import sys
import logging
import traceback
from cStringIO import StringIO

import dbus
import dbus.dbus_bindings
import gobject

__queue = None

CONSOLE_BUS_NAME = 'org.laptop.Sugar.Console'
CONSOLE_OBJECT_PATH = '/org/laptop/Sugar/Console'
CONSOLE_IFACE = 'org.laptop.Sugar.Console'

class MessageQueue:
	def __init__(self, console, console_id):
		self._idle_id = 0
		self._console = console
		self._console_id = console_id
		self._levels = []
		self._messages = []
		self._bus = dbus.SessionBus()
		
		if self._console == None:
			con = self._bus._connection
			if dbus.dbus_bindings.bus_name_has_owner(con, CONSOLE_BUS_NAME):
				self.setup_console()
			else:
				self._bus.add_signal_receiver(
									self.__name_owner_changed,
									dbus_interface = "org.freedesktop.DBus",
									signal_name = "NameOwnerChanged")

	def setup_console(self):
		proxy_obj = self._bus.get_object(CONSOLE_BUS_NAME,
										 CONSOLE_OBJECT_PATH)
		self._console = dbus.Interface(proxy_obj, CONSOLE_IFACE)
		self._queue_log()

	def __name_owner_changed(self, service_name, old_name, new_name):
		if service_name == CONSOLE_BUS_NAME:
			if new_name != None:
				self.setup_console()
			else:
				self._console = None

	def _queue_log(self):
		if self._idle_id == 0:
			self._idle_id = gobject.idle_add(self._log)

	def _log(self):
		if self._console == None or len(self._messages) == 0:
			return False

		if isinstance(self._console, dbus.Interface):
			self._console.log(self._console_id, self._levels,
							  self._messages, timeout = 1000)
		else:
			self._console.log(self._console_id, self._levels,
							  self._messages)
		
		self._levels = []
		self._messages = []
		self._idle_id = 0

		return False

	def append_record(self, record):
		self.append(record.levelno, record.msg)

	def append(self, level, message):
		self._levels.append(level)
		self._messages.append(message)
		self._queue_log()

class Handler(logging.Handler):
	def __init__(self, queue):
		logging.Handler.__init__(self)

		self._queue = queue

	def emit(self, record):
		self._queue.append_record(record)

def __exception_handler(typ, exc, tb):
	trace = StringIO()
	traceback.print_exception(typ, exc, tb, None, trace)
	print >> sys.stderr, trace.getvalue()

	__queue.append(logging.ERROR, trace.getvalue())

def start(console_id, console = None):
	queue = MessageQueue(console, console_id)

	root_logger = logging.getLogger('')
	root_logger.setLevel(logging.DEBUG)
	root_logger.addHandler(Handler(queue))

	global __queue
	__queue = queue
	sys.excepthook = __exception_handler