package main

import (
	"AOC2022/helper"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"
)

type Simulation struct {
	headPos  [2]int
	tailPos  [][2]int
	tailPast map[[2]int]bool
}

func main() {
	args := os.Args[1:]
	lines := helper.ReadTextFile(args[0])
	tails := [][2]int{{0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}}
	simulation := Simulation{[2]int{0, 0}, tails, make(map[[2]int]bool)}
	for _, line := range lines {
		direction, distance := getDirectionAndDistance(line)
		for i := 0; i < distance; i++ {
			move(&simulation.headPos, direction)
			for i, _ := range tails {
				simulation.moveTail(i)
			}
		}
	}

	fmt.Println(len(simulation.tailPast))
}

func getDirectionAndDistance(line string) ([2]int, int) {
	splitLine := strings.Split(line, " ")
	distance := helper.RemoveError(strconv.Atoi(splitLine[1]))
	switch splitLine[0] {
	case "U":
		return [2]int{0, 1}, distance
	case "D":
		return [2]int{0, -1}, distance
	case "R":
		return [2]int{1, 0}, distance
	case "L":
		return [2]int{-1, 0}, distance
	default:
		return [2]int{0, 0}, distance
	}
}

func (simulation *Simulation) moveTail(i int) {
	activeTail := &simulation.tailPos[i]
	if len(simulation.tailPos)-1 == i {
		simulation.tailPast[*activeTail] = true
	}
	var nextKnot [2]int
	if i == 0 {
		nextKnot = simulation.headPos
	} else {
		nextKnot = simulation.tailPos[i-1]
	}
	direction := getDirectionFromTo(nextKnot[:], activeTail[:])
	if getLength(direction[:]) < 2 {
		return
	}
	if direction[0] > 0 {
		activeTail[0]++
	}
	if direction[0] < 0 {
		activeTail[0]--
	}
	if direction[1] > 0 {
		activeTail[1]++
	}
	if direction[1] < 0 {
		activeTail[1]--
	}
	if len(simulation.tailPos)-1 == i {
		simulation.tailPast[*activeTail] = true
	}
}

func move(object *[2]int, direction [2]int) {
	object[0] += direction[0]
	object[1] += direction[1]
}

func getDirectionFromTo(X, Y []int) []int {
	direction := []int{}
	for i, _ := range X {
		direction = append(direction, X[i]-Y[i])
	}
	return direction
}

func getLength(X []int) float64 {
	temp := float64(0)
	for i, _ := range X {
		temp += math.Pow(float64(X[i]), 2)
	}
	return math.Sqrt(temp)
}

func (simulation *Simulation) print(size int) {
	for i := 0; i < size; i++ {
		tempArr := ""
		for j := 0; j < size; j++ {
			pos := [2]int{j, size - 1 - i}
			if [2]int{0, 0} == pos {
				tempArr += "S"
			} else if simulation.tailPast[pos] {
				tempArr += "#"
			} else if simulation.headPos == pos {
				tempArr += "H"
			} else if helper.Contains2Int(simulation.tailPos, pos) {
				tempArr += "T"
			} else {
				tempArr += "."
			}
		}
		fmt.Println(tempArr)
	}
}