--[[**
	<description>
	Run this once to combine all keys provided into one "main key".
	Internally, this means that data will be stored in a table with the key mainKey.
	This is used to get around the 2-DataStore2 reliability caveat.
	</description>

	<parameter name = "mainKey">
	The key that will be used to house the table.
	</parameter>

	<parameter name = "...">
	All the keys to combine under one table.
	</parameter>
**--]]
function DataStore2.Combine(mainKey, ...)
	for _, name in pairs({...}) do
		combinedDataStoreInfo[name] = mainKey
	end
end

function DataStore2.ClearCache()
	DataStoreCache = {}
end

function DataStore2.SaveAll(player)
	if DataStoreCache[player] then
		for _, dataStore in pairs(DataStoreCache[player]) do
			if dataStore.combinedStore == nil then
				dataStore:Save()
			end
		end
	end
end

function DataStore2.PatchGlobalSettings(patch)
	for key, value in pairs(patch) do
		assert(Settings[key] ~= nil, "No such key exists: " .. key)
		-- TODO: Implement type checking with this when osyris' t is in
		Settings[key] = value
	end
end

function DataStore2.__call(_, dataStoreName, player)
	assert(
		typeof(dataStoreName) == "string" and typeof(player) == "Instance",
		("DataStore2() API call expected {string dataStoreName, Instance player}, got {%s, %s}")
		:format(
			typeof(dataStoreName),
			typeof(player)
		)
	)

	if DataStoreCache[player] and DataStoreCache[player][dataStoreName] then
		return DataStoreCache[player][dataStoreName]
	elseif combinedDataStoreInfo[dataStoreName] then
		local dataStore = DataStore2(combinedDataStoreInfo[dataStoreName], player)

		dataStore:BeforeSave(function(combinedData)
			for key in pairs(combinedData) do
				if combinedDataStoreInfo[key] then
					local combinedStore = DataStore2(key, player)
					local value = combinedStore:Get(nil, true)
					if value ~= nil then
						if combinedStore.combinedBeforeSave then
							value = combinedStore.combinedBeforeSave(clone(value))
						end
						combinedData[key] = value
					end
				end
			end

			return combinedData
		end)

		local combinedStore = setmetatable({
			combinedName = dataStoreName,
			combinedStore = dataStore,
		}, {
			__index = function(_, key)
				return CombinedDataStore[key] or dataStore[key]
			end
		})

		if not DataStoreCache[player] then
			DataStoreCache[player] = {}
		end

		DataStoreCache[player][dataStoreName] = combinedStore
		return combinedStore
	end

	local dataStore = {}

	dataStore.Name = dataStoreName
	dataStore.UserId = player.UserId

	dataStore.callbacks = {}
	dataStore.beforeInitialGet = {}
	dataStore.afterSave = {}
	dataStore.bindToClose = {}
	dataStore.savingMethod = SavingMethods[Settings.SavingMethod].new(dataStore)

	setmetatable(dataStore, DataStoreMetatable)

	local event, fired = Instance.new("BindableEvent"), false

	game:BindToClose(function()
		if not fired then
			spawn(function()
				player.Parent = nil -- Forces AncestryChanged to fire and save the data
			end)

			event.Event:wait()
		end

		local value = dataStore:Get(nil, true)

		for _, bindToClose in pairs(dataStore.bindToClose) do
			bindToClose(player, value)
		end
	end)

	local playerLeavingConnection
	playerLeavingConnection = player.AncestryChanged:Connect(function()
		if player:IsDescendantOf(game) then return end
		playerLeavingConnection:Disconnect()
		dataStore:SaveAsync():andThen(function()
			print("player left, saved " .. dataStoreName)
		end):catch(function(error)
			-- TODO: Something more elegant
			warn("error when player left! " .. error)
		end):finally(function()
			event:Fire()
			fired = true
		end)

		delay(40, function() --Give a long delay for people who haven't figured out the cache :^(
			DataStoreCache[player] = nil
		end)
	end)

	if not DataStoreCache[player] then
		DataStoreCache[player] = {}
	end

	DataStoreCache[player][dataStoreName] = dataStore

	return dataStore
end

DataStore2.Constants = Constants

return setmetatable(DataStore2, DataStore2)