package two

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

type command struct {
	instruction string
	value       int
}

type sub struct {
	input      []command
	depth      int
	horizontal int
	aim        int
}

// load Loads the commands from input.txt into the sub
func (s *sub) load(filename string) error {
	s.input = []command{}

	file, err := os.Open(filename)
	if err != nil {
		return err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		parts := strings.Split(scanner.Text(), " ")
		if len(parts) != 2 {
			return fmt.Errorf("Unable to parse input: %s", parts)
		}

		value, err := strconv.Atoi(parts[1])
		if err != nil {
			return err
		}
		s.input = append(s.input, command{
			instruction: parts[0],
			value:       value,
		})
	}

	return nil
}

func (s *sub) reset() {
	s.horizontal = 0
	s.depth = 0
	s.aim = 0
}

func (s *sub) execute() {
	for _, command := range s.input {
		switch command.instruction {
		case "forward":
			s.horizontal += command.value
		case "up":
			s.depth -= command.value
			if s.depth < 0 {
				s.depth = 0
			}
		case "down":
			s.depth += command.value
		}
	}
}

func (s *sub) executeWithAim() {
	for _, command := range s.input {
		switch command.instruction {
		case "forward":
			s.horizontal += command.value
			s.depth += s.aim * command.value
		case "up":
			s.aim -= command.value
		case "down":
			s.aim += command.value
		}
	}
}