Add startable legacy code

exp_util/module/storage.lua

@@ -0,0 +1,100 @@
+--[[-- Util Module - Storage
+- Provides a method of using storage with the guarantee that keys will not conflict
+@core Storage
+@alias Storage
+
+@usage--- Drop in boiler plate:
+-- Below is a drop in boiler plate which ensures your storage access will not conflict with other modules
+local storage = {}
+Storage.register(storage, function(tbl)
+    storage = tbl
+end)
+
+@usage--- Registering new storage tables:
+-- The boiler plate above is not recommend because it is not descriptive in its function
+-- Best practice is to list out all variables you are storing in storage and their function
+local MyModule = {
+    public_data = {} -- Stores data which other modules can access
+}
+
+local private_data = {} -- Stores data which other modules cant access
+local more_private_data = {} -- Stores more data which other modules cant access
+-- You can not store a whole module in storage because not all data types are serialisable
+Storage.register({
+    MyModule.public_data,
+    private_data,
+    more_private_data
+}, function(tbl)
+    -- You can also use this callback to set metatable on class instances you have stored in storage
+    MyModule.public_data = tbl[1]
+    private_data = tbl[2]
+    more_private_data = tbl[3]
+end)
+
+]]
+
+local Clustorio = require("modules/clusterio/api")
+local ExpUtil = require("modules/exp_util/common")
+
+local Storage = {
+    registered = {}, -- Map of all registered values and their initial values
+}
+
+--- Register a new table to be stored in storage, can only be called once per file, can not be called during runtime
+-- @tparam table tbl The initial value for the table you are registering, this should be a local variable
+-- @tparam function callback The callback used to replace local references and metatables
+function Storage.register(tbl, callback)
+    ExpUtil.assert_not_runtime()
+    ExpUtil.assert_argument_type(tbl, "table", 1, "tbl")
+    ExpUtil.assert_argument_type(callback, "function", 2, "callback")
+
+    local name = ExpUtil.safe_file_path(2)
+    if Storage.registered[name] then
+        error("Storage.register can only be called once per file", 2)
+    end
+
+    Storage.registered[name] = {
+        init = tbl,
+        callback = callback
+    }
+end
+
+--- Register a metatable which will be automatically restored during on_load
+-- @tparam string name The name of the metatable to register, must be unique within your module
+function Storage.register_metatable(name, tbl)
+    local module_name = ExpUtil.get_module_name(2)
+    script.register_metatable(module_name.."."..name, tbl)
+end
+
+--- Restore aliases on load, we do not need to initialise data during this event
+function Storage.on_load()
+    local exp_storage = storage.exp_storage
+	if exp_storage == nil then return end
+	for name, info in pairs(Storage.registered) do
+        if exp_storage[name] ~= nil then
+			info.callback(exp_storage[name])
+        end
+    end
+end
+
+--- Event Handler, sets initial values if needed and calls all callbacks
+function Storage.on_init()
+    local exp_storage = storage.exp_storage
+    if exp_storage == nil then
+        exp_storage = {}
+        storage.exp_storage = exp_storage
+    end
+
+    for name, info in pairs(Storage.registered) do
+        if exp_storage[name] == nil then
+            exp_storage[name] = info.init
+        end
+        info.callback(exp_storage[name])
+    end
+end
+
+Storage.events = {
+    [Clustorio.events.on_server_startup] = Storage.on_init
+}
+
+return Storage