package main

// RIGHT : x
// FORWARD : Y
// UP : Z

import (
	"fmt"
	"math"
	"runtime"
	"sync"

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

const WIDTH = 200
const HEIGHT = 200
const TEXTURE_SCALE = 2

const MAX_DIST = 500.0
const MAX_STEP = 100
const EPS = 0.1
const PI = math.Pi

const SOFT_SHADOW_COEFF = 16

var lightPos Vector3
var scene SDF

// radius, theta, phi
var screenSpherical Vector3
var screenPhysicalSize float64
var cameraPos Vector3

func init() {
	lightPos = Vector3{100, -400, 400}

	cameraPos = Vector3{0, -10, 25}
	screenSpherical = Vector3{10, PI/2 + 0.2, PI / 2}
	screenPhysicalSize = 5
}

func update(t float64) {

	sphereMat := RED_MAT
	sphereMat.specularFac = 0.5
	sphere := TranslatedSDF{Sphere{10, sphereMat}, Vector3{-15, 100, 10}}
	sphere2 := TranslatedSDF{Sphere{10, sphereMat}, Vector3{15, 100, 10}}

	// boxMat := BLUE_MAT
	// box := TranslatedSDF{Box{Vector3{10, 2, 10}, boxMat}, Vector3{0, 100, 10}}
	// sphere := RepeatSDF{Sphere{20, sphereMat}, Vector3{50, 50, 50}}
	plane := Plane{Vector3{0, 0, 1}, WHITE_GREY_GRID_MAT}

	sphere.translate.Z = 20 * math.Sin(t)
	sphere2.translate.Z = 20 * math.Sin(t*0.5)
	scene = SmoothUnionSDF{SmoothUnionSDF{sphere, plane, 2.5}, sphere2, 2.5}
	// scene = UnionSDF{UnionSDF{sphere, plane}, sphere2}
	// scene = UnionSDF{plane, sphere}
}

func compute_pixel(y0 int, y1 int, wg *sync.WaitGroup, screenCenter Vector3, phiVec Vector3, thetaVec Vector3, image *rl.Image) {
	defer wg.Done()

	for pixelY := y0; pixelY < y1; pixelY++ {
		for pixelX := range WIDTH {
			sx := screenPhysicalSize * (float64(pixelX)/WIDTH - 0.5)
			sy := screenPhysicalSize * (float64(pixelY)/HEIGHT - 0.5)

			origin := screenCenter.Add(phiVec.Scale(-sx)).Add(thetaVec.Scale(sy))
			direction := (origin.Sub(cameraPos)).Normalized()

			hit, colorVec := rayMarch(origin, direction, 5)
			var fr, fg, fb float64
			if hit {
				fr, fg, fb = colorVec.Unpack()
			} else {
				fr, fg, fb = 0, 0, 0
			}
			fr, fg, fb = Clamp(fr, 0, 255), Clamp(fg, 0, 255), Clamp(fb, 0, 255)
			r, g, b := uint8(fr), uint8(fg), uint8(fb)

			rl.ImageDrawPixel(image, int32(pixelX), int32(pixelY), rl.Color{R: r, G: g, B: b, A: 255})
		}
	}
}
func genImage() *rl.Image {
	screenCartesian, _, thetaVec, phiVec := screenSpherical.SphericalToCartesian()
	screenCenter := cameraPos.Add(screenCartesian)

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

	// numWorkers := 1
	numWorkers := runtime.NumCPU()

	var wg sync.WaitGroup
	wg.Add(numWorkers)

	bandHeight := HEIGHT / numWorkers

	for worker := range numWorkers {
		startY := worker * bandHeight
		endY := startY + bandHeight
		if worker == numWorkers-1 {
			endY = HEIGHT
		}

		go compute_pixel(startY, endY, &wg, screenCenter, phiVec, thetaVec, image)
	}

	wg.Wait()
	return image
}

func main() {
	rl.InitWindow(WIDTH*TEXTURE_SCALE, HEIGHT*TEXTURE_SCALE, "raymarching")
	var texture rl.Texture2D
	time := rl.GetTime()
	t := 0.0

	for !rl.WindowShouldClose() {
		new_time := rl.GetTime()
		dt := new_time - time
		t += dt * 0.4
		time = new_time

		update(t)
		fmt.Println("FPS ", 1/dt)
		rl.BeginDrawing()
		rl.ClearBackground(rl.Black)
		texture = rl.LoadTextureFromImage(genImage())
		rl.DrawTextureEx(texture, rl.Vector2{X: 0, Y: 0}, 0.0, TEXTURE_SCALE, rl.White)
		rl.EndDrawing()
	}
}