local scr_x, scr_y = term.getSize()

local grid = {
	x1 = -80,
	y1 = -80,
	x2 = 80,
	y2 = 80,
	border = "#",
	voidcol = "f",
	forecol = "8",
	backcol = "7",
	edgecol = "0"
}

local scrollX = 0
local scrollY = 0

local scrollAdjX = 0
local scrollAdjY = 0

local lockInput = false

local player

local resetPlayers = function()
	player = {
		[1] = {
			x = -2,
			y = -5,
			direction = -1,
			char = "@",
			color = {
				colors.blue,
				colors.blue,
				colors.blue,
				colors.cyan,
				colors.cyan,
				colors.lightBlue,
				colors.lightBlue,
				colors.cyan,
				colors.cyan
			},
			dead = false,
			putTrail = true
		},
		[2] = {
			x = 2,
			y = -5,
			direction = -1,
			char = "@",
			color = {
				colors.red,
				colors.red,
				colors.red,
				colors.orange,
				colors.orange,
				colors.yellow,
				colors.yellow,
				colors.orange,
				colors.orange
			},
			dead = false,
			putTrail = true
		}
	}
end
resetPlayers()

local trail = {}

local putTrail = function(p)
	trail[p.y] = trail[p.y] or {}
	trail[p.y][p.x] = {
		player = p,
		age = 0
	}
end

local getTrail = function(x, y)
	if trail[y] then
		if trail[y][x] then
			if doAge then
				trail[y][x].age = trail[y][x].age + 1
			end
			return trail[y][x].player.char, trail[y][x].player.color, trail[y][x].age
		end
	end
	return false
end

local ageTrails = function()
	for y,l in pairs(trail) do
		for x,v in pairs(l) do
			trail[y][x].age = trail[y][x].age + 1
		end
	end
end

local toblit = {
	[0] = " ",
	[colors.white] = "0",
	[colors.orange] = "1",
	[colors.magenta] = "2",
	[colors.lightBlue] = "3",
	[colors.yellow] = "4",
	[colors.lime] = "5",
	[colors.pink] = "6",
	[colors.gray] = "7",
	[colors.lightGray] = "8",
	[colors.cyan] = "9",
	[colors.purple] = "a",
	[colors.blue] = "b",
	[colors.brown] = "c",
	[colors.green] = "d",
	[colors.red] = "e",
	[colors.black] = "f"
}

local you = 1
local nou = 2

local control = {
	up = keys.up,
	down = keys.down,
	left = keys.left,
	right = keys.right,
	lookUp = keys.w,
	lookDown = keys.s,
	lookLeft = keys.a,
	lookRight = keys.d,
	release = keys.space
}

-- keeps track of where you are
local gamemode = ""

-- foreground grid
local gridFore = {
	"+-------",
	"|       ",
	"|       ",
	"|       ",
	"|       "

}

-- background grid
local gridBack = {
	"+------------",
	"|            ",
	"|            ",
	"|            ",
	"|            ",
	"|            ",
	"|            ",
	"|            "
}

local dirArrow = {
	[-1] = "^",
	[0] = ">",
	[1] = "V",
	[2] = "<"
}

local doesIntersectBorder = function(x, y)
	return x == grid.x1 or x == grid.x2 or y == grid.y1 or y == grid.y2
end

--draws grid and background at scroll 'x' and 'y'
local drawGrid = function(x, y)
	x, y = math.floor(x + 0.5), math.floor(y + 0.5)
	local bg = {{},{},{}}
	local foreX, foreY
	local backX, backY
	local adjX, adjY
	local trailChar, trailColor, trailAge, isPlayer
	for sy = 1, scr_y do
		bg[1][sy] = ""
		bg[2][sy] = ""
		bg[3][sy] = ""
		for sx = 1, scr_x do
			adjX = (sx + x)
			adjY = (sy + y)
			foreX = 1 + (sx + x) % #gridFore[1]
			foreY = 1 + (sy + y) % #gridFore
			backX = 1 + math.floor(sx + (x / 3)) % #gridBack[1]
			backY = 1 + math.floor(sy + (y / 3)) % #gridBack
			trailChar, trailColor, trailAge = getTrail(adjX, adjY)
			isPlayer = false
			for i = 1, #player do
				if player[i].x == adjX and player[i].y == adjY then
					isPlayer = i
					break
				end
			end
			if isPlayer and not (doesIntersectBorder(adjX, adjY)) then
				bg[1][sy] = bg[1][sy] .. dirArrow[player[isPlayer].direction]
				bg[2][sy] = bg[2][sy] .. toblit[player[isPlayer].color[1]]
				bg[3][sy] = bg[3][sy] .. grid.voidcol
			else
				if trailChar and trailColor then
					trailColor = trailColor[1 + ((trailAge - 1) % #trailColor)]
					bg[1][sy] = bg[1][sy] .. trailChar
					bg[2][sy] = bg[2][sy] .. toblit[trailColor]
					bg[3][sy] = bg[3][sy] .. grid.voidcol
				else
					if adjX < grid.x1 or adjX > grid.x2 or adjY < grid.y1 or adjY > grid.y2 then
						bg[1][sy] = bg[1][sy] .. " "
						bg[2][sy] = bg[2][sy] .. grid.voidcol
						bg[3][sy] = bg[3][sy] .. grid.voidcol
					elseif doesIntersectBorder(adjX, adjY) then
						bg[1][sy] = bg[1][sy] .. grid.border
						bg[2][sy] = bg[2][sy] .. grid.voidcol
						bg[3][sy] = bg[3][sy] .. grid.edgecol
					else
						if gridFore[foreY]:sub(foreX,foreX) ~= " " then
							bg[1][sy] = bg[1][sy] .. gridFore[foreY]:sub(foreX,foreX)
							bg[2][sy] = bg[2][sy] .. grid.forecol
							bg[3][sy] = bg[3][sy] .. grid.voidcol
						elseif gridBack[backY]:sub(backX,backX) ~= " " then
							bg[1][sy] = bg[1][sy] .. gridBack[backY]:sub(backX,backX)
							bg[2][sy] = bg[2][sy] .. grid.backcol
							bg[3][sy] = bg[3][sy] .. grid.voidcol
						else
							bg[1][sy] = bg[1][sy] .. " "
							bg[2][sy] = bg[2][sy] .. grid.voidcol
							bg[3][sy] = bg[3][sy] .. grid.voidcol
						end
					end
				end
			end
		end
	end
	for sy = 1, scr_y do
		term.setCursorPos(1,sy)
		term.blit(bg[1][sy], bg[2][sy], bg[3][sy])
	end
end

local render = function()
	local p = player[you]
	drawGrid(scrollX + scrollAdjX, scrollY + scrollAdjY)
end

local deepCopy
deepCopy = function(tbl, ...)
	local output = {}
	for k,v in pairs(tbl) do
		if type(v) == "table" then
			output[k] = deepCopy(v)
		else
			output[k] = v
		end
	end
	for i = 1, #arg do
		output[#output+1] = arg[i]
	end
	return output
end

local makeMenu = function(x, y, options)
	local cpos = 1
	local cursor = "> "
	local render = function()
		for i = 1, #options do
			term.setCursorPos(x, y + (i - 1))
			if i == cpos then
				term.setTextColor(colors.white)
				term.write(cursor .. options[i])
			else
				term.setTextColor(colors.gray)
				term.write((" "):rep(#cursor) .. options[i])
			end
		end
	end
	local evt
	while true do
		render()
		evt = {os.pullEvent()}
		if evt[1] == "key" then
			if evt[2] == keys.up then
				cpos = math.max(cpos - 1, 1)
			elseif evt[2] == keys.down then
				cpos = math.min(cpos + 1, #options)
			elseif evt[2] == keys.enter then
				return cpos
			end
		end
	end
end

local titleScreen = function()
	local logo = {
		{
			" •ƒƒƒƒƒƒƒƒƒ•—ƒƒƒƒƒƒƒ‹‹   ‡‡ƒƒƒ‹‹  Ÿ‹    •ƒƒ•",
			" •ƒƒƒ”€—ƒƒƒ•‚ƒƒƒƒƒ‹€€€Š —€Ÿƒƒƒ€” •‚‚  •€€•",
			"     •€•          ‚‚ƒƒ•€€—€€€”€€••€€‹‹ •€€•",
			"     •€•    —ƒ”‹“ƒƒ‹€€€•€€•€€€•€€••€•ˆƒ€€•",
			"     •€•    •€• ‚‹€€‹€Š€‹‡€Ÿ…•€•  ‚‚€•",
			"     •€•    •€•   ‹€‚‹ ‹‹€€€Ÿ‡‡ •€•    ‹‹•",
			"             Š  ‚‹‡       ‚…",
		},
		{
			" f7777777777777777777f   f77777f  7f    f777",
			" f99979999979999999999f 799999799 77f7  f997",
			"     799          79999f997ffff9977997f f997",
			"     799    7797777fffff997ffff9977997797997",
			"     799    799 799977f7797fff7997799  79797",
			"     799    799   7797f 797999997 799    797",
			"     777    777    7777  7777777  777     77",
		},
		{
			" 7999999999f9999999997   7999997  97    799f",
			" 7777997777f77777779997 997777997 997f  799f",
			"     997          f7777799ffff799f99997 799f",
			"     997    997f9997fff799ffff799f997ff7999f",
			"     997    997 f7999fff999777997f997  f799f",
			"     997    997   f9997 f7999977f 997    f7f",
			"     fff    fff    ffff  fffffff  fff     ff",
		}
	}
	
	local drawLogo = function(x, y, darkmod)
		local cx, cy = term.getCursorPos()
		for iy = 1, #logo[1] do
			term.setCursorPos(x,y+(iy-1))
			term.blit(logo[1][iy], logo[2][iy], logo[3][iy])
		end
		term.setCursorPos(cx,cy)
	end

	term.clear()
	drawLogo(3,3)
	
	local choice = makeMenu(2, scr_y - 4, {
		"Start Game",
		"Grid Demo",
		"Exit"
	})
	if choice == 1 then
		return "start"
	elseif choice == 2 then
		return "demo"
	elseif choice == 3 then
		return "exit"
	end
end

local cleanExit = function()
	term.setBackgroundColor(colors.black)
	term.setTextColor(colors.white)
	term.clear()
	term.setCursorPos(1,1)
	print("Buh-bye.")
end

-- test background drawing

local evt
local keysDown = {}

local getInput = function()
	while true do
		evt = {os.pullEvent()}
		if lockInput then
			keysDown = {}
		else
			if evt[1] == "key" then
				keysDown[evt[2]] = true
			elseif evt[1] == "key_up" then
				keysDown[evt[2]] = false
			end
		end
	end
end

scrollToPosition = function(x, y)
	for i = 1, 16 do
		scrollX = (scrollX + x - (scr_x/2)) / 2
		scrollY = (scrollY + y - (scr_y/2)) / 2
		render()
		sleep(0.05)
	end
end

local gridDemo = function()
	while true do
		if keysDown[keys.left] then
			scrollX = scrollX - 1
		end
		if keysDown[keys.right] then
			scrollX = scrollX + 1
		end
		if keysDown[keys.up] then
			scrollY = scrollY - 1
		end
		if keysDown[keys.down] then
			scrollY = scrollY + 1
		end
		if keysDown[keys.q] then
			return "end"
		end
		drawGrid(scrollX, scrollY)
		ageTrails()
		sleep(0.05)
	end
end

local moveTick = function()
	local p
	local deadGuys = {}
	for i = 1, #player do
		p = player[i]
		if not p.dead then
			p.x = p.x + math.floor(math.cos(math.rad(p.direction * 90)))
			p.y = p.y + math.floor(math.sin(math.rad(p.direction * 90)))
			if getTrail(p.x, p.y) or (p.x == grid.x1 or p.x == grid.x2 or p.y == grid.y1 or p.y == grid.y2) then
				p.dead = true
				deadGuys[i] = true
				p.char = "X"
				lockInput = true
			else
				if p.putTrail then
					putTrail(p)
				end
			end
		end
	end
	if deadGuys[you] or deadGuys[nou] then
		term.setTextColor(colors.white)
		if deadGuys[you] and deadGuys[nou] then
			scrollToPosition(player[nou].x, player[nou].y)
			scrollToPosition(player[you].x, player[you].y)
			term.setCursorPos(1,scr_y)
			term.write("It's a tie!")
			sleep(1.5)
			return "end"
		else
			if deadGuys[you] then
				sleep(0.5)
				term.setCursorPos(1,scr_y)
				term.write("You're loser.")
				sleep(1.5)
				return "end"
			elseif deadGuys[nou] then
				scrollToPosition(player[nou].x, player[nou].y)
				term.setCursorPos(1,scr_y)
				term.write("You're winner!")
				sleep(1.5)
				return "end"
			end
		end
	end
	ageTrails()
end

local game = function()
	local p = player[you]
	local outcome
	while true do
		p.putTrail = not keysDown[control.release]
		if keysDown[control.left] and p.direction ~= 0 then
			p.direction = 2
		elseif keysDown[control.right] and p.direction ~= 2 then
			p.direction = 0
		end
		if keysDown[control.up] and p.direction ~= 1 then
			p.direction = -1
		elseif keysDown[control.down] and p.direction ~= -1 then
			p.direction = 1
		end
		
		if keysDown[control.lookLeft] then
			scrollAdjX = scrollAdjX - 2
		end
		if keysDown[control.lookRight] then
			scrollAdjX = scrollAdjX + 2
		end
		if keysDown[control.lookUp] then
			scrollAdjY = scrollAdjY - 1.5
		end
		if keysDown[control.lookDown] then
			scrollAdjY = scrollAdjY + 1.5
		end
		scrollAdjX = scrollAdjX * 0.8
		scrollAdjY = scrollAdjY * 0.8
		
		outcome = moveTick()
		
		if outcome == "end" then
			return
		else
			scrollX = p.x - math.floor(scr_x / 2)
			scrollY = p.y - math.floor(scr_y / 2)

			render()
			sleep(0.05)
		end
	end
end

local decision

while true do
	decision = titleScreen()
	lockInput = false
	if decision == "start" then
		trail = {}
		resetPlayers()
		parallel.waitForAny(getInput, game)
	elseif decision == "demo" then
		parallel.waitForAny(getInput, gridDemo)
	elseif decision == "exit" then
		return cleanExit()
	end
end