aoc2020 day 8.go

package main

import (
	vm "aoc/vm"
	"fmt"
	"os"
)

func main() {
	if len(os.Args) < 2 {
		panic(fmt.Sprintf("usage: %s <input>", os.Args[0]))
	}
	fh, err := os.Open(os.Args[1])
	if err != nil {
		panic(err)
	}

	v0 := vm.NewVM()
	err = v0.LoadCode(fh)
	if err != nil {
		panic(err)
	}

	// part 1
	v1 := v0.Clone()
	v1.Run(doneOnInfinite)
	fmt.Printf("part 1: accumulator=%d\n", v1.Accumulator())

	// part 2
	var i2 *vm.Instruction
	var v2 *vm.VM
	for k, i := range v0.Code() {
		switch i.Op {
		case "jmp":
			i2 = i.Clone()
			i2.Op = "nop"
			i2.Func = vm.NopFunc
		case "nop":
			i2 = i.Clone()
			i2.Op = "jmp"
			i2.Func = vm.JmpFunc
		default:
			continue
		}
		v2 = v0.Clone()
		err = v2.SetInstruction(k, i2)
		if err != nil {
			panic(err)
		}
		v2.Run(doneOnInfinite)
		if !v2.IsInfinite() {
			break
		}
	}

	switch {
	case v2==nil:
		fmt.Println("part 2: There were no nop:s or jmp:s in the code")
	case v2.IsInfinite():
		fmt.Println("part 2: I didn't find any finite execution")
	default:
		fmt.Printf("part 2: The program exited normally, accumulator=%d\n", v2.Accumulator())
	}

}

func doneOnInfinite(v *vm.VM) bool {
	return v.IsInfinite()
}