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_storage_config(host)

	-- COMPAT w/ unreleased Prosody 0.10 and the once-experimental mod_storage_sql2 in peoples' config files

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

	local found_sql2;

	if storage_config == "sql2" then

		storage_config, found_sql2 = "sql", true;

	elseif type(storage_config) == "table" then

		for store_name, driver_name in pairs(storage_config) do

			if driver_name == "sql2" then

				storage_config[store_name] = "sql";

				found_sql2 = true;

			end

		end

	end

	if found_sql2 then

		log("error", "The temporary 'sql2' storage module has now been renamed to 'sql', "

			.."please update your config file: https://prosody.im/doc/modules/mod_storage_sql2");

	end

	return storage_config;

end

local function get_driver(host, store)

	local storage = get_storage_config(host);

	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 map_shim_mt = {

	__index = {

		get = function(self, username, key)

			local ret, err = self.keyval_store:get(username);

			if ret == nil then return nil, err end

			return ret[key];

		end;

		set = function(self, username, key, data)

			local current, err = self.keyval_store:get(username);

			if current == nil then

				if err then

					return nil, err;

				else

					current = {};

				end

			end

			current[key] = data;

			return self.keyval_store:set(username, current);

		end;

		set_keys = function (self, username, keydatas)

			local current, err = self.keyval_store:get(username);

			if current == nil then

				if err then

					return nil, err;

				end

				current = {};

			end

			for k,v in pairs(keydatas) do

				if v == self.remove then v = nil; end

				current[k] = v;

			end

			return self.keyval_store:set(username, current);

		end;

		remove = {};

	};

}

local open;

local function create_map_shim(host, store)

	local keyval_store, err = open(host, store, "keyval");

	if keyval_store == nil then return nil, err end

	return setmetatable({

		keyval_store = keyval_store;

	}, map_shim_mt);

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

			if typ == "map" then -- Use shim on top of keyval store

				log("debug", "map storage driver unavailable, using shim on top of keyval store.");

				ret, err = create_map_shim(host, store);

			else

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

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

				ret, err = null_storage_driver, nil;

			end

		end

	end

	if ret then

		local event_data = { host = host, store_name = store, store_type = typ, store = ret };

		ret, err = event_data.store, event_data.store_err;

	end

	return ret, err;

end

local function purge(user, host)

	local storage = get_storage_config(host);

	if type(storage) == "table" then

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

		local purged = {};

		for store, driver_name in pairs(storage) do

			if not purged[driver_name] then

				local driver = get_driver(host, store);

				if driver.purge then

					purged[driver_name] = driver:purge(user);

				else

					log("warn", "Storage driver %s does not support removing all user data, "

						.."you may need to delete it manually", driver_name);

				end

			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;

};