pattern_lexer.js

    // Pattern Lexer ------
    //=====================

    crossroads.patternLexer = (function () {

        var
            //match chars that should be escaped on string regexp
            ESCAPE_CHARS_REGEXP = /[\\.+*?\^$\[\](){}\/'#]/g,

            //trailing slashes (begin/end of string)
            LOOSE_SLASHES_REGEXP = /^\/|\/$/g,
            LEGACY_SLASHES_REGEXP = /\/$/g,

            //params - everything between `{ }` or `: :`
            PARAMS_REGEXP = /(?:\{|:)([^}:]+)(?:\}|:)/g,

            //used to save params during compile (avoid escaping things that
            //shouldn't be escaped).
            TOKENS = {
                'OS' : {
                    //optional slashes
                    //slash between `::` or `}:` or `\w:` or `:{?` or `}{?` or `\w{?`
                    rgx : /([:}]|\w(?=\/))\/?(:|(?:\{\?))/g,
                    save : '$1{{id}}$2',
                    res : '\\/?'
                },
                'RS' : {
                    //required slashes
                    //used to insert slash between `:{` and `}{`
                    rgx : /([:}])\/?(\{)/g,
                    save : '$1{{id}}$2',
                    res : '\\/'
                },
                'RQ' : {
                    //required query string - everything in between `{? }`
                    rgx : /\{\?([^}]+)\}/g,
                    //everything from `?` till `#` or end of string
                    res : '\\?([^#]+)'
                },
                'OQ' : {
                    //optional query string - everything in between `:? :`
                    rgx : /:\?([^:]+):/g,
                    //everything from `?` till `#` or end of string
                    res : '(?:\\?([^#]*))?'
                },
                'OR' : {
                    //optional rest - everything in between `: *:`
                    rgx : /:([^:]+)\*:/g,
                    res : '(.*)?' // optional group to avoid passing empty string as captured
                },
                'RR' : {
                    //rest param - everything in between `{ *}`
                    rgx : /\{([^}]+)\*\}/g,
                    res : '(.+)'
                },
                // required/optional params should come after rest segments
                'RP' : {
                    //required params - everything between `{ }`
                    rgx : /\{([^}]+)\}/g,
                    res : '([^\\/?]+)'
                },
                'OP' : {
                    //optional params - everything between `: :`
                    rgx : /:([^:]+):/g,
                    res : '([^\\/?]+)?\/?'
                }
            },

            LOOSE_SLASH = 1,
            STRICT_SLASH = 2,
            LEGACY_SLASH = 3,

            _slashMode = LOOSE_SLASH;


        function precompileTokens(){
            var key, cur;
            for (key in TOKENS) {
                if (TOKENS.hasOwnProperty(key)) {
                    cur = TOKENS[key];
                    cur.id = '__CR_'+ key +'__';
                    cur.save = ('save' in cur)? cur.save.replace('{{id}}', cur.id) : cur.id;
                    cur.rRestore = new RegExp(cur.id, 'g');
                }
            }
        }
        precompileTokens();


        function captureVals(regex, pattern) {
            var vals = [], match;
            while (match = regex.exec(pattern)) {
                vals.push(match[1]);
            }
            return vals;
        }

        function getParamIds(pattern) {
            return captureVals(PARAMS_REGEXP, pattern);
        }

        function getOptionalParamsIds(pattern) {
            return captureVals(TOKENS.OP.rgx, pattern);
        }

        function compilePattern(pattern, ignoreCase) {
            pattern = pattern || '';

            if(pattern){
                if (_slashMode === LOOSE_SLASH) {
                    pattern = pattern.replace(LOOSE_SLASHES_REGEXP, '');
                }
                else if (_slashMode === LEGACY_SLASH) {
                    pattern = pattern.replace(LEGACY_SLASHES_REGEXP, '');
                }

                //save tokens
                pattern = replaceTokens(pattern, 'rgx', 'save');
                //regexp escape
                pattern = pattern.replace(ESCAPE_CHARS_REGEXP, '\\$&');
                //restore tokens
                pattern = replaceTokens(pattern, 'rRestore', 'res');

                if (_slashMode === LOOSE_SLASH) {
                    pattern = '\\/?'+ pattern;
                }
            }

            if (_slashMode !== STRICT_SLASH) {
                //single slash is treated as empty and end slash is optional
                pattern += '\\/?';
            }
            return new RegExp('^'+ pattern + '$', ignoreCase? 'i' : '');
        }

        function replaceTokens(pattern, regexpName, replaceName) {
            var cur, key;
            for (key in TOKENS) {
                if (TOKENS.hasOwnProperty(key)) {
                    cur = TOKENS[key];
                    pattern = pattern.replace(cur[regexpName], cur[replaceName]);
                }
            }
            return pattern;
        }

        function getParamValues(request, regexp, shouldTypecast) {
            var vals = regexp.exec(request);
            if (vals) {
                vals.shift();
                if (shouldTypecast) {
                    vals = typecastArrayValues(vals);
                }
            }
            return vals;
        }

        function interpolate(pattern, replacements) {
            if (typeof pattern !== 'string') {
                throw new Error('Route pattern should be a string.');
            }

            var replaceFn = function(match, prop){
                    var val;
                    if (prop in replacements) {
                        val = replacements[prop];
                        if (match.indexOf('*') === -1 && val.indexOf('/') !== -1) {
                            throw new Error('Invalid value "'+ val +'" for segment "'+ match +'".');
                        }
                    }
                    else if (match.indexOf('{') !== -1) {
                        throw new Error('The segment '+ match +' is required.');
                    }
                    else {
                        val = '';
                    }
                    return val;
                };

            if (! TOKENS.OS.trail) {
                TOKENS.OS.trail = new RegExp('(?:'+ TOKENS.OS.id +')+$');
            }

            return pattern
                        .replace(TOKENS.OS.rgx, TOKENS.OS.save)
                        .replace(PARAMS_REGEXP, replaceFn)
                        .replace(TOKENS.OS.trail, '') // remove trailing
                        .replace(TOKENS.OS.rRestore, '/'); // add slash between segments
        }

        //API
        return {
            strict : function(){
                _slashMode = STRICT_SLASH;
            },
            loose : function(){
                _slashMode = LOOSE_SLASH;
            },
            legacy : function(){
                _slashMode = LEGACY_SLASH;
            },
            getParamIds : getParamIds,
            getOptionalParamsIds : getOptionalParamsIds,
            getParamValues : getParamValues,
            compilePattern : compilePattern,
            interpolate : interpolate
        };

    }());