Module:AgeCalculator

Documentation for this module may be created at Module:AgeCalculator/doc

local p = {}

-- Helper function to format singular/plural correctly
local function format_unit(value, singular, plural)
    if value == 1 then
        return string.format("%d %s", value, singular)
    else
        return string.format("%d %s", value, plural)
    end
end

-- Function to calculate the difference between two dates
function p.calculate(frame)
    -- Parse inputs from the template
    local year1 = tonumber(frame.args[1]) -- Start year
    local month1 = tonumber(frame.args[2]) -- Start month
    local day1 = tonumber(frame.args[3]) -- Start day
    local year2 = tonumber(frame.args[4]) or tonumber(os.date("%Y")) -- Current year
    local month2 = tonumber(frame.args[5]) or tonumber(os.date("%m")) -- Current month
    local day2 = tonumber(frame.args[6]) or tonumber(os.date("%d")) -- Current day

    -- Validate inputs
    if not (year1 and month1 and day1) then
        return "Error: Invalid input. Provide at least year, month, and day for the first date."
    end

    -- Calculate initial year, month, and day differences
    local years = year2 - year1
    local months = month2 - month1
    local days = day2 - day1

    -- Adjust days if negative
    if days < 0 then
        -- Handle previous month wrapping
        local prevYear, prevMonth = year2, month2 - 1
        if prevMonth < 1 then
            prevMonth = 12
            prevYear = prevYear - 1
        end

        local daysInPrevMonth = os.date("*t", os.time{year = prevYear, month = prevMonth + 1, day = 0}).day
        days = days + daysInPrevMonth
        months = months - 1
    end

    -- Adjust months if negative
    if months < 0 then
        months = months + 12
        years = years - 1
    end

    -- Ensure years do not go negative (for future dates)
    if years < 0 then
        return "Error: The input date is in the future."
    end

    -- Format years, months, and days with singular/plural correctly
    local year_str = format_unit(years, "year", "years")
    local month_str = format_unit(months, "month", "months")
    local day_str = format_unit(days, "day", "days")

    -- Return the result as a string with "and" before days
    if years > 0 or months > 0 then
        return string.format("%s, %s, and %s", year_str, month_str, day_str)
    else
        return string.format("%s and %s", month_str, day_str)
    end
end

return p