local screen_width, screen_height = love.graphics.getDimensions()

local function distance(x1, y1, x2, y2)
  delta_x = x1 - x2
  delta_y = y1 - y2
  return math.sqrt(delta_x^2 + delta_y^2)
end

orbital_speed = 0.0625 * 2500 -- I have no idea what the fuck this means
local function new_body(orbital_radius, body_radius)
  local body = {
    orbital_radius = orbital_radius,
    body_radius = body_radius,
    rotation_offset = math.pi * 2 * love.math.random(),
    color = { love.math.random(), love.math.random(), love.math.random(), 1 },
  }
  return body
end

local function get_body_position(body, time)
  local argument = time * orbital_speed / body.orbital_radius^1.337 + body.rotation_offset
  if (argument == math.huge) or (argument ~= argument) then
    argument = 0
  end
  return body.orbital_radius * math.cos(argument), body.orbital_radius * math.sin(argument)
end

local function draw_body(body, time)
  local x, y = get_body_position(body, time)
  love.graphics.setColor(body.color)
  love.graphics.circle("fill", x, y, body.body_radius)
  love.graphics.setColor(1, 1, 1, 1) -- TEMP delete this if it works without it
end

local function new_ship()
  local ship = {
    orbital_radius = 0,
    rotation_offset = 0,
    x = 30, y = 30,
    orbiting = false,
    time_offset = 0,
    parent = nil,
  }
  return ship
end

local function get_ship_position(ship, time)
  if ship.orbiting then
    local x, y
    if ship.parent then
      x, y = get_body_position(ship.parent, time) -- WARNING this should work the same for all objects or things will suck
    else
      x, y = 0, 0
    end
    local argument = (time - ship.time_offset) * orbital_speed / ship.orbital_radius^1.337 + ship.rotation_offset
    if (argument == math.huge) or (argument ~= argument) then
      argument = 0
    end
    return x + ship.orbital_radius * math.cos(argument), y + ship.orbital_radius * math.sin(argument)
  else
    return ship.x, ship.y
  end
end

local function draw_ship(ship, time)
  local x, y = get_ship_position(ship, time)
  love.graphics.rectangle("line", x - 3, y - 3, 6, 6)
end

local time = os.time()
love.math.setRandomSeed(time)
local speed = 1

local bodies = {}
table.insert(bodies, new_body(0, 25))
for i = 1, 1 do -- TEMP only adding 1 secondary body
  table.insert(bodies, new_body(love.math.random() * 200 + 100, love.math.random() * 4 + 1))
end

local ship = new_ship()
-- ship was in bodies table; not currently possible here

local camera = { x = 0, y = 0, }
function love.update(dt)
  time = time + dt * speed
  -- NOTE camera controls 200 * dt

  if not ship.orbiting then
    if love.keyboard.isDown("w") then
      ship.y = ship.y - 100 * dt
    end
    if love.keyboard.isDown("s") then
      ship.y = ship.y + 100 * dt
    end
    if love.keyboard.isDown("a") then
      ship.x = ship.x - 100 * dt
    end
    if love.keyboard.isDown("d") then
      ship.x = ship.x + 100 * dt
    end
  end
end

local font_size = love.graphics.getFont():getHeight()
function love.draw()
  love.graphics.print("wasd: Move. o: Toggle orbit.", 1, screen_height - (font_size + 1))

  love.graphics.translate(screen_width / 2 - camera.x, screen_height / 2 - camera.y)

  for i = 1, #bodies do
    local body = bodies[i]
    draw_body(body, time)
  end
  draw_ship(ship, time)
end

-- TEMP ship is always orbiting body 2
ship.parent = bodies[2]

function love.keypressed(key)
  if key == "escape" then
    love.event.quit()
  -- NOTE ignoring speed control
  elseif key == "o" then
    if ship.orbiting then
      local x, y = get_ship_position(ship, time)
      ship.x = x
      ship.y = y
      ship.orbiting = false
    else
      -- only works with center (fuck)
      -- ship.orbital_radius = math.sqrt(ship.x^2 + ship.y^2)
      -- ship.rotation_offset = math.atan2(ship.y, ship.x)
      -- ship.time_offset = time
      -- ship.orbiting = true

      local x, y = get_body_position(ship.parent, time)
      ship.orbital_radius = distance(x, ship.x, y, ship.y)
      ship.rotation_offset = math.atan2(ship.y - y, ship.x - x)
      ship.time_offset = time
      ship.orbiting = true
    end
  end
end