JavaScriptMinifier.php

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<?php
// @codingStandardsIgnoreFile File external to MediaWiki. Ignore coding conventions checks.
class JavaScriptMinifier {

    /* Class constants */
    /* Parsing states.
     * The state machine is only necessary to decide whether to parse a slash as division
     * operator or as regexp literal.
     * States are named after the next expected item. We only distinguish states when the
     * distinction is relevant for our purpose.
     */
    const STATEMENT                = 0;
    const CONDITION                = 1;
    const PROPERTY_ASSIGNMENT      = 2;
    const EXPRESSION               = 3;
    const EXPRESSION_NO_NL         = 4; // only relevant for semicolon insertion
    const EXPRESSION_OP            = 5;
    const EXPRESSION_FUNC          = 6;
    const EXPRESSION_TERNARY       = 7; // used to determine the role of a colon
    const EXPRESSION_TERNARY_OP    = 8;
    const EXPRESSION_TERNARY_FUNC  = 9;
    const PAREN_EXPRESSION         = 10; // expression which is not on the top level
    const PAREN_EXPRESSION_OP      = 11;
    const PAREN_EXPRESSION_FUNC    = 12;
    const PROPERTY_EXPRESSION      = 13; // expression which is within an object literal
    const PROPERTY_EXPRESSION_OP   = 14;
    const PROPERTY_EXPRESSION_FUNC = 15;

    /* Token types */
    const TYPE_UN_OP       = 1; // unary operators
    const TYPE_INCR_OP     = 2; // ++ and --
    const TYPE_BIN_OP      = 3; // binary operators
    const TYPE_ADD_OP      = 4; // + and - which can be either unary or binary ops
    const TYPE_HOOK        = 5; // ?
    const TYPE_COLON       = 6; // :
    const TYPE_COMMA       = 7; // ,
    const TYPE_SEMICOLON   = 8; // ;
    const TYPE_BRACE_OPEN  = 9; // {
    const TYPE_BRACE_CLOSE = 10; // }
    const TYPE_PAREN_OPEN  = 11; // ( and [
    const TYPE_PAREN_CLOSE = 12; // ) and ]
    const TYPE_RETURN      = 13; // keywords: break, continue, return, throw
    const TYPE_IF          = 14; // keywords: catch, for, with, switch, while, if
    const TYPE_DO          = 15; // keywords: case, var, finally, else, do, try
    const TYPE_FUNC        = 16; // keywords: function
    const TYPE_LITERAL     = 17; // all literals, identifiers and unrecognised tokens

    // Sanity limit to avoid excessive memory usage
    const STACK_LIMIT = 1000;

    /* Static functions */

    public static function minify( $s, $statementsOnOwnLine = false, $maxLineLength = 1000 ) {
        // First we declare a few tables that contain our parsing rules

        // $opChars : characters, which can be combined without whitespace in between them
        $opChars = array(
            '!' => true,
            '"' => true,
            '%' => true,
            '&' => true,
            "'" => true,
            '(' => true,
            ')' => true,
            '*' => true,
            '+' => true,
            ',' => true,
            '-' => true,
            '.' => true,
            '/' => true,
            ':' => true,
            ';' => true,
            '<' => true,
            '=' => true,
            '>' => true,
            '?' => true,
            '[' => true,
            ']' => true,
            '^' => true,
            '{' => true,
            '|' => true,
            '}' => true,
            '~' => true
        );

        // $tokenTypes : maps keywords and operators to their corresponding token type
        $tokenTypes = array(
            '!'          => self::TYPE_UN_OP,
            '~'          => self::TYPE_UN_OP,
            'delete'     => self::TYPE_UN_OP,
            'new'        => self::TYPE_UN_OP,
            'typeof'     => self::TYPE_UN_OP,
            'void'       => self::TYPE_UN_OP,
            '++'         => self::TYPE_INCR_OP,
            '--'         => self::TYPE_INCR_OP,
            '!='         => self::TYPE_BIN_OP,
            '!=='        => self::TYPE_BIN_OP,
            '%'          => self::TYPE_BIN_OP,
            '%='         => self::TYPE_BIN_OP,
            '&'          => self::TYPE_BIN_OP,
            '&&'         => self::TYPE_BIN_OP,
            '&='         => self::TYPE_BIN_OP,
            '*'          => self::TYPE_BIN_OP,
            '*='         => self::TYPE_BIN_OP,
            '+='         => self::TYPE_BIN_OP,
            '-='         => self::TYPE_BIN_OP,
            '.'          => self::TYPE_BIN_OP,
            '/'          => self::TYPE_BIN_OP,
            '/='         => self::TYPE_BIN_OP,
            '<'          => self::TYPE_BIN_OP,
            '<<'         => self::TYPE_BIN_OP,
            '<<='        => self::TYPE_BIN_OP,
            '<='         => self::TYPE_BIN_OP,
            '='          => self::TYPE_BIN_OP,
            '=='         => self::TYPE_BIN_OP,
            '==='        => self::TYPE_BIN_OP,
            '>'          => self::TYPE_BIN_OP,
            '>='         => self::TYPE_BIN_OP,
            '>>'         => self::TYPE_BIN_OP,
            '>>='        => self::TYPE_BIN_OP,
            '>>>'        => self::TYPE_BIN_OP,
            '>>>='       => self::TYPE_BIN_OP,
            '^'          => self::TYPE_BIN_OP,
            '^='         => self::TYPE_BIN_OP,
            '|'          => self::TYPE_BIN_OP,
            '|='         => self::TYPE_BIN_OP,
            '||'         => self::TYPE_BIN_OP,
            'in'         => self::TYPE_BIN_OP,
            'instanceof' => self::TYPE_BIN_OP,
            '+'          => self::TYPE_ADD_OP,
            '-'          => self::TYPE_ADD_OP,
            '?'          => self::TYPE_HOOK,
            ':'          => self::TYPE_COLON,
            ','          => self::TYPE_COMMA,
            ';'          => self::TYPE_SEMICOLON,
            '{'          => self::TYPE_BRACE_OPEN,
            '}'          => self::TYPE_BRACE_CLOSE,
            '('          => self::TYPE_PAREN_OPEN,
            '['          => self::TYPE_PAREN_OPEN,
            ')'          => self::TYPE_PAREN_CLOSE,
            ']'          => self::TYPE_PAREN_CLOSE,
            'break'      => self::TYPE_RETURN,
            'continue'   => self::TYPE_RETURN,
            'return'     => self::TYPE_RETURN,
            'throw'      => self::TYPE_RETURN,
            'catch'      => self::TYPE_IF,
            'for'        => self::TYPE_IF,
            'if'         => self::TYPE_IF,
            'switch'     => self::TYPE_IF,
            'while'      => self::TYPE_IF,
            'with'       => self::TYPE_IF,
            'case'       => self::TYPE_DO,
            'do'         => self::TYPE_DO,
            'else'       => self::TYPE_DO,
            'finally'    => self::TYPE_DO,
            'try'        => self::TYPE_DO,
            'var'        => self::TYPE_DO,
            'function'   => self::TYPE_FUNC
        );

        // $goto : This is the main table for our state machine. For every state/token pair
        //         the following state is defined. When no rule exists for a given pair,
        //         the state is left unchanged.
        $goto = array(
            self::STATEMENT => array(
                self::TYPE_UN_OP      => self::EXPRESSION,
                self::TYPE_INCR_OP    => self::EXPRESSION,
                self::TYPE_ADD_OP     => self::EXPRESSION,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_RETURN     => self::EXPRESSION_NO_NL,
                self::TYPE_IF         => self::CONDITION,
                self::TYPE_FUNC       => self::CONDITION,
                self::TYPE_LITERAL    => self::EXPRESSION_OP
            ),
            self::CONDITION => array(
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION
            ),
            self::PROPERTY_ASSIGNMENT => array(
                self::TYPE_COLON      => self::PROPERTY_EXPRESSION,
                self::TYPE_BRACE_OPEN => self::STATEMENT
            ),
            self::EXPRESSION => array(
                self::TYPE_SEMICOLON  => self::STATEMENT,
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_FUNC       => self::EXPRESSION_FUNC,
                self::TYPE_LITERAL    => self::EXPRESSION_OP
            ),
            self::EXPRESSION_NO_NL => array(
                self::TYPE_SEMICOLON  => self::STATEMENT,
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_FUNC       => self::EXPRESSION_FUNC,
                self::TYPE_LITERAL    => self::EXPRESSION_OP
            ),
            self::EXPRESSION_OP => array(
                self::TYPE_BIN_OP     => self::EXPRESSION,
                self::TYPE_ADD_OP     => self::EXPRESSION,
                self::TYPE_HOOK       => self::EXPRESSION_TERNARY,
                self::TYPE_COLON      => self::STATEMENT,
                self::TYPE_COMMA      => self::EXPRESSION,
                self::TYPE_SEMICOLON  => self::STATEMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION
            ),
            self::EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::STATEMENT
            ),
            self::EXPRESSION_TERNARY => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_FUNC       => self::EXPRESSION_TERNARY_FUNC,
                self::TYPE_LITERAL    => self::EXPRESSION_TERNARY_OP
            ),
            self::EXPRESSION_TERNARY_OP => array(
                self::TYPE_BIN_OP     => self::EXPRESSION_TERNARY,
                self::TYPE_ADD_OP     => self::EXPRESSION_TERNARY,
                self::TYPE_HOOK       => self::EXPRESSION_TERNARY,
                self::TYPE_COMMA      => self::EXPRESSION_TERNARY,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION
            ),
            self::EXPRESSION_TERNARY_FUNC => array(
                self::TYPE_BRACE_OPEN => self::STATEMENT
            ),
            self::PAREN_EXPRESSION => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_FUNC       => self::PAREN_EXPRESSION_FUNC,
                self::TYPE_LITERAL    => self::PAREN_EXPRESSION_OP
            ),
            self::PAREN_EXPRESSION_OP => array(
                self::TYPE_BIN_OP     => self::PAREN_EXPRESSION,
                self::TYPE_ADD_OP     => self::PAREN_EXPRESSION,
                self::TYPE_HOOK       => self::PAREN_EXPRESSION,
                self::TYPE_COLON      => self::PAREN_EXPRESSION,
                self::TYPE_COMMA      => self::PAREN_EXPRESSION,
                self::TYPE_SEMICOLON  => self::PAREN_EXPRESSION,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION
            ),
            self::PAREN_EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::STATEMENT
            ),
            self::PROPERTY_EXPRESSION => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION,
                self::TYPE_FUNC       => self::PROPERTY_EXPRESSION_FUNC,
                self::TYPE_LITERAL    => self::PROPERTY_EXPRESSION_OP
            ),
            self::PROPERTY_EXPRESSION_OP => array(
                self::TYPE_BIN_OP     => self::PROPERTY_EXPRESSION,
                self::TYPE_ADD_OP     => self::PROPERTY_EXPRESSION,
                self::TYPE_HOOK       => self::PROPERTY_EXPRESSION,
                self::TYPE_COMMA      => self::PROPERTY_ASSIGNMENT,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION
            ),
            self::PROPERTY_EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::STATEMENT
            )
        );

        // $push : This table contains the rules for when to push a state onto the stack.
        //         The pushed state is the state to return to when the corresponding
        //         closing token is found
        $push = array(
            self::STATEMENT => array(
                self::TYPE_BRACE_OPEN => self::STATEMENT,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_OP
            ),
            self::CONDITION => array(
                self::TYPE_PAREN_OPEN => self::STATEMENT
            ),
            self::PROPERTY_ASSIGNMENT => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_ASSIGNMENT
            ),
            self::EXPRESSION => array(
                self::TYPE_BRACE_OPEN => self::EXPRESSION_OP,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_OP
            ),
            self::EXPRESSION_NO_NL => array(
                self::TYPE_BRACE_OPEN => self::EXPRESSION_OP,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_OP
            ),
            self::EXPRESSION_OP => array(
                self::TYPE_HOOK       => self::EXPRESSION,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_OP
            ),
            self::EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::EXPRESSION_OP
            ),
            self::EXPRESSION_TERNARY => array(
                self::TYPE_BRACE_OPEN => self::EXPRESSION_TERNARY_OP,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_TERNARY_OP
            ),
            self::EXPRESSION_TERNARY_OP => array(
                self::TYPE_HOOK       => self::EXPRESSION_TERNARY,
                self::TYPE_PAREN_OPEN => self::EXPRESSION_TERNARY_OP
            ),
            self::EXPRESSION_TERNARY_FUNC => array(
                self::TYPE_BRACE_OPEN => self::EXPRESSION_TERNARY_OP
            ),
            self::PAREN_EXPRESSION => array(
                self::TYPE_BRACE_OPEN => self::PAREN_EXPRESSION_OP,
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION_OP
            ),
            self::PAREN_EXPRESSION_OP => array(
                self::TYPE_PAREN_OPEN => self::PAREN_EXPRESSION_OP
            ),
            self::PAREN_EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::PAREN_EXPRESSION_OP
            ),
            self::PROPERTY_EXPRESSION => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_EXPRESSION_OP,
                self::TYPE_PAREN_OPEN => self::PROPERTY_EXPRESSION_OP
            ),
            self::PROPERTY_EXPRESSION_OP => array(
                self::TYPE_PAREN_OPEN => self::PROPERTY_EXPRESSION_OP
            ),
            self::PROPERTY_EXPRESSION_FUNC => array(
                self::TYPE_BRACE_OPEN => self::PROPERTY_EXPRESSION_OP
            )
        );

        // $pop : Rules for when to pop a state from the stack
        $pop = array(
            self::STATEMENT              => array( self::TYPE_BRACE_CLOSE => true ),
            self::PROPERTY_ASSIGNMENT    => array( self::TYPE_BRACE_CLOSE => true ),
            self::EXPRESSION             => array( self::TYPE_BRACE_CLOSE => true ),
            self::EXPRESSION_NO_NL       => array( self::TYPE_BRACE_CLOSE => true ),
            self::EXPRESSION_OP          => array( self::TYPE_BRACE_CLOSE => true ),
            self::EXPRESSION_TERNARY_OP  => array( self::TYPE_COLON       => true ),
            self::PAREN_EXPRESSION       => array( self::TYPE_PAREN_CLOSE => true ),
            self::PAREN_EXPRESSION_OP    => array( self::TYPE_PAREN_CLOSE => true ),
            self::PROPERTY_EXPRESSION    => array( self::TYPE_BRACE_CLOSE => true ),
            self::PROPERTY_EXPRESSION_OP => array( self::TYPE_BRACE_CLOSE => true )
        );

        // $semicolon : Rules for when a semicolon insertion is appropriate
        $semicolon = array(
            self::EXPRESSION_NO_NL => array(
                self::TYPE_UN_OP      => true,
                self::TYPE_INCR_OP    => true,
                self::TYPE_ADD_OP     => true,
                self::TYPE_BRACE_OPEN => true,
                self::TYPE_PAREN_OPEN => true,
                self::TYPE_RETURN     => true,
                self::TYPE_IF         => true,
                self::TYPE_DO         => true,
                self::TYPE_FUNC       => true,
                self::TYPE_LITERAL    => true
            ),
            self::EXPRESSION_OP => array(
                self::TYPE_UN_OP      => true,
                self::TYPE_INCR_OP    => true,
                self::TYPE_BRACE_OPEN => true,
                self::TYPE_RETURN     => true,
                self::TYPE_IF         => true,
                self::TYPE_DO         => true,
                self::TYPE_FUNC       => true,
                self::TYPE_LITERAL    => true
            )
        );

        // Rules for when newlines should be inserted if
        // $statementsOnOwnLine is enabled.
        // $newlineBefore is checked before switching state,
        // $newlineAfter is checked after
        $newlineBefore = array(
            self::STATEMENT => array(
                self::TYPE_BRACE_CLOSE => true,
            ),
        );
        $newlineAfter = array(
            self::STATEMENT => array(
                self::TYPE_BRACE_OPEN => true,
                self::TYPE_PAREN_CLOSE => true,
                self::TYPE_SEMICOLON => true,
            ),
        );

        // $divStates : Contains all states that can be followed by a division operator
        $divStates = array(
            self::EXPRESSION_OP          => true,
            self::EXPRESSION_TERNARY_OP  => true,
            self::PAREN_EXPRESSION_OP    => true,
            self::PROPERTY_EXPRESSION_OP => true
        );

        // Here's where the minifying takes place: Loop through the input, looking for tokens
        // and output them to $out, taking actions to the above defined rules when appropriate.
        $out = '';
        $pos = 0;
        $length = strlen( $s );
        $lineLength = 0;
        $newlineFound = true;
        $state = self::STATEMENT;
        $stack = array();
        $last = ';'; // Pretend that we have seen a semicolon yet
        while( $pos < $length ) {
            // First, skip over any whitespace and multiline comments, recording whether we
            // found any newline character
            $skip = strspn( $s, " \t\n\r\xb\xc", $pos );
            if( !$skip ) {
                $ch = $s[$pos];
                if( $ch === '/' && substr( $s, $pos, 2 ) === '/*' ) {
                    // Multiline comment. Search for the end token or EOT.
                    $end = strpos( $s, '*/', $pos + 2 );
                    $skip = $end === false ? $length - $pos : $end - $pos + 2;
                }
            }
            if( $skip ) {
                // The semicolon insertion mechanism needs to know whether there was a newline
                // between two tokens, so record it now.
                if( !$newlineFound && strcspn( $s, "\r\n", $pos, $skip ) !== $skip ) {
                    $newlineFound = true;
                }
                $pos += $skip;
                continue;
            }
            // Handle C++-style comments and html comments, which are treated as single line
            // comments by the browser, regardless of whether the end tag is on the same line.
            // Handle --> the same way, but only if it's at the beginning of the line
            if( ( $ch === '/' && substr( $s, $pos, 2 ) === '//' )
                || ( $ch === '<' && substr( $s, $pos, 4 ) === '<!--' )
                || ( $ch === '-' && $newlineFound && substr( $s, $pos, 3 ) === '-->' )
            ) {
                $pos += strcspn( $s, "\r\n", $pos );
                continue;
            }

            // Find out which kind of token we're handling. $end will point past the end of it.
            $end = $pos + 1;
            // Handle string literals
            if( $ch === "'" || $ch === '"' ) {
                // Search to the end of the string literal, skipping over backslash escapes
                $search = $ch . '\\';
                do{
                    $end += strcspn( $s, $search, $end ) + 2;
                } while( $end - 2 < $length && $s[$end - 2] === '\\' );
                $end--;
            // We have to distinguish between regexp literals and division operators
            // A division operator is only possible in certain states
            } elseif( $ch === '/' && !isset( $divStates[$state] ) ) {
                // Regexp literal, search to the end, skipping over backslash escapes and
                // character classes
                for( ; ; ) {
                    do{
                        $end += strcspn( $s, '/[\\', $end ) + 2;
                    } while( $end - 2 < $length && $s[$end - 2] === '\\' );
                    $end--;
                    if( $end - 1 >= $length || $s[$end - 1] === '/' ) {
                        break;
                    }
                    do{
                        $end += strcspn( $s, ']\\', $end ) + 2;
                    } while( $end - 2 < $length && $s[$end - 2] === '\\' );
                    $end--;
                };
                // Search past the regexp modifiers (gi)
                while( $end < $length && ctype_alpha( $s[$end] ) ) {
                    $end++;
                }
            } elseif(
                $ch === '0'
                && ($pos + 1 < $length) && ($s[$pos + 1] === 'x' || $s[$pos + 1] === 'X' )
            ) {
                // Hex numeric literal
                $end++; // x or X
                $len = strspn( $s, '0123456789ABCDEFabcdef', $end );
                if ( !$len ) {
                    return self::parseError($s, $pos, 'Expected a hexadecimal number but found ' . substr( $s, $pos, 5 ) . '...' );
                }
                $end += $len;
            } elseif(
                ctype_digit( $ch )
                || ( $ch === '.' && $pos + 1 < $length && ctype_digit( $s[$pos + 1] ) )
            ) {
                $end += strspn( $s, '0123456789', $end );
                $decimal = strspn( $s, '.', $end );
                if ($decimal) {
                    if ( $decimal > 2 ) {
                        return self::parseError($s, $end, 'The number has too many decimal points' );
                    }
                    $end += strspn( $s, '0123456789', $end + 1 ) + $decimal;
                }
                $exponent = strspn( $s, 'eE', $end );
                if( $exponent ) {
                    if ( $exponent > 1 ) {
                        return self::parseError($s, $end, 'Number with several E' );
                    }
                    $end++;

                    // + sign is optional; - sign is required.
                    $end += strspn( $s, '-+', $end );
                    $len = strspn( $s, '0123456789', $end );
                    if ( !$len ) {
                        return self::parseError($s, $pos, 'No decimal digits after e, how many zeroes should be added?' );
                    }
                    $end += $len;
                }
            } elseif( isset( $opChars[$ch] ) ) {
                // Punctuation character. Search for the longest matching operator.
                while(
                    $end < $length
                    && isset( $tokenTypes[substr( $s, $pos, $end - $pos + 1 )] )
                ) {
                    $end++;
                }
            } else {
                // Identifier or reserved word. Search for the end by excluding whitespace and
                // punctuation.
                $end += strcspn( $s, " \t\n.;,=<>+-{}()[]?:*/%'\"!&|^~\xb\xc\r", $end );
            }

            // Now get the token type from our type array
            $token = substr( $s, $pos, $end - $pos ); // so $end - $pos == strlen( $token )
            $type = isset( $tokenTypes[$token] ) ? $tokenTypes[$token] : self::TYPE_LITERAL;

            if( $newlineFound && isset( $semicolon[$state][$type] ) ) {
                // This token triggers the semicolon insertion mechanism of javascript. While we
                // could add the ; token here ourselves, keeping the newline has a few advantages.
                $out .= "\n";
                $state = self::STATEMENT;
                $lineLength = 0;
            } elseif( $maxLineLength > 0 && $lineLength + $end - $pos > $maxLineLength &&
                    !isset( $semicolon[$state][$type] ) && $type !== self::TYPE_INCR_OP )
            {
                // This line would get too long if we added $token, so add a newline first.
                // Only do this if it won't trigger semicolon insertion and if it won't
                // put a postfix increment operator on its own line, which is illegal in js.
                $out .= "\n";
                $lineLength = 0;
            // Check, whether we have to separate the token from the last one with whitespace
            } elseif( !isset( $opChars[$last] ) && !isset( $opChars[$ch] ) ) {
                $out .= ' ';
                $lineLength++;
            // Don't accidentally create ++, -- or // tokens
            } elseif( $last === $ch && ( $ch === '+' || $ch === '-' || $ch === '/' ) ) {
                $out .= ' ';
                $lineLength++;
            }
            if (
                $type === self::TYPE_LITERAL
                && ( $token === 'true' || $token === 'false' )
                && ( $state === self::EXPRESSION || $state === self::PROPERTY_EXPRESSION )
                && $last !== '.'
            ) {
                $token = ( $token === 'true' ) ? '!0' : '!1';
            }

            $out .= $token;
            $lineLength += $end - $pos; // += strlen( $token )
            $last = $s[$end - 1];
            $pos = $end;
            $newlineFound = false;

            // Output a newline after the token if required
            // This is checked before AND after switching state
            $newlineAdded = false;
            if ( $statementsOnOwnLine && !$newlineAdded && isset( $newlineBefore[$state][$type] ) ) {
                $out .= "\n";
                $lineLength = 0;
                $newlineAdded = true;
            }

            // Now that we have output our token, transition into the new state.
            if( isset( $push[$state][$type] ) && count( $stack ) < self::STACK_LIMIT ) {
                $stack[] = $push[$state][$type];
            }
            if( $stack && isset( $pop[$state][$type] ) ) {
                $state = array_pop( $stack );
            } elseif( isset( $goto[$state][$type] ) ) {
                $state = $goto[$state][$type];
            }

            // Check for newline insertion again
            if ( $statementsOnOwnLine && !$newlineAdded && isset( $newlineAfter[$state][$type] ) ) {
                $out .= "\n";
                $lineLength = 0;
            }
        }
        return $out;
    }

    static function parseError($fullJavascript, $position, $errorMsg) {
        // TODO: Handle the error: trigger_error, throw exception, return false...
        return false;
    }
}