local modulemanager = require "core.modulemanager";
local usermanager = require "core.usermanager";

local id = require "util.id";
local jid = require "util.jid";
local st = require "util.stanza";

local strict = module:get_option_boolean("enforce_client_ids", false);

local tokenauth = module:depends("tokenauth");
local mod_fast = module:depends("sasl2_fast");

local client_store = assert(module:open_store("clients", "keyval+"));
--[[{
	id = id;
	first_seen =
	last_seen =
	user_agent = {
		name =
		os =
	}
--}]]

local xmlns_sasl2 = "urn:xmpp:sasl:2";

local function get_user_agent(sasl_handler, token_info)
	local sasl_agent = sasl_handler and sasl_handler.user_agent;
	local token_agent = token_info and token_info.data and token_info.data.oauth2_client;
	if not (sasl_agent or token_agent) then return; end
	return {
		software = sasl_agent and sasl_agent.software or token_agent and token_agent.name or nil;
		uri = token_agent and token_agent.uri or nil;
		device = sasl_agent and sasl_agent.device or nil;
	};
end

module:hook("sasl2/c2s/success", function (event)
	local session = event.session;
	local username, client_id = session.username, session.client_id;
	local mechanism = session.sasl_handler.selected;
	local token_info = session.sasl_handler.token_info;
	local token_id = token_info and token_info.id or nil;

	local now = os.time();
	if client_id then -- SASL2, have client identifier
		local is_new_client;

		local client_state = client_store:get_key(username, client_id);
		if not client_state then
			is_new_client = true;
			client_state = {
				id = client_id;
				first_seen = now;
				user_agent = get_user_agent(session.sasl_handler, token_info);
				full_jid = nil;
				last_seen = nil;
				mechanisms = {};
			};
		end
		-- Update state
		client_state.full_jid = session.full_jid;
		client_state.last_seen = now;
		client_state.mechanisms[mechanism] = now;
		if session.sasl_handler.fast_auth then
			client_state.fast_auth = now;
		end
		if token_id then
			client_state.auth_token_id = token_id;
		end
		-- Store updated state
		client_store:set_key(username, client_id, client_state);

		if is_new_client then
			module:fire_event("client_management/new-client", { client = client_state });
		end
	end
end);

local function find_client_by_resource(username, resource)
	local full_jid = jid.join(username, module.host, resource);
	local clients = client_store:get(username);
	if not clients then return; end

	for _, client_state in pairs(clients) do
		if client_state.full_jid == full_jid then
			return client_state;
		end
	end
end

module:hook("resource-bind", function (event)
	local session = event.session;
	if session.client_id then return; end
	local is_new_client;
	local client_state = find_client_by_resource(event.session.username, event.session.resource);
	local now = os.time();
	if not client_state then
		is_new_client = true;
		client_state = {
			id = id.short();
			first_seen = now;
			user_agent = nil;
			full_jid = nil;
			last_seen = nil;
			mechanisms = {};
			legacy = true;
		};
	end

	-- Update state
	local legacy_info = session.client_management_info;
	client_state.full_jid = session.full_jid;
	client_state.last_seen = now;
	client_state.mechanisms[legacy_info.mechanism] = now;
	if legacy_info.fast_auth then
		client_state.fast_auth = now;
	end

	local token_id = legacy_info.token_info and legacy_info.token_info.id;
	if token_id then
		client_state.auth_token_id = token_id;
	end

	-- Store updated state
	client_store:set_key(session.username, client_state.id, client_state);

	if is_new_client then
		module:fire_event("client_management/new-client", { client = client_state });
	end
end);

if strict then
	module:hook_tag(xmlns_sasl2, "authenticate", function (session, auth)
		local user_agent = auth:get_child("user-agent");
		if not user_agent or not user_agent.attr.id then
			local failure = st.stanza("failure", { xmlns = xmlns_sasl2 })
				:tag("malformed-request", { xmlns = "urn:ietf:params:xml:ns:xmpp-sasl" }):up()
				:text_tag("text", "Client identifier required but not supplied");
			session.send(failure);
			return true;
		end
	end, 500);

	if modulemanager.get_modules_for_host(module.host):contains("saslauth") then
		module:log("error", "mod_saslauth is enabled, but enforce_client_ids is enabled and will prevent it from working");
	end

	module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:auth", function (event)
		-- Block legacy SASL, if for some reason it is being used (either mod_saslauth is loaded,
		-- or clients try it without advertisement)
		module:log("warn", "Blocking legacy SASL authentication because enforce_client_ids is enabled");
		local failure = st.stanza("failure", { xmlns = xmlns_sasl2 })
			:tag("malformed-request", { xmlns = "urn:ietf:params:xml:ns:xmpp-sasl" }):up()
			:text_tag("text", "Legacy SASL authentication is not available on this server");
		event.session.send(failure);
		return true;
	end);
else
	-- Legacy client compat code
	module:hook("authentication-success", function (event)
		local session = event.session;
		if session.client_id then return; end -- SASL2 client

		local sasl_handler = session.sasl_handler;
		session.client_management_info = {
			mechanism = sasl_handler.selected;
			token_info = sasl_handler.token_info;
			fast_auth = sasl_handler.fast_auth;
		};
	end);
end

local function is_password_mechanism(mech_name)
	if mech_name == "OAUTHBEARER" then return false; end
	if mech_name:match("^HT%-") then return false; end
	return true;
end

local function is_client_active(client)
	local username, host = jid.split(client.full_jid);
	local account_info = usermanager.get_account_info(username, host);
	local last_password_change = account_info and account_info.password_updated;

	local status = {};

	-- Check for an active token grant that has been previously used by this client
	if client.auth_token_id then
		local grant = tokenauth.get_grant_info(client.auth_token_id);
		if grant then
			status.active_grant = grant;
		end
	end

	-- Check for active FAST tokens
	if client.fast_auth then
		if mod_fast.is_client_fast(username, client.id, last_password_change) then
			status.active_fast = client.fast_auth;
		end
	end

	-- Client has access if any password-based SASL mechanisms have been used since last password change
	for mech, mech_last_used in pairs(client.mechanisms) do
		if is_password_mechanism(mech) and mech_last_used >= last_password_change then
			status.active_password = mech_last_used;
		end
	end

	if prosody.full_sessions[client.full_jid] then
		status.active_connected = true;
	end

	if next(status) == nil then
		return nil;
	end
	return status;
end

-- Public API
--luacheck: ignore 131
function get_active_clients(username)
	local clients = client_store:get(username);
	local active_clients = {};
	local used_grants = {};

	-- Go through known clients, check whether they could possibly log in
	for client_id, client in pairs(clients or {}) do --luacheck: ignore 213/client_id
		local active = is_client_active(client);
		if active then
			client.type = "session";
			client.active = active;
			table.insert(active_clients, client);
			if active.active_grant then
				used_grants[active.active_grant.id] = true;
			end
		end
	end

	-- Next, account for any grants that have been issued, but never actually logged in
	for grant_id, grant in pairs(tokenauth.get_user_grants(username) or {}) do
		if not used_grants[grant_id] then -- exclude grants already accounted for
			table.insert(active_clients, {
				id = grant_id;
				type = "access";
				first_seen = grant.created;
				last_seen = grant.accessed;
				active = {
					active_grant = grant;
				};
				user_agent = get_user_agent(nil, grant);
			});
		end
	end

	table.sort(active_clients, function (a, b)
		if a.last_seen and b.last_seen then
			return a.last_seen < b.last_seen;
		elseif not (a.last_seen or b.last_seen) then
			if a.first_seen and b.first_seen then
				return a.first_seen < b.first_seen;
			end
		elseif b.last_seen then
			return true;
		elseif a.last_seen then
			return false;
		end
		return a.id < b.id;
	end);

	return active_clients;
end