#!/usr/bin/env swift;
/******************************************************************************
 * This program solves the Tower of Hanoi
 * 
 * Copyright © 2021 Richard Lesh.  All rights reserved.
 *****************************************************************************/

import Foundation
import Utils

var numDisks:Int = 0
var pegs:[[Int]?] = Array(repeating: nil, count: 3)
var moveNumber:Int = 0
var printMod:Int = 1

func printPegs() -> Void {
    print("Move: " + String(moveNumber))
    for i:Int in 0..<numDisks {
        for j:Int in 0..<3 {
            let DISK:Int = pegs[j]![i]
            print(DISK == 0 ? "|" : String(DISK), terminator: "")
            print("   ", terminator: "")
        }
        print()
    }
    print("=========")
    print()
}

func move(_ source:Int, _ dest:Int) -> Void {
    moveNumber += 1
    var disk:Int = 0
    for i:Int in 0..<numDisks {
        if pegs[source]![i] != 0 {
            disk = pegs[source]![i]
            pegs[source][i] = 0
            break
        }
    }
    var pos:Int = numDisks - 1
    for i:Int in 0..<numDisks {
        if pegs[dest]![i] != 0 {
            pos = i - 1
            break
        }
    }
    pegs[dest][pos] = disk
    if moveNumber % printMod == 0 {
        printPegs()
    }
}

func solve(_ numDisks:Int, _ source:Int, _ dest:Int, _ aux:Int) -> Void {
    if numDisks == 1 {
        move(source, dest)
    } else {
        solve(numDisks - 1, source, aux, dest)
        move(source, dest)
        solve(numDisks - 1, aux, dest, source)
    }
}

func main() -> Void {
    if CommandLine.arguments.count != 2 {
        print("Syntax: " + CommandLine.arguments[0] + " [disks]")
        exit(1)
    }
    numDisks = Int(CommandLine.arguments[1]) ?? 3

    for i:Int in 0..<3 {
        var positions:[Int] = []
        for _:Int in 0..<numDisks {
            positions.append(0)
        }
        pegs[i] = positions
    }
    for i:Int in 0..<numDisks {
        pegs[0][i] = i + 1
    }

    let SOLUTION_STEPS:Int = Int(pow(2.0, Double(numDisks)) - 1.0)
    printMod = Int(SOLUTION_STEPS / 5) + 2
    printMod -= printMod % 5
    printMod = max(printMod, 1)
    printPegs()
    solve(numDisks, 0, 2, 1)
    if moveNumber % printMod != 0 {
        printPegs()
    }
    exit(EXIT_SUCCESS)
}
main()