package main

import (
	"math/rand/v2"
	"strconv"
)

// The game config
type Config struct {
	Width  int
	Height int
	Mines  int
}

// The game states
type Game struct {
	// Game config stored for g.G() to check border
	Config *Config

	//  0b0000_0000
	// &0b1000_0000 = Mine
	// &0b0100_0000 = Visible
	// &0b0011_0000 = Flag
	// &0b0000_1111 = Number
	Grids []uint8

	// 0b0000_0000 == Gaming
	// 0b0000_0001 == Win
	// 0b0000_0010 == Loss
	Status uint8
}

// New creates a new game, initialize mines and number
func New(config *Config) *Game {
	// Panic when code goes wrong
	if config.Width <= 0 || config.Height <= 0 || config.Mines <= 0 {
		panic("width, height and mines should be larger than 0")
	} else if config.Mines > config.Width*config.Height {
		panic("grids should be larger than mines")
	}

	// Create a new game instance
	g := &Game{
		Config: config,
		Grids:  make([]uint8, config.Width*config.Height),
	}

	// Initialize mines
	for range config.Mines {
		x, y := rand.IntN(config.Width), rand.IntN(config.Height)
		for *g.G(x, y) != 0 {
			x, y = rand.IntN(config.Width), rand.IntN(config.Height)
		}
		*g.G(x, y) = 0b1000_0000

		// Add numbers arounds the mine grid
		for _, a := range [][]int{{x - 1, y}, {x + 1, y}, {x, y - 1}, {x, y + 1}} {
			if p := g.G(a[0], a[1]); p != nil {
				*p += 1
			}
		}
	}

	return g
}

// G returns a pointer to the destination grid by (x, y) coordinate, starts from left top
func (g *Game) G(x, y int) *uint8 {
	if x < 0 || x >= g.Config.Width || y < 0 || y >= g.Config.Height {
		return nil
	}

	return &g.Grids[y*g.Config.Width+x]
}

// Click run a DFS algorithm for (x, y) coordinate to bring all empty grids visible
func (g *Game) Click(x, y int) *Game {
	// Check if the coordinate is valid
	c := g.G(x, y)
	if c == nil {
		panic("invalid coordinate")
	}

	// Make the grid visible
	*c |= 0b0100_0000

	// If the grid has number greater than 0, can go back
	if *c&0b0000_1111 != 0 {
		return g
	}

	// Click grids around the 0 number grid
	for _, a := range [][]int{{x - 1, y}, {x + 1, y}, {x, y - 1}, {x, y + 1}} {
		if p := g.G(a[0], a[1]); p != nil && *p&0b0100_0000 == 0 {
			g.Click(a[0], a[1])
		}
	}

	return g
}

// SetAllVisible simply set all grids visible
func (g *Game) SetAllVisible() *Game {
	for y := range g.Config.Height {
		for x := range g.Config.Width {
			*g.G(x, y) |= 0b0100_0000
		}
	}

	return g
}

// Print will output the game grids into console
func (g *Game) Print() *Game {
	s := ""
	for y := range g.Config.Height {
		for x := range g.Config.Width {
			if v := *g.G(x, y); v&0b0100_0000 != 0 {
				if v&0b1000_0000 != 0 {
					s += "*"
				} else if f := v & 0b0011_0000; f != 0 {
					if f == 0b0001_0000 {
						s += "X"
					} else if f == 0b0010_0000 {
						s += "O"
					} else if f == 0b0011_0000 {
						s += "?"
					}
				} else {
					s += strconv.Itoa(int(v & 0b0000_1111))
				}
			} else {
				s += "."
			}
		}
		s += "\n"
	}
	print(s)
	return g
}

func main() {
	New(&Config{
		Width:  10,
		Height: 10,
		Mines:  10,
	}).Click(1, 1).Print().SetAllVisible().Print()
}