route.js

var XRegExp = require('xregexp').XRegExp;

exports = module.exports = Route;

function Route(path, options) {
  this.options = {
    recursiveWildcard:true,
    caseSensitive:    false,
    wildcardInPairs:  false
  }
  this.setOptions(options);
  this.path = path;
  this.regex = null;
}

/**
 * Set route options
 * @param options
 */
Route.prototype.setOptions = function (options) {
  for (var prop in options) {
    this.options[prop] = options[prop];
  }
}
/**
 * Creates a regular expression from the provided `path` to match the URL against
 * @return XRegExp
 * @todo add parameter-specific regexes like :id => [\d]+, clean the regex items like `\.` so `\` => `\\`
 * @todo if a Regex object passed => extract pattern
 */
Route.prototype.compile = function () {
  var path = this.path;
  // force all inner `masked` parameters to be required
  path = path.replace(/\/\*\*/g, '/*');

  // store the cleaned path to be used for URL generation
  this.cleanedPath = path;

  // make bracketed groups in url path a optional regex group
  path = path.replace(/\)/g, ')?');

  //the last `masked` parameter is optional
  if (path.slice(-2) == '/*') {
    path = path.slice(0, -2) + "/**";
  }

  //escape full stops
  path = path.replace(/\./g, '\\.');

  // change wildcards , the `*` (calling them `masked` parameters) to masked0, masked1...
  var maskedWildcardName = '';
  var hasMaskedWildcard = false;
  var masked = [];
  var i = 0;

  path = XRegExp.replace(path, XRegExp('/\\*\\*?', 'g'), function (match) {
    var splatName = 'splat' + i;
    i++;
    masked.push(splatName);
    // last `splat` is optional and allows having `/` inside of it
    if (match == '/**') {
      hasMaskedWildcard = true;
      maskedWildcardName = splatName;
      return '(/(?<' + splatName + '>.*))?';
    }
    // any other `masked` parameters are required and don't allow `/` inside of them
    return '/(?<' + splatName + '>[^/]+)';
  });

  //the last `masked` parameter is optional
  if (path.slice(-1) == '/') {
    path = path.slice(0, -1);
  }

  this.hasMaskedWildcard = hasMaskedWildcard;
  this.masked = masked;
  this.maskedWildcardName = maskedWildcardName;


  // change & count named parameters ( `:params`)
  var params = [];
  path = XRegExp.replace(path, XRegExp(':[\\p{L}0-9_]+', 'g'), function (match) {
    match = match.replace(':', '');
    if (params.indexOf(match) > -1) return ':' + match;
    params.push(match);
    return '(?<' + match + '>[^/]+)';
  });
  this.params = params;


  // Check if there is optional parts in the path
  var optionalParams = [];
  var bracketGroups = [];
  var self = this;

  // Performance: only check if there's a bracket character in the path
  if (self.cleanedPath.indexOf('(') > -1) {
    var unclosed = [];
    for (var i = 0; i <= self.cleanedPath.length - 1; i++) {
      var currentChar = self.cleanedPath[i];
      if (currentChar == '(') {
        bracketGroups.push({
          start: i,
          end:   null,
          params:[]
        });
        unclosed.push(bracketGroups.length - 1);
        continue;
      }
      if (currentChar == ')') {
        bracketGroups[unclosed.pop()].end = i;
      }
    }
    // Order by opening bracket position, descending
    bracketGroups.sort(function (a, b) {
      return a.start > b.start ? -1 : 1;
    })
    // Check for parameters in the optional parts, i.e. optional parameters
    params.forEach(function (paramName) {
      var index = self.cleanedPath.indexOf(':' + paramName);
      bracketGroups.every(function (group) {
        if (group.start < index && group.end > index && optionalParams.indexOf(paramName) == -1) {
          optionalParams.push(paramName);
          group.params.push(paramName);
          return false;
        }
        return true;
      })
    })
  }
  this.optionalParams = optionalParams;
  this.optionalParts = bracketGroups;

  // Store compiled regex
  this.regex = XRegExp('^' + path + '$', this.options.caseSensitive ? 'i' : undefined);
  return this.regex;
}


/**
 * Check if URL matches the route and if it does extract parameters
 * @param url
 * @return {*}
 */
Route.prototype.match = function (url) {
  //make sure the last `/` is trimmed off the url, otherwise last splash can falsely be empty string, i.e. ''
  if (url.slice(-1) == '/') {
    url = url.slice(0, -1);
  }
  var path = this.path;

  // Matches url?
  // Performance: If there isn't any regex characters `*:()` then simply check for equality
  if (path.indexOf('*') == -1 && path.indexOf(':') == -1 && path.indexOf('(') == -1 && path.indexOf(')') == -1 && path == url) {
    return true;
  }
  var regex = this.regex ? this.regex : this.compile();
  var matches = XRegExp.exec(url, regex);
  if (matches == null) return false;

  // Initialise the return value (found parameters)
  var self = this;
  var RequestParams = {_masked:[]};

  // All named parameters
  self.params.forEach(function (param) {
    if (matches[param] == undefined) return;
    RequestParams[param] = matches[param];
  });

  // All masked/unnamed parameters
  var masked = self.masked;
  masked.every(function (maskedName) {
    if (matches[maskedName] == undefined) return true;
    if (maskedName != self.maskedWildcardName) {
      RequestParams._masked.push(matches[maskedName]);
      return true;
    }
    // there is a anything-goes wildcard in the end of the url path, handle it:
    if (self.options.recursiveWildcard) {
      var maskedWildcardData = matches[maskedName].split('/');
      // If we have `.../id/23` then:
      // 1) parse is as 0=>id, 1=>23
      if (!self.options.wildcardInPairs) {
        RequestParams._masked = RequestParams._masked.concat(maskedWildcardData);
        return false;
      }
      // 2) parse is as id => 23
      var i = 0;
      while (maskedWildcardData[i + 1] != undefined) {
        if (i % 2 != 0) {
          i++;
          continue;
        }
        RequestParams[maskedWildcardData[i]] = maskedWildcardData[i + 1];
        i++;
      }
    } else {
      RequestParams._masked.push(matches[maskedName]);
    }
    return false;
  });

  return RequestParams;
}


/**
 * Builds a URL using provided parameters
 *
 * @param {array} userParams The parameters, example: {id:4, _masked:[2, 1, 2]}
 * @return {String}
 */
Route.prototype.generate = function (userParams) {
  // Initialise return value
  var self = this;
  if (!this.regex) this.compile();
  var url = this.cleanedPath;
  var foundParameters = [];
  var knownNamedParameters = this.params;
  userParams = userParams == undefined ? {_masked:[]} : userParams;
  userParams._masked = userParams._masked == undefined ? [] : userParams._masked;
  // Check what parameters were provided by the user
  knownNamedParameters.forEach(function (name) {
    if (userParams[name] == undefined) return;
    foundParameters.push(name);
  })

  // Has the user provided all parameters?
  if (foundParameters.length != knownNamedParameters.length) {
    // Don't match this route if there can't be any optional parameters
    if (this.optionalParams.length == 0) throw new Error('not all url parameters are provided');
    // Remove optional parts with missing parameters inside
    url = this.removePartsWithMissingParams(url, userParams);
  }
  if (this.optionalParams.length) {
    url = url.replace(/[\(\)]/g, '');
  }

  // Replace named parameters
  foundParameters.forEach(function (name) {
    url = url.replace(':' + name, userParams[name]);
  })

  // Replace masked/unnamed parameters, account for masked parameters that could have been removed in the optional parts
  var maskCount = url.match(/\*/g);
  var requiredMaskedNum = maskCount == null ? 0 : maskCount.length;
  requiredMaskedNum = this.hasMaskedWildcard ? requiredMaskedNum - 1 : requiredMaskedNum;
  var usedMasked = 0;

  // Handle masked parameters
  userParams._masked.forEach(function (value, i) {
    // fill in required masked parameters
    if (usedMasked < requiredMaskedNum) {
      url = url.replace('*', value);
      usedMasked++;
      return true;
    }
    if (url.indexOf('*') == -1) throw new Error('too much `_masked` values provided. if you think this is not the problem check if you forgot to pass a named parameter you wanted');
    // if wildcard parameters are enabled and are not parsed in pairs join the remaining of userParams._masked
    if (self.hasMaskedWildcard && !self.options.wildcardInPairs) {
      url = url.replace('*', userParams._masked.splice(i).join('/'));
    }
    return false;
  });
  if (userParams._masked.length < requiredMaskedNum) throw new Error('not enough `_masked` values provided');
  delete userParams._masked;

  // Handle optional masked parameters
  if (this.hasMaskedWildcard && url.indexOf('*') > -1) {
    // Make sure we replace the last `*` with something (even if it is an empty string)
    var lastMaskReplacement = '';
    // Handle masked wildcard parameters parsed in pairs
    if (this.options.wildcardInPairs) {
      for (var name in userParams) {
        var value = userParams[name];
        if (foundParameters.indexOf(name) > -1) continue;
        lastMaskReplacement += name + '/' + value + '/';
      }
    }
    url = url.replace('*', lastMaskReplacement);
  }

  return url;
}


Route.prototype.removePartsWithMissingParams = function (url, userParams) {
  var groupsToRemove = [];
  this.optionalParts.forEach(function (part) {
    part.params.every(function (optionalParam) {
      if (userParams[optionalParam] == undefined) {
        groupsToRemove.push(part);
        return false;
      }
      return true;
    });
  });
  var subtractPairs = [];
  groupsToRemove.forEach(function (group) {
    var from = group.start, to = group.end, accountedForRemoval = false;
    subtractPairs.forEach(function (subtract, i) {
      if (from < subtract.start && to > subtract.end) {
        to = to - (subtract.end + 1 - subtract.start);
        subtractPairs[i] = {start:from, end:to};
        accountedForRemoval = true;
      }
    });
    url = url.substr(0, from) + url.substr(to + 1);
    if (!accountedForRemoval) subtractPairs.push({start:group.start, end:group.end});
  });
  return url;
}