Minesweeper

--[[  BOARD SETTINGS  ]]--
local size = 9          -- side length of the board (e.g. 5 = 5x5 board)
local mines = 10        -- how many mines are on the board

-- Classic difficulty settings: (SIZE x MINES)
--   beginner     = 09x10  (12.35%)
--   intermediate = 16x40  (15.63%)
--   expert       = 22x99  (20.63%)

--[[  CELL TABLES  ]]--
local realBoard = {}    -- stores which cells have mines
local gameBoard = {}    -- stores how many mines are near each cell
local liveBoard = {}    -- stores current state of each cell (unknown, known, or flagged)
local showBoard = {}    -- stores what is currently being shown to the player

local rng = Random.new()


local function toXY(i)
    local x = (i-1)%size+1
    local y = math.floor((i-1)/size)+1
    return x,y
end

local function toIndex(x,y)
    return x+(y-1)*size
end

local function isValid(x,y)
    return x > 0 and x <= size and y > 0 and y <= size
end

local function getNeighbors(x,y)
    local neighbors = {}
    for ix = x-1, x+1 do
        for iy = y-1, y+1 do
            if isValid(ix,iy) then
                table.insert(neighbors,toIndex(ix,iy))
            end
        end
    end
    return neighbors
end

local function countNearbyMines(x,y)
    local count = 0
    for _, i in ipairs(getNeighbors(x,y)) do
        count = count + if realBoard[i] then 1 else 0
    end
end

local function display()
    local board = '\n\n   '
    for i = 1, size do
        board = board..i..' '
    end
    board = board..'\n   '
    for i = 1, size-1 do
        board = board..'‾‾'
    end
    board = board..'‾\n'

    for y = 1, size do
        local line = ""
        for x = 1, size do
            local v = showBoard[toIndex(x,y)]
            if v ~= 0 then
                line = line..v
            else
                line = line..'·'
            end
            line = line..' '
        end
        line = y.."| "..line..'\n'
        board = board..line
    end
    print(board..'\n')
end

local function update()
    for i, v in ipairs(liveBoard) do
        showBoard[i] = ''
        if v == 0 then
            showBoard[i] = '■'
        elseif v == 1 then
            if realBoard[i] then
                warn("game ova")
            end
            showBoard[i] = gameBoard[i]
        else
            showBoard[i] = '▲'
        end
    end
    display()
end

local function expand(x,y)
    local nextLayer = {}
    for _, i in ipairs(getNeighbors(x,y)) do
        if liveBoard[i] ~= 0 then continue end
        liveBoard[i] = 1
        if gameBoard[i] == 0 then
            table.insert(nextLayer,i)
        end
    end
    for _, v in ipairs(nextLayer) do
        expand(toXY(v))
    end
end

local firstMove
local isFirst = true
local function open(x,y)
    if isFirst then
        isFirst = false
        firstMove(x,y)
    end
    liveBoard[toIndex(x,y)] = 1
    if gameBoard[toIndex(x,y)] == 0 then
        expand(x,y)
    end
    update()
end

local function chord(x,y)
    local flagCount = 0
    for _, i in ipairs(getNeighbors(x,y)) do
        if liveBoard[i] == 2 then
            flagCount += 1
        end
    end
    if flagCount == gameBoard[toIndex(x,y)] then
        for _, i in ipairs(getNeighbors(x,y)) do
            if liveBoard[i] ~= 0 then continue end
            open(toXY(i))
        end
    end
end

local function getAvailableSpots(myTable,exclude)
    local available = {}
    for i, v in ipairs(myTable) do
        if v ~= exclude then
            table.insert(available,i)
        end
    end
    return available
end

local function labelCells()
    for _, m in ipairs(getAvailableSpots(realBoard,false)) do
        for _, c in ipairs(getNeighbors(toXY(m))) do
            gameBoard[c] += 1
        end
    end
end

function firstMove(x,y)
    local c = toIndex(x,y)
    local available = getAvailableSpots(realBoard,true)
    for _, i in ipairs(getNeighbors(x,y)) do
        table.remove(available,table.find(available,i))
        if realBoard[i] then
            local newPos = rng:NextInteger(1,#available)
            table.remove(available,newPos)
            realBoard[i] = false
            realBoard[newPos] = true
        end
    end

    labelCells()
    open(x,y)
end

local function flag(x,y)
    local c = toIndex(x,y)
    if liveBoard[c] == 1 then return end
    liveBoard[c] = (liveBoard[c]+2)%4
    update()
end

local function shuffle(myTable)
    local buffer
    for i = #myTable, 1, -1 do
        local r = rng:NextInteger(1,i)
        buffer = myTable[i]
        myTable[i] = myTable[r]
        myTable[r] = buffer
    end
    return myTable
end

local function setup()
    realBoard = {}
    gameBoard = {}
    liveBoard = {}
    showBoard = {}
    isFirst = true

    if mines > size^2+9 then
        error("Too many mines. (Max mine count: "..(size^2+9)..")")
    end

    for i = 1, size^2 do
        realBoard[i] = false
        gameBoard[i] = 0
        liveBoard[i] = 0

        if i <= mines then
            realBoard[i] = true
        end
    end
    shuffle(realBoard)
end

setup()