package main

import (
	"fmt"
	"os"
)

func main() {
	if len(os.Args) < 2 {
		panic("Provide input file")
	}
	inputFile := os.Args[1]

	part1, part2 := solution(inputFile)
	fmt.Printf("(%s) Part 1: %d\n(%s) Part 2: %d\n", inputFile, part1, inputFile, part2)
}

type Patroller struct {
	x, y      int
	direction int
	walkMap   [][]bool
	height    int
	width     int
}

func solution(inputFile string) (int, int) {
	var part2 int

	// Read line by line
	input, err := os.Open(inputFile)
	if err != nil {
		panic(err)
	}
	defer input.Close()
	// patrolMap is a 2D bool array to keep track of the patrol
	var pX, pY int
	patrolMap := make([][]bool, 0)
	for {
		var line string
		_, err := fmt.Fscanf(input, "%s\n", &line)
		if err != nil {
			break
		}
		// Add the line to the patrolMap
		patrolMap = append(patrolMap, make([]bool, len(line)))
		for i, c := range line {
			if c == '#' {
				patrolMap[len(patrolMap)-1][i] = false
			}
			if c == '.' {
				patrolMap[len(patrolMap)-1][i] = true
			}
			if c == '^' {
				pX = i
				pY = len(patrolMap)
				patrolMap[len(patrolMap)-1][i] = true
			}
		}
	}

	fmt.Println(pX+1, pY+1)

	steps := 0
	escaped := false
	p := NewPatroller(pX, pY, 0, patrolMap)
	for {
		steps++
		switch p.direction {
		case 0: // NORTH
			if p.y-1 < 0 {
				escaped = true
				break
			} else if !p.walkMap[p.x][p.y-1] {
				p.turnRight()
				break
			}
			p.y--
		case 1: // EAST
			if p.x+1 >= len(p.walkMap[0]) {
				escaped = true
				break
			}
			if !p.walkMap[p.x+1][p.y] {
				p.turnRight()
				break
			}
			p.x++
		case 2: // SOUTH
			if p.y+1 >= len(p.walkMap) {
				escaped = true
				break
			}
			if !p.walkMap[p.x][p.y+1] {
				p.turnRight()
				break
			}
			p.y++
		case 3: // WEST
			if p.x-1 < 0 {
				escaped = true
				break
			}
			if !p.walkMap[p.x-1][p.y] {
				p.turnRight()
				break
			}
			p.x--
		}
		if escaped {
			break
		}
	}
	return steps, part2
}

func NewPatroller(x, y, direction int, walkMap [][]bool) *Patroller {
	return &Patroller{
		x:         x,
		y:         y,
		direction: direction,
		walkMap:   walkMap,
	}
}

func (p *Patroller) turnRight() {
	p.direction = (p.direction + 1) % 4
}