export function getDayViewHourGrid(
    { viewDate, hourSegments, dayStart, dayEnd }:
        { viewDate: Date, hourSegments: number, dayStart: any, dayEnd: any }
): DayViewHour[] {

    const hours: DayViewHour[] = [];

    const startOfView: Date = dateFns.setMinutes(dateFns.setHours(dateFns.startOfDay(viewDate), dayStart.hour), dayStart.minute);
    const endOfView: Date = dateFns.setMinutes(dateFns.setHours(dateFns.startOfMinute(dateFns.endOfDay(viewDate)), dayEnd.hour), dayEnd.minute);
    const segmentDuration: number = MINUTES_IN_HOUR / hourSegments;
    const startOfViewDay: Date = dateFns.startOfDay(viewDate);

    for (let i: number = 0; i < HOURS_IN_DAY; i++) {
        const segments: DayViewHourSegment[] = [];
        for (let j: number = 0; j < hourSegments; j++) {
            const date: Date = dateFns.addMinutes(dateFns.addHours(startOfViewDay, i), j * segmentDuration);
            if (date >= startOfView && date < endOfView) {
                segments.push({
                    date,
                    isStart: j === 0
                });
            }
        }
        if (segments.length > 0) {
            hours.push({ segments });
        }
    }

    return hours;
}

function getWeekViewEventSpan(
    { event, offset, startOfWeek, excluded }: { event: CalendarEvent, offset: number, startOfWeek: Date, excluded: number[] }): number {
    const begin: Date = event.start < startOfWeek ? startOfWeek : event.start;
    let span: number = 1;
    if (event.end) {
        span = dateFns.differenceInDays(dateFns.addMinutes(dateFns.endOfDay(event.end), 1), dateFns.startOfDay(begin));
    }
    const totalLength: number = offset + span;
    if (totalLength > DAYS_IN_WEEK) {
        span = DAYS_IN_WEEK - offset;
    }
    return span - getExcludedDays({ startDate: begin, days: span, excluded });
}

export function iCalEventForExam(module: Module, semester: Semester): EventOption | null {
  const semesterData = getModuleSemesterData(module, semester);
  if (!semesterData) return null;

  const { examDate, examDuration } = semesterData;
  if (!examDate) return null;

  const start = new Date(examDate);
  if (!isValid(start)) return null;

  return {
    start,
    end: addMinutes(start, examDuration || DEFAULT_EXAM_DURATION),
    summary: `${module.moduleCode} Exam`,
    description: module.title,
  };
}

function addLessonOffset(date: Date, hourOffset: number): Date {
  return addMinutes(date, hourOffset * 60);
}