package main

import "fmt" // for IO and standard library
import "os" // for handling the progress bar
import "math" // for maths

// ================ VEC3 CLASS =====================

type Vec3 struct {
	E [3]float32
}

//Basic vector functions

func NewVec3(e0, e1, e2 float32) Vec3 {
	return Vec3{E: [3]float32{e0, e1, e2}}
}

func (v Vec3) X() float32 {
	return v.E[0]
}

// can be executed as v.X() in main

func (v Vec3) Y() float32 {
	return v.E[1]
}

func (v Vec3) Z() float32 {
	return v.E[2]
}

func (v Vec3) Neg() Vec3 {
	return NewVec3(-v.E[0], -v.E[1], -v.E[2])
}

func (v Vec3) Get(i int) float32 {
	return v.E[i]
}

func (v *Vec3) Set(i int, val float32) {
	v.E[i] = val
}

func (v *Vec3) Add(v2 Vec3) {
	v.E[0] += v2.E[0]
	v.E[1] += v2.E[1]
	v.E[2] += v2.E[2]
}

func (v *Vec3) Mult(t float32) {
	v.E[0] *= t
	v.E[1] *= t
	v.E[2] *= t
}

func (v *Vec3) Div(t float32) {
	if t != 0 {
		v.E[0] /= t
		v.E[1] /= t
		v.E[2] /= t
	}
}

func (v Vec3) Length() float32 {
	return float32(math.Sqrt(float64(v.E[0]*v.E[0] + v.E[1]*v.E[1] + v.E[2]*v.E[2])))
}

// Vector utility functions

func (v Vec3) String() string {
	return fmt.Sprintf("%v %v %v", v.E[0], v.E[1], v.E[2])
}

func (v *Vec3) Sub(v2 Vec3) {
	v.E[0] -= v2.E[0]
	v.E[1] -= v2.E[1]
	v.E[2] -= v2.E[2]
}

func (v *Vec3) MultVec(v2 Vec3) {
	v.E[0] *= v2.E[0]
	v.E[1] *= v2.E[1]
	v.E[2] *= v2.E[2]
}

func (v *Vec3) DivVec(v2 Vec3) {
		v.E[0] /= v2.E[0]
		v.E[1] /= v2.E[1]
		v.E[2] /= v2.E[2]
}

func Dot(v1 Vec3, v2 Vec3) float32 {
	return (v1.E[0]*v2.E[0] + v1.E[1]*v2.E[1] + v1.E[2]*v2.E[2])
}

func Cross(v1 Vec3, v2 Vec3) Vec3 {
	return NewVec3(v1.E[1]*v2.E[2] - v1.E[2]*v2.E[1],
		v1.E[2]*v2.E[0] - v1.E[0]*v2.E[2],
		v1.E[0]*v2.E[1] - v1.E[1]*v2.E[0])
}

func Unit_vector(v Vec3) Vec3 {
	v.Div(v.Length())
     return v
}

// ============== COLOUR CLASS ==============

func Write_color(v Vec3) {
	fmt.Println(int(255.999*v.E[0]), int(255.999*v.E[1]), int(255.999*v.E[2]))
}

// ============== RAY CLASS =================

type Point3 Vec3
type Ray struct {
	Orig Point3
	Dir Vec3
}

func NewRay(orig Point3, dir Vec3) *Ray {
    return &Ray{Orig: orig, Dir: dir}
}

func (r *Ray) Origin() Point3 {
	return r.Orig
}

func (r *Ray) Direction() Vec3 {
	return r.Dir
}

func (r *Ray) At(t float32) Point3 {
	return Point3{
		X: r.Orig.X + t*r.Dir.X,
		Y: r.Orig.Y + t*r.Dir.Y,
		Z: r.Orig.Z + t*r.Dir.Z
	}
}

// =============== MAIN =====================
func main() {

     // Image
	 var aspect_ratio := 16.0 / 9.0;
     var image_width int = 400;
     var image_height int = int(image_width / aspect_ratio)
	 if image_height < 1 {
		image_height = 1
	 }

	 // Viewport
	 var viewport_height := 2.0
	 var viewport_width := viewport_height * float32(image_width/image_height)

     // Rendering
     fmt.Println("P3")
     fmt.Println(image_width, " ", image_height, "\n255")
     for j := 0; j < image_height; j++ {
          fmt.Fprintf(os.Stderr, "\rScanlines remaining: %d ", image_height-j)
          for i := 0; i < image_width; i++ {
               // r := float32(i) / float32(image_width - 1)
               // g := float32(j) / float32(image_height-1)
               // b := 0

               // ir := int(r * 256)
               // ig := int(g * 256)
               // ib := int(b * 256)
               // fmt.Println(ir, " ", ig, " ", ib)

               pixel_colour := NewVec3(float32(i) / float32(image_width - 1), float32(j) / float32(image_height-1), 0)
               Write_color(pixel_colour)
          }
     }
     // INFO: The pixels are written out in rows.
     // Image file can be created with
     // go run main.go > image.ppm
}