cipher.tao

import "../lib/main.tao"

data OutOfRange = Char

member OutOfRange of Show =
    => show = fn OutOfRange c => "character '" ++ [c] ++ "' is out of range!"

data Character =
    | A
    | B
    | C
    | D
    | E
    | F
    | G
    | H
    | I
    | J
    | K
    | L
    | M
    | N
    | O
    | P
    | Q
    | R
    | S
    | T
    | U
    | V
    | W
    | X
    | Y
    \ Z

member Character of Show =
    => show = fn
        | A => "a"
        | B => "b"
        | C => "c"
        | D => "d"
        | E => "e"
        | F => "f"
        | G => "g"
        | H => "h"
        | I => "i"
        | J => "j"
        | K => "k"
        | L => "l"
        | M => "m"
        | N => "n"
        | O => "o"
        | P => "p"
        | Q => "q"
        | R => "r"
        | S => "s"
        | T => "t"
        | U => "u"
        | V => "v"
        | W => "w"
        | X => "x"
        | Y => "y"
        \ Z => "z"

fn parse_char =
    | 'a' => Ok A
    | 'b' => Ok B
    | 'c' => Ok C
    | 'd' => Ok D
    | 'e' => Ok E
    | 'f' => Ok F
    | 'g' => Ok G
    | 'h' => Ok H
    | 'i' => Ok I
    | 'j' => Ok J
    | 'k' => Ok K
    | 'l' => Ok L
    | 'm' => Ok M
    | 'n' => Ok N
    | 'o' => Ok O
    | 'p' => Ok P
    | 'q' => Ok Q
    | 'r' => Ok R
    | 's' => Ok S
    | 't' => Ok T
    | 'u' => Ok U
    | 'v' => Ok V
    | 'w' => Ok W
    | 'x' => Ok X
    | 'y' => Ok Y
    | 'z' => Ok Z
    \ c => Err OutOfRange c

fn parse_str =
    | [] => Ok []
    \ [c .. cs] => when c -> parse_char is
        | Ok c => when cs -> parse_str is
            | Ok cs => Ok [c .. cs]
            \ Err e => Err e
        \ Err e => Err e

fn shift_char =
    | 0, c => c
    \ n + 1, c => when c is
        | A => B -> shift_char(n)
        | B => C -> shift_char(n)
        | C => D -> shift_char(n)
        | D => E -> shift_char(n)
        | E => F -> shift_char(n)
        | F => G -> shift_char(n)
        | G => H -> shift_char(n)
        | H => I -> shift_char(n)
        | I => J -> shift_char(n)
        | J => K -> shift_char(n)
        | K => L -> shift_char(n)
        | L => M -> shift_char(n)
        | M => N -> shift_char(n)
        | N => O -> shift_char(n)
        | O => P -> shift_char(n)
        | P => Q -> shift_char(n)
        | Q => R -> shift_char(n)
        | R => S -> shift_char(n)
        | S => T -> shift_char(n)
        | T => U -> shift_char(n)
        | U => V -> shift_char(n)
        | V => W -> shift_char(n)
        | W => X -> shift_char(n)
        | X => Y -> shift_char(n)
        | Y => Z -> shift_char(n)
        \ Z => A -> shift_char(n)

fn shift_str =
    n => map(shift_char(n))

def main : io ~ () = @{
    let text = "hello";
    print("Input = " ++ text)!;
    when text -> parse_str is
    | Ok s => @{
        print("Parsed = " + s)!;
        let n = 1;
        let shifted = s -> shift_str(n);
        print("Shifted(" + n + ") = " + shifted)!;
    }!
    \ Err e => print("Error: " + e)!
}