local type, pairs = type, pairs;

local setmetatable = setmetatable;

local config = require "core.configmanager";

local datamanager = require "util.datamanager";

local modulemanager = require "core.modulemanager";

local multitable = require "util.multitable";

local hosts = hosts;

local log = require "util.logger".init("storagemanager");

local prosody = prosody;

local _ENV = nil;

local olddm = {}; -- maintain old datamanager, for backwards compatibility

for k,v in pairs(datamanager) do olddm[k] = v; end

local null_storage_method = function () return false, "no data storage active"; end

local null_storage_driver = setmetatable(

	{

		name = "null",

		open = function (self) return self; end

	}, {

		__index = function (self, method) --luacheck: ignore 212

			return null_storage_method;

		end

	}

);

local stores_available = multitable.new();

local function initialize_host(host)

	local host_session = hosts[host];

	host_session.events.add_handler("item-added/storage-provider", function (event)

		local item = event.item;

		stores_available:set(host, item.name, item);

	end);

	host_session.events.add_handler("item-removed/storage-provider", function (event)

		local item = event.item;

		stores_available:set(host, item.name, nil);

	end);

end

prosody.events.add_handler("host-activated", initialize_host, 101);

local function load_driver(host, driver_name)

	if driver_name == "null" then

		return null_storage_driver;

	end

	local driver = stores_available:get(host, driver_name);

	if driver then return driver; end

	local ok, err = modulemanager.load(host, "storage_"..driver_name);

	if not ok then

		log("error", "Failed to load storage driver plugin %s on %s: %s", driver_name, host, err);

	end

	return stores_available:get(host, driver_name);

end

local function get_driver(host, store)

	local storage = config.get(host, "storage");

	local driver_name;

	local option_type = type(storage);

	if option_type == "string" then

		driver_name = storage;

	elseif option_type == "table" then

		driver_name = storage[store];

	end

	if not driver_name then

		driver_name = config.get(host, "default_storage") or "internal";

	end

	local driver = load_driver(host, driver_name);

	if not driver then

		log("warn", "Falling back to null driver for %s storage on %s", store, host);

		driver_name = "null";

		driver = null_storage_driver;

	end

	return driver, driver_name;

end

local function open(host, store, typ)

	local driver, driver_name = get_driver(host, store);

	local ret, err = driver:open(store, typ);

	if not ret then

		if err == "unsupported-store" then

			log("debug", "Storage driver %s does not support store %s (%s), falling back to null driver",

				driver_name, store, typ or "<nil>");

			ret = null_storage_driver;

			err = nil;

		end

	end

	return ret, err;

end

local function purge(user, host)

	local storage = config.get(host, "storage");

	if type(storage) == "table" then

		-- multiple storage backends in use that we need to purge

		local purged = {};

			end

		end

	end

	get_driver(host):purge(user); -- and the default driver

	olddm.purge(user, host); -- COMPAT list stores, like offline messages end up in the old datamanager

	return true;

end

function datamanager.load(username, host, datastore)

	return open(host, datastore):get(username);

end

function datamanager.store(username, host, datastore, data)

	return open(host, datastore):set(username, data);

end

function datamanager.users(host, datastore, typ)

	local driver = open(host, datastore, typ);

	if not driver.users then

		return function() log("warn", "storage driver %s does not support listing users", driver.name) end

	end

	return driver:users();

end

function datamanager.stores(username, host, typ)

	return get_driver(host):stores(username, typ);

end

function datamanager.purge(username, host)

	return purge(username, host);

end

return {

	initialize_host = initialize_host;

	load_driver = load_driver;

	get_driver = get_driver;

	open = open;

	purge = purge;

	olddm = olddm;

};