package main

import (
	"bufio"
	"fmt"
	"image"
	"image/color"
	"image/png"
	"os"
	"strconv"
	"time"
)

const FILE_PATH = "./input.txt"
const WIDTH = 101
const HEIGHT = 103

//const FILE_PATH = "./sample.txt"
//const WIDTH = 11
//const HEIGHT = 7

func LoadInput(filename string) ([]string, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var lines []string
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}

	if err := scanner.Err(); err != nil {
		return nil, err
	}

	return lines, nil
}

type Vector2 struct {
	x int
	y int
}

type Robot struct {
	p Vector2
	v Vector2
}

type structuredInput = []Robot

func TransformInput(lines []string) structuredInput {
	var result = make([]Robot, 0)
	var j int
	var m int
	var numbX int
	var numbY int
	var position Vector2
	var temp Robot
	for i := 0; i < len(lines); i++ {
		j = 2
		for ; j < len(lines[i]); j++ {
			if lines[i][j] == ',' {
				break
			}
		}

		numbX, _ = strconv.Atoi(lines[i][2:j])
		m = j + 1
		for ; j < len(lines[i]); j++ {
			if lines[i][j] == ' ' {
				break
			}
		}
		numbY, _ = strconv.Atoi(lines[i][m:j])

		position = Vector2{numbX, numbY}

		m = j + 3

		for ; j < len(lines[i]); j++ {
			if lines[i][j] == ',' {
				break
			}
		}

		numbX, _ = strconv.Atoi(lines[i][m:j])
		numbY, _ = strconv.Atoi(lines[i][j+1:])
		temp = Robot{position, Vector2{numbX, numbY}}
		result = append(result, temp)
	}

	return result
}

func Part1(input structuredInput) int {
	var result = 0

	var robots = make([]Robot, 0)
	var temp Robot
	for _, robot := range input {
		temp = Robot{Vector2{robot.p.x, robot.p.y}, Vector2{robot.v.x, robot.v.y}}
		robots = append(robots, temp)
	}

	for i := 0; i < len(input); i++ {
		robots[i].p.x += 100 * robots[i].v.x
		robots[i].p.y += 100 * robots[i].v.y

		for robots[i].p.x < 0 {
			robots[i].p.x += WIDTH
		}

		for robots[i].p.y < 0 {
			robots[i].p.y += HEIGHT
		}
		for robots[i].p.x >= WIDTH {
			robots[i].p.x -= WIDTH
		}

		for robots[i].p.y >= HEIGHT {
			robots[i].p.y -= HEIGHT
		}
	}

	var count = 0
	var quads = make([]int, 0)
	for offsetY := 0; offsetY < 2; offsetY++ {
		for offsetX := 0; offsetX < 2; offsetX++ {
			count = 0
			for y := 0 + (offsetY * (HEIGHT/2 + 1)); y < (HEIGHT/2)+(offsetY*(HEIGHT/2+1)); y++ {
				for x := 0 + (offsetX * (WIDTH/2 + 1)); x < (WIDTH/2)+(offsetX*(WIDTH/2+1)); x++ {
					for _, robot := range robots {
						if robot.p.x == x && robot.p.y == y {
							count++
						}
					}
				}
			}
			quads = append(quads, count)
		}
	}
	result = 1

	for _, quadCount := range quads {
		result *= quadCount
	}

	return result
}

func simulateSecond(robots []Robot) []Robot {
	for i := 0; i < len(robots); i++ {
		robots[i].p.x += robots[i].v.x
		robots[i].p.y += robots[i].v.y

		for robots[i].p.x < 0 {
			robots[i].p.x += WIDTH
		}

		for robots[i].p.y < 0 {
			robots[i].p.y += HEIGHT
		}
		for robots[i].p.x >= WIDTH {
			robots[i].p.x -= WIDTH
		}

		for robots[i].p.y >= HEIGHT {
			robots[i].p.y -= HEIGHT
		}
	}
	return robots
}

func Part2(input structuredInput) int {
	var result = 0

	var robots = make([]Robot, 0)
	var temp Robot
	var count int

	for _, robot := range input {
		temp = Robot{Vector2{robot.p.x, robot.p.y}, Vector2{robot.v.x, robot.v.y}}
		robots = append(robots, temp)
	}
	var img *image.Gray
	for i := 0; i < 10000; i++ {
		img = image.NewGray(image.Rect(0, 0, WIDTH, HEIGHT))
		robots = simulateSecond(robots)
		count = 0
		for y := 0; y < HEIGHT; y++ {
			for x := 0; x < WIDTH; x++ {
				count = 0
				for _, robot := range robots {
					if robot.p.x == x && robot.p.y == y {
						count++
					}
				}
				if count == 0 {
					img.Set(x, y, color.White)
				} else {
					img.Set(x, y, color.Black)
				}
			}
		}
		f, _ := os.Create("./images/" + strconv.Itoa(i+1) + ".png")
		defer f.Close()

		png.Encode(f, img)
	}
	// Find result manualy
	result = 6876
	return result
}

func main() {
	var start time.Time
	var elapsed time.Duration = 0
	input, err := LoadInput(FILE_PATH)
	if err != nil {
		fmt.Println("Error loading input:", err)
		return
	}

	structuredInput := TransformInput(input)
	fmt.Println("Structured Input:", structuredInput)

	start = time.Now()
	fmt.Println("Solution Part 1: ", Part1(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 1 took %s\n", elapsed)

	start = time.Now()
	fmt.Println("Solution Part 2: ", Part2(structuredInput))
	elapsed = time.Since(start)
	fmt.Printf("Part 2 took %s\n", elapsed)
}