refact: date handling

lua/telekasten/utils/dates.lua

@@ -1,7 +1,7 @@
 local M = {}
-local date = require("telekasten.utils.luadate")
+local luadate = require("telekasten.utils.luadate")
 
---- returns the day of week (1..Monday, ..., 7..Sunday) for Dec, 31st of year
+--- 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)
@@ -70,7 +70,7 @@ end
 
 -- the algo on wikipedia seems wrong, so we opt for full-blown luadate
 M.isoweek_to_date = function(year, isoweek)
-    local ret = date(year .. "-W" .. string.format("%02d", isoweek) .. "-1")
+    local ret = luadate(year .. "-W" .. string.format("%02d", isoweek) .. "-1")
     return {
         year = ret:getyear(),
         month = ret:getmonth(),
@@ -78,6 +78,131 @@ M.isoweek_to_date = function(year, isoweek)
     }
 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)