-local strftime = require "luatz.strftime".strftime
-local strformat = string.format
-local floor = math.floor
-local idiv do
- -- Try and use actual integer division when available (Lua 5.3+)
- local idiv_loader = (loadstring or load)([[return function(n,d) return n//d end]], "idiv") -- luacheck: ignore 113
- if idiv_loader then
- idiv = idiv_loader()
- else
- idiv = function(n, d)
- return floor(n/d)
- end
- end
-end
-
-
-local mon_lengths = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
--- Number of days in year until start of month; not corrected for leap years
-local months_to_days_cumulative = {0}
-for i = 2, 12 do
- months_to_days_cumulative[i] = months_to_days_cumulative[i-1] + mon_lengths[i-1]
-end
--- For Sakamoto's Algorithm (day of week)
-local sakamoto = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
-
-local function is_leap(y)
- if (y % 4) ~= 0 then
- return false
- elseif (y % 100) ~= 0 then
- return true
- else
- return (y % 400) == 0
- end
-end
-
-local function month_length(m, y)
- if m == 2 then
- return is_leap(y) and 29 or 28
- else
- return mon_lengths[m]
- end
-end
-
-local function leap_years_since(year)
- return idiv(year, 4) - idiv(year, 100) + idiv(year, 400)
-end
-
-local function day_of_year(day, month, year)
- local yday = months_to_days_cumulative[month]
- if month > 2 and is_leap(year) then
- yday = yday + 1
- end
- return yday + day
-end
-
-local function day_of_week(day, month, year)
- if month < 3 then
- year = year - 1
- end
- return(year + leap_years_since(year) + sakamoto[month] + day) % 7 + 1
-end
-
-local function borrow(tens, units, base)
- local frac = tens % 1
- units = units + frac * base
- tens = tens - frac
- return tens, units
-end
-
-local function carry(tens, units, base)
- if units >= base then
- tens = tens + idiv(units, base)
- units = units % base
- elseif units < 0 then
- tens = tens + idiv(units, base)
- units = (base + units) % base
- end
- return tens, units
-end
-
--- Modify parameters so they all fit within the "normal" range
-local function normalise(year, month, day, hour, min, sec)
- -- `month` and `day` start from 1, need -1 and +1 so it works modulo
- month, day = month - 1, day - 1
-
- -- Convert everything (except seconds) to an integer
- -- by propagating fractional components down.
- year , month = borrow(year , month, 12)
- -- Carry from month to year first, so we get month length correct in next line around leap years
- year , month = carry(year, month, 12)
- month, day = borrow(month, day , month_length(floor(month + 1), year))
- day , hour = borrow(day , hour , 24)
- hour , min = borrow(hour , min , 60)
- min , sec = borrow(min , sec , 60)
-
- -- Propagate out of range values up
- -- e.g. if `min` is 70, `hour` increments by 1 and `min` becomes 10
- -- This has to happen for all columns after borrowing, as lower radixes may be pushed out of range
- min , sec = carry(min , sec , 60) -- TODO: consider leap seconds?
- hour , min = carry(hour, min , 60)
- day , hour = carry(day , hour, 24)
- -- Ensure `day` is not underflowed
- -- Add a whole year of days at a time, this is later resolved by adding months
- -- TODO[OPTIMIZE]: This could be slow if `day` is far out of range
- while day < 0 do
- month = month - 1
- if month < 0 then
- year = year - 1
- month = 11
- end
- day = day + month_length(month + 1, year)
- end
- year, month = carry(year, month, 12)
-
- -- TODO[OPTIMIZE]: This could potentially be slow if `day` is very large
- while true do
- local i = month_length(month + 1, year)
- if day < i then break end
- day = day - i
- month = month + 1
- if month >= 12 then
- month = 0
- year = year + 1
- end
- end
-
- -- Now we can place `day` and `month` back in their normal ranges
- -- e.g. month as 1-12 instead of 0-11
- month, day = month + 1, day + 1
-
- return year, month, day, hour, min, sec
-end
-
-local leap_years_since_1970 = leap_years_since(1970)
-local function timestamp(year, month, day, hour, min, sec)
- year, month, day, hour, min, sec = normalise(year, month, day, hour, min, sec)
-
- local days_since_epoch = day_of_year(day, month, year)
- + 365 * (year - 1970)
- -- Each leap year adds one day
- + (leap_years_since(year - 1) - leap_years_since_1970) - 1
-
- return days_since_epoch * (60*60*24)
- + hour * (60*60)
- + min * 60
- + sec
-end
-
-
-local timetable_methods = {}
-
-function timetable_methods:unpack()
- return assert(self.year , "year required"),
- assert(self.month, "month required"),
- assert(self.day , "day required"),
- self.hour or 12,
- self.min or 0,
- self.sec or 0,
- self.yday,
- self.wday
-end
-
-function timetable_methods:normalise()
- local year, month, day
- year, month, day, self.hour, self.min, self.sec = normalise(self:unpack())
-
- self.day = day
- self.month = month
- self.year = year
- self.yday = day_of_year(day, month, year)
- self.wday = day_of_week(day, month, year)
-
- return self
-end
-timetable_methods.normalize = timetable_methods.normalise -- American English
-
-function timetable_methods:timestamp()
- return timestamp(self:unpack())
-end
-
-function timetable_methods:rfc_3339()
- local year, month, day, hour, min, fsec = self:unpack()
- local sec, msec = borrow(fsec, 0, 1000)
- msec = math.floor(msec)
- return strformat("%04u-%02u-%02uT%02u:%02u:%02d.%03d", year, month, day, hour, min, sec, msec)
-end
-
-function timetable_methods:strftime(format_string)
- return strftime(format_string, self)
-end
-
-local timetable_mt
-
-local function coerce_arg(t)
- if getmetatable(t) == timetable_mt then
- return t:timestamp()
- end
- return t
-end
-
-timetable_mt = {
- __index = timetable_methods;
- __tostring = timetable_methods.rfc_3339;
- __eq = function(a, b)
- return a:timestamp() == b:timestamp()
- end;
- __lt = function(a, b)
- return a:timestamp() < b:timestamp()
- end;
- __sub = function(a, b)
- return coerce_arg(a) - coerce_arg(b)
- end;
-}
-
-local function cast_timetable(tm)
- return setmetatable(tm, timetable_mt)
-end
-
-local function new_timetable(year, month, day, hour, min, sec, yday, wday)
- return cast_timetable {
- year = year;
- month = month;
- day = day;
- hour = hour;
- min = min;
- sec = sec;
- yday = yday;
- wday = wday;
- }
-end
-
-function timetable_methods:clone()
- return new_timetable(self:unpack())
-end
-
-local function new_from_timestamp(ts)
- if type(ts) ~= "number" then
- error("bad argument #1 to 'new_from_timestamp' (number expected, got " .. type(ts) .. ")", 2)
- end
- return new_timetable(1970, 1, 1, 0, 0, ts):normalise()
-end
-
-return {
- is_leap = is_leap;
- day_of_year = day_of_year;
- day_of_week = day_of_week;
- normalise = normalise;
- timestamp = timestamp;
-
- new = new_timetable;
- new_from_timestamp = new_from_timestamp;
- cast = cast_timetable;
- timetable_mt = timetable_mt;
-}