package main

import (
    "errors"
    "fmt"
    "io/ioutil"
    "strconv"
    "strings"
)

const (
    expected = 19690720
    tryRange = 1000
)

func inputToInt(fileName string) ([]int64, error) {
    allInput, err := ioutil.ReadFile(fileName)

    if err != nil {
        return nil, err
    }

    intList := make([]int64, 0)

    for _, v := range strings.Split(string(allInput), ",") {
        intVal, err := strconv.ParseInt(v, 10, 64)

        if err != nil {
            return nil, err
        }

        intList = append(intList, intVal)
    }

    return intList, nil
}

type intCode struct {
    opCode  int64
    srcPos1 int64
    srcPos2 int64
    destPos int64
}

func loadOps(data []int64, pos int) intCode {
    if pos+4 >= len(data) {
        return intCode{opCode: data[pos]}
    }

    return intCode{data[pos], data[pos+1], data[pos+2], data[pos+3]}
}

func doMultOp(data []int64, srcpos1 int64, srcpos2 int64, dstpos int64) {
    data[dstpos] = data[srcpos1] * data[srcpos2]
}

func doAddOp(data []int64, srcpos1 int64, srcpos2 int64, dstpos int64) {
    data[dstpos] = data[srcpos1] + data[srcpos2]
}

func performOps(data []int64) error {
    for i := 0; i < len(data); i += 4 {
        op := loadOps(data, i)

        dLen := int64(len(data))

        if op.srcPos1 >= dLen || op.srcPos2 >= dLen || op.destPos >= dLen {
            return errors.New("Out of bounds")
        }

        if op.opCode == 1 {
            doAddOp(data, op.srcPos1, op.srcPos2, op.destPos)
        }

        if op.opCode == 2 {
            doMultOp(data, op.srcPos1, op.srcPos2, op.destPos)
        }

        if op.opCode == 99 {
            return nil
        }
    }

    return nil
}

func main() {
    saved, err := inputToInt("input.txt")

    if err != nil {
        fmt.Println("Wimp wimp")
    }

    for noun := 0; noun < tryRange; noun++ {
        for verb := 0; verb < tryRange; verb++ {
            runData := make([]int64, len(saved))
            copy(runData, saved)

            runData[1] = int64(noun)
            runData[2] = int64(verb)

            err = performOps(runData)

            if err != nil {
                continue
            }

            if runData[0] == expected {
                fmt.Println("Found solution (verb, noun) =", verb, noun, ". (100 * noun + verb)=", 100*noun+verb)
                return
            }
        }
    }
}