export function formatStartEnd(start: Date, end: Date, timezone: Timezone): string {
  var startWallTime = WallTime.UTCToWallTime(start, timezone.toString());
  var endWallTime = WallTime.UTCToWallTime(end, timezone.toString());
  var endShiftWallTime = WallTime.UTCToWallTime(new Date(end.valueOf() - 1), timezone.toString());

  var formatted: string;
  if (startWallTime.getFullYear() !== endShiftWallTime.getFullYear()) {
    formatted = [formatWithYear(startWallTime), formatWithYear(endShiftWallTime)].join(JOIN);
  } else {
    if (startWallTime.getMonth() !== endShiftWallTime.getMonth() || startWallTime.getDate() !== endShiftWallTime.getDate()) {
      formatted = [formatWithoutYear(startWallTime), formatWithYear(endShiftWallTime)].join(JOIN);
    } else {
      formatted = formatWithYear(startWallTime);
    }
  }

  if (startWallTime.getHours() || endWallTime.getHours()) {
    var timeString: string;
    if (startWallTime.getHours() !== endShiftWallTime.getHours()) {
      timeString = [formatTimeOfDay(startWallTime), formatTimeOfDay(endShiftWallTime)].join(JOIN);
    } else {
      timeString = formatTimeOfDay(startWallTime);
    }
    formatted += ' ' + timeString.toLowerCase();
  }

  return formatted;
}

export function getWallTimeString(date: Date, timezone: Timezone, includeTime?: boolean, delimiter?: string): string {
  const wallTimeISOString = wallTimeHelper(WallTime.UTCToWallTime(date, timezone.toString())).toISOString();
  if (includeTime) {
    return wallTimeISOString.replace(/(\.\d\d\d)?Z?$/, '').replace('T', delimiter || ', ');
  }
  return wallTimeISOString.replace( /:\d\d(\.\d\d\d)?Z?$/, '').split('T')[0];
}

export function formatTimeBasedOnGranularity(range: TimeRange, granularity: Duration, timezone: Timezone, locale: Locale): string {
  const wallTimeStart = WallTime.UTCToWallTime(range.start, timezone.toString());

  const year = wallTimeStart.getFullYear();
  const month = wallTimeStart.getMonth();
  const day = wallTimeStart.getDate();
  const hour = wallTimeStart.getHours();
  const minute = wallTimeStart.getMinutes();
  const second = wallTimeStart.getSeconds();

  const monthString = locale.shortMonths[month];
  const hourToTwelve = hour % 12 === 0 ? 12 : hour % 12;
  const amPm = (hour / 12) >= 1 ? 'pm' : 'am';

  var granularityString = granularity.toJS();
  var unit = granularityString.substring(granularityString.length - 1);

  switch (unit) {
    case 'S':
      return `${monthString} ${day}, ${pad(hour)}:${pad(minute)}:${pad(second)}`;
    case 'M':
      var prefix = granularityString.substring(0, 2);
      return prefix === "PT" ? `${monthString} ${day}, ${hourToTwelve}:${pad(minute)}${amPm}` : `${monthString}, ${year}`;
    case 'H':
      return `${monthString} ${day}, ${year}, ${hourToTwelve}${amPm}`;
    case 'D':
      return `${monthString} ${day}, ${year}`;
    case 'W':
      return `${formatTimeRange(range, timezone, DisplayYear.ALWAYS)}`;
    default:
      return cleanISOString(wallTimeHelper(wallTimeStart).toISOString());
  }
}

export function formatTimeRange(timeRange: TimeRange, timezone: Timezone, displayYear: DisplayYear): string {
  var { start, end } = timeRange;
  var startWallTime = WallTime.UTCToWallTime(start, timezone.toString());
  var endWallTime = WallTime.UTCToWallTime(end, timezone.toString());
  var endWallTimeInclusive = getEndWallTimeInclusive(end, timezone);

  var showingYear = true;
  var formatted: string;
  if (startWallTime.getFullYear() !== endWallTimeInclusive.getFullYear()) {
    formatted = [FORMAT_WITH_YEAR(startWallTime), FORMAT_WITH_YEAR(endWallTimeInclusive)].join(' - ');
  } else {
    showingYear = displayYear === DisplayYear.ALWAYS || (displayYear === DisplayYear.IF_DIFF && !isCurrentYear(endWallTimeInclusive.getFullYear(), timezone));
    var fmt = showingYear ? FORMAT_WITH_YEAR : FORMAT_WITHOUT_YEAR;
    if (startWallTime.getMonth() !== endWallTimeInclusive.getMonth() || startWallTime.getDate() !== endWallTimeInclusive.getDate()) {
      formatted = [FORMAT_WITHOUT_YEAR(startWallTime), fmt(endWallTimeInclusive)].join(' - ');
    } else {
      formatted = fmt(startWallTime);
    }
  }

  if (startWallTime.getHours() || startWallTime.getMinutes() || endWallTime.getHours() || endWallTime.getMinutes()) {
    formatted += (showingYear ? ' ' : ', ');

    var startTimeStr = formatTimeOfDay(startWallTime).toLowerCase();
    var endTimeStr = formatTimeOfDay(endWallTime).toLowerCase();

    if (startTimeStr === endTimeStr) {
      formatted += startTimeStr;
    } else {
      if (startTimeStr.substr(-2) === endTimeStr.substr(-2)) {
        startTimeStr = startTimeStr.substr(0, startTimeStr.length - 2);
      }
      formatted += [startTimeStr, endTimeStr].join('-');
    }
  }

  return formatted;
}

export function monthToWeeks(firstDayOfMonth: Date, timezone: Timezone, locale: Locale): Date[][] {
  const weeks: Date[][] = [];
  const firstDayNextMonth = month.shift(firstDayOfMonth, timezone, 1);

  let week: Date[] = [];
  let currentPointer = day.floor(firstDayOfMonth, timezone);
  while (currentPointer < firstDayNextMonth) {
    var wallTime = WallTime.UTCToWallTime(currentPointer, timezone.toString());
    if ((wallTime.getDay() === locale.weekStart || 0) && week.length > 0) {
      weeks.push(week);
      week = [];
    }

    week.push(currentPointer);
    currentPointer = day.shift(currentPointer, timezone, 1);
  }
  // push last week
  if (week.length > 0) weeks.push(week);
  return weeks;
}

export function getEndWallTimeInclusive(exclusiveEnd: Date, timezone: Timezone) {
  return WallTime.UTCToWallTime(exclusiveToInclusiveEnd(exclusiveEnd), timezone.toString());
}

function isCurrentYear(year: number, timezone: Timezone): boolean {
  var nowWallTime = WallTime.UTCToWallTime(new Date(), timezone.toString());
  return nowWallTime.getFullYear() === year;
}

export function getWallTimeMonthWithYear(date: Date, timezone: Timezone) {
  return FORMAT_FULL_MONTH_WITH_YEAR(WallTime.UTCToWallTime(date, timezone.toString()));
}

export function getWallTimeDay(date: Date, timezone: Timezone) {
  return WallTime.UTCToWallTime(date, timezone.toString()).getDate();
}