--
-- Adds holidays to Rainlendar. They events are not stored permanently
-- so they are added every time Rainlendar is refreshed.
--
function WeekHolidays_CreateHolidays()
   WeekHolidays_CreateWeekEvent(42, 10)
end

function WeekHolidays_CreateWeekEvent(weekNumber, count)
  year = tonumber(os.date("%Y"))
  for i = 1,count do
    WeekHolidays_CreateWeekEventFromYear(weekNumber, year)
    year = year + 1
  end
end

function WeekHolidays_CreateWeekEventFromYear(weekNumber, year)
  date = WeekHolidays_CalculateFirstDayOfWeekN(weekNumber, year)

  strEvent = "BEGIN:VEVENT\n"
  strEvent = strEvent .. "UID:Week" .. weekNumber .. "-Year" .. year .. "\n"
  strEvent = strEvent .. "SUMMARY:Week " .. weekNumber .. " of Year " .. year .. "\n"
  strEvent = strEvent .. "DTSTART;VALUE=DATE:" .. string.format("%04i%02i%02i", date[1], date[2], date[3]) .. "\n"
  strEvent = strEvent .. "DTEND;VALUE=DATE:" .. string.format("%04i%02i%02i", date[1], date[2], date[3] + 7) .. "\n"
  strEvent = strEvent .. "CATEGORIES:Holidays\n"
  strEvent = strEvent .. "END:VEVENT"
  Rainlendar_CreateComponent(strEvent)
end

--
-- Calculates the first days of the week WW
--
function WeekHolidays_CalculateFirstDayOfWeekN(weekNumber, year)
  weekday7 = tonumber(os.date("%w", os.time{year=year, month=1, day=7}))
  if (weekday7 > 3) then
    firstThursday = 11 - weekday7
  else
    firstThursday = 4 - weekday7
  end

  firstDayOfWeekN = firstThursday + (weekNumber - 1) * 7 - 3
  date = WeekHolidays_ConvertDOYToDate(firstDayOfWeekN, year)
  return {year, date[1], date[2]}
end

function WeekHolidays_ConvertDOYToDate(day, year)
  MonthDays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
  MonthDaysL = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
  month = 1
 
  if WeekHolidays_IsLeapYear(year) then
    while (day > MonthDaysL[month]) do
      day = day - MonthDaysL[month]
      month = month + 1
    end
  else
    while (day > MonthDays[month]) do
      day = day - MonthDays[month]
      month = month + 1
    end
  end
 
  return {month, day}
end

function WeekHolidays_IsLeapYear(year)
  if (year % 4 == 0 and year % 100 ~= 0) or (year % 400 == 0) then
    return true
  else
    return false
  end
end

--
-- This gets executed when the script is read (i.e. on every refresh)
--
WeekHolidays_CreateHolidays()