LoTROInterface SVN Calendar

-- A set of calendar utility functions

CalTools = {};

-- --------------------------------------------------------------
-- CalTools is a set of useful calendar methods
-- --------------------------------------------------------------

-- Returns the 12 hour label corresponding to the hour of the day
--! @param 24 hour of the day (starting at zero)
--! @return a string corresponding to the specified weekday
function CalTools:hourLabel(hourOfDay)
        -- todo: add multi-lingual support
        hourLabels = { 
                [0] = "12a", "1a", "2a", "3a", "4a", "5a", "6a", "7a", "8a", "9a", "10a", "11a",
                "12p", "1p", "2p", "3p", "4p", "5p", "6p", "7p", "8p", "9p", "10p", "11p",
        };
        if (nil == hourOfDay) then
        error("missing required argument: hourOfDay", 2)        
        elseif type(hourOfDay) ~= "number" then
        error("expected number for hourOfDay, not " .. type(weekday), 2)
        elseif ( (hourOfDay < 0) or (hourOfDay>#hourLabels) ) then
        error("invalid value for hourOfDay (" .. hourOfDay .. ") must be between 0 and " .. #hourLabels, 2);
        end
        return hourLabels[hourOfDay];
end

-- Returns the name of the day of the week
--! @param weekday the day of the week (starting at zero)
--! @return a string corresponding to the specified weekday
function CalTools:dayLabel(weekday)
        -- todo: add multi-lingual support
        dayLabels = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };
        if (nil == weekday) then
        error("missing required argument: weekday", 2)  
        elseif type(weekday) ~= "number" then
        error("expected number for weekday, not " .. type(weekday), 2)
        elseif ( (weekday < 1) or (weekday>#dayLabels) ) then
        error("invalid value for weekday (" .. weekday .. ") must be between 1 and " .. #dayLabels, 2);
        end
        return dayLabels[weekday];
end

MonthLabels = { 
    "January", "February", "March", 
    "April", "May", "June", 
    "July", "August", "September", 
    "October", "November", "December" };

-- Returns the name of the month
--! @param month of the year (starting at 1)
--! @return a string corresponding to the specified month
function CalTools:monthLabel(month)
        if (nil == month) then
        error("missing required argument: month", 2)    
        elseif type(month) ~= "number" then
        error("expected number for month, not " .. type(month), 2)
        elseif ( (month < 1) or (month>#MonthLabels) ) then
        error("invalid value for month (" .. month .. ") must be between 1 and " .. #MonthLabels, 2);
        end
        return MonthLabels[month];
end

-- Returns the name of the month
--! @param month of the year (starting at 1)
--! @return the index corresponding to monthLabel, or nil on error
function CalTools:monthForLabel(monthLabel)
        for idx,label in ipairs(MonthLabels) do
        if( monthLabel == label ) then
            return idx;
        end
    end
    return nil; -- invalid month name?
end

-- --------------------------------------------------------------
-- isLeapYear (Gregorian calendar)
--
-- Description: determine if year is a leap year
-- Returns: true if the specified year is a leap year, false otherwise
-- Note: Algorithm assumes AD 4 is a leap year in the calendar.
-- --------------------------------------------------------------
function CalTools:isLeapYear(year)
        if type(year) ~= "number" then
        error("expected number for year, not " .. type(year), 2);
        end
        local isLeapYear = (math.fmod(year,4)==0 and math.fmod(year,100) ~= 0) or math.fmod(year,400)==0;
        return isLeapYear;
end

-- --------------------------------------------------------------
-- daysInMonth (Gregorian calendar)
--
-- Description: Returns the number of days in the specified month & year 
-- --------------------------------------------------------------
function CalTools:daysInMonth(month, year)
    local daysPerMonth = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        if (nil == month) then
        error("missing required argument: month", 2)    
        elseif type(month) ~= "number" then
        error("expected number for month, not " .. type(month), 2)
        end
        if (nil == year) then
        error("missing required argument: year", 2)     
        elseif type(year) ~= "number" then
        error("expected number for year, not " .. type(year), 2)
        end
    if ( (month == 2) and CalTools:isLeapYear(year)) then
                return 29;
        end 
        local days = daysPerMonth[ month ];
        return days;
end

-- --------------------------------------------------------------
-- dayOfWeek (Gregorian calendar)
--
-- Description: Returns the weekday (Sunday thru Saturday )
-- for the specified date 
-- Returns:  0 for Sunday, 1 for Monday, 2 for Tuesday, etc.
-- Reference: Section 2.6 of version 2.9 of the CALFAQ.
-- --------------------------------------------------------------
function CalTools:dayOfWeek(year, month, day)
        --assert(type(year) == "number","year must be a number");
        --assert(year >= 1970 ,"year must be >= 1970");
        if (nil == year) then
        error("missing required argument: year", 2)     
        elseif type(year) ~= "number" then
        error("expected number for year, not " .. type(year), 2)
        end
        if (nil == month) then
        error("missing required argument: month", 2)    
        elseif type(month) ~= "number" then
        error("expected number for month, not " .. type(month), 2)
        end
        if (nil == day) then
        error("missing required argument: day", 2)      
        elseif type(day) ~= "number" then
        error("expected number for day, not " .. type(day), 2)
        end
        
    local a = math.floor((14 - month) / 12);    -- anchor day
    local y = year - a;
    local m = month + 12*a - 2;
    return math.fmod(math.floor(day + y + math.floor(y/4) - math.floor(y/100) + math.floor(y/400) + (31*m)/12),7);
end

return CalTools;