package collatz

import (
	"collatz/io"
	"fmt"
	"log"
	"math/big"
)

type Calculator struct {
	parser *io.Cliargs
	three  *big.Int
	two    *big.Int
	one    *big.Int
}

func NewCalculator(parser *io.Cliargs) Calculator {
	r := Calculator{
		parser: parser,
		three:  new(big.Int).SetInt64(3),
		two:    new(big.Int).SetInt64(2),
		one:    new(big.Int).SetInt64(1),
	}
	return r
}

func (o Calculator) Collatz() {
	number, err := o.parser.Parse()
	if err != nil {
		log.Panicf("Couldn't parse input: %s\n", err)
	}
	fmt.Print(number.Text(10))
	o.nextNumber(number)
	fmt.Println()
}

func (o Calculator) nextNumber(in *big.Int) {
	if in.Cmp(o.one) < 0 {
		log.Panicln("Must be greater than 0")
	}
	if in.Cmp(o.one) == 0 {
		return
	}
	var newNumber *big.Int
	if new(big.Int).And(in, o.one).Cmp(o.one) == 0 {
		newNumber = new(big.Int).Add(new(big.Int).Mul(in, o.three), o.one)
	} else {
		newNumber = new(big.Int).Div(in, o.two)
	}

	fmt.Printf(" -> %s", newNumber.Text(10))
	o.nextNumber(newNumber)
}