local error, type = error, type;

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

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

module("storagemanager")

local default_driver_mt = { name = "internal" };

default_driver_mt.__index = default_driver_mt;

function default_driver_mt:open(store)

	return setmetatable({ host = self.host, store = store }, default_driver_mt);

end

function default_driver_mt:get(user) return olddm.load(user, self.host, self.store); end

function default_driver_mt:set(user, data) return olddm.store(user, self.host, self.store, data); end

local stores_available = multitable.new();

function initialize_host(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

local function load_driver(host, driver_name)

	if not driver_name then

		return;

	end

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

	if not driver then

		if driver_name ~= "internal" then

			modulemanager.load(host, "storage_"..driver_name);

			return stores_available:get(host, driver_name);

		else

			return setmetatable({host = host}, default_driver_mt);

		end

	end

end

function open(host, store, typ)

	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

	local driver = load_driver(host, driver_name);

	if not driver then

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

		driver = load_driver(host, driver_name);

		if not driver then

			if storage or driver_name then

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

			end

			driver_name = "internal";

			driver = load_driver(host, driver_name);

		end

	end

	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 internal driver",

				driver_name, store, typ);

			ret = setmetatable({ host = host, store = store }, default_driver_mt); -- default to default 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

return _M;