<!--
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
-->
<script>
function StateHeader(state) {
  this.state = state;
  this.headerOrder = 1;
};

function LetterHeader(letter) {
  this.letter = letter;
  this.headerOrder = 2;
}

function CitySequence(cities)
{
  this.items = [];
  this.cursor = 0;

  var lastState;
  var lastLetter;

  for (var i = 0; i < cities.length; i++) {
    var city = cities[i];
    if (!lastState || lastState.state != city.state) {
      lastState = new StateHeader(city.state);
      this.items.push(lastState);
      lastLetter = undefined;
    }
    if (!lastLetter || lastLetter.letter != city.name[0]) {
      lastLetter = new LetterHeader(city.name[0]);
      this.items.push(lastLetter);
    }
    this.items.push(city);
  }
};

CitySequence.prototype = {
  append: function(other) {
    var lastCity = this.items[this.items.length - 1];
    var firstOtherCity = other.items[2];

    var index = 0;
    if (firstOtherCity.state == lastCity.state) {
      // skip StateHeader
      if (firstOtherCity.name[0] == lastCity.name[0]) {
        // skip LetterHeader
        index = 2;
      } else {
        index = 1;
      }
    }

    for (; index < other.items.length; index++) {
      this.items.push(other.items[index]);
    }
  }
};

module.exports = CitySequence;

</script>