-- TODO: Characters

-- TODO: Bytes

type Optional a = Some a | None

type Words = Words (List Nat)

type Integer = Integer

Integer.zero : Integer

Integer.zero = _

shiftLeft : Nat -> Integer -> Integer

shiftLeft x y = _

(+) : Integer -> Integer -> Integer

(+) x y = _

unfoldRight : ∀ a b . (a -> Optional (a, b)) -> a -> List b

unfoldRight f z = _

foldLeft : ∀ a b . a -> (a -> b -> a) -> List b -> a

foldLeft z f s = _

toInteger : Nat -> Integer

toInteger x = _

bigEndian : Words -> Integer

bigEndian = cases

Words.Words s ->

foldLeft Integer.zero (acc w -> shiftLeft 8 acc + toInteger w) s

-- TODO: Need some conversions between integers and machine integers

divmod : Integer -> Nat -> (Integer, Nat)

divmod x y = _

(|>) : ∀ a b c . (a -> b) -> (b -> c) -> a -> c

(|>) g f x = f (g x)

(==) : Integer -> Nat -> Boolean

(==) a b = _

charAt : Nat -> Text -> Text

charAt n = Text.drop n |> Text.take 1

codeString : Text

codeString = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"

base58Encode : Words -> Text

base58Encode ws =

x = bigEndian ws

base58 : Integer -> Optional (Integer, Text)

base58 a =

if a == 0

then Optional.None

else match divmod a 58 with

(d, m) -> Optional.Some (d, charAt m codeString)

foldLeft "" Text.concatenate (unfoldRight base58 x)

base58Decode : Text -> Words

base58Decode txt = _