#
# This file is part of Plinth.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

"""
Python action utility functions.
"""

from django.utils.translation import ugettext as _
import psutil
import socket
import subprocess


def service_is_running(servicename):
    """Return whether a service is currently running.

    Does not need to run as root.
    """
    try:
        subprocess.check_output(['systemctl', 'status', servicename])
        return True
    except subprocess.CalledProcessError:
        # If a service is not running we get a status code != 0 and
        # thus a CalledProcessError
        return False


def service_is_enabled(service_name):
    """Check if service is enabled in systemd."""
    try:
        subprocess.check_output(['systemctl', 'is-enabled', service_name])
        return True
    except subprocess.CalledProcessError:
        return False


def service_enable(service_name):
    """Enable and start a service in systemd and sysvinit using update-rc.d."""
    subprocess.call(['systemctl', 'enable', service_name])
    service_start(service_name)


def service_disable(service_name):
    """Disable and stop service in systemd and sysvinit using update-rc.d."""
    try:
        service_stop(service_name)
    except subprocess.CalledProcessError:
        pass
    subprocess.call(['systemctl', 'disable', service_name])


def service_start(service_name):
    """Start a service."""
    subprocess.call(['systemctl', 'start', service_name])


def service_stop(service_name):
    """Stop a service."""
    subprocess.call(['systemctl', 'stop', service_name])


def service_restart(service_name):
    """Restart service with systemd."""
    subprocess.call(['systemctl', 'restart', service_name])


def service_reload(service_name):
    """Reload service with systemd."""
    subprocess.call(['systemctl', 'reload', service_name])


def webserver_is_enabled(name, kind='config'):
    """Return whether a config/module/site is enabled in Apache."""
    option_map = {'config': '-c', 'site': '-s', 'module': '-m'}
    try:
        # Don't print anything on the terminal
        subprocess.check_output(['a2query', option_map[kind], name],
                                stderr=subprocess.STDOUT)
        return True
    except subprocess.CalledProcessError:
        return False


def webserver_enable(name, kind='config', apply_changes=True):
    """Enable a config/module/site in Apache.

    Restart/reload the webserver if apply_changes is True.  Return
    whether restart(True) or reload(False) is required.  If changes
    have been applied, return None.
    """
    command_map = {'config': 'a2enconf',
                   'site': 'a2ensite',
                   'module': 'a2enmod'}
    subprocess.check_output([command_map[kind], name])

    if not apply_changes:
        return kind == 'module'

    if kind == 'module':
        service_restart('apache2')
    else:
        service_reload('apache2')


def webserver_disable(name, kind='config', apply_changes=True):
    """Disable config/module/site in Apache.

    Restart/reload the webserver if apply_changes is True.  Return
    whether restart(True) or reload(False) is required.  If changes
    have been applied, return None.
    """
    command_map = {'config': 'a2disconf',
                   'site': 'a2dissite',
                   'module': 'a2dismod'}
    subprocess.check_output([command_map[kind], name])

    if not apply_changes:
        return kind == 'module'

    if kind == 'module':
        service_restart('apache2')
    else:
        service_reload('apache2')


class WebserverChange(object):
    """Context to restart/reload Apache after configuration changes."""

    def __init__(self):
        """Initialize the context object state."""
        self.restart_required = False

    def __enter__(self):
        """Return the context object so methods could be called on it."""
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        """Restart or reload the webserver.

        Don't supress exceptions.  If an exception occurs
        restart/reload the webserver based on enable/disable
        operations done so far.
        """
        if self.restart_required:
            service_restart('apache2')
        else:
            service_reload('apache2')


    def enable(self, name, kind='config'):
        """Enable a config/module/site in Apache.

        Don't apply the changes until the context is exited.
        """
        restart_required = webserver_enable(name, kind, apply_changes=False)
        self.restart_required = self.restart_required or restart_required

    def disable(self, name, kind='config'):
        """Disable a config/module/site in Apache.

        Don't apply the changes until the context is exited.
        """
        restart_required = webserver_disable(name, kind, apply_changes=False)
        self.restart_required = self.restart_required or restart_required


def diagnose_port_listening(port, kind='tcp', listen_address=None):
    """Run a diagnostic on whether a port is being listened on.

    Kind must be one of inet, inet4, inet6, tcp, tcp4, tcp6, udp,
    udp4, udp6, unix, all.  See psutil.net_connection() for more
    information.
    """
    result = _check_port(port, kind, listen_address)

    if listen_address:
        test = _('Listening on {kind} port {listen_address}:{port}') \
        .format(kind=kind, listen_address=listen_address, port=port)
    else:
        test = _('Listening on {kind} port {port}') \
        .format(kind=kind, port=port)

    return [test, 'passed' if result else 'failed']


def _check_port(port, kind='tcp', listen_address=None):
    """Return whether a port is being listened on."""
    run_kind = kind

    if kind == 'tcp4':
        run_kind = 'tcp'

    if kind == 'udp4':
        run_kind = 'udp'

    for connection in psutil.net_connections(run_kind):
        # TCP connections must have status='listen'
        if kind in ('tcp', 'tcp4', 'tcp6') and \
           connection.status != psutil.CONN_LISTEN:
            continue

        # UDP connections must have empty remote address
        if kind in ('udp', 'udp4', 'udp6') and \
           connection.raddr != ():
            continue

        # Port should match
        if connection.laddr[1] != port:
            continue

        # Listen address if requested should match
        if listen_address and connection.laddr[0] != listen_address:
            continue

        # Special additional checks only for IPv4
        if kind != 'tcp4' and kind != 'udp4':
            return True

        # Found socket is IPv4
        if connection.family == socket.AF_INET:
            return True

        # Full IPv6 address range includes mapped IPv4 address also
        if connection.laddr[0] == '::':
            return True

    return False


def diagnose_url(url, kind=None, env=None, extra_options=None, wrapper=None,
                 expected_output=None):
    """Run a diagnostic on whether a URL is accessible.

    Kind can be '4' for IPv4 or '6' for IPv6.
    """
    command = ['wget', '-q', '-O', '-', url]

    if wrapper:
        command.insert(0, wrapper)

    if extra_options:
        command.extend(extra_options)

    if kind:
        command.append({'4': '-4', '6': '-6'}[kind])

    try:
        output = subprocess.check_output(command, env=env)
        result = 'passed'
        if expected_output and expected_output not in output.decode():
            result = 'failed'
    except subprocess.CalledProcessError as exception:
        result = 'failed'
        # Authorization failed is a success
        if exception.returncode == 6:
            result = 'passed'
    except FileNotFoundError:
        result = 'error'

    if kind:
        return [_('Access URL {url} on tcp{kind}')
                .format(url=url, kind=kind), result]
    else:
        return [_('Access URL {url}').format(url=url), result]


def diagnose_url_on_all(url, extra_options=None):
    """Run a diagnostic on whether a URL is accessible."""
    results = []
    for address in get_addresses():
        if address['kind'] == '6' and ':' in address['address']:
            address['address'] = '[{0}]'.format(address['address'])

        current_url = url.format(host=address['address'])
        results.append(diagnose_url(current_url, kind=address['kind'],
                                    extra_options=extra_options))

    return results


def diagnose_netcat(host, port, input='', negate=False):
    """Run a diagnostic using netcat."""
    try:
        process = subprocess.Popen(
            ['nc', host, str(port)], stdin=subprocess.PIPE,
            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        process.communicate(input=input.encode())
        if process.returncode != 0:
            result = 'failed'
        else:
            result = 'passed'
    except Exception:
        result = 'failed'

    test = _('Connect to {host}:{port}')
    if negate:
        result = 'failed' if result == 'passed' else 'passed'
        test = _('Cannot connect to {host}:{port}')

    return [test.format(host=host, port=port), result]


def get_addresses():
    """Return a list of IP addreses and hostnames."""
    addresses = get_ip_addresses()

    hostname = get_hostname()
    addresses.append({'kind': '4', 'address': 'localhost'})
    addresses.append({'kind': '6', 'address': 'localhost'})
    addresses.append({'kind': '4', 'address': hostname})
    addresses.append({'kind': '6', 'address': hostname})

    return addresses


def get_ip_addresses():
    """Return a list of IP addresses assigned to the system."""
    addresses = []

    output = subprocess.check_output(['ip', '-o', 'addr'])
    for line in output.decode().splitlines():
        parts = line.split()
        addresses.append({'kind': '4' if parts[2] == 'inet' else '6',
                          'address': parts[3].split('/')[0]})

    return addresses


def get_hostname():
    """Return the current hostname."""
    return subprocess.check_output(['hostname']).decode().strip()