# Copyright (C) 2000-2014 Bastian Kleineidam
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# 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
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
Main function module for link checking.
"""

# version checks
import sys
if sys.version_info < (3, 5, 0, 'final', 0):
    import platform
    raise SystemExit("This program requires Python 3.5.0 or later instead of %s." % platform.python_version())
# require a reasonably recent requests module: 2.4.0 from 2014-08-29
import requests
# PEP 396 has only version strings, bummer! PEP 386 is also not helpful.
requests_version = requests.__version__.split('.')
# Depends on the version scheme of Python requests
if int(requests_version[0]) < 2 or \
   (int(requests_version[0]) == 2 and int(requests_version[1]) < 4):
    raise SystemExit("This program requires Python requests 2.4.0 or later instead of %s." % requests.__version__)

import os
import re
import signal
import traceback

from . import i18n, log
from .logconf import (
    LOG_ROOT,
    LOG_CMDLINE,
    LOG_CHECK,
    LOG_CACHE,
    LOG_THREAD,
    LOG_PLUGIN,
)
import _LinkChecker_configdata as configdata


def module_path():
    """Return absolute directory of system executable."""
    return os.path.dirname(os.path.abspath(sys.executable))


def get_install_data():
    """Return absolute path of LinkChecker data installation directory."""
    from .loader import is_frozen
    if is_frozen():
        return module_path()
    return configdata.install_data


class LinkCheckerError(Exception):
    """Exception to be raised on linkchecker-specific check errors."""
    pass

class LinkCheckerInterrupt(Exception):
    """Used for testing."""
    pass


def get_link_pat(arg, strict=False):
    """Get a link pattern matcher for intern/extern links.
    Returns a compiled pattern and a negate and strict option.

    @param arg: pattern from config
    @type arg: string
    @param strict: if pattern is to be handled strict
    @type strict: bool
    @return: dictionary with keys 'pattern', 'negate' and 'strict'
    @rtype: dict
    @raises: re.error on invalid regular expressions
    """
    log.debug(LOG_CHECK, "Link pattern %r strict=%s", arg, strict)
    if arg.startswith('!'):
        pattern = arg[1:]
        negate = True
    else:
        pattern = arg
        negate = False
    try:
        regex = re.compile(pattern)
    except re.error as msg:
        log.warn(LOG_CHECK, "invalid regular expression %r: %s" % (pattern, msg))
        raise
    return {
        "pattern": regex,
        "negate": negate,
        "strict": strict,
    }


def init_i18n(loc=None):
    """Initialize i18n with the configured locale dir. The environment
    variable LOCPATH can also specify a locale dir.

    @return: None
    """
    if 'LOCPATH' in os.environ:
        locdir = os.environ['LOCPATH']
    else:
        locdir = os.path.join(get_install_data(), 'share', 'locale')
    i18n.init(configdata.name.lower(), locdir, loc=loc)
    # install translated log level names
    import logging
    logging.addLevelName(logging.CRITICAL, _('CRITICAL'))
    logging.addLevelName(logging.ERROR, _('ERROR'))
    logging.addLevelName(logging.WARN, _('WARN'))
    logging.addLevelName(logging.WARNING, _('WARNING'))
    logging.addLevelName(logging.INFO, _('INFO'))
    logging.addLevelName(logging.DEBUG, _('DEBUG'))
    logging.addLevelName(logging.NOTSET, _('NOTSET'))


# initialize i18n, puts _() and _n() function into global namespace
init_i18n()


def drop_privileges():
    """Make sure to drop root privileges on POSIX systems."""
    if os.name != 'posix':
        return
    if os.geteuid() == 0:
        log.warn(LOG_CHECK, _("Running as root user; "
                       "dropping privileges by changing user to nobody."))
        import pwd
        os.seteuid(pwd.getpwnam('nobody')[3])


if hasattr(signal, "SIGUSR1"):
    # install SIGUSR1 handler
    from .decorators import signal_handler
    @signal_handler(signal.SIGUSR1)
    def print_threadstacks(sig, frame):
        """Print stack traces of all running threads."""
        log.warn(LOG_THREAD, "*** STACKTRACE START ***")
        for threadId, stack in sys._current_frames().items():
            log.warn(LOG_THREAD, "# ThreadID: %s" % threadId)
            for filename, lineno, name, line in traceback.extract_stack(stack):
                log.warn(LOG_THREAD, 'File: "%s", line %d, in %s' % (filename, lineno, name))
                line = line.strip()
                if line:
                    log.warn(LOG_THREAD, "  %s" % line)
        log.warn(LOG_THREAD, "*** STACKTRACE END ***")