package main

import (
	"fmt"
	"golang.org/x/term"
	"log"
	"math/big"
	"time"
)

type color int

const (
	black color = iota
	red
	yellow
	green
	cyan
	blue
	magenta
)

func (c color) print() {
	var i int
	switch c {
	case red:
		i = 41
	case yellow:
		i = 43
	case green:
		i = 42
	case cyan:
		i = 46
	case blue:
		i = 44
	case magenta:
		i = 45
	default:
		i = 40
	}
	if _, err := fmt.Printf("\033[%dm ", i); err != nil {
		log.Fatal(err)
	}
}

var rat2 = big.NewRat(2, 1)

func mandelbrot(x0, y0 *big.Rat) color {
	x := new(big.Rat)
	y := new(big.Rat)
	x2 := new(big.Rat)
	y2 := new(big.Rat)
	i := 0
	for ; x2.Cmp(rat2) <= 0 && y2.Cmp(rat2) <= 0; i++ {
		y.Add(y, y).Mul(y, x).Add(y, y0)
		x.Sub(x2, y2).Add(x, x0)
		x2.Mul(x, x)
		y2.Mul(y, y)
	}
	return color(i-1)%magenta + 1
}

func printMandelbrot(xMin, xRange, yMin, yRange *big.Rat) {
	width, height, err := term.GetSize(0)
	if err != nil {
		log.Fatalf("Terminal size: %s.", err)
	}

	xStep := new(big.Rat).Quo(xRange, big.NewRat(int64(width), 1))
	yStep := new(big.Rat).Quo(yRange, big.NewRat(int64(height), 1))
	grid := make([]color, width*height)
	y := new(big.Rat)
	x := new(big.Rat)
	y.Set(yMin)
	for i := 0; i < height; i++ {
		x.Set(xMin)
		for j := 0; j < width; j++ {
			go func(i, j int, x, y *big.Rat) {
				grid[i*width+j] = mandelbrot(x, y)
			}(i, j, new(big.Rat).Set(x), new(big.Rat).Set(y))
			x.Add(x, xStep)
		}
		y.Add(y, yStep)
	}
	time.Sleep(time.Minute)
	for _, c := range grid {
		c.print()
	}
}

func main() {
	printMandelbrot(big.NewRat(-3, 2), big.NewRat(247, 100), big.NewRat(-112, 100), big.NewRat(224, 100))
}