--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/muc/history.lib.lua	Thu Apr 03 15:14:52 2014 -0400
@@ -0,0 +1,161 @@
+-- Prosody IM
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain
+-- Copyright (C) 2014 Daurnimator
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+local gettime = os.time;
+local datetime = require "util.datetime";
+local st = require "util.stanza";
+
+local default_history_length, max_history_length = 20, math.huge;
+
+local function set_max_history_length(_max_history_length)
+	max_history_length = _max_history_length or math.huge;
+end
+
+local function get_historylength(room)
+	return math.min(room._data.history_length or default_history_length, max_history_length);
+end
+
+local function set_historylength(room, length)
+	length = assert(tonumber(length), "Length not a valid number");
+	if length == default_history_length then length = nil; end
+	room._data.history_length = length;
+	return true;
+end
+
+module:hook("muc-config-form", function(event)
+	table.insert(event.form, {
+		name = "muc#roomconfig_historylength";
+		type = "text-single";
+		label = "Maximum Number of History Messages Returned by Room";
+		value = tostring(get_historylength(event.room));
+	});
+end);
+
+module:hook("muc-config-submitted", function(event)
+	local new = event.fields["muc#roomconfig_historylength"];
+	if new ~= nil and set_historylength(event.room, new) then
+		event.status_codes["104"] = true;
+	end
+end);
+
+local function parse_history(stanza)
+	local x_tag = stanza:get_child("x", "http://jabber.org/protocol/muc");
+	local history_tag = x_tag and x_tag:get_child("history", "http://jabber.org/protocol/muc");
+	if not history_tag then
+		return nil, default_history_length, nil;
+	end
+
+	local maxchars = tonumber(history_tag.attr.maxchars);
+
+	local maxstanzas = tonumber(history_tag.attr.maxstanzas);
+
+	-- messages received since the UTC datetime specified
+	local since = history_tag.attr.since;
+	if since then
+		since = datetime.parse(since);
+	end
+
+	-- messages received in the last "X" seconds.
+	local seconds = tonumber(history_tag.attr.seconds);
+	if seconds then
+		seconds = gettime() - seconds;
+		if since then
+			since = math.max(since, seconds);
+		else
+			since = seconds;
+		end
+	end
+
+	return maxchars, maxstanzas, since;
+end
+
+module:hook("muc-get-history", function(event)
+	local room = event.room;
+	local history = room._data["history"]; -- send discussion history
+	if not history then return nil end
+	local history_len = #history;
+
+	local to = event.to;
+	local maxchars = event.maxchars;
+	local maxstanzas = event.maxstanzas or history_len;
+	local since = event.since;
+	local n = 0;
+	local charcount = 0;
+	for i=history_len,1,-1 do
+		local entry = history[i];
+		if maxchars then
+			if not entry.chars then
+				entry.stanza.attr.to = "";
+				entry.chars = #tostring(entry.stanza);
+			end
+			charcount = charcount + entry.chars + #to;
+			if charcount > maxchars then break; end
+		end
+		if since and since > entry.timestamp then break; end
+		if n + 1 > maxstanzas then break; end
+		n = n + 1;
+	end
+
+	local i = history_len-n+1
+	function event:next_stanza()
+		if i > history_len then return nil end
+		local entry = history[i];
+		local msg = entry.stanza;
+		msg.attr.to = to;
+		i = i + 1;
+		return msg;
+	end
+	return true;
+end);
+
+local function send_history(room, stanza)
+	local maxchars, maxstanzas, since = parse_history(stanza);
+	local event = {
+		room = room;
+		to = stanza.attr.from; -- `to` is required to calculate the character count for `maxchars`
+		maxchars = maxchars, maxstanzas = maxstanzas, since = since;
+		next_stanza = function() end; -- events should define this iterator
+	};
+	module:fire_event("muc-get-history", event);
+	for msg in event.next_stanza, event do
+		room:route_stanza(msg);
+	end
+end
+
+-- Send history on join
+module:hook("muc-occupant-joined", function(event)
+	send_history(event.room, event.stanza);
+end, 50); -- Between occupant list (80) and subject(20)
+
+-- add to history
+module:hook("muc-broadcast-message", function(event)
+	local historic = event.stanza:get_child("body");
+	if historic then
+		local room = event.room
+		local history = room._data["history"];
+		if not history then history = {}; room._data["history"] = history; end
+		local stanza = st.clone(event.stanza);
+		stanza.attr.to = "";
+		local ts = gettime();
+		local stamp = datetime.datetime(ts);
+		stanza:tag("delay", {xmlns = "urn:xmpp:delay", from = module.host, stamp = stamp}):up(); -- XEP-0203
+		stanza:tag("x", {xmlns = "jabber:x:delay", from = module.host, stamp = datetime.legacy()}):up(); -- XEP-0091 (deprecated)
+		local entry = { stanza = stanza, timestamp = ts };
+		table.insert(history, entry);
+		while #history > get_historylength(room) do table.remove(history, 1) end
+	end
+end);
+
+return {
+	set_max_length = set_max_history_length;
+	parse_history = parse_history;
+	send = send_history;
+	get_length = get_historylength;
+	set_length = set_historylength;
+};