class DescriptionFactory

class DescriptionFactory {
    private Factory $tagFactory;
    
    /**
     * Initializes this factory with the means to construct (inline) tags.
     */
    public function __construct(Factory $tagFactory) {
        $this->tagFactory = $tagFactory;
    }
    
    /**
     * Returns the parsed text of this description.
     */
    public function create(string $contents, ?TypeContext $context = null) : Description {
        $tokens = $this->lex($contents);
        $count = count($tokens);
        $tagCount = 0;
        $tags = [];
        for ($i = 1; $i < $count; $i += 2) {
            $tags[] = $this->tagFactory
                ->create($tokens[$i], $context);
            $tokens[$i] = '%' . ++$tagCount . '$s';
        }
        
        //In order to allow "literal" inline tags, the otherwise invalid
        
        //sequence "{@}" is changed to "@", and "{}" is changed to "}".
        
        //"%" is escaped to "%%" because of vsprintf.
        
        //See unit tests for examples.
        for ($i = 0; $i < $count; $i += 2) {
            $tokens[$i] = str_replace([
                '{@}',
                '{}',
                '%',
            ], [
                '@',
                '}',
                '%%',
            ], $tokens[$i]);
        }
        return new Description(implode('', $tokens), $tags);
    }
    
    /**
     * Strips the contents from superfluous whitespace and splits the description into a series of tokens.
     *
     * @return string[] A series of tokens of which the description text is composed.
     */
    private function lex(string $contents) : array {
        $contents = $this->removeSuperfluousStartingWhitespace($contents);
        // performance optimalization; if there is no inline tag, don't bother splitting it up.
        if (strpos($contents, '{@') === false) {
            return [
                $contents,
            ];
        }
        return Utils::pregSplit('/\\{
                # "{@}" is not a valid inline tag. This ensures that we do not treat it as one, but treat it literally.
                (?!@\\})
                # We want to capture the whole tag line, but without the inline tag delimiters.
                (\\@
                    # Match everything up to the next delimiter.
                    [^{}]*
                    # Nested inline tag content should not be captured, or it will appear in the result separately.
                    (?:
                        # Match nested inline tags.
                        (?:
                            # Because we did not catch the tag delimiters earlier, we must be explicit with them here.
                            # Notice that this also matches "{}", as a way to later introduce it as an escape sequence.
                            \\{(?1)?\\}
                            |
                            # Make sure we match hanging "{".
                            \\{
                        )
                        # Match content after the nested inline tag.
                        [^{}]*
                    )* # If there are more inline tags, match them as well. We use "*" since there may not be any
                       # nested inline tags.
                )
            \\}/Sux', $contents, 0, PREG_SPLIT_DELIM_CAPTURE);
    }
    
    /**
     * Removes the superfluous from a multi-line description.
     *
     * When a description has more than one line then it can happen that the second and subsequent lines have an
     * additional indentation. This is commonly in use with tags like this:
     *
     *     {@}since 1.1.0 This is an example
     *         description where we have an
     *         indentation in the second and
     *         subsequent lines.
     *
     * If we do not normalize the indentation then we have superfluous whitespace on the second and subsequent
     * lines and this may cause rendering issues when, for example, using a Markdown converter.
     */
    private function removeSuperfluousStartingWhitespace(string $contents) : string {
        $lines = Utils::pregSplit("/\r\n?|\n/", $contents);
        // if there is only one line then we don't have lines with superfluous whitespace and
        // can use the contents as-is
        if (count($lines) <= 1) {
            return $contents;
        }
        // determine how many whitespace characters need to be stripped
        $startingSpaceCount = 9999999;
        for ($i = 1, $iMax = count($lines); $i < $iMax; ++$i) {
            // lines with a no length do not count as they are not indented at all
            if (trim($lines[$i]) === '') {
                continue;
            }
            // determine the number of prefixing spaces by checking the difference in line length before and after
            // an ltrim
            $startingSpaceCount = min($startingSpaceCount, strlen($lines[$i]) - strlen(ltrim($lines[$i])));
        }
        // strip the number of spaces from each line
        if ($startingSpaceCount > 0) {
            for ($i = 1, $iMax = count($lines); $i < $iMax; ++$i) {
                $lines[$i] = substr($lines[$i], $startingSpaceCount);
            }
        }
        return implode("\n", $lines);
    }

}