(function () {
  'use strict';

  var symbol = {
    param: '&',
    key: ':',
    keyValue: '=',
    array: '@',
    flagString: "'",
    flagNumber: 'n',
    flagBool: 'b',
    flagDate: 'd',
    flagNull: '_',
    flagUndefined: ''
  };

  var toString = Object.prototype.toString;
  var isObject = function (value) { return value != null && typeof value === 'object'; };
  var isArray = function (value) { return toString.call(value) === '[object Array]'; };
  var notDefined = function (value) { return typeof value === 'undefined'; };

  var encodeObject = function (x, prefix) {
    var result = '', name, sub, key;
    for (name in x) {
      if (x.hasOwnProperty(name)) {
        key = (prefix ? prefix + symbol.key : '') + encodeURIComponent(name);
        sub = encode(x[name], key);

        result += (result ? symbol.param : '')
          + (sub[0] ? '' : key + symbol.keyValue)
          + sub[1];
      }
    }
    return result;
  };

  var encodeArray = function (x, prefix) {
    var result = '', i, c, sub, key;
    for (i = 0, c = x.length; i < c; ++i) {
      key = (prefix ? prefix + symbol.key : '') + symbol.array + i;
      sub = encode(x[i], key);
      result += (result ? symbol.param : '')
        + (sub[0] ? '' : key + symbol.keyValue)
        + sub[1];
    }
    return result;
  };

  var setProp = function (target, path, value) {
    var data, raw, key, i, n, count;

    if (!isObject(target) && !isArray(target)) {
      throw new Error('setProp: target is not an object or array: ' + toString.call(data));
    }
    data = target;
    for (i = 0, count = path.length; i < count; ++i) {
      n = i + 1;
      raw = path[i];
      key = (symbol.array === raw[0]) ? 0|raw.substring(1) : decodeURIComponent(raw);
      if (n === count) {
        if (symbol.array === raw[0] ? isArray(data) : isObject(data)) {
          data[key] = value;
        } else {
          throw new Error('setProp: property "' + path.join(':') + '" has wrong type: ' + toString.call(data));
        }
      } else {
        if (notDefined(data[key])) {
          data[key] = (symbol.array === path[n][0]) ? [] : {};
          data = data[key];
        } else if ((symbol.array === path[n][0]) ? isArray(data[key]) : isObject(data[key])) {
          data = data[key];
        } else {
          throw new Error('setProp: property "' + path.slice(0, n).join(':') + '" has wrong type: ' + toString.call(data[key]));
        }
      }
    }
    return true;
  };


  // todo: prevent cycle encoding
  function encode(x, prefix) {
    var complex = false, result, type;
    type = toString.call(x);
    switch (type) {
      case '[object String]':
        result = "'" + encodeURIComponent(x) + "'";
        break;
      case '[object Number]':
        result = isFinite(x) ? '' + x : symbol.flagNumber + x;
        break;
      case '[object Boolean]':
        result = symbol.flagBool + (+x);
        break;
      case '[object Object]':
        complex = true;
        result = encodeObject(x, prefix);
        break;
      case '[object Array]':
        complex = true;
        result = encodeArray(x, prefix);
        break;
      case '[object Date]':
        result = symbol.flagDate + x;
        break;
      case '[object Null]':
        result = symbol.flagNull;
        break;
      case '[object Undefined]':
        result = symbol.flagUndefined;
        break;
      default:
        result = symbol.flagUndefined;
        break;
    }
    return [complex, result];
  }

  function decode(s) {
    var result = {}, i, c, pos, parts, item, path, value;
    parts = ('' + s).split(symbol.param);
    for (i = 0, c = parts.length; i < c; ++i) {
      item = parts[i];
      if (-1 !== (pos = item.indexOf(symbol.keyValue))) {
        path = item.substring(0, pos).split(symbol.key);
        value = decodeURIComponent(item.substring(pos + 1));
        switch (value[0]) {
          case symbol.flagString:
            value = value.substring(1, value.length - 1);
            break;
          case symbol.flagNumber:
            value = +value.substring(1);
            break;
          case symbol.flagBool:
            value = !!(~~value.substring(1));
            break;
          case symbol.flagDate:
            value = new Date(value.substring(1));
            break;
          case symbol.flagNull:
            value = null;
            break;
          default:
            if (/^\d+$/.test(value)) {
              value = +value;
            } else {
              value = undefined;
            }
            break;
        }
        setProp(result, path, value);
      }
    }

    return result;
  }

  var query = {
    encode: function (x) { return encode(x, '')[1]; },
    decode: function (s) { return decode(s); }
  };

  angular.module('query', [])
    .factory('query', function () {
      return query;
    });

})();