Files
2023-04-29 00:38:15 +02:00

242 lines
6.9 KiB
Lua

local M = {}
local luadate = require("telekasten.utils.luadate")
--- Returns the day of week (1..Monday, ..., 7..Sunday) for Dec, 31st of year
--- see https://webspace.science.uu.nl/~gent0113/calendar/isocalendar.htm
--- see https://en.wikipedia.org/wiki/ISO_week_date
M.dow_for_year = function(year)
return (
year
+ math.floor(year / 4)
- math.floor(year / 100)
+ math.floor(year / 400)
) % 7
end
M.weeks_in_year = function(year)
local d = 0
local dy = M.dow_for_year(year) == 4 -- current year ends Thursday
local dyy = M.dow_for_year(year - 1) == 3 -- previous year ends Wednesday
if dy or dyy then
d = 1
end
return 52 + d
end
M.days_in_year = function(year)
local t = os.time({ year = year, month = 12, day = 31 })
return os.date("*t", t).yday
end
M.date_from_doy = function(year, doy)
local ret = {
year = year,
month = 1,
day = doy,
}
-- january is clear immediately
if doy < 32 then
return ret
end
local dmap = {
[1] = 31,
[2] = 28, -- will be fixed further down
[3] = 31,
[4] = 30,
[5] = 31,
[6] = 30,
[7] = 31,
[8] = 31,
[9] = 30,
[10] = 31,
[11] = 30,
[12] = 31,
}
if M.days_in_year(year) == 366 then
dmap[2] = 29
end
for month, d in pairs(dmap) do
doy = doy - d
if doy < 0 then
ret.day = doy + d
ret.month = month
return ret
end
end
return ret -- unreachable if input values are sane
end
-- the algo on wikipedia seems wrong, so we opt for full-blown luadate
M.isoweek_to_date = function(year, isoweek)
local ret = luadate(year .. "-W" .. string.format("%02d", isoweek) .. "-1")
return {
year = ret:getyear(),
month = ret:getmonth(),
day = ret:getday(),
}
end
local function daysuffix(day)
day = tostring(day)
if (day == "1") or (day == "21") or (day == "31") then
return "st"
end
if (day == "2") or (day == "22") then
return "nd"
end
if (day == "3") or (day == "23") then
return "rd"
end
return "th"
end
local daymap = {
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
"Sunday",
}
local monthmap = {
"January",
"February",
"March",
"April",
"May",
"June",
"July",
"August",
"September",
"October",
"November",
"December",
}
M.dateformats = {
date = "%Y-%m-%d",
week = "%V",
isoweek = "%Y-W%V",
time24 = "%H:%M:%S",
time12 = "%I:%M:%S %p",
}
function M.calculate_dates(date, calendar_monday)
local time = os.time(date)
local dinfo = os.date("*t", time) -- this normalizes the input to a full date table
local oneday = 24 * 60 * 60 -- hours * days * seconds
local oneweek = 7 * oneday
local df = M.dateformats
local dates = {}
-- this is to compensate for the calendar showing M-Su, but os.date Su is
-- always wday = 1
local wday = dinfo.wday - 1
if wday == 0 then
wday = 7
end
dates.year = dinfo.year
dates.month = dinfo.month
dates.day = dinfo.day
dates.hdate = daymap[wday]
.. ", "
.. monthmap[dinfo.month]
.. " "
.. dinfo.day
.. daysuffix(dinfo.day)
.. ", "
.. dinfo.year
local zonehour = string.sub(os.date("%z"), 1, 3)
local zonemin = string.sub(os.date("%z"), 4, 5)
dates.rfc3339 = os.date(df.date, time)
.. os.date("T%H:%M:%S")
.. "Z"
.. zonehour
.. ":"
.. zonemin
dates.time24 = os.date(df.time24, time)
dates.time12 = os.date(df.time12, time)
dates.date = os.date(df.date, time)
dates.prevday = os.date(df.date, time - oneday)
dates.nextday = os.date(df.date, time + oneday)
dates.week = os.date(df.week, time)
dates.prevweek = os.date(df.week, time - oneweek)
dates.nextweek = os.date(df.week, time + oneweek)
dates.isoweek = os.date(df.isoweek, time)
dates.isoprevweek = os.date(df.isoweek, time - oneweek)
dates.isonextweek = os.date(df.isoweek, time + oneweek)
-- things get a bit hairy at the year rollover. W01 only starts the first week ofs
-- January if it has more than 3 days. Partial weeks with less than 4 days are
-- considered W52, but os.date still sets the year as the new year, so Jan 1 2022
-- would appear as being in 2022-W52. That breaks linear linking respective
-- of next/prev week, so we want to put the days of that partial week in
-- January in 2021-W52. This tweak will only change the ISO formatted week string.
if tonumber(dates.week) == 52 and tonumber(dates.month) == 1 then
dates.isoweek = tostring(dates.year - 1) .. "-W52"
end
-- Find the Sunday that started this week regardless of the calendar
-- display preference. Then use that as the base to calculate the dates
-- for the days of the current week.
-- Finally, adjust Sunday to suit user calendar preference.
local starting_sunday = time - (wday * oneday)
local sunday_offset = 0
if calendar_monday == 1 then
sunday_offset = 7
end
dates.monday = os.date(df.date, starting_sunday + (1 * oneday))
dates.tuesday = os.date(df.date, starting_sunday + (2 * oneday))
dates.wednesday = os.date(df.date, starting_sunday + (3 * oneday))
dates.thursday = os.date(df.date, starting_sunday + (4 * oneday))
dates.friday = os.date(df.date, starting_sunday + (5 * oneday))
dates.saturday = os.date(df.date, starting_sunday + (6 * oneday))
dates.sunday = os.date(df.date, starting_sunday + (sunday_offset * oneday))
return dates
end
local function check_isoweek(year, isoweek, ydate)
print("*********** KW " .. isoweek .. " " .. year .. ": ")
-- local ret = M.weeknumber_to_date(year, isoweek)
local ret = M.isoweek_to_date(year, isoweek)
local result = ret.year == ydate.year
and ret.month == ydate.month
and ret.day == ydate.day
print(
ret.year
.. "-"
.. ret.month
.. "-"
.. ret.day
.. " == "
.. ydate.year
.. "-"
.. ydate.month
.. "-"
.. ydate.day
.. " : "
.. tostring(result)
)
end
M.run_tests = function()
print(check_isoweek(2020, 1, { year = 2019, month = 12, day = 30 })) -- 30.12.2019
print(check_isoweek(2020, 52, { year = 2020, month = 12, day = 21 })) -- 21.12.2020
print(check_isoweek(2020, 53, { year = 2020, month = 12, day = 28 })) -- 28.12.2020
print(check_isoweek(2021, 1, { year = 2021, month = 1, day = 4 })) -- 4.1.2020
print(check_isoweek(2021, 52, { year = 2021, month = 12, day = 27 })) -- 27.12.2021
print(check_isoweek(2022, 1, { year = 2022, month = 1, day = 3 })) -- 3.1.2022
end
-- M.run_tests()
return M