'use strict';

var required = require('requires-port')
  , lolcation = require('./lolcation')
  , qs = require('querystringify')
  , relativere = /^\/(?!\/)/;

/**
 * These are the parse instructions for the URL parsers, it informs the parser
 * about:
 *
 * 0. The char it Needs to parse, if it's a string it should be done using
 *    indexOf, RegExp using exec and NaN means set as current value.
 * 1. The property we should set when parsing this value.
 * 2. Indication if it's backwards or forward parsing, when set as number it's
 *    the value of extra chars that should be split off.
 * 3. Inherit from location if non existing in the parser.
 * 4. `toLowerCase` the resulting value.
 */
var instructions = [
  ['#', 'hash'],                        // Extract from the back.
  ['?', 'query'],                       // Extract from the back.
  ['//', 'protocol', 2, 1, 1],          // Extract from the front.
  ['/', 'pathname'],                    // Extract from the back.
  ['@', 'auth', 1],                     // Extract from the front.
  [NaN, 'host', undefined, 1, 1],       // Set left over value.
  [/\:(\d+)$/, 'port'],                 // RegExp the back.
  [NaN, 'hostname', undefined, 1, 1]    // Set left over.
];

/**
 * The actual URL instance. Instead of returning an object we've opted-in to
 * create an actual constructor as it's much more memory efficient and
 * faster and it pleases my CDO.
 *
 * @constructor
 * @param {String} address URL we want to parse.
 * @param {Boolean|function} parser Parser for the query string.
 * @param {Object} location Location defaults for relative paths.
 * @api public
 */
function URL(address, location, parser) {
  if (!(this instanceof URL)) {
    return new URL(address, location, parser);
  }

  var relative = relativere.test(address)
    , parse, instruction, index, key
    , type = typeof location
    , url = this
    , i = 0;

  //
  // The following if statements allows this module two have compatibility with
  // 2 different API:
  //
  // 1. Node.js's `url.parse` api which accepts a URL, boolean as arguments
  //    where the boolean indicates that the query string should also be parsed.
  //
  // 2. The `URL` interface of the browser which accepts a URL, object as
  //    arguments. The supplied object will be used as default values / fall-back
  //    for relative paths.
  //
  if ('object' !== type && 'string' !== type) {
    parser = location;
    location = null;
  }

  if (parser && 'function' !== typeof parser) {
    parser = qs.parse;
  }

  location = lolcation(location);

  for (; i < instructions.length; i++) {
    instruction = instructions[i];
    parse = instruction[0];
    key = instruction[1];

    if (parse !== parse) {
      url[key] = address;
    } else if ('string' === typeof parse) {
      if (~(index = address.indexOf(parse))) {
        if ('number' === typeof instruction[2]) {
          url[key] = address.slice(0, index);
          address = address.slice(index + instruction[2]);
        } else {
          url[key] = address.slice(index);
          address = address.slice(0, index);
        }
      }
    } else if (index = parse.exec(address)) {
      url[key] = index[1];
      address = address.slice(0, address.length - index[0].length);
    }

    url[key] = url[key] || (instruction[3] || ('port' === key && relative) ? location[key] || '' : '');

    //
    // Hostname, host and protocol should be lowercased so they can be used to
    // create a proper `origin`.
    //
    if (instruction[4]) {
      url[key] = url[key].toLowerCase();
    }
  }

  //
  // Also parse the supplied query string in to an object. If we're supplied
  // with a custom parser as function use that instead of the default build-in
  // parser.
  //
  if (parser) url.query = parser(url.query);

  //
  // We should not add port numbers if they are already the default port number
  // for a given protocol. As the host also contains the port number we're going
  // override it with the hostname which contains no port number.
  //
  if (!required(url.port, url.protocol)) {
    url.host = url.hostname;
    url.port = '';
  }

  //
  // Parse down the `auth` for the username and password.
  //
  url.username = url.password = '';
  if (url.auth) {
    instruction = url.auth.split(':');
    url.username = instruction[0] || '';
    url.password = instruction[1] || '';
  }

  //
  // The href is just the compiled result.
  //
  url.href = url.toString();
}

/**
 * This is convenience method for changing properties in the URL instance to
 * insure that they all propagate correctly.
 *
 * @param {String} prop Property we need to adjust.
 * @param {Mixed} value The newly assigned value.
 * @returns {URL}
 * @api public
 */
URL.prototype.set = function set(part, value, fn) {
  var url = this;

  if ('query' === part) {
    if ('string' === typeof value && value.length) {
      value = (fn || qs.parse)(value);
    }

    url[part] = value;
  } else if ('port' === part) {
    url[part] = value;

    if (!required(value, url.protocol)) {
      url.host = url.hostname;
      url[part] = '';
    } else if (value) {
      url.host = url.hostname +':'+ value;
    }
  } else if ('hostname' === part) {
    url[part] = value;

    if (url.port) value += ':'+ url.port;
    url.host = value;
  } else if ('host' === part) {
    url[part] = value;

    if (/\:\d+/.test(value)) {
      value = value.split(':');
      url.hostname = value[0];
      url.port = value[1];
    }
  } else {
    url[part] = value;
  }

  url.href = url.toString();
  return url;
};

/**
 * Transform the properties back in to a valid and full URL string.
 *
 * @param {Function} stringify Optional query stringify function.
 * @returns {String}
 * @api public
 */
URL.prototype.toString = function toString(stringify) {
  if (!stringify || 'function' !== typeof stringify) stringify = qs.stringify;

  var query
    , url = this
    , result = url.protocol +'//';

  if (url.username) {
    result += url.username;
    if (url.password) result += ':'+ url.password;
    result += '@';
  }

  result += url.hostname;
  if (url.port) result += ':'+ url.port;

  result += url.pathname;

  query = 'object' === typeof url.query ? stringify(url.query) : url.query;
  if (query) result += '?' !== query.charAt(0) ? '?'+ query : query;

  if (url.hash) result += url.hash;

  return result;
};

//
// Expose the URL parser and some additional properties that might be useful for
// others.
//
URL.qs = qs;
URL.location = lolcation;
module.exports = URL;