index.js

'use strict';

module.exports = reversePath;

// regex from https://github.com/component/path-to-regexp
var PATH_REGEXP = new RegExp([
  // Match already escaped characters that would otherwise incorrectly appear
  // in future matches. This allows the user to escape special characters that
  // shouldn't be transformed.
  '(\\\\.)',
  // Match Express-style parameters and un-named parameters with a prefix
  // and optional suffixes. Matches appear as:
  //
  // "/:test(\\d+)?" => ["/", "test", "\d+", undefined, "?"]
  // "/route(\\d+)" => [undefined, undefined, undefined, "\d+", undefined]
  '([\\/.])?(?:\\:(\\w+)(?:\\(((?:\\\\.|[^)])*)\\))?|\\(((?:\\\\.|[^)])*)\\))([+*?])?',
  // Match regexp special characters that should always be escaped.
  '([.+*?=^!:${}()[\\]|\\/])'
].join('|'), 'g');

function reversePath(path, params, options) {
    var index = 0;
    params = params || {};
    options = options || {};

    return path.replace(PATH_REGEXP, replace);

    function replace(match, escaped, prefix, key, capture, group, optional, escape) {
        if(escaped) return escaped;
        if(escape) return escape;

        prefix = prefix || '';

        var value = params[key || index++];

        if(value === undefined) {
            if(optional) {
                value = '';
            } else {
                throw new Error('Parameter "' + key + '" is required.');
            }
        }

        return prefix + value;
    }
}