package main

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

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 lightPos Vector3 = Vector3{0, 200, 400}
var sphere Sphere = Sphere{Vector3{0, 100, 10}, 10, WHITE_GREY_GRID_MAT}
var plane Plane = Plane{Vector3{0, 0, 1}, -10, GRID_OF_GRID_MAT}
var scene UnionSDF = UnionSDF{sphere, plane}

var cameraPos Vector3 = Vector3{0, -10, 0}

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

func phongShading(point Vector3, normal Vector3, mat Material) Vector3 {
	lightVec := (lightPos.Sub(point)).Normalized()
	reflectLight := Reflect(lightVec, normal)
	eyeVec := (cameraPos.Sub(point)).Normalized()

	ambiant := mat.ambiantColor.GetColor(point).Scale(0.1)

	diffusePower := mat.diffuseFac * max(0, normal.Dot(lightVec)) * 0.5
	diffuse := mat.diffuseColor.GetColor(point).Scale(diffusePower)

	specularPower := mat.specularFac * math.Pow(max(0, reflectLight.Dot(eyeVec)), mat.specularExp)
	specular := mat.specularColor.GetColor(point).Scale(specularPower)

	return ambiant.Add(diffuse).Add(specular)
}

func rayMarch(origin Vector3, direction Vector3) (bool, Vector3) {
	p := origin
	for range MAX_STEP {
		dist, mat := scene.Distance(p)
		// fmt.Println(dist)
		if dist < EPS {
			// fmt.Println("hit")
			normal := Gradient(scene, p, EPS).Normalized()
			return true, phongShading(p, normal, mat)
		}
		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(phi_vec.Scale(-sx)).Add(theta_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()
	}
}