package main

import "fmt"
import "os" //for handling the logging output
import "math"

// ================ 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]))
}

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

     // Image
     var image_width int = 256
     var image_height int = 256

     // 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
}