package main

import (
	"flag"
	"fmt"
	"image"
	"image/color"
	"image/jpeg"
	"math/rand"
	"os"
	"time"
)

const (
	// Grid size
	//size = 150
	size = 30
	// Image zoom value
	zoom = 8
	// Generations per second
	gps = 2
)

type Grid struct {
	G [size][size]bool
}

func (g *Grid) Blinker() {
	g.G[14][13] = true
	g.G[14][14] = true
	g.G[14][15] = true
}

func (g *Grid) Bipole() {
	g.G[14][14] = true
	g.G[14][15] = true
	g.G[15][14] = true
	g.G[16][17] = true
	g.G[17][16] = true
	g.G[17][17] = true
}

func (g *Grid) Tripole() {
	g.G[14][14] = true
	g.G[14][15] = true
	g.G[15][14] = true
	g.G[16][15] = true
	g.G[16][17] = true
	g.G[17][18] = true
	g.G[18][17] = true
	g.G[18][18] = true
}

func (g *Grid) Pulsator() {
	for i := 10; i < 20; i++ {
		g.G[i][14] = true
	}
}

func (g *Grid) Glider() {
	g.G[1][0] = true
	g.G[2][1] = true
	g.G[2][2] = true
	g.G[1][2] = true
	g.G[0][2] = true
}

func (g *Grid) Random() {
	rand.Seed(size)
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			g.G[i][j] = rand.Intn(2) == 1
		}
	}
}

/*
func (g *Grid) Pentomino() {
	g.G[75][74] = true
	g.G[76][74] = true
	g.G[74][75] = true
	g.G[75][75] = true
	g.G[75][76] = true
}
*/

type GOL struct {
	grid1 *Grid
	grid2 *Grid
	Gen   int
}

func NewGOL() (g *GOL) {
	g = &GOL{grid1: new(Grid), grid2: new(Grid)}
	g.grid1.Blinker()
	//g.grid1.Bipole()
	//g.grid1.Tripole()
	//g.grid1.Pulsator()
	//g.grid1.Random()
	//g.grid1.Pentomino()
	return
}

func min(i int) int {
	if i == -1 {
		return i + 1
	}
	return i
}

func max(i int) int {
	if i == size {
		return i - 1
	}
	return i
}

func (g *GOL) n(x, y int) (n int) {
	for i := min(x - 1); i <= max(x+1); i++ {
		for j := min(y - 1); j <= max(y+1); j++ {
			if g.grid1.G[i][j] {
				n++
			}
		}
	}
	return
}

func (g *GOL) check(x, y int) {
	n := g.n(x, y)
	if g.grid1.G[x][y] {
		n--
		switch n {
		case 0, 1:
			g.grid2.G[x][y] = false
		case 2, 3:
			g.grid2.G[x][y] = true
		default:
			g.grid2.G[x][y] = false
		}
	} else {
		if n == 3 {
			g.grid2.G[x][y] = true
		} else {
			g.grid2.G[x][y] = false
		}
	}
}

func (g *GOL) grid() (gr *Grid) {
	gr = new(Grid)
	for i := 0; i < size; i++ {
		gr.G[i] = g.grid1.G[i]
	}
	g.grid1, g.grid2 = g.grid2, g.grid1
	return
}

func (g *GOL) Calc() (gr *Grid) {
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			g.check(i, j)
		}
	}
	g.Gen++
	return g.grid()
}

var text bool

func main() {
	flag.BoolVar(&text, "text", false, "text mode")
	flag.Parse()
	gol := NewGOL()
	gc := make(chan *Grid, 10)
	if text {
		go func() {
			var buf [size * (size + 6)]byte
			for {
				buf[0] = '+'
				c := 1
				for ; c < size+1; c++ {
					buf[c] = '-'
				}
				buf[c] = '+'
				c++
				buf[c] = '\n'
				c++
				grid := <-gc
				for i := 0; i < size; i++ {
					buf[c] = '|'
					c++
					for j := 0; j < size; j++ {
						if grid.G[j][i] {
							buf[c] = '#'
						} else {
							buf[c] = ' '
						}
						c++
					}
					buf[c] = '|'
					c++
					buf[c] = '\n'
					c++
				}
				buf[c] = '+'
				c++
				for i := 0; i < size; i++ {
					buf[c] = '-'
					c++
				}
				buf[c] = '+'
				c++
				buf[c] = '\n'
				fmt.Printf("\r%s", string(buf[:]))
			}
		}()
	} else {
		ic := make(chan image.Image, 10)
		go func() {
			o := jpeg.Options{100}
			img := <-ic
			for {
				select {
				case img = <-ic:
				default:
				}
				if jpeg.Encode(os.Stdout, img, &o) == nil {
					os.Stdout.Sync()
				}
				time.Sleep(time.Millisecond * 16)
			}
		}()
		go func() {
			s := size * zoom
			r := image.Rect(0, 0, s, s)
			for {
				img := image.NewGray(r)
				grid := <-gc
				x := 0
				y := 0
				var c color.Color
				for i := 0; i < size; i++ {
					for j := 0; j < size; j++ {
						if grid.G[i][j] {
							c = color.Black
						} else {
							c = color.White
						}
						for a := 0; a < zoom; a++ {
							for b := 0; b < zoom; b++ {
								img.Set(x+a, y+b, c)
							}
						}
						y += zoom
					}
					x += zoom
					y = 0
				}
				ic <- img
			}
		}()
	}

	for {
		gc <- gol.Calc()
		if !text {
			fmt.Fprintf(os.Stderr, "\rGeneration: %d", gol.Gen)
		}
		time.Sleep(time.Second / gps)
	}
}