Tiny Lua stage management module

stagestack.lua

-- manages "stages" with a stack interface
-- stage is Lua module with callbacks (load, update, draw, keypress...)
-- only single stage is active, one on top of the stack
-- after push and pop operation another stage takes over the callbacks
-- example stack: os > main_menu > level_selection > game_play > overlay_menu
-- example usage:
--   local stagestack = require'stagestack'
--   stagestack.push(require'main_menu')
local m = {}

m.stack = {}
m.active = nil
m.loaded = {}

local callbacks = {
  -- not touched 'conf', 'load', 'log', 'mirror',
  -- 'errhand', 'threaderror',
  'update', 'draw',
  'keypressed', 'keyreleased', 'textinput',
  'mousepressed', 'mousemoved', 'mousereleased', 'wheelmoved',
  'quit', 'restart',
  'focus', 'resize',
  'permission',
}

local function switch(stage)
  if not stage then
    lovr.event.quit()
  end
  if not m.loaded[stage] then
    if stage.load then
      stage.load()
    end
    m.loaded[stage] = true
  end
  for i, callback in ipairs(callbacks) do
    lovr[callback] = stage[callback] or lovr[callback]
  end
  m.active = stage
end


function m.push(stage)
  table.insert(m.stack, stage)
  switch(stage)
end


function m.pop()
  local stage = table.remove(m.stack)
  switch(m.stack[#m.stack])
  return stage
end


return m