Factorio Lua EventLib by AivanF

event_lib.lua

--[[
EventLib v2023.09.19
Made by AivanF.
License: GPL3
https://gist.github.com/AivanF/13b5cecd1a80efc7704f39bdbcc66e08
]]

Lib = {}
Lib.__index = Lib

function empty() end

function Lib.new()
  local lib = {
    content = {
      events = {},
      on_nth_tick = {},
      -- on_init = empty,
      -- on_load = empty,
      -- on_configuration_changed = empty,
      -- add_remote_interface = empty,
      -- add_commands = empty,
    }
  }
  setmetatable(lib, Lib)
  lib.__index = Lib
  return lib
end

function Lib:on_nth_tick(n, callback)
  if self.content.on_nth_tick[n] then
    error("Trying to register same on_nth_tick "..n.." again")
  end
  self.content.on_nth_tick[n] = callback
end

function Lib:on_event(event_list, callback)
  if type(event_list) ~= "table" then event_list = {event_list} end
  for _, event in pairs(event_list) do
    if self.content.events[event] then
      error("Trying to register same on_event "..event.." again")
    end
    self.content.events[event] = callback
  end
end

local push_names = {"add_remote_interface", "add_commands"}
function Lib:export()
  for _, name in pairs(push_names) do
    if self[name] then
      self.content[name] = self[name]
    end
  end
  return self.content
end

local basic_methods = {"on_init", "on_load", "on_configuration_changed"}
for _, name in pairs(basic_methods) do
  Lib[name] = function(self, callback)
    self.content[name] = callback
  end
end

local combined_events = {
  on_any_built = {
    defines.events.on_built_entity,
    defines.events.on_robot_built_entity,
    defines.events.script_raised_built,
    defines.events.script_raised_revive,
    defines.events.on_entity_cloned,
  },
  on_any_remove = {
    defines.events.on_player_mined_entity,
    defines.events.on_robot_mined_entity,
    defines.events.on_entity_died,
    defines.events.script_raised_destroy,
  },
}
for name, event_list in pairs(combined_events) do
  Lib[name] = function(self, callback)
    Lib.on_event(self, event_list, callback)
  end
end

return Lib

Factorio-EventLib-Description.md

The script is intended be used for simpler migration from a single control.lua file to libs with Factorio's builtin lualib.event_handler.

Single file:

-- control.lua
script.on_init(on_init)
script.on_configuration_changed(on_configuration_changed)
script.on_event({defines.events.on_built_entity, defines.events.on_robot_built_entity}, handler1)
script.on_event(defines.events.on_entity_died, handler2)
script.on_nth_tick(5, handle_5_step)
add_commands()

Nice, but for only one file 😒

Old libs approach:

-- script/my_lib.lua
local lib = {}
lib.on_init = on_init
lib.on_configuration_changed = on_configuration_changed
lib.events = {
  [defines.events.on_built_entity] = handler1,
  [defines.events.on_robot_built_entity] = handler1,
  [defines.events.on_entity_died] = handler2,
}
lib.on_nth_tick = {
  [5] = handle_5_step,
}
lib.add_commands = add_commands
return lib

-- control.lua
local handler = require("event_handler")
handler.add_lib(require("script.mylib"))

Scalable, but leads to ugly mixed syntax 😒

New way:

-- script/my_lib.lua
local Lib = require("event_lib")
local lib = Lib.new()
lib:on_init(on_init)
lib:on_configuration_changed(on_configuration_changed)
lib:on_event({defines.events.on_built_entity, defines.events.on_robot_built_entity}, handler1)
lib:on_event(defines.events.on_entity_died, handler2)
lib:on_nth_tick(5, handle_5_step)
lib.add_commands = add_commands
return lib

-- control.lua
local handler = require("event_handler")
handler.add_lib(require("script.mylib"):export())

This supports having multiple files too! 😊 But it is more similar to the original syntax, also easier to add conditional events.

The EventLib also aims to provide common shortcuts, simplifying this:

lib:on_event({
  defines.events.on_built_entity,
  defines.events.on_robot_built_entity,
  defines.events.script_raised_built,
  defines.events.script_raised_revive,
  defines.events.on_entity_cloned,
}, on_any_built)

lib:on_event({
  defines.events.on_player_mined_entity,
  defines.events.on_robot_mined_entity,
  defines.events.on_entity_died,
  defines.events.script_raised_destroy,
}, on_any_remove)

Into this:

lib:on_any_built(on_any_built)
lib:on_any_remove(on_any_remove)