package main

import (
	"fmt"
	"regexp"
	"strings"

	helpers "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := helpers.StdinToString()
	part1(inp)
	part2(inp)
}

func part1(inp string) {
	mulCmds := regexp.MustCompile(`mul\(\d\d?\d?,\d\d?\d?\)`)
	cmds := mulCmds.FindAllString(inp, -1)
	var total int
	for _, v := range cmds {
		var num1, num2 int
		fmt.Sscanf(v, "mul(%d,%d)", &num1, &num2)
		total = total + (num1 * num2)
	}
	fmt.Println("# Part 1")
	fmt.Printf("Total: %d\n\n", total)
}

func part2(inp string) {
	var total int
	do, run := true, true
	for run {
		var cmd Command
		prev := inp
		cmd, inp = getNextCommand(inp)
		if prev == inp {
			panic("Remainder didn't change")
		}
		run = len(inp) > 0
		switch cmd.Name {
		case "mul":
			if do {
				total = total + cmd.Run()
			}
		case "do":
			do = true
		case "don't":
			do = false
		}
	}
	fmt.Println("# Part 2")
	fmt.Printf("Total: %d\n", total)
}

type Command struct {
	Name   string
	Values []int
}

func (c *Command) Run() int {
	if c.Name == "mul" {
		return c.Values[0] * c.Values[1]
	}
	return 0
}

func (c Command) String() string {
	switch c.Name {
	case "mul":
		return fmt.Sprintf("%s(%d,%d)", c.Name, c.Values[0], c.Values[1])
	default:
		return fmt.Sprintf("%s()", c.Name)
	}
}

func getNextCommand(inp string) (Command, string) {
	c := Command{
		Values: make([]int, 2),
	}
	for i := range inp {
		switch inp[i] {
		case 'm':
			if _, err := fmt.Sscanf(inp[i:], "mul(%d,%d)", &c.Values[0], &c.Values[1]); err == nil {
				c.Name = "mul"
				return c, inp[i+len(c.String()):]
			}
		case 'd':
			if strings.HasPrefix(inp[i:], "do()") {
				c.Name = "do"
				return c, strings.TrimPrefix(inp[i:], "do()")
			} else if strings.HasPrefix(inp[i:], "don't()") {
				c.Name = "don't"
				return c, strings.TrimPrefix(inp[i:], "don't()")
			}
		}
	}
	return Command{}, ""
}