package main

import (
	"math"

	rl "github.com/gen2brain/raylib-go/raylib"
)

const MAX_DIST = 1000.0
const MAX_STEP = 100
const EPS = 0.1
const WIDTH = 500
const HEIGHT = 500
const PI = math.Pi

// var sphere Sphere = Sphere{Vector3{0, 0, 100}, 10, RED}
// var plane Plane = Plane{Vector3{0, 1, 0}, -10, GREY}
// var scene UnionSDF = UnionSDF{sphere, plane}

// x right, y forward, z up
var scene Sphere = Sphere{Vector3{0, 100, 0}, 5, RED}
var cameraPos Vector3 = Vector3{0, -10, 0}

// radius, theta, phi
var screenSpherical Vector3 = Vector3{10, PI / 2, PI / 2}
var screenPhysicalSize float64 = 5

func rayMarch(origin Vector3, direction Vector3) (bool, Vector3) {
	p := origin
	for range MAX_STEP {
		dist, color := scene.Distance(p)
		// fmt.Println(dist)
		if dist < EPS {
			// fmt.Println("hit")
			return true, color.GetColor(p)
		}
		if dist > MAX_DIST {
			break
		}
		// fmt.Println("Before")
		// fmt.Println(p, dist)
		p = p.Add(direction.Scale(dist))
		// fmt.Println("After")
		// fmt.Println(p, DistanceOnly(scene, p))
	}
	return false, GREY
}

func genImage() *rl.Image {
	screenCartesian, _, theta_vec, phi_vec := screenSpherical.SphericalToCartesian()
	screenCenter := cameraPos.Add(screenCartesian)
	// fmt.Println(theta_vec, phi_vec)

	image := rl.GenImageColor(WIDTH, HEIGHT, rl.Black)

	for pixel_x := range WIDTH {
		for pixel_y := range HEIGHT {
			sx := screenPhysicalSize * (float64(pixel_x)/WIDTH - 0.5)
			sy := screenPhysicalSize * (float64(pixel_y)/WIDTH - 0.5)

			origin := screenCenter.Add(theta_vec.Scale(-sx)).Add(phi_vec.Scale(-sy))
			direction := (origin.Sub(cameraPos)).Normalized()
			// fmt.Println(origin, direction)

			hit, color_vec := rayMarch(origin, direction)
			var fr, fg, fb float64
			if hit {
				fr, fg, fb = color_vec.Unpack()
			} else {
				fr, fg, fb = 0, 0, 0
			}
			r, g, b := uint8(fr), uint8(fg), uint8(fb)
			rl.ImageDrawPixel(image, int32(pixel_x), int32(pixel_y), rl.Color{R: r, G: g, B: b, A: 255})
		}
	}

	return image
}

func main() {
	rl.InitWindow(WIDTH, HEIGHT, "raymarching")
	texture := rl.LoadTextureFromImage(genImage())

	for !rl.WindowShouldClose() {
		rl.BeginDrawing()
		rl.ClearBackground(rl.Black)
		rl.DrawTexture(texture, 0, 0, rl.White)
		rl.EndDrawing()
	}
}

// func main() {
// 	screenWidth := int32(800)
// 	screenHeight := int32(450)

// 	rl.InitWindow(screenWidth, screenHeight, "Bouncing Ball in Go - raylib")
// 	defer rl.CloseWindow()

// 	rl.SetTargetFPS(60)

// 	// Ball properties
// 	ballRadius := float32(20)
// 	ballPos := rl.NewVector2(float32(screenWidth)/2.0, float32(screenHeight)/2.0)
// 	ballSpeed := rl.NewVector2(4, 3)
// 	ballColor := rl.Red

// 	for !rl.WindowShouldClose() {
// 		// Update
// 		ballPos.X += ballSpeed.X
// 		ballPos.Y += ballSpeed.Y

// 		// Bounce on edges
// 		if ballPos.X >= float32(screenWidth)-ballRadius || ballPos.X <= ballRadius {
// 			ballSpeed.X *= -1
// 		}
// 		if ballPos.Y >= float32(screenHeight)-ballRadius || ballPos.Y <= ballRadius {
// 			ballSpeed.Y *= -1
// 		}

// 		// Draw
// 		rl.BeginDrawing()
// 		rl.ClearBackground(rl.RayWhite)

// 		rl.DrawText("Bouncing Ball Example", 10, 10, 20, rl.DarkGray)
// 		rl.DrawCircleV(ballPos, ballRadius, ballColor)

// 		rl.EndDrawing()
// 	}
// }