-- title:  Snake
-- author: Bob Grant
-- script: lua

gameStateInit = 5
gameStateStart = 10
gameStatePlay = 20
gameStateDead = 30
gameStateEnd = 40
gameState = gameStateStart

snakeSpawnPosition = {
	x = 5,
	y = 5
}
snakeStartLength = 5
snakeDirectionUp = 0
snakeDirectionDown = 1
snakeDirectionLeft = 2
snakeDirectionRight = 3
snakeStartSpeed = 10
snakeMaxHunger = 99

snake = {
	body = {},
	direction = snakeDirectionRight,
	speed = snakeStartSpeed,
	growCounter = 0,
	hunger = 0
}

food = {}
maxFood = 10
foodMaxTimer = 600
foodMinTimer = 180
foodMaxGrowth = 10
foodNumSprites = 5
foodBaseSprite = 16

score = 0

boardXMin = 1
boardXMax = 58
boardYMin = 3
boardYMax = 32


function TIC()

	if gameState == gameStateStart then
		startGame()
	elseif gameState == gameStateInit then
		initGame()
	elseif gameState == gameStatePlay then
		playGame()
	elseif gameState == gameStateEnd then
		endGame()
	end -- if

end -- TIC

function startGame()
 if btnp(4) then
		gameState = gameStateInit
	end --if
end -- startGame

function initGame()

	score = 0
	
	-- generate snake
	snake.body = {}
	
	-- head
	table.insert(snake.body,
			{
				x = snakeSpawnPosition.x + 1,
				y = snakeSpawnPosition.y
			}
		) 
		
	-- body
	for bodyPart = 1,snakeStartLength - 1 do
		table.insert(snake.body,
			{
				x = snakeSpawnPosition.x,
				y = snakeSpawnPosition.y
			}
		)
	end -- for
	
	snake.direction = snakeDirectionRight
	snake.speed = snakeStartSpeed
	snake.moveCounter = snakeStartSpeed
	snake.growCounter = 0
	snake.hunger = 0
	
	food = {} -- reset food
	
	gameState = gameStatePlay

end -- initGame

function endGame()
 cls()
	
	drawOutline()
	drawScore()
	drawHungerBar()
	drawSnake()
	drawFood()
	
	print("Game Over - Press Z to play SNAKE", 30, 50)
	
	if btnp(4) then
		gameState = gameStateInit
	end --if
end -- endGame

function playGame()

	cls()
	drawOutline()
	drawScore()
	checkKeys()
	moveSnake()
	drawHungerBar()
	checkCollision()
	drawSnake()
	handleFood()
	drawFood()

end -- gameStatePlay

function drawOutline()
	line(3,11,236,11,14)
	line(236,11,236,132,14)
	line(236,132,3,132,14)
	line(3,132,3,11,14)
end -- drawOutline

function drawScore()
	print("Score : "..score,0,0)
end -- drawScore

function checkKeys()
	if btnp(0) 
		and snake.direction ~= snakeDirectionDown then
		snake.direction = snakeDirectionUp
	elseif btnp(1) 
		and snake.direction ~= snakeDirectionUp then
		snake.direction = snakeDirectionDown
	elseif btnp(2) 
		and snake.direction ~= snakeDirectionRight then
		snake.direction = snakeDirectionLeft
	elseif btnp(3) 
		and snake.direction ~= snakeDirectionLeft then
		snake.direction = snakeDirectionRight
	end -- if
end -- checkKeys

function moveSnake()

	snake.moveCounter = snake.moveCounter - 1
	if 	snake.moveCounter <= 0 then
		snake.moveCounter = snake.speed
		
	 -- move body parts
	 for bodyPart = #snake.body, 2, -1 do
		 snake.body[bodyPart].x =	snake.body[bodyPart - 1].x
		 snake.body[bodyPart].y =	snake.body[bodyPart - 1].y
	 end -- for
	 -- move head
	 if snake.direction == snakeDirectionUp then
		 snake.body[1].y = snake.body[1].y - 1
	 elseif snake.direction == snakeDirectionDown then
		 snake.body[1].y = snake.body[1].y + 1
	 elseif snake.direction == snakeDirectionLeft then
		 snake.body[1].x = snake.body[1].x - 1
	 elseif snake.direction == snakeDirectionRight then
		 snake.body[1].x = snake.body[1].x + 1
	 end -- if
		
		-- snake health timer
	 snake.hunger = snake.hunger + 1
		if snake.hunger > 75 then
		 sfx(0,snake.hunger-40,5,0,10,0)
		end -- if
	 if snake.hunger > snakeMaxHunger then
		 gameState = gameStateEnd
	 end -- if
	end -- if moveCounter
	
	-- check growing
	if snake.growCounter > 0 then
		table.insert(snake.body,
			{
				x = snake.body[#snake.body].x,
				y = snake.body[#snake.body].y
			}
		)
		snake.growCounter = snake.growCounter - 1
		if 	snake.growCounter < 0 then
			snake.growCounter = 0
		end
	end -- if
	
	snake.speed = snakeStartSpeed 
		- math.floor(#snake.body / 20)
	if snake.speed < 0 then
		snake.speed = 0
	end -- if

end -- moveSnake

function drawHungerBar()

	rect(135,3,102,4,15)
	if snake.hunger > 50 then
		rect(136,4,50,2,5)
	else
		rect(136,4,snake.hunger,2,5)
	end -- if
	if snake.hunger > 75 then
		rect(186,4,25,2,9)
	else
		rect(186,4,snake.hunger-50,2,9)
	end -- if
 if snake.hunger > 75 then
		rect(211,4,snake.hunger-75,2,6)
	end -- if
end -- drawHungerBar()

function	checkCollision()
	-- walls
	--boardXMin = 2
 --boardXMax = 59
 --boardYMin = 3
 --boardYMax = 33
	if snake.body[1].x < boardXMin
	 or snake.body[1].x > boardXMax
		or snake.body[1].y < boardYMin
		or snake.body[1].y > boardYMax then
		gameState = gameStateEnd
	elseif checkBodyCollision( snake.body[1].x,  snake.body[1].y) then
	 gameState = gameStateEnd
	end 
	
	local foodPiece = 
	 checkFoodCollision( snake.body[1].x,  snake.body[1].y)
	if foodPiece ~= 0 then
		snake.growCounter = snake.growCounter
			+ food[foodPiece].growth
		score = score + food[foodPiece].growth
		sfx(1,20 + (food[foodPiece].growth * 2),20,1,15,0)
		table.remove(food, foodPiece)
		snake.hunger = 0
	end -- if
	
end -- checkCollision

function checkFoodCollision(x, y)
	for index, foodPiece in ipairs(food) do
		if foodPiece.x == x and foodPiece.y == y then
			return index
		end -- if
	end -- for
	return 0 -- no food
end -- if

function checkBodyCollision(x, y)
	for bodyPart = #snake.body, 2, -1 do
	 if snake.body[bodyPart].x == x
		 and snake.body[bodyPart].y == y then
			return true
		end -- if
	end -- for
	return false
end -- checkBodyCollision

function 	drawSnake()
	--body
	for bodyPart = #snake.body, 2, -1 do
		spr(0,snake.body[bodyPart].x * 4,
			snake.body[bodyPart].y * 4,
			0)
	end -- for
	-- head
	local headSprite = 1 + snake.direction
	spr(headSprite,snake.body[1].x * 4,
			snake.body[1].y * 4,
			0)
end -- drawSnake

function handleFood()
	
	-- time food
	for index, foodObject in ipairs(food) do
		foodObject.timer = foodObject.timer - 1
		if foodObject.timer < 0 then
			table.remove(food, index)
		end -- if
	end -- for
	
 -- check for food spawn
	if (#food < maxFood)
		and (math.random(180) <= 4) then
		local foodX = 
			math.random(boardXMin, boardXMax)
		local foodY = 
			math.random(boardYMin, boardYMax)
		local foodTime = 
			math.random(foodMinTimer, foodMaxTimer)
		local foodGrowth = 
		 math.random(1,foodMaxGrowth)
		local foodSprite = 
			math.random(0,foodNumSprites)
		table.insert(food,
		 {
				x = foodX,
				y = foodY,
				timer = foodTime,
				growth = foodGrowth,
				sprite = foodSprite
			}
		)
		end -- if

end -- spawnFood

function	drawFood()

	for index, foodObject in ipairs(food) do
		spr(foodBaseSprite + foodObject.sprite,
			foodObject.x * 4,
			foodObject.y * 4,
			0
		)
	end -- for

end -- drawFood