##############################################################################
# Copyright (c) 2013-2018, Lawrence Livermore National Security, LLC.
# Produced at the Lawrence Livermore National Laboratory.
#
# This file is part of Spack.
# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
# LLNL-CODE-647188
#
# For details, see https://github.com/spack/spack
# Please also see the NOTICE and LICENSE files for our notice and the LGPL.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License (as
# published by the Free Software Foundation) version 2.1, February 1999.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
# conditions of the GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##############################################################################
"""Debug signal handler: prints a stack trace and enters interpreter.

``register_interrupt_handler()`` enables a ctrl-C handler that prints
a stack trace and drops the user into an interpreter.

"""
import os
import code
import traceback
import signal


def debug_handler(sig, frame):
    """Interrupt running process, and provide a python prompt for
    interactive debugging."""
    d = {'_frame': frame}         # Allow access to frame object.
    d.update(frame.f_globals)    # Unless shadowed by global
    d.update(frame.f_locals)

    i = code.InteractiveConsole(d)
    message  = "Signal received : entering python shell.\nTraceback:\n"
    message += ''.join(traceback.format_stack(frame))
    i.interact(message)
    os._exit(1)  # Use os._exit to avoid test harness.


def register_interrupt_handler():
    """Print traceback and enter an interpreter on Ctrl-C"""
    signal.signal(signal.SIGINT, debug_handler)
