local THEME={
    cur=false,--Current theme
}
local themeColor={
    xmas={COLOR.R,COLOR.Z,COLOR.G},
    sprfes={COLOR.R,COLOR.O,COLOR.Y},
}

function THEME.calculate(Y,M,D)
    if not Y then
        Y,M,D=os.date('%Y'),os.date('%m'),os.date('%d')
    end
    --Festival calculate within one statement
    return
        --Christmas
        M=='12'and math.abs(D-25)<4 and
        'xmas'or

        --Birthday
        M=='06'and D=='06'and
        'birth'or

        --Spring festival
        M<'03'and math.abs((({
            --Festival days. Jan 26=26, Feb 1=32, etc.
            24,43,32,22,40,29,49,38,26,45,
            34,23,41,31,50,39,28,47,36,25,
            43,32,22,41,29,48,37,26,44,34,
            23,42,31,50,39,28,46,35,24,43,
            32,22,41,30,48,37,26,45,33,23,
            42,32,50,39,28,46,35,24,43,33,
            21,40,
        })[Y-2000]or -26)-((M-1)*31+D))<6 and
        'sprfes'or

        --April fool's day
        M=='04'and D=='01'and
        'fool'or

        --Z day
        D=='26'and(
            (M=='01'or M=='02'or M=='03')and'zday1'or
            (M=='04'or M=='05')and'zday2'or
            (M=='06'or M=='07')and'zday3'or
            (M=='08'or M=='09')and'zday4'or
            (M=='10'or M=='11'or M=='12')and'zday5'
        )or

        'classic'
end

function THEME.set(theme)
    if theme=='classic'then
        BG.setDefault('space')
        BGM.setDefault('nil')
    elseif theme=='xmas'then
        BG.setDefault('snow')
        BGM.setDefault('xmas')
        MES.new('info',"==Merry Christmas==")
    elseif theme=='birth'then
        BG.setDefault('firework')
        BGM.setDefault('magicblock')
    elseif theme=='sprfes'then
        BG.setDefault('firework')
        BGM.setDefault('spring festival')
        MES.new('info',"★☆新年快乐☆★")
    elseif theme=='zday1'then
        BG.setDefault('lanterns')
        BGM.setDefault('null')
    elseif theme=='zday2'then
        BG.setDefault('lanterns')
        BGM.setDefault('overzero')
    elseif theme=='zday3'then
        BG.setDefault('lanterns')
        BGM.setDefault('vacuum')
    elseif theme=='zday4'then
        BG.setDefault('lanterns')
        BGM.setDefault('jazz nihilism')
    elseif theme=='zday5'then
        BG.setDefault('lanterns')
        BGM.setDefault('empty')
    elseif theme=='fool'then
        BG.setDefault('blockrain')
        BGM.setDefault('how feeling')
    else
        return
    end
    THEME.cur=theme
    BG.set()
    BGM.play()
    return true
end

function THEME.getThemeColor(theme)
    if not theme then
        theme=THEME.cur
    end
    return themeColor[theme]
end

function THEME.fresh()
    THEME.set(THEME.calculate(os.date('%Y'),os.date('%m'),os.date('%d')))
end

return THEME