-- XEP-0280: Message Carbons implementation for Prosody

-- Copyright (C) 2011 Kim Alvefur

--

-- This file is MIT/X11 licensed.

local st = require "util.stanza";

local jid_bare = require "util.jid".bare;

local xmlns_carbons = "urn:xmpp:carbons:2";

local xmlns_carbons_old = "urn:xmpp:carbons:1";

local xmlns_carbons_really_old = "urn:xmpp:carbons:0";

local xmlns_forward = "urn:xmpp:forward:0";

local full_sessions, bare_sessions = full_sessions, bare_sessions;

local function toggle_carbons(event)

	local origin, stanza = event.origin, event.stanza;

	if stanza.attr.type == "set" then

		local state = stanza.tags[1].name;

		module:log("debug", "%s %sd carbons", origin.full_jid, state);

		origin.want_carbons = state == "enable" and stanza.tags[1].attr.xmlns;

		origin.send(st.reply(stanza));

		return true

	end

end

module:hook("iq/self/"..xmlns_carbons..":disable", toggle_carbons);

module:hook("iq/self/"..xmlns_carbons..":enable", toggle_carbons);

-- COMPAT

module:hook("iq/self/"..xmlns_carbons_old..":disable", toggle_carbons);

module:hook("iq/self/"..xmlns_carbons_old..":enable", toggle_carbons);

-- COMPAT :(

if module:get_option_boolean("carbons_v0") then

	module:hook("iq/self/"..xmlns_carbons_really_old..":carbons", function(event)

		local origin, stanza = event.origin, event.stanza;

		if stanza.attr.type == "set" then

			local state = stanza.tags[1].attr.mode;

			origin.want_carbons = state == "enable" and xmlns_carbons_really_old;

			origin.send(st.reply(stanza));

			return true;

		end

	end);

end

local function message_handler(event, c2s)

	local origin, stanza = event.origin, event.stanza;

	local orig_type = stanza.attr.type;

	local orig_from = stanza.attr.from;

	local orig_to = stanza.attr.to;

	if not (orig_type == nil

			or orig_type == "normal"

			or orig_type == "chat") then

		return -- No carbons for messages of type error or headline

	end

	-- Stanza sent by a local client

	local bare_jid = jid_bare(orig_from);

	local target_session = origin;

	local top_priority = false;

	local user_sessions = bare_sessions[bare_jid];

	-- Stanza about to be delivered to a local client

	if not c2s then

		bare_jid = jid_bare(orig_to);

		target_session = full_sessions[orig_to];

		user_sessions = bare_sessions[bare_jid];

		if not target_session and user_sessions then

			-- The top resources will already receive this message per normal routing rules,

			-- so we are going to skip them in order to avoid sending duplicated messages.

			local top_resources = user_sessions.top_resources;

			top_priority = top_resources and top_resources[1].priority

		end

	end

	if not user_sessions then

		module:log("debug", "Skip carbons for offline user");

		return -- No use in sending carbons to an offline user

	end

	if not c2s and stanza:get_child("private", xmlns_carbons) then

		stanza:maptags(function(tag)

			return tag.attr.xmlns == xmlns_carbons

				and tag.name == "private" and tag or nil;

		end);

		module:log("debug", "Message tagged private, ignoring");

		return

	end

	-- Create the carbon copy and wrap it as per the Stanza Forwarding XEP

	local copy = st.clone(stanza);

	copy.attr.xmlns = "jabber:client";

	local carbon = st.message{ from = bare_jid, type = orig_type, }

		:tag(c2s and "sent" or "received", { xmlns = xmlns_carbons })

			:tag("forwarded", { xmlns = xmlns_forward })

				:add_child(copy):reset();

	-- COMPAT

	local carbon_old = st.message{ from = bare_jid, type = orig_type, }

		:tag(c2s and "sent" or "received", { xmlns = xmlns_carbons_old }):up()

		:tag("forwarded", { xmlns = xmlns_forward })

			:add_child(copy):reset();

	-- COMPAT

	local carbon_really_old = st.clone(stanza)

		:tag(c2s and "sent" or "received", { xmlns = xmlns_carbons_really_old }):up()

	user_sessions = user_sessions and user_sessions.sessions;

	for _, session in pairs(user_sessions) do

		-- Carbons are sent to resources that have enabled it

		if session.want_carbons

		-- but not the resource that sent the message, or the one that it's directed to

		and session ~= target_session

		-- and isn't among the top resources that would receive the message per standard routing rules

		and (c2s or session.priority ~= top_priority)

		-- don't send v0 carbons (or copies) for c2s

		and (not c2s or session.want_carbons ~= xmlns_carbons_really_old) then

			carbon.attr.to = session.full_jid;

			module:log("debug", "Sending carbon to %s", session.full_jid);

			local carbon = session.want_carbons == xmlns_carbons_old and carbon_old -- COMPAT

			or session.want_carbons == xmlns_carbons_really_old and carbon_really_old -- COMPAT

			or carbon;

			session.send(carbon);

		end

	end

end

local function c2s_message_handler(event)

	return message_handler(event, true)

end

-- Stanzas sent by local clients

module:hook("pre-message/bare", c2s_message_handler, 1);

module:hook("pre-message/full", c2s_message_handler, 1);

-- Stanzas to local clients

module:hook("message/bare", message_handler, 1);

module:hook("message/full", message_handler, 1);

module:add_feature(xmlns_carbons);

module:add_feature(xmlns_carbons_old);

if module:get_option_boolean("carbons_v0") then

	module:add_feature(xmlns_carbons_really_old);

end