package day24

import (
	"strings"

	"gitea.paas.celticinfo.fr/oabrivard/aoc2023/utils"
)

type Hailstone struct {
	px, py, pz, vx, vy, vz int64
}

type Line struct {
	m, b float64
}

func getLine(h Hailstone) Line {
	y2 := h.py + h.vy
	x2 := h.px + h.vx
	m := float64((y2 - h.py)) / float64((x2 - h.px))
	b := float64(y2) - m*float64(x2)
	return Line{m, b}
}

func crossCoord(h1, h2 Hailstone) (bool, float64, float64) {
	l1 := getLine(h1)
	l2 := getLine(h2)

	if l1.m == l2.m {
		return false, -1, -1
	}

	x := (l2.b - l1.b) / (l1.m - l2.m)
	y := l2.m*x + l2.b

	if h1.px > int64(x) && h1.vx >= 0 || h1.px < int64(x) && h1.vx <= 0 {
		return false, -1, -1
	}

	if h2.px > int64(x) && h2.vx >= 0 || h2.px < int64(x) && h2.vx <= 0 {
		return false, -1, -1
	}

	return true, x, y
}

func Part1(lines []string, min, max float64) int {
	stones := []Hailstone{}

	for _, line := range lines {
		values := utils.ParseInt64Array(strings.Replace(line, " @", ",", -1), ", ")
		stone := Hailstone{values[0], values[1], values[2], values[3], values[4], values[5]}
		stones = append(stones, stone)
	}

	result := 0
	for i := range stones {
		for j := i + 1; j < len(stones); j++ {
			areCrossing, x, y := crossCoord(stones[i], stones[j])
			if !areCrossing {
				continue
			}
			if x >= min && y >= min && x <= max && y <= max {
				result++
			}
			//fmt.Println("x : ", x, ", y : ", y)
		}
	}

	return result
}