# Adapted from http://timlehr.com/python-exception-hooks-with-qt-message-box/

import sys
import traceback
from PyQt4 import QtCore, QtGui


def show_exception_box(log_msg):
	"""
	Checks if a QApplication instance is available and shows a messagebox with the exception message
	If unavailable (non-console application), log an additional notice.
	"""
	print "[ERROR]: An unexpected error occured: %s" % log_msg
	if QtGui.QApplication.instance() is not None:
			QtGui.QMessageBox.critical(
				None,
				"FOFB: Unexpected error",
				"""
					<b>An unexpected error occured:</b>
					<br>
					<br>
					%s
				""" % log_msg.replace("\n", "<br>")
			)


class UncaughtHook(QtCore.QObject):
	_exception_caught = QtCore.Signal(object)

	def __init__(self, *args, **kwargs):
		super(UncaughtHook, self).__init__(*args, **kwargs)

		# this registers the exception_hook() function as hook with the Python interpreter
		sys.excepthook = self.exception_hook

		# connect signal to execute the message box function always on main thread
		self._exception_caught.connect(show_exception_box)

	def exception_hook(self, exc_type, exc_value, exc_traceback):
		"""Function handling uncaught exceptions.
		It is triggered each time an uncaught exception occurs.
		"""
		if issubclass(exc_type, KeyboardInterrupt):
			# ignore keyboard interrupt to support console applications
			sys.__excepthook__(exc_type, exc_value, exc_traceback)
		else:
			exc_info = (exc_type, exc_value, exc_traceback)
			log_msg = "\n".join([
				"".join(traceback.format_tb(exc_traceback)),
				"%s: %s" % (exc_type.__name__, exc_value)
			])
			# trigger message box show
			self._exception_caught.emit(log_msg)

# create a global instance of our class to register the hook
qt_exception_hook = UncaughtHook()