Editing Module:Birth date and age

local p = {}

local function pad2digit(num)
    return string.format("%02d", num)
end

local function getZodiacSign(day, month)
    local zodiacSigns = {
        { name = "Capricorn",     start = { day = 22, month = 12 }, end_ = { day = 19, month = 1 } },
        { name = "Aquarius",      start = { day = 20, month = 1  }, end_ = { day = 18, month = 2 } },
        { name = "Pisces",        start = { day = 19, month = 2  }, end_ = { day = 20, month = 3 } },
        { name = "Aries",         start = { day = 21, month = 3  }, end_ = { day = 19, month = 4 } },
        { name = "Taurus",        start = { day = 20, month = 4  }, end_ = { day = 20, month = 5 } },
        { name = "Gemini",        start = { day = 21, month = 5  }, end_ = { day = 20, month = 6 } },
        { name = "Cancer",        start = { day = 21, month = 6  }, end_ = { day = 22, month = 7 } },
        { name = "Leo",           start = { day = 23, month = 7  }, end_ = { day = 22, month = 8 } },
        { name = "Virgo",         start = { day = 23, month = 8  }, end_ = { day = 22, month = 9 } },
        { name = "Libra",         start = { day = 23, month = 9  }, end_ = { day = 22, month = 10} },
        { name = "Scorpio",       start = { day = 23, month = 10 }, end_ = { day = 21, month = 11} },
        { name = "Sagittarius",   start = { day = 22, month = 11 }, end_ = { day = 21, month = 12} },
    }

    for _, sign in ipairs(zodiacSigns) do
        if
            (month == sign.start.month and day >= sign.start.day)
            or
            (month == sign.end_.month and day <= sign.end_.day)
        then
            return sign.name
        end
    end

    return nil
end

local function calculateAge(year, month, day)
    local currentYear  = tonumber(os.date('%Y'))
    local currentMonth = tonumber(os.date('%m'))
    local currentDay   = tonumber(os.date('%d'))

    local age = currentYear - year
    if (currentMonth < month) or (currentMonth == month and currentDay < day) then
        age = age - 1
    end

    return age
end

function p.main(frame)
    local args = require('Module:Arguments').getArgs(frame, {wrappers = 'Template:Birth date and age'})
    
    local year  = tonumber(args[1] or args.year)
    local month = tonumber(args[2] or args.month)
    local day   = tonumber(args[3] or args.day)
    
    if not day or not month then
        return ''
    end
    
    local output = ""
    local categories = {}
    
    local function addZodiac(day, month)
        local zodiacSign = getZodiacSign(day, month)
        if zodiacSign then
            local zodiacCategory = (mw.title.getCurrentTitle().namespace == 0)
                and string.format('[[Category:%s]]', zodiacSign)
                or ''
            
            return string.format(
                '<br>Astrology: [[File:%s.svg|13px|link=Category:%s|%s|class=noviewer]]%s',
                zodiacSign, zodiacSign, zodiacSign, zodiacCategory
            )
        end
        return ""
    end
    
    if year then
        local monthName = os.date('%B', os.time({year = year, month = month, day = day}))
        
        local birthDate = string.format(
            "[[:Category:%s %s birthdays|%s %s]] [[:Category:%s births|%s]]",
            monthName, day, day, monthName, year, year
        )
        local age = calculateAge(year, month, day)
        local ageString = string.format(" (age&nbsp;%d)", age)
        
        output = birthDate .. ageString
        
        output = output .. addZodiac(day, month)
    
    else
        local ok, monthName = pcall(function()
            return os.date('%B', os.time({year = 2000, month = month, day = day}))
        end)
        if not ok or not monthName then
            return ''
        end
        
        categories[#categories + 1] = string.format("[[Category:%s %s birthdays]]", monthName, day)
        categories[#categories + 1] = "[[Category:Birth year needed]]"
        
        output = string.format(
            "[[:Category:%s %s birthdays|%s %s]]",
            monthName, day, monthName, day
        )
        
        output = output .. addZodiac(day, month)
    end
    
    return output .. table.concat(categories, "")
end

return p