module Exercise01 where

import Test.QuickCheck

{-H1.1a)-}
myPair :: Integer -> Integer -> Integer
myPair x y | x >= 0, y >= 0 = (2 ^ y) * (2 * x + 1) - 1

{-H1.1b)-}
mySnd :: Integer -> Integer
mySnd pair = mySndIntern pair 0
mySndIntern :: Integer -> Integer -> Integer
mySndIntern pair count
    | remainder == 0 = count
    | otherwise = mySndIntern division (count + 1)
    where
        (division, remainder) = divMod pair 2

{-H1.1c)-}
myFst :: Integer -> Integer
myFst pair =
    ((pair + 1) `div` (2 ^ mySnd pair) - 1) `div` 2

{-H1.1d)-}
prop_myPair :: Integer -> Integer -> Integer -> Property
prop_myPair p x y =
    (p >= 0 && x >= 0 && y >= 0) ==> 
        (myPair x y == p) && (mySnd p == y) && (myFst p == x)

{-H2-}
digitToEo :: Integer -> String
digitToEo 0 = "nul"
digitToEo 1 = "unu"
digitToEo 2 = "du"
digitToEo 3 = "tri"
digitToEo 4 = "kvar"
digitToEo 5 = "kvin"
digitToEo 6 = "ses"
digitToEo 7 = "sep"
digitToEo 8 = "ok"
digitToEo 9 = "nau"

{-WETT-}
powerTokenTuples = zip
    [10 ^ x | x <- [1,2] ++ [3,6..66]]
    (
        ["dek", "cent", "mil", "miliono", "miliardo"]
        ++ [ numberToEo x ++ y | x <- [2..10], y <- ["iliono", "iliardo"]]
    )

numberToEo :: Integer -> String
numberToEo n
    | n < 10 = digitToEo n
    | otherwise = numberToEoDetail n x y
    where (x, y) = last (filter (\(x,y) -> x <= n) powerTokenTuples)

numberToEoDetail :: Integer -> Integer -> String -> String
numberToEoDetail n divisor token =
    (if division > 1 || divisor > 1000 then numberToEo division ++ (if divisor > 100 then " " else "") else "")
    ++ token
    ++ (if divisor > 1000 && division > 1 then "j" else "")
    ++ (if remainder > 0 then " " ++ numberToEo remainder else "")
    where (division, remainder) = divMod n divisor

{-TTEW-}