the explicit form:
					 * <permalink>/attachment/some-text
					 */
					$sub2 = $submatchbase . '/attachment/([^/]+)/';

					// And add trackbacks <permalink>/attachment/trackback.
					$sub2tb = $sub2 . $trackbackregex;

					// Feeds, <permalink>/attachment/feed/(atom|...)
					$sub2feed = $sub2 . $feedregex;

					// And feeds again on to this <permalink>/attachment/(feed|atom...)
					$sub2feed2 = $sub2 . $feedregex2;

					// And <permalink>/comment-page-xx
					$sub2comment = $sub2 . $commentregex;

					// And <permalink>/embed/...
					$sub2embed = $sub2 . $embedregex;

					// Create queries for these extra tag-ons we've just dealt with.
					$subquery = $index . '?attachment=' . $this->preg_index(1);
					$subtbquery = $subquery . '&tb=1';
					$subfeedquery = $subquery . '&feed=' . $this->preg_index(2);
					$subcommentquery = $subquery . '&cpage=' . $this->preg_index(2);
					$subembedquery = $subquery . '&embed=true';

					// Do endpoints for attachments.
					if ( !empty($endpoints) ) {
						foreach ( (array) $ep_query_append as $regex => $ep ) {
							if ( $ep[0] & EP_ATTACHMENT ) {
								$rewrite[$sub1 . $regex] = $subquery . $ep[1] . $this->preg_index(3);
								$rewrite[$sub2 . $regex] = $subquery . $ep[1] . $this->preg_index(3);
							}
						}
					}

					/*
					 * Now we've finished with endpoints, finish off the $sub1 and $sub2 matches
					 * add a ? as we don't have to match that last slash, and finally a $ so we
					 * match to the end of the URL
					 */
					$sub1 .= '?$';
					$sub2 .= '?$';

					/*
					 * Post pagination, e.g. <permalink>/2/
					 * Previously: '(/[0-9]+)?/?$', which produced '/2' for page.
					 * When cast to int, returned 0.
					 */
					$match = $match . '(?:/([0-9]+))?/?$';
					$query = $index . '?' . $query . '&page=' . $this->preg_index($num_toks + 1);

				// Not matching a permalink so this is a lot simpler.
				} else {
					// Close the match and finalise the query.
					$match .= '?$';
					$query = $index . '?' . $query;
				}

				/*
				 * Create the final array for this dir by joining the $rewrite array (which currently
				 * only contains rules/queries for trackback, pages etc) to the main regex/query for
				 * this dir
				 */
				$rewrite = array_merge($rewrite, array($match => $query));

				// If we're matching a permalink, add those extras (attachments etc) on.
				if ( $post ) {
					// Add trackback.
					$rewrite = array_merge(array($trackbackmatch => $trackbackquery), $rewrite);

					// Add embed.
					$rewrite = array_merge( array( $embedmatch => $embedquery ), $rewrite );

					// Add regexes/queries for attachments, attachment trackbacks and so on.
					if ( ! $page ) {
						// Require <permalink>/attachment/stuff form for pages because of confusion with subpages.
						$rewrite = array_merge( $rewrite, array(
							$sub1        => $subquery,
							$sub1tb      => $subtbquery,
							$sub1feed    => $subfeedquery,
							$sub1feed2   => $subfeedquery,
							$sub1comment => $subcommentquery,
							$sub1embed   => $subembedquery
						) );
					}

					$rewrite = array_merge( array( $sub2 => $subquery, $sub2tb => $subtbquery, $sub2feed => $subfeedquery, $sub2feed2 => $subfeedquery, $sub2comment => $subcommentquery, $sub2embed => $subembedquery ), $rewrite );
				}
			}
			// Add the rules for this dir to the accumulating $post_rewrite.
			$post_rewrite = array_merge($rewrite, $post_rewrite);
		}

		// The finished rules. phew!
		return $post_rewrite;
	}