package minesweeper

import (
	"bytes"
	"errors"
	"strconv"
)

const testVersion = 1

type Board [][]byte

// Count fills in the number of mines in adjacent squares on the board
func (b Board) Count() error {
	if !b.isValid() {
		return errors.New("Invalid Board")
	}
	for i := range b {
		for j := range b[i] {
			switch b[i][j] {
			case '+', '-', '|', '*':
				continue
			case ' ':
				num := b.countAdjacentMines(j, i)
				if num != 0 {
					b[i][j] = []byte(strconv.Itoa(num))[0]
				}
			default:
				return errors.New("Invalid Board")
			}
		}
	}
	return nil
}

// countAdjacentMines returns the number of mines adjacent to x,y
// or -1 if x,y is invalid
func (b Board) countAdjacentMines(x, y int) int {
	var numMines int
	if b.isMine(x-1, y-1) {
		numMines++
	}
	if b.isMine(x, y-1) {
		numMines++
	}
	if b.isMine(x+1, y-1) {
		numMines++
	}
	if b.isMine(x-1, y) {
		numMines++
	}
	if b.isMine(x, y) {
		numMines++
	}
	if b.isMine(x+1, y) {
		numMines++
	}
	if b.isMine(x-1, y+1) {
		numMines++
	}
	if b.isMine(x, y+1) {
		numMines++
	}
	if b.isMine(x+1, y+1) {
		numMines++
	}
	return numMines
}

func (b Board) isMine(x, y int) bool {
	if x < 0 || y < 0 || x > len(b[0])-1 || y > len(b)-1 {
		return false
	}
	return b[y][x] == '*'
}

func (b Board) isValid() bool {
	if len(b) <= 0 {
		// no size
		return false
	}
	for i := range b {
		if len(b[i]) != len(b[0]) {
			// All rows must be same length
			return false
		}
		for j := range b[i] {
			// Check top & bottom row for border
			if i == 0 || i == len(b)-1 {
				// Check corners for border
				if j == 0 || j == len(b[i])-1 {
					if b[i][j] != '+' {
						return false
					}
				} else if b[i][j] != '-' {
					return false
				}
			} else {
				if j == 0 || j == len(b[i])-1 {
					if b[i][j] != '|' {
						return false
					}
				}
			}
		}
	}
	return true
}

func (b Board) String() string {
	return "\n" + string(bytes.Join(b, []byte{'\n'}))
}