package main

import (
	"fmt"
	"gopkg.in/cheggaaa/pb.v1"
	"math"
	"math/rand"
	"os"
)

const (
	sigma = 200.0
	f_0   = 0.1
	G     = 4.302e-3
	R_s   = 1e4
)

type star struct {
	x float64
	y float64
	z float64
}

func rho(x, y, z float64) float64 {
	var r float64 = math.Sqrt((x * x) + (y * y) + (z * z))
	var a float64 = (1) / (math.Sqrt(2*math.Pi) * sigma)
	var b float64 = math.Exp(-(phi(r) / float64(sigma*sigma)))
	//aphi := phi(r)
	//asigma := float64(sigma * sigma)
	//fmt.Println(aphi, asigma, math.Exp( - (aphi / asigma)))
	return a * b
}

func phi(x float64) float64 {
	if x == 0 {
		return (-4 * math.Pi * f_0 * G * (R_s * R_s))
	} else {
		var a float64 = -(4 * math.Pi * G * f_0 * (R_s * R_s * R_s) / x)
		var b float64 = math.Log(1.0 + (x / R_s))
		return (a * b)
	}
}

func genStar(f *os.File) (bool, star) {
	var length float64 = 1.5e7

	var rangeMin float64 = -length
	var rangeMax float64 = length

	var randMin float64 = rho(0, 0, 0)
	var randMax float64 = rho(length, length, length)

	//(max - min) * rand.Float64()) + min
	var x float64 = ((rangeMax - rangeMin) * rand.Float64()) + rangeMin
	var y float64 = ((rangeMax - rangeMin) * rand.Float64()) + rangeMin
	var z float64 = ((rangeMax - rangeMin) * rand.Float64()) + rangeMin

	var randVal float64 = (randMax-randMin)*rand.Float64() + randMin

	var rhoVal float64 = rho(x, y, z)

	//fmt.Printf("x: %-20f y: %-20f z: %-20f randVal: %-20f rhoVal: %-20f\n", x, y, z, randVal, rhoVal)

	if randVal < rhoVal {
		var starString string = fmt.Sprintf("%f, %f, %f\n", x, y, z)
		_, err := f.WriteString(starString)
		if err != nil {
			panic(err)
		}
		f.Sync()

		//fmt.Printf("x: %-20f y: %-20f z: %-20f randVal: %-20f rhoVal: %-20f\n", x, y, z, randVal, rhoVal)

		newStar := star{
			x: x,
			y: y,
			z: z,
		}

		// return that a star was generated
		return true, newStar
	}

	// return that no star was generated
	return false, star{
		x: 0,
		y: 0,
		z: 0,
	}
}

func generateGoMethods(starCount int, f *os.File, channel chan star) {
	var generatedStars int = 0

	// for the amount of stars
	for generatedStars < starCount {

		// try to generate a new star
		result, star := genStar(f)
		if result == true {
			generatedStars += 1
			channel <- star
		}
	}
}

func main() {
	// define some arguments
	var stars int = 1e6
	var threads int = 1
	var threadStarCount int = stars / threads

	// create a channel with a buffer of 10
	channel := make(chan star, 10)

	// create a file that stores the data
	hostname, _ := os.Hostname()
	pid := os.Getpid()
	f, err := os.Create(fmt.Sprintf("%s_%d.csv", hostname, pid))
	if err != nil {
		panic(err)
	}

	// use 8 threads
	// each thread should generate stars / 8 stars
	for i := 0; i < threads; i++ {
		fmt.Printf("Creating a happy worker! He/She is trying to generate %d stars!", threadStarCount)
		// generate a go-method creating threadStarCound stars
		go generateGoMethods(threadStarCount, f, channel)
		fmt.Printf(" He/She just started working!\n")
	}

	// start the missing threads threads
	var missingStars int = stars - (threadStarCount * threads)
	fmt.Printf("A special worker was assigned to generate the last %d stars.\n", missingStars)
	go generateGoMethods(missingStars, f, channel)

	var starSlice []star

	// Initialize a new progress bar
	bar := pb.New(stars).Prefix("Stars: ")
	bar.Start()

	// get the stars
	for i := 0; i < stars; i++ {
		var newStar = <-channel
		bar.Increment()
		starSlice = append(starSlice, newStar)
	}

	bar.Finish()

	// print all elements in the starslice
	for _, element := range starSlice {
		fmt.Println(element)
	}
}