/*
 * file: rational.kt
 * author: SS
 * date: 2019-11-03
 */

fun main() {
    val a = Rational(-6L, -2L)
    val b = Rational(4L, -16L)
    val sum = a + b
    val difference = a - b
    val product = a * b
    val quotient = a / b
    println("($a) + ($b) = $sum")
    println("($a) - ($b) = $difference")
    println("($a) * ($b) = $product")
    println("($a) / ($b) = $quotient")

    val bad = Rational(3L, 7L-7L)
}

class Rational(a: Long, b: Long) {
    val numer: Long
    val denom: Long

    init {
        if (b == 0L) {
            println("Can't create a rational with denominator 0.  Bye.")
            kotlin.system.exitProcess(-1)
        }
        val d = gcd(a, b)
        var tobenumer = a / d
        var tobedenom = b / d
        if (tobedenom < 0L) {
            tobedenom = -tobedenom
            tobenumer = -tobenumer
        }
        numer = tobenumer
        denom = tobedenom
    }

    private fun gcd(aparam: Long, bparam: Long): Long {
        if (aparam < 0L && bparam >= 0L)
            return gcd(-aparam, bparam)
        else if (aparam >= 0L && bparam < 0L)
            return gcd(aparam, -bparam)
        else if (aparam < 0L && bparam < 0L)
            return gcd(-aparam, -bparam)

        var a = aparam
        var b = bparam
        while (b > 0L) {
            val r = a % b
            a = b
            b = r
        }
        return a
    }

    operator fun plus(o: Rational): Rational {
        val nu = numer * o.denom + o.numer * denom
        val de = denom * o.denom
        return Rational(nu, de)
    }

    operator fun minus(o: Rational): Rational {
        val nu = numer * o.denom - o.numer * denom
        val de = denom * o.denom
        return Rational(nu, de)
    }

    operator fun times(o: Rational): Rational {
        val nu = numer * o.numer
        val de = denom * o.denom
        return Rational(nu, de)
    }

    operator fun div(o: Rational): Rational {
        val nu = numer * o.denom
        val de = denom * o.numer
        return Rational(nu, de)
    }

    override fun toString(): String {
        return "$numer / $denom"
    }
}