package main

import (
	"encoding/json"
	"log"
	"net/http"
	"net/url"
	"strconv"

	"github.com/lucasb-eyer/go-colorful"
)

type Mandelbrot []uint

func (m Mandelbrot) SetPixel(width int, x int, y int, color []uint) {
	start := y*int(width)*4 + x*4
	for i := 0; i < 4; i++ {
		m[start+i] = color[i]
	}
}

func GetColor(iteration uint, maxIterations uint) []uint {
	c := colorful.Hsl(float64(iteration)/256, 1.0, float64(iteration)/(float64(iteration)+8.0))
	return []uint{
		uint(c.R * 255),
		uint(c.G * 255),
		uint(c.B * 255),
		255,
	}
	//return []uint{0, 0, 0, 255}
}

func CalculateMandelbrot(maxIterations uint, minX float64, minY float64, maxX float64, maxY float64, width int, height int) Mandelbrot {
	mandelbrot := make(Mandelbrot, width*height*4)

	dx := maxX - minX
	dy := maxY - minY
	for row := 0; row < height; row++ {
		for col := 0; col < width; col++ {
			cRe := (float64(col)*dx)/float64(width) + minX
			cIm := (float64(row)*dy)/float64(height) + minY

			var x float64
			var y float64

			var iteration uint
			for ; x*x+y*y <= 4 && iteration < maxIterations; iteration++ {
				newX := x*x - y*y + cRe
				y = 2*x*y + cIm
				x = newX
			}

			mandelbrot.SetPixel(width, col, row, GetColor(iteration, maxIterations))
		}
	}

	return mandelbrot
}

func GetFloatParameter(query url.Values, name string, defaultValue float64) float64 {
	if str := query.Get(name); len(str) > 0 {
		value, err := strconv.ParseFloat(str, 64)
		if err == nil {
			return value
		}
	}
	return defaultValue
}

func GetIntParameter(query url.Values, name string, defaultValue int) int {
	if str := query.Get(name); len(str) > 0 {
		value, err := strconv.ParseInt(str, 10, 64)
		if err == nil {
			return int(value)
		}
	}
	return defaultValue
}

func MainHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Access-Control-Allow-Origin", "*")

	query := r.URL.Query()

	var maxIterations uint = 1000
	minX := GetFloatParameter(query, "minX", -2.0)
	minY := GetFloatParameter(query, "minY", -2.0)
	maxX := GetFloatParameter(query, "maxX", 2.0)
	maxY := GetFloatParameter(query, "maxY", 2.0)
	width := GetIntParameter(query, "width", 1000)
	height := GetIntParameter(query, "height", 1000)

	log.Println(minX, minY, maxX, maxY, width, height)

	json.NewEncoder(w).Encode(CalculateMandelbrot(maxIterations, minX, minY, maxX, maxY, width, height))
}

func main() {
	http.HandleFunc("/", MainHandler)

	log.Fatal(http.ListenAndServe(":8001", nil))
}