-- XEP-0280: Message Carbons implementation for Prosody

-- Copyright (C) 2011-2016 Kim Alvefur

--

-- This file is MIT/X11 licensed.

local st = require "util.stanza";

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

local jid_resource = require "util.jid".resource;

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

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

local full_sessions, bare_sessions = prosody.full_sessions, prosody.bare_sessions;

local function is_bare(jid)

	return not jid_resource(jid);

end

local function toggle_carbons(event)

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

	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

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

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

local function should_copy(stanza, c2s, user_bare) --> boolean, reason: string

	local st_type = stanza.attr.type or "normal";

	if stanza:get_child("private", xmlns_carbons) then

		return false, "private";

	end

	if stanza:get_child("no-copy", "urn:xmpp:hints") then

		return false, "hint";

	end

	if not c2s and stanza.attr.to ~= user_bare and stanza:get_child("x", "http://jabber.org/protocol/muc#user") then

		-- MUC PMs are normally sent to full JIDs

		return false, "muc-pm";

	end

	if st_type == "chat" then

		return true, "type";

	end

	if st_type == "normal" and stanza:get_child("body") then

		return true, "type";

	end

	-- Normal outgoing chat messages are sent to=bare JID. This clause should

	-- match the error bounces from those, which would have from=bare JID and

	-- be incoming (not c2s).

	if st_type == "error" and not c2s and is_bare(stanza.attr.from) then

		return true, "bounce";

	end

	for archived in stanza:childtags("stanza-id", "urn:xmpp:sid:0") do

		if archived and archived.attr.by == user_bare then

			return true, "archived";

		end

	end

	return false, "default";

end

local function message_handler(event, c2s)

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

	local orig_type = stanza.attr.type or "normal";

	local orig_from = stanza.attr.from;

	local bare_from = jid_bare(orig_from);

	local orig_to = stanza.attr.to;

	local bare_to = jid_bare(orig_to);

	-- Stanza sent by a local client

	local bare_jid = bare_from; -- JID of the local user

	local target_session = origin;

	local top_priority = false;

	local user_sessions = bare_sessions[bare_from];

	-- Stanza about to be delivered to a local client

	if not c2s then

		bare_jid = bare_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

	local should, why = should_copy(stanza, c2s, bare_jid);

	if not should then

		module:log("debug", "Not copying stanza: %s (%s)", stanza:top_tag(), why);

		if why == "private" and not c2s then

			stanza:maptags(function(tag)

				if not ( tag.attr.xmlns == xmlns_carbons and tag.name == "private" ) then

					return tag;

				end

			end);

		end

		return;

	end

	local carbon;

	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) then

			if not carbon then

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

				local copy = st.clone(stanza);

				if c2s and not orig_to then

					stanza.attr.to = bare_from;

				end

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

				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();

			end

			carbon.attr.to = session.full_jid;

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

			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/host", c2s_message_handler, -0.5);

module:hook("pre-message/bare", c2s_message_handler, -0.5);

module:hook("pre-message/full", c2s_message_handler, -0.5);

-- Stanzas to local clients

module:hook("message/bare", message_handler, -0.5);

module:hook("message/full", message_handler, -0.5);

module:add_feature(xmlns_carbons);