#!/usr/bin/env mars

# Guessing Game

import prelude

# Result of asking user for input
type Guess:
    Higher
    Lower
    Equal

# Presents a guess and asks the user whether it's higher, lower, or equal.
def ask(num :: Num) :: io Guess:
    var l :: Array(Num)
    print_string("My guess: ")
    print_value(num)
    print_string(". Higher (h), lower (l) or equal (e)? ")
    l = get_line()
    if l == "h":
        return Higher
    elif l == "l":
        return Lower
    elif l == "e":
        return Equal
    else:
        print_string("Please enter h, l or e.\n")
        return ask(num)

# Given a range, makes a guess
def guess(min :: Num, max :: Num) :: Num:
    return (max - min) // 2 + min

# Plays the game until success
def guessing_loop(min :: Num, max :: Num) :: io Num:
    var myguess :: Num
    var result :: Guess
    if min > max:
        print_string("You seem a bit confused. Let's start again.\n")
        min = 0
        max = 100
    myguess = guess(min, max)
    result = ask(myguess)
    switch result:
        case Equal:
            print_string("I win!\n")
            return 0
        case Lower:
            max = myguess - 1
        case Higher:
            min = myguess + 1
    return guessing_loop(min, max)

def main() :: io Num:
    print_string("Think of a number [0,100].\n")
    return guessing_loop(0, 100)