-- This program is a Gateway between a xAP client that subscribe via a
-- mqtt broker and those that publish their messages via the iServer
-- or directly as UDP packets.  It operates by subscribing to the mqtt
-- broker and listening for all topics being published.  As each
-- message via the broker is an xAP packet it picks up the
-- xap-hbeat/xap-header and extracts the source= tag.  From this it
-- can create an xAP FILTER that allows it to redirect xAP messages to
-- the broker.
module(...,package.seeall)
require("xap")
MQTT = require("mqtt_library")

info = {version="1.1", description="xAP/MQTT gateway"}
-- nil port means use the default
broker = {host="172.16.10.150", port=nil} --mqtt broker location
subscribedTopics = {}

function xAPAddrToTopic(addr)
   -- convert a.b.c:d.e -> a/b/c/d/e
   return addr:gsub("[%.:]", "/")
end

function sendJsonValue(frame)
	
	local value = frame:getValue("input.state", "text")
	local state = frame:getValue("input.state", "state")
	if state == '?' then
		-- state = "Unknown"
	end
	-- converts xAP payload into usefull info in JSON format for HomeAssistant
	return '{"text":"' .. value .. '","state":"' .. state .. '"}'
end

function bumpHop(f, section)
   if f[section] == nil then
      return
   end
   if f[section]['hop'] then
      f[section].hop = f[section].hop + 1
   else
      f[section].hop = 2
   end
end

function toMqtt(frame)
    local source = frame:getValue("xap-header", "source")
	local target = frame:getValue("xap-header", "target")
	
	-- Filtering out some pointless messages
	if frame:getValue("input.state", "text") == nil then
		return
	end

	bumpHop(frame)
	
	-- Build MQTT topic from source address
    local topic = xAPAddrToTopic(source)
	-- If target is empty(and it usually is), fill it with the source address
	if target == nil then
		frame:setValue('xap-header', 'target', source)
	end
	-- rebadge the message as coming from the GW. (this changes the source asddress to 'dbzoo.hah.plugboard'
    -- we use this fact later to ignore messages from ourself.
	frame:setValue("xap-header", "source", xap.defaultKeys.source)
	
	-- Assuming we're connected
	if broker.c.connected then
		-- Sends stripped out frame in name:value pair format
		broker.c:publish(topic, sendJsonValue(frame))
	end
	print("Publish to topic: "..topic)
	-- print("Payload: "..tostring(frame))
end

function fromMqtt(topic, payload)
	local f = xap.Frame(payload)
	if f:getValue("xap-header", "class") == 'xAPBSC.event' then
      return -- Dont want events from MQTT
	end
	-- This happens as we subscribe to # so we get our own publish.
	if f:getValue("xap-header", "source") == xap.defaultKeys.source then
	-- print(xap.defaultKeys.source);
      return -- Message was from us to the MQTT
	end

	-- For New Topics
	if subscribedTopics[topic] == nil then
	  local source = f:getValue("xap-header", "source")
	  if source  == nil then 
		 source = f:getValue("xap-hbeat", "source")
	  end 
	  if source == nil then
		-- Handle a bad xAP packet - missing source!
		return
	  end
	  print("Bind topic "..topic.." to "..source)
	  local flt = xap.Filter()
	  flt:add("xap-header", "target", topic)
	  flt:callback(toMqtt)
	  subscribedTopics[topic] = true
	end

	-- Sending 
	if f['xap-header'] then
	  -- sendShort only for xap-header messages
	  bumpHop(f, 'xap-header')
	  xap.sendShort(tostring(f))
	  -- print("shortSending: "..tostring(f));
	else
	  -- expect the xap-hbeat to be fully formed
	  bumpHop(f, 'xap-hbeat')
	  xap.send(tostring(f))
	  -- print("Sending: "..tostring(f));
	end

end

function connect()
   print("Connecting...")
   broker.c = MQTT.client.create(broker.host, broker.port, fromMqtt)
   broker.c:connect(xap.defaultKeys.source)
      print("@connect: "..xap.defaultKeys.source);
   if broker.c.connected then
      print("Connected")
      -- As long as we don't have a lot of topics and high volumes we
      -- should be able to keep up with filtering and forwarding.
      -- I know subscribing to # is not recommended.  :(
      broker.c:subscribe({"#"})
   end
end

function init()
	connect()
	-- pump the mqtt client every second
	local flt = xap.Filter() --Create a filter for all event msgs out.
		-- Tried to use multiple 'adds' but this didn't work, so just doing all
		flt:add("xap-header", "source", "dbzoo.hal.*:>")
		flt:add("xap-header", "class", "xAPBSC.event")
		flt:callback(toMqtt) -- straight to MQTT out

	xap.Timer(function() 
       -- If the mqtt server goes away recover.
       if broker.c.connected then
          broker.c:handler()
       else
          connect()
       end
   end, 1):start(true) -- and fire now to get us going at 0sec.
end