import Control.Applicative
import System.Random
import Data.Tuple
import Data.List

main :: IO ()
main = mapM_ printChristmasTree [1..7]

printChristmasTree :: Int -> IO ()
printChristmasTree n = christmasTree <$> getStdGen <*> pure n >>= putStrLn

christmasTree :: StdGen -> Int -> String
christmasTree gen h = unlines $ center w $ concat [["☆"], body, ["||"]]
  where
    body = snd $ mapAccumL ((swap .) . flip splitAt) a [2, 4 .. w]
    a = map (chars !!) $ randomRs (1, length chars - 1) gen
    w = 2 * (h - 1)

center :: Int -> [String] -> [String]
center w xs = map padding xs
  where
    padding s = replicate ((w - length s) `div` 2) ' ' ++ s

chars :: [Char]
chars = "**********NiXJo%b"