local _sprites = {}
local _active_sprites = {}

--- Registers a sprite definition.
-- @param sprite_data table A table containing the sprite definition.
function Sprite.register(sprite_data)
  if not sprite_data or not sprite_data.id then
    trace("Error: Invalid sprite object registered (missing id)!")
    return
  end
  if _sprites[sprite_data.id] then
    trace("Warning: Overwriting sprite with id: " .. sprite_data.id)
  end
  _sprites[sprite_data.id] = sprite_data
end

--- Schedules a sprite for drawing.
-- @param id string The unique identifier of the sprite.
-- @param x number The x-coordinate.
-- @param y number The y-coordinate.
-- @param[opt] colorkey number The color index for transparency.
-- @param[opt] scale number The scaling factor.
-- @param[opt] flip_x number Set to 1 to flip horizontally.
-- @param[opt] flip_y number Set to 1 to flip vertically.
-- @param[opt] rot number The rotation in degrees.
function Sprite.show(id, x, y, colorkey, scale, flip_x, flip_y, rot)
  if not _sprites[id] then
    trace("Error: Attempted to show non-registered sprite with id: " .. id)
    return
  end

  _active_sprites[id] = {
    id = id,
    x = x,
    y = y,
    colorkey = colorkey,
    scale = scale,
    flip_x = flip_x,
    flip_y = flip_y,
    rot = rot,
  }
end

--- Hides a displayed sprite.
-- @param id string The unique identifier of the sprite.
function Sprite.hide(id)
  _active_sprites[id] = nil
end

--- Draws all scheduled sprites.
function Sprite.draw()
  for id, params in pairs(_active_sprites) do
    local sprite_data = _sprites[id]
    if not sprite_data then
      trace("Error: Sprite id " .. id .. " in _active_sprites is not registered.")
      _active_sprites[id] = nil
    end

    local colorkey = params.colorkey or sprite_data.colorkey or 0
    local scale = params.scale or sprite_data.scale or 1
    local flip_x = params.flip_x or sprite_data.flip_x or 0
    local flip_y = params.flip_y or sprite_data.flip_y or 0
    local rot = params.rot or sprite_data.rot or 0

    if sprite_data.sprites then
      for i = 1, #sprite_data.sprites do
        local sub_sprite = sprite_data.sprites[i]
        spr(
          sub_sprite.s,
          params.x + (sub_sprite.x_offset or 0),
          params.y + (sub_sprite.y_offset or 0),
          sub_sprite.colorkey or colorkey,
          sub_sprite.scale or scale,
          sub_sprite.flip_x or flip_x,
          sub_sprite.flip_y or flip_y,
          sub_sprite.rot or rot
        )
      end
    else
      spr(sprite_data.s, params.x, params.y, colorkey, scale, flip_x, flip_y, rot)
    end
  end
end