"""
NETCONF for APK Distributions server:
    adelie-services module, OpenRC edition

Copyright © 2020 Adélie Software in the Public Benefit, Inc.

Released under the terms of the NCSA license.  See the LICENSE file included
with this source distribution for more information.

SPDX-License-Identifier: NCSA
"""

import errno
import logging
import os
import pathlib
import subprocess

from netconf import error, util

from ncserver.base.service import Service, ServiceStatus
from ncserver.base.util import _, yang_dt_for_timestamp


LOGGER = logging.getLogger(__name__)
"""The object used for logging informational messages."""


M_ABI_VERSION = 1
"""The ABI version of this NETCONF module."""


M_PREFIX = "svcs"
"""The XML tag prefix for this module's tags."""


M_NS = "http://netconf.adelielinux.org/ns/service"
"""The XML namespace for this module."""


M_NAME = "adelie-services"
"""The YANG model name for this module."""


M_REVISION = "2020-09-22"
"""The YANG revision date for this module."""


M_IMPORTS = {
    'ietf-yang-types@2013-07-15': {
        'ns': "urn:ietf:params:xml:ns:yang:ietf-yang-types", 'prefix': "yang"
    }
}
"""The imported YANG modules for this module."""


def valid_name(name):
    """Determine if the given name is a valid OpenRC service name."""
    valid = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890_-."
    return all(char in valid for char in name)


def is_enabled(name):
    """Determine if this OpenRC service is enabled."""
    runlevels = (pathlib.Path('/etc/runlevels/boot'),
                 pathlib.Path('/etc/runlevels/sysinit'),
                 pathlib.Path('/etc/runlevels/default'))
    for level in runlevels:
        for service in level.iterdir():
            # Resolve the symlink.  If it's the service name, we have a match.
            if pathlib.Path(service).resolve().name == name:
                return True
    return False


def get_var(shell_like, var_name: str, default="") -> str:
    """Retrieve the value of var_name from a shell script-like file shell_like.

    :param shell_like:
    The path to the shell script-like file.

    :param str var_name:
    The name of the variable to extract.

    :param str default:
    The default value to return if the variable is not set.
    """
    script = ". /etc/init.d/functions.sh;(. {shlike} && printf %s \"${var}\")"
    script = script.format(shlike=shell_like, var=var_name)
    proc = subprocess.run(
            ['/bin/sh', '-e', '-c', script], check=True,
            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
    )
    value = proc.stdout.decode('utf-8')
    if value == "":
        return default
    return value


def check_alive(pidfile) -> bool:
    """Determine if the PID contained in a pidfile is alive."""
    pid = 0
    try:
        with open(pidfile) as fhandle:
            pid = int(fhandle.read().rstrip())
    except OSError as ose:
        if ose.errno == errno.EPERM or ose.errno == errno.EACCES:
            return True  # the pidfile cannot be accessed
        return False  # sounds bad to me
    except ValueError:
        return False  # the pidfile doesn't contain a PID

    if pid <= 0:
        return False

    try:
        os.kill(pid, 0)
    except OSError as ose:
        # If EPERM, we can't send the signal because it's alive.
        return ose.errno == errno.EPERM
    else:
        return True


class OpenRCService(Service):
    """The OpenRC implementation of the Service class."""
    def __init__(self, name):
        """Initialise the structure."""
        super().__init__()

        if not valid_name(name):
            raise NameError(_("{}: invalid service name").format(name))

        svcpath = "/etc/init.d/{name}".format(name=name)
        if not os.path.exists(svcpath):
            raise ValueError(_("{} does not exist").format(name))

        self._name = name
        self._description = get_var(svcpath, "description", name)
        self._enabled = is_enabled(name)
        # Update status and start-time.
        self.status()

    def status(self):
        """Retrieve the service's status."""
        stat = ServiceStatus.Stopped
        path = None

        status_dirs = {
                ServiceStatus.Starting: "/run/openrc/starting",
                ServiceStatus.Running: "/run/openrc/started",
                ServiceStatus.Stopping: "/run/openrc/stopping"
        }

        for value, directory in status_dirs.items():
            for service in pathlib.Path(directory).iterdir():
                if pathlib.Path(service).resolve().name == self.name:
                    stat = value
                    path = service
                    break

        if stat == ServiceStatus.Running:
            # Check if crashed
            for service in pathlib.Path("/run/openrc/daemons").iterdir():
                svcdir = pathlib.Path(service)
                if svcdir.name == self.name:
                    for daemon in svcdir.iterdir():
                        dpid = get_var(daemon, 'pidfile')
                        if dpid and not check_alive(dpid):
                            return ServiceStatus.Crashed
            # Update start-time
            self._start_time = pathlib.Path(path).lstat().st_mtime

        return stat

    def start(self):
        """Start the service."""
        if self.status() in (ServiceStatus.Starting, ServiceStatus.Running):
            return

        subprocess.Popen(["/sbin/rc-service", self.name, "start"])

    def stop(self):
        """Stop the service."""
        subprocess.Popen(["/sbin/rc-service", self.name, "stop"])

    def reload(self):
        """Reload the service's configuration, if possible."""

    def restart(self, full: bool):
        """Restart the service.

        OpenRC does not support a concept of full restart, so this parameter
        is always ignored.
        """
        subprocess.Popen(["/sbin/rc-service", self.name, "restart"])

    def __str__(self):
        return self.name

    def __repr__(self):
        return "<OpenRC service {name} ({status})>".format(
                name=self.name, status=self.status()
        )


def service_list():
    """Return the list of services available on this device."""
    services = list()

    for service in pathlib.Path('/etc/init.d').iterdir():
        if service.suffix == '.sh':
            continue

        services.append(OpenRCService(service.name))

    return services


def info(service: str) -> OpenRCService:
    """Return the Service object associated with the specified service.

    :param str service:
    The name of the service to look up.

    :returns:
    The Service object, or None if a service with that name does not exist.
    """
    try:
        return OpenRCService(service)
    except ValueError:
        return None


def running(node):
    """Retrieve the service configuration for this device."""
    svcs = util.subelm(node, 'svcs:services')

    for service in service_list():
        svcnode = util.subelm(svcs, 'svcs:service')
        svcnode.append(util.leaf_elm('svcs:name', service.name))
        svcnode.append(util.leaf_elm('svcs:enabled', service.enabled))


def operational(node):
    """Retrieve the service state for this device."""
    svcs = util.subelm(node, 'svcs:services')

    for service in service_list():
        svcnode = util.subelm(svcs, 'svcs:service')
        svcnode.append(util.leaf_elm('svcs:name', service.name))
        svcnode.append(util.leaf_elm('svcs:description', service.description))
        svcnode.append(util.leaf_elm('svcs:enabled', service.enabled))
        svcnode.append(util.leaf_elm(
            'svcs:status', service.status().name.lower()
        ))
        if service.status() == ServiceStatus.Running:
            svcnode.append(util.leaf_elm(
                'svcs:start-time', yang_dt_for_timestamp(service.start_time)
            ))


def edit(session, rpc, node, def_op):
    """Edit the service configuration for this device."""