local serialize = require "util.serialization".serialize;

local array = require "util.array";

local envload = require "util.envload".envload;

local st = require "util.stanza";

local is_stanza = st.is_stanza or function (s) return getmetatable(s) == st.stanza_mt end

local new_id = require "util.id".medium;

local auto_purge_enabled = module:get_option_boolean("storage_memory_temporary", false);

local auto_purge_stores = module:get_option_set("storage_memory_temporary_stores", {});

local memory = setmetatable({}, {

	__index = function(t, k)

		local store = module:shared(k)

		t[k] = store;

		return store;

	end

});

local function NULL() return nil end

local function _purge_store(self, username)

	self.store[username or NULL] = nil;

	return true;

end

local function _users(self)

	return next, self.store, nil;

end

local keyval_store = {};

keyval_store.__index = keyval_store;

function keyval_store:get(username)

	return (self.store[username or NULL] or NULL)();

end

function keyval_store:set(username, data)

	if data ~= nil then

		data = envload("return "..serialize(data), "=(data)", {});

	end

	self.store[username or NULL] = data;

	return true;

end

keyval_store.purge = _purge_store;

keyval_store.users = _users;

local archive_store = {};

archive_store.__index = archive_store;

archive_store.users = _users;

function archive_store:append(username, key, value, when, with)

	if is_stanza(value) then

		value = st.preserialize(value);

		value = envload("return xml"..serialize(value), "=(stanza)", { xml = st.deserialize })

	else

		value = envload("return "..serialize(value), "=(data)", {});

	end

	local a = self.store[username or NULL];

	if not a then

		a = {};

		self.store[username or NULL] = a;

	end

	local v = { key = key, when = when, with = with, value = value };

	if not key then

		key = new_id();

		v.key = key;

	end

	if a[key] then

		table.remove(a, a[key]);

	end

	local i = #a+1;

	a[i] = v;

	a[key] = i;

	return key;

end

function archive_store:find(username, query)

	local items = self.store[username or NULL];

	if not items then

		return function () end, 0;

	end

	local count = #items;

	local i = 0;

	if query then

		items = array():append(items);

		if query.key then

			items:filter(function (item)

				return item.key == query.key;

			end);

		end

		if query.with then

			items:filter(function (item)

				return item.with == query.with;

			end);

		end

		if query.start then

			items:filter(function (item)

				return item.when >= query.start;

			end);

		end

		if query["end"] then

			items:filter(function (item)

				return item.when <= query["end"];

			end);

		end

		count = #items;

		if query.reverse then

			items:reverse();

			if query.before then

				for j = 1, count do

					if (items[j].key or tostring(j)) == query.before then

						i = j;

						break;

					end

				end

			end

		elseif query.after then

			for j = 1, count do

				if (items[j].key or tostring(j)) == query.after then

					i = j;

					break;

				end

			end

		end

		if query.limit and #items - i > query.limit then

			items[i+query.limit+1] = nil;

		end

	end

	return function ()

		i = i + 1;

		local item = items[i];

		if not item then return; end

		return item.key, item.value(), item.when, item.with;

	end, count;

end

function archive_store:delete(username, query)

	if not query or next(query) == nil then

		self.store[username or NULL] = nil;

		return true;

	end

	local items = self.store[username or NULL];

	if not items then

		-- Store is empty

		return 0;

	end

	items = array(items);

	local count_before = #items;

	if query then

		if query.key then

			items:filter(function (item)

				return item.key ~= query.key;

			end);

		end

		if query.with then

			items:filter(function (item)

				return item.with ~= query.with;

			end);

		end

		if query.start then

			items:filter(function (item)

				return item.when < query.start;

			end);

		end

		if query["end"] then

			items:filter(function (item)

				return item.when > query["end"];

			end);

		end

		if query.truncate and #items > query.truncate then

			if query.reverse then

				-- Before: { 1, 2, 3, 4, 5, }

				-- After: { 1, 2, 3 }

				for i = #items, query.truncate + 1, -1 do

					items[i] = nil;

				end

			else

				-- Before: { 1, 2, 3, 4, 5, }

				-- After: { 3, 4, 5 }

				local offset = #items - query.truncate;

				for i = 1, #items do

					items[i] = items[i+offset];

				end

			end

		end

	end

	local count = count_before - #items;

	if count == 0 then

		return 0; -- No changes, skip write

	end

	setmetatable(items, nil);

	do -- re-index by key

		for k in pairs(items) do

			if type(k) == "string" then

				items[k] = nil;

			end

		end

		for i = 1, #items do

			items[ items[i].key ] = i;

		end

	end

	return count;

end

archive_store.purge = _purge_store;

local stores = {

	keyval = keyval_store;

	archive = archive_store;

}

local driver = {};

function driver:open(store, typ) -- luacheck: ignore 212/self

	local store_mt = stores[typ or "keyval"];

	if store_mt then

		return setmetatable({ store = memory[store] }, store_mt);

	end

	return nil, "unsupported-store";

end

function driver:purge(user) -- luacheck: ignore 212/self

	for _, store in pairs(memory) do

		store[user] = nil;

	end

end

if auto_purge_enabled then

	module:hook("resource-unbind", function (event)

		local user_bare_jid = event.session.username.."@"..event.session.host;

		if not prosody.bare_sessions[user_bare_jid] then -- User went offline

			module:log("debug", "Clearing store for offline user %s", user_bare_jid);

			local f, s, v;

			if auto_purge_stores:empty() then

				f, s, v = pairs(memory);

			else

				f, s, v = auto_purge_stores:items();

			end

			for store_name in f, s, v do

				if memory[store_name] then

					memory[store_name][event.session.username] = nil;

				end

			end

		end

	end);

end

module:provides("storage", driver);