local paddle_x = nil
local paddle_y = nil
local paddle_width = 0.1
local paddle_height = 0.02

local wall_thickness = 0.01

local missiles = {}
local missile_radius = 0.005

local window_width = nil
local window_height = nil
local viewport_x_offset = nil
local viewport_y_offset = nil
local scale = nil

function setScreenDimensions(width, height)
	window_width = width
	window_height = height

	viewport_x_offset = 0
	viewport_y_offset = 0
	scale = math.min(width, height)
	viewport_x_offset = (window_width - scale) / 2
	viewport_y_offset = (window_height - scale) / 2
end

function toScreenCoordinates(x, y)
	local screen_x = x * scale + viewport_x_offset
	local screen_y = y * scale + viewport_y_offset
	return screen_x, screen_y
end

function toScreenSize(size)
	return size * scale
end

function fromScreenCoordinate(x, y)
	local logical_x = (x - viewport_x_offset) / scale
	local logical_y = (y - viewport_y_offset) / scale
	return logical_x, logical_y
end

function love.load()
	love.mouse.setVisible(false)
	local width, height = love.graphics.getDimensions()
	setScreenDimensions(width, height)
	movePaddle(0)
	spawnMissile(0.5, 0.1, -0.1, -0.2)
	spawnMissile(0.5, 0.1, 0.1, 0.1)
end

function spawnMissile(x, y, dx, dy)
	table.insert(missiles, {
		x = x,
		y = y,
		dx = dx,
		dy = dy,
		reflected = false,
	})
end

function updateMissiles(dt)
	for i, missile in ipairs(missiles) do
		missile.x = missile.x + missile.dx * dt
		missile.y = missile.y + missile.dy * dt

		if missile.y < wall_thickness + missile_radius then
			-- Collision with top wall
			missile.y = wall_thickness + missile_radius
			missile.dy = -missile.dy
		end

		if missile.x < wall_thickness + missile_radius then
			-- Collision with left wall
			missile.x = wall_thickness + missile_radius
			missile.dx = -missile.dx
		elseif missile.x > 1 - (wall_thickness + missile_radius) then
			-- Collision with right wall
			missile.x = 1 - (wall_thickness + missile_radius)
			missile.dx = -missile.dx
		end

		local paddle_left = paddle_x - paddle_width/2
		local paddle_right = paddle_x + paddle_width/2
		local paddle_top = paddle_y - paddle_height/2
		if paddle_left <= missile.x and missile.x <= paddle_right and paddle_top <= missile.y and missile.y <= paddle_y then
			-- Collision with the paddle
			missile.y = paddle_top
			missile.dy = -missile.dy
			missile.reflected = true
		end
	end

	local i = 1
	while i <= #missiles do
		if missiles[i].y > 1 + missile_radius then
			-- Went off the bottom of the screen, delete
			table.remove(missiles, i)
		else
			i = i +1
		end
	end
end

function love.update(dt)
	updateMissiles(dt)
end

function movePaddle(screen_x)
	paddle_x = fromScreenCoordinate(screen_x, 0)
	paddle_x = math.max(paddle_x, paddle_width/2 + wall_thickness)
	paddle_x = math.min(paddle_x, 1 - (paddle_width/2 + wall_thickness))
	paddle_y = 0.9
end

love.mousemoved = movePaddle

love.resize = setScreenDimensions

function drawWalls()
	love.graphics.setColor(0, 0, 1)
	local x, y = toScreenCoordinates(0, 0)
	local width = toScreenSize(1)
	local height =toScreenSize(wall_thickness)
	love.graphics.rectangle('fill', x, y, width, height)
	local width = toScreenSize(wall_thickness)
	local height = toScreenSize(1)
	love.graphics.rectangle('fill', x, y, width, height)
	local x, y = toScreenCoordinates(1 - wall_thickness, 0)
	love.graphics.rectangle('fill', x, y, width, height)
end

function drawMissiles()
	for _, missile in ipairs(missiles) do
		local style = 'fill'
		if missile.reflected then
			love.graphics.setColor(1, 0.5, 0)
			style = 'line'
		else
			love.graphics.setColor(1, 0.5, 0.5)
		end
		local x, y = toScreenCoordinates(missile.x, missile.y)
		local radius = toScreenSize(missile_radius)
		love.graphics.circle(style, x, y, radius)
	end
end

function drawPaddle()
	love.graphics.setColor(1, 1, 1)
	local x, y = toScreenCoordinates(paddle_x - paddle_width / 2, paddle_y - paddle_height / 2)
	local width = toScreenSize(paddle_width)
	local height = toScreenSize(paddle_height)
	love.graphics.rectangle('fill', x, y, width, height)
end

function love.draw()
	drawWalls()
	drawMissiles()
	drawPaddle()
end