local error, type, pairs = error, 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;

module("storagemanager")

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

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

_M.olddm = olddm;

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)

			return null_storage_method;

		end

	}

);

local stores_available = multitable.new();

function initialize_host(host)

	local host_session = hosts[host];

	host_session.events.add_handler("item-added/data-driver", function (event)

		local item = event.item;

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

	end);

	host_session.events.add_handler("item-removed/data-driver", function (event)

		local item = event.item;

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

	end);

end

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

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

function get_driver(host, store)

	local storage = config.get(host, "core", "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, "core", "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

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);

			ret = null_storage_driver;

			err = nil;

		end

	end

	return ret, err;

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.list_stores(username, host)

	return get_driver(host):list_stores(username, host);

end

return _M;