#
# Copyright 2025, Martin Owens <doctormo@gmail.com>
#
# This library 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; either
# version 3.0 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.
#
# pylint: disable=logging-format-interpolation,too-many-lines
"""
from crontab import CronTab
import sys
import tempfile

# Create a new non-installed crontab
cron = CronTab(tab='')
job  = cron.new(command='/usr/bin/echo')

job.minute.during(5,50).every(5)
job.hour.every(4)

job.dow.on('SUN')
job.month.during('APR', 'JUN')
job.month.also.during('OCT', 'DEC')

job.every(2).days()
job.setall(1, 12, None, None, None)

job2 = cron.new(command='/foo/bar', comment='SomeID')
job2.every_reboot()

jobs = list(cron.find_command('bar'))
job3 = jobs[0]
job3.clear()
job3.minute.every(1)

sys.stdout.write(str(cron.render()))

job3.enable(False)

for job4 in cron.find_command('echo'):
    sys.stdout.write(job4)

for job5 in cron.find_comment('SomeID'):
    sys.stdout.write(job5)

for job6 in cron:
    sys.stdout.write(job6)

for job7 in cron:
    job7.every(3).hours()
    sys.stdout.write(job7)
    job7.every().dow()

cron.remove_all(command='/foo/bar')
cron.remove_all(comment='This command')
cron.remove_all(time='* * * * *')
cron.remove_all()

output = cron.render()

cron.write()

with tempfile.NamedTemporaryFile() as fp:
    cron.write(filename=fp.name)

#cron.write_to_user(user=True)

#cron.write_to_user(user='root')

# Croniter Extentions allow you to ask for the scheduled job times, make
# sure you have croniter installed, it's not a hard dependancy.

job3.schedule().get_next()
job3.schedule().get_prev()

"""

import os
import re
import shlex

import types
import codecs
import logging
import tempfile
import platform
import subprocess as sp

from calendar import monthrange
from time import sleep
from datetime import time, date, datetime, timedelta
from collections import OrderedDict
from shutil import which

__pkgname__ = 'python-crontab'
__version__ = '3.3.0'

ITEMREX = re.compile(r'^\s*([^@#\s]+)\s+([^@#\s]+)\s+([^@#\s]+)\s+([^@#\s]+)'
                     r'\s+([^@#\s]+)\s+([^\n]*?)(\s+#\s*([^\n]*)|$)')
SPECREX = re.compile(r'^\s*@(\w+)\s([^#\n]*)(\s+#\s*([^\n]*)|$)')
DEVNULL = ">/dev/null 2>&1"

WEEK_ENUM = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat', 'sun']

MONTH_ENUM = [None, 'jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug',
              'sep', 'oct', 'nov', 'dec']

SPECIALS_CONVERSION = True
SPECIALS = {"reboot":   '@reboot',
            "hourly":   '0 * * * *',
            "daily":    '0 0 * * *',
            "weekly":   '0 0 * * 0',
            "monthly":  '0 0 1 * *',
            "yearly":   '0 0 1 1 *',
            "annually": '0 0 1 1 *',
            "midnight": '0 0 * * *'}

SPECIAL_IGNORE = ['midnight', 'annually']

S_INFO = [
    {'max': 59, 'min': 0, 'name': 'Minutes'},
    {'max': 23, 'min': 0, 'name': 'Hours'},
    {'max': 31, 'min': 1, 'name': 'Day of Month'},
    {'max': 12, 'min': 1, 'name': 'Month', 'enum': MONTH_ENUM},
    {'max': 6, 'min': 0, 'name': 'Day of Week', 'enum': WEEK_ENUM},
]

# Detect Python3 and which OS for temperments.
WINOS = platform.system() == 'Windows'
POSIX = os.name == 'posix'
SYSTEMV = not WINOS and os.uname()[0] in ["SunOS", "AIX", "HP-UX"]
SYSTEMV = not WINOS and (
    os.uname()[0] in ["SunOS", "AIX", "HP-UX"]
    or
    os.uname()[4] in ["mips"]
)

# Switch this on if you want your crontabs to have zero padding.
ZERO_PAD = False

LOG = logging.getLogger('crontab')

CRON_COMMAND = which("crontab") or "/usr/bin/crontab"
SHELL = os.environ.get('SHELL', '/bin/sh')
# The shell won't actually work on windows here, but
# it should be updated later in the below conditional.

# pylint: disable=W0622,invalid-name,too-many-public-methods
# pylint: disable=function-redefined,too-many-instance-attributes
current_user = lambda: None
if not WINOS:
    import pwd
    def current_user():
        """Returns the username of the current user"""
        return pwd.getpwuid(os.getuid())[0]


def _str(text):
    """Convert to the best string format for this python version"""
    if isinstance(text, bytes):
        return text.decode('utf-8')
    return text


class Process:
    """Runs a program and orders the arguments for compatability.

    a. keyword args are flags and always appear /before/ arguments for bsd
    """
    def __init__(self, cmd, *args, **flags):
        cmd_args = tuple(shlex.split(cmd, posix=flags.pop('posix', POSIX)))
        self.env = flags.pop('env', None)
        for (key, value) in flags.items():
            if len(key) == 1:
                cmd_args += (f"-{key}",)
                if value is not None:
                    cmd_args += (str(value),)
            else:
                cmd_args += (f"--{key}={value}",)
        self.args = tuple(arg for arg in (cmd_args + tuple(args)) if arg)
        self.has_run = False
        self.stdout = None
        self.stderr = None
        self.returncode = None

    def _run(self):
        """Run this process and return the popen process object"""
        return sp.Popen(self.args, stdout=sp.PIPE, stderr=sp.PIPE, env=self.env)

    def run(self):
        """Run this process and store whatever is returned"""
        process = self._run()
        (out, err) = process.communicate()
        self.returncode = process.returncode
        self.stdout = out.decode("utf-8")
        self.stderr = err.decode("utf-8")
        return self

    def __str__(self):
        return self.stdout.strip()

    def __repr__(self):
        return f"Process({self.args})"

    def __int__(self):
        return self.returncode

    def __eq__(self, other):
        return str(self) == other


class CronTab:
    """
    Crontab object which can access any time based cron using the standard.

    user    - Set the user of the crontab (default: None)
      * 'user' = Load from $username's crontab (instead of tab or tabfile)
      * None   = Don't load anything from any user crontab.
      * True   = Load from current $USER's crontab (unix only)
      * False  = This is a system crontab, each command has a username

    tab     - Use a string variable as the crontab instead of installed crontab
    tabfile - Use a file for the crontab instead of installed crontab
    log     - Filename for logfile instead of /var/log/syslog
    """
    def __init__(self, user=None, tab=None, tabfile=None, log=None):
        self.lines = None
        self.crons = None
        self.filen = None
        self.cron_command = CRON_COMMAND
        self.env = None
        self._parked_env = OrderedDict()
        # Protect windows users
        self.root = not WINOS and os.getuid() == 0
        # Storing user flag / username
        self._user = user
        # Load string or filename as inital crontab
        self.intab = tab
        self.tabfile = tabfile
        self.read(tabfile)
        self._log = log

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.write()

    @property
    def log(self):
        """Returns the CronLog object for this tab (user or root tab only)"""
        from cronlog import CronLog # pylint: disable=import-outside-toplevel
        if self._log is None or isinstance(self._log, str):
            self._log = CronLog(self._log, user=self.user or 'root')
        return self._log

    @property
    def user(self):
        """Return user's username of this crontab if applicable"""
        if self._user is True:
            return current_user()
        return self._user

    @property
    def user_opt(self):
        """Returns the user option for the crontab commandline"""
        # Fedora and Mac require the current user to not specify
        # But Ubuntu/Debian doesn't care. Be careful here.
        if self._user and self._user is not True:
            if self._user != current_user():
                return {'u': self._user}
        return {}

    def __setattr__(self, name, value):
        """Catch setting crons and lines directly"""
        if name == 'lines' and value:
            for line in value:
                self.append(CronItem.from_line(line, cron=self), line, read=True)
        elif name == 'crons' and value:
            raise AttributeError("You can NOT set crons attribute directly")
        else:
            super().__setattr__(name, value)

    def read(self, filename=None):
        """
        Read in the crontab from the system into the object, called
        automatically when listing or using the object. use for refresh.
        """
        self.crons = []
        self.lines = []
        self.env = OrderedVariableList()
        lines = []

        if self.intab is not None:
            lines = self.intab.split('\n')

        elif filename:
            self.filen = filename
            with codecs.open(filename, 'r', encoding='utf-8') as fhl:
                lines = fhl.readlines()

        elif self.user:
            try:
                process = Process(self.cron_command, l='', **self.user_opt).run()
            except FileNotFoundError:
                raise IOError(f"Can't read crontab; No crontab program '{self.cron_command}'")
            if process.stderr and 'no crontab for' not in process.stderr:
                raise IOError(f"Read crontab {self.user}: {process.stderr}")
            lines = process.stdout.split("\n")

        self.lines = lines

    def append(self, item, line='', read=False, before=None):
        """Append a CronItem object to this CronTab

        Keyword arguments:
         item   - The CronItem object to append
         line   - The textual line which this item is.
         read   - Internal use only
         before - Append before this CronItem, comment regex or generator
        """
        cron_id = len(self.crons)
        line_id = len(self.lines)

        if isinstance(before, (str, type(ITEMREX))):
            before = self.find_comment(before)

        try:
            if isinstance(before, (list, tuple, types.GeneratorType)):
                *_, before = before

            if before is not None:
                cron_id = self.crons.index(before)
                line_id = self.lines.index(before)

        except ValueError as err:
            raise ValueError("Can not find CronItem in crontab to insert before") from err

        if item.is_valid():
            item.env.update(self._parked_env)
            self._parked_env = OrderedDict()
            if read and not item.comment and self.lines and \
              self.lines[-1] and self.lines[-1][0] == '#':
                item.set_comment(self.lines.pop()[1:].strip(), True)

            self.crons.insert(cron_id, item)
            self.lines.insert(line_id, item)
        elif '=' in line:
            if ' ' not in line or line.index('=') < line.index(' '):
                (name, value) = line.split('=', 1)
                value = value.strip()
                for quot in "\"'":
                    if value[0] == quot and value[-1] == quot:
                        value = value.strip(quot)
                        break
                self._parked_env[name.strip()] = value
        else:
            if not self.crons and self._parked_env:
                self.env.update(self._parked_env)
                self._parked_env = OrderedDict()
            self.lines.append(line.replace('\n', ''))

    def write(self, filename=None, user=None, errors=False):
        """Write the crontab to it's source or a given filename."""
        if filename:
            self.filen = filename
        elif user is not None:
            self.filen = None
            self.intab = None
            self._user = user

        # Add to either the crontab or the internal tab.
        if self.intab is not None:
            self.intab = self.render()
            # And that's it if we never saved to a file
            if not self.filen:
                return

        if self.filen:
            fileh = open(self.filen, 'wb') # pylint: disable=consider-using-with
        else:
            filed, path = tempfile.mkstemp()
            fileh = os.fdopen(filed, 'wb')

        fileh.write(self.render(errors=errors).encode('utf-8'))
        fileh.close()

        if not self.filen:
            # Add the entire crontab back to the user crontab
            if not self.user:
                os.unlink(path)
                raise IOError("Please specify user or filename to write.")

            try:
                proc = Process(self.cron_command, path, **self.user_opt)._run()
            except FileNotFoundError:
                raise IOError(f"Can't write crontab, no crontab program '{self.cron_command}'")
            ret = proc.wait()
            if ret != 0:
                msg = proc.stderr.read()
                raise IOError(f"Program Error: {self.cron_command} returned {ret}: {msg}")
            proc.stdout.close()
            proc.stderr.close()
            os.unlink(path)

    def write_to_user(self, user=True):
        """Write the crontab to a user (or root) instead of a file."""
        return self.write(user=user)

    def run_pending(self, **kwargs):
        """Run all commands in this crontab if pending (generator)"""
        for job in self:
            ret = job.run_pending(**kwargs)
            if ret not in [None, -1]:
                yield ret

    def run_scheduler(self, timeout=-1, cadence=60, warp=False):
        """Run the CronTab as an internal scheduler (generator)"""
        count = 0
        while count != timeout:
            now = datetime.now()
            if warp:
                now += timedelta(seconds=count * 60)
            for value in self.run_pending(now=now):
                yield value

            sleep(cadence)
            count += 1

    def render(self, errors=False):
        """Render this crontab as it would be in the crontab.

        errors - Should we not comment out invalid entries and cause errors?
        """
        crons = []
        for line in self.lines:
            if isinstance(line, (str, str)):
                if line.strip().startswith('#') or not line.strip():
                    crons.append(line.strip())
                elif not errors:
                    crons.append('# DISABLED LINE\n# ' + line)
                else:
                    raise ValueError(f"Invalid line: {line}")
            elif isinstance(line, CronItem):
                if not line.is_valid() and not errors:
                    line.enabled = False
                crons.append(line.render().strip())

        # Environment variables are attached to cron lines so order will
        # always work no matter how you add lines in the middle of the stack.
        result = str(self.env) + '\n'.join(crons)
        if result and result[-1] not in ('\n', '\r'):
            result += '\n'
        return result

    def new(self, command='', comment='', user=None, pre_comment=False, before=None): # pylint: disable=too-many-arguments
        """
        Create a new CronItem and append it to the cron.

        Keyword arguments:
         command     - The command that will be run.
         comment     - The comment that should be associated with this command.
         user        - For system cron tabs, the user this command should run as.
         pre_comment - If true the comment will apear just before the command line.
         before      - Append this command before this item instead of at the end.

        Returns the new CronItem object.
        """
        if not user and self.user is False:
            raise ValueError("User is required for system crontabs.")
        item = CronItem(command, comment, user=user, pre_comment=pre_comment)
        item.cron = self
        self.append(item, before=before)
        return item

    def find_command(self, command):
        """Return an iter of jobs matching any part of the command."""
        for job in list(self.crons):
            if isinstance(command, type(ITEMREX)):
                if command.findall(job.command):
                    yield job
            elif command in job.command:
                yield job

    def find_comment(self, comment):
        """Return an iter of jobs that match the comment field exactly."""
        for job in list(self.crons):
            if isinstance(comment, type(ITEMREX)):
                if comment.findall(job.comment):
                    yield job
            elif comment == job.comment:
                yield job

    def find_time(self, *args):
        """Return an iter of jobs that match this time pattern"""
        for job in list(self.crons):
            if job.slices == CronSlices(*args):
                yield job

    @property
    def commands(self):
        """Return a generator of all unqiue commands used in this crontab"""
        returned = []
        for cron in self.crons:
            if cron.command not in returned:
                yield cron.command
                returned.append(cron.command)

    @property
    def comments(self):
        """Return a generator of all unique comments/Id used in this crontab"""
        returned = []
        for cron in self.crons:
            if cron.comment and cron.comment not in returned:
                yield cron.comment
                returned.append(cron.comment)

    def remove_all(self, *args, **kwargs):
        """Removes all crons using the stated command OR that have the
        stated comment OR removes everything if no arguments specified.

           command - Remove all with this command
           comment - Remove all with this comment or ID
           time    - Remove all with this time code
        """
        if args:
            raise AttributeError("Invalid use: remove_all(command='cmd')")
        if 'command' in kwargs:
            return self.remove(*self.find_command(kwargs['command']))
        if 'comment' in kwargs:
            return self.remove(*self.find_comment(kwargs['comment']))
        if 'time' in kwargs:
            return self.remove(*self.find_time(kwargs['time']))
        return self.remove(*self.crons[:])

    def remove(self, *items):
        """Remove a selected cron from the crontab."""
        result = 0
        for item in items:
            if isinstance(item, (list, tuple, types.GeneratorType)):
                for subitem in item:
                    result += self._remove(subitem)
            elif isinstance(item, CronItem):
                result += self._remove(item)
            else:
                raise TypeError("You may only remove CronItem objects, "\
                    "please use remove_all() to specify by name, id, etc.")
        return result

    def _remove(self, item):
        """Internal removal of an item"""
        # Manage siblings when items are deleted
        for sibling in self.lines[self.lines.index(item)+1:]:
            if isinstance(sibling, CronItem):
                env = sibling.env
                sibling.env = item.env
                sibling.env.update(env)
                sibling.env.job = sibling
                break
            if sibling != '':
                break
            self.lines.remove(sibling)

        self.crons.remove(item)
        self.lines.remove(item)
        return 1

    def __repr__(self):
        kind = 'System ' if self._user is False else ''
        if self.filen:
            return f"<{kind}CronTab '{self.filen}'>"
        if self.user and not self.user_opt:
            return "<My CronTab>"
        if self.user:
            return f"<User CronTab '{self.user}'>"
        return f"<Unattached {kind}CronTab>"

    def __iter__(self):
        """Return generator so we can track jobs after removal"""
        for job in list(self.crons.__iter__()):
            yield job

    def __getitem__(self, i):
        return self.crons[i]

    def __len__(self):
        return len(self.crons)

    def __str__(self):
        return self.render()


class CronItem:
    """
    An item which objectifies a single line of a crontab and
    May be considered to be a cron job object.
    """
    def __init__(self, command='', comment='', user=None, pre_comment=False):
        self.cron = None
        self.user = user
        self.valid = False
        self.enabled = True
        self.special = False
        self.comment = None
        self.command = None
        self.last_run = None
        self.env = OrderedVariableList(job=self)

        # Marker labels Ansible jobs etc
        self.pre_comment = False
        self.marker = None
        self.stdin = None
        self._log = None

        # Initalise five cron slices using static info.
        self.slices = CronSlices()

        self.set_comment(comment, pre_comment)

        if command:
            self.set_command(command)

    def __hash__(self):
        return hash((self.command, self.comment, self.hour, self.minute, self.dow))

    def __eq__(self, other):
        if not isinstance(other, CronItem):
            return False
        return self.__hash__() == other.__hash__()

    @classmethod
    def from_line(cls, line, user=None, cron=None):
        """Generate CronItem from a cron-line and parse out command and comment"""
        obj = cls(user=user)
        obj.cron = cron
        obj.parse(line.strip())
        return obj

    def delete(self):
        """Delete this item and remove it from it's parent"""
        if not self.cron:
            raise UnboundLocalError("Cron item is not in a crontab!")
        self.cron.remove(self)

    def set_command(self, cmd, parse_stdin=False):
        """Set the command and filter as needed"""
        if parse_stdin:
            cmd = cmd.replace('%', '\n').replace('\\\n', '%')
            if '\n' in cmd:
                cmd, self.stdin = cmd.split('\n', 1)
        self.command = _str(cmd.strip())
        self.valid = True

    def set_comment(self, cmt, pre_comment=False):
        """Set the comment and don't filter, pre_comment indicates comment appears
        before the cron, otherwise it appears ont he same line after the command.
        """
        if cmt and cmt[:8] == 'Ansible:':
            self.marker = 'Ansible'
            cmt = cmt[8:].lstrip()
            pre_comment = True

        self.comment = cmt
        self.pre_comment = pre_comment

    def parse(self, line):
        """Parse a cron line string and save the info as the objects."""
        line = _str(line)
        if not line or line[0] == '#':
            self.enabled = False
            line = line.strip().lstrip('#').strip()
        # We parse all lines so we can detect disabled entries.
        self._set_parse(ITEMREX.findall(line), line)
        self._set_parse(SPECREX.findall(line), line)

    def _set_parse(self, result, line=""):
        """Set all the parsed variables into the item"""
        if not result:
            return
        self.comment = result[0][-1]
        if self.cron.user is False:
            # Special flag to look for per-command user
            ret = result[0][-3].split(None, 1)
            self.set_command(ret[-1], True)
            if len(ret) == 2:
                self.user = ret[0]
            else:
                # Disabled jobs might be ordinary comments, so log as DEBUG
                level = logging.ERROR if self.enabled else logging.DEBUG
                self.valid = False
                self.enabled = False
                LOG.log(level,
                        str("Missing user or command in system cron %s: %s"),
                        '' if self.cron is None else (self.cron.tabfile or ''),
                        line)
        else:
            self.set_command(result[0][-3], True)
        try:
            self.setall(*result[0][:-3])
        except (ValueError, KeyError) as err:
            if self.enabled:
                LOG.error(str(err))
            self.valid = False
            self.enabled = False

    def enable(self, enabled=True):
        """Set if this cron job is enabled or not"""
        if enabled in [True, False]:
            self.enabled = enabled
        return self.enabled

    def is_enabled(self):
        """Return true if this job is enabled (not commented out)"""
        return self.enabled

    def is_valid(self):
        """Return true if this job is valid"""
        return self.valid

    def render(self):
        """Render this set cron-job to a string"""
        if not self.is_valid() and self.enabled:
            raise ValueError('Refusing to render invalid crontab.'
                             ' Disable to continue.')
        command = _str(self.command).replace('%', '\\%')
        user = ''
        if self.cron and self.cron.user is False:
            if not self.user:
                raise ValueError("Job to system-cron format, no user set!")
            user = self.user + ' '
        rend = self.slices.render()
        result = f"{rend} {user}{command}"
        if self.stdin:
            result += ' %' + self.stdin.replace('\n', '%')
        if not self.enabled:
            result = "# " + result
        if self.comment:
            comment = self.comment = _str(self.comment)
            if self.marker:
                comment = f"#{self.marker}: {comment}"
            else:
                comment = "# " + comment

            if SYSTEMV or self.pre_comment or self.stdin:
                result = comment + "\n" + result
            else:
                result += ' ' + comment

        return str(self.env) + result

    def every_reboot(self):
        """Set to every reboot instead of a time pattern: @reboot"""
        self.clear()
        return self.slices.setall('@reboot')

    def every(self, unit=1):
        """
        Replace existing time pattern with a single unit, setting all lower
        units to first value in valid range.

        For instance job.every(3).days() will be `0 0 */3 * *`
        while job.day().every(3) would be `* * */3 * *`

        Many of these patterns exist as special tokens on Linux, such as
        `@midnight` and `@hourly`
        """
        return Every(self.slices, unit)

    def setall(self, *args):
        """Replace existing time pattern with these five values given as args:

           job.setall("1 2 * * *")
           job.setall(1, 2) == '1 2 * * *'
           job.setall(0, 0, None, '>', 'SUN') == '0 0 * 12 SUN'
        """
        return self.slices.setall(*args)

    def clear(self):
        """Clear the special and set values"""
        return self.slices.clear()

    def frequency(self, year=None):
        """Returns the number of times this item will execute in a given year
           (defaults to this year)
        """
        return self.slices.frequency(year=year)

    def frequency_at_hour(self, year=None, month=None, day=None, hour=None):
        """Returns the number of times this item will execute in a given hour
           (defaults to this hour)
        """
        return self.slices.frequency_at_hour(year=year, month=month, day=day, hour=hour)

    def frequency_at_day(self, year=None, month=None, day=None):
        """Returns the number of times this item will execute in a given day
           (defaults to today)
        """
        return self.slices.frequency_at_day(year=year, month=month, day=day)

    def frequency_at_month(self, year=None, month=None):
        """Returns the number of times this item will execute in a given month
           (defaults to this month)
        """
        return self.slices.frequency_at_month(year=year, month=month)

    def frequency_at_year(self, year=None):
        """Returns the number of times this item will execute in a given year
           (defaults to this year)
        """
        return self.slices.frequency_at_year(year=year)

    def frequency_per_year(self, year=None):
        """Returns the number of /days/ this item will execute on in a year
           (defaults to this year)
        """
        return self.slices.frequency_per_year(year=year)

    def frequency_per_day(self):
        """Returns the number of time this item will execute in any day"""
        return self.slices.frequency_per_day()

    def frequency_per_hour(self):
        """Returns the number of times this item will execute in any hour"""
        return self.slices.frequency_per_hour()

    def run_pending(self, now=None):
        """Runs the command if scheduled"""
        now = now or datetime.now()
        if self.is_enabled():
            if self.last_run is None:
                self.last_run = now

            next_time = self.schedule(self.last_run).get_next()
            if next_time < now:
                self.last_run = now
                return self.run()
        return -1

    def run(self):
        """Runs the given command as a pipe"""
        env = os.environ.copy()
        env.update(self.env.all())
        shell = self.env.get('SHELL', SHELL)
        process = Process(shell, '-c', self.command, env=env).run()
        if process.stderr:
            LOG.error(process.stderr)
        return process

    def schedule(self, date_from=None):
        """Return a croniter schedule if available."""
        if not date_from:
            date_from = datetime.now()
        try:
            # Croniter is an optional import
            from croniter.croniter import croniter # pylint: disable=import-outside-toplevel
        except ImportError as err:
            raise ImportError("Croniter not available. Please install croniter"
                              " python module via pip or your package manager") from err
        return croniter(self.slices.clean_render(), date_from, ret_type=datetime)

    def description(self, **kw):
        """
        Returns a description of the crontab's schedule (if available)

        **kw - Keyword arguments to pass to cron_descriptor (see docs)
        """
        try:
            from cron_descriptor import ExpressionDescriptor # pylint: disable=import-outside-toplevel
        except ImportError as err:
            raise ImportError("cron_descriptor not available. Please install"\
              "cron_descriptor python module via pip or your package manager") from err

        exdesc = ExpressionDescriptor(self.slices.clean_render(), **kw)
        return exdesc.get_description()

    @property
    def log(self):
        """Return a cron log specific for this job only"""
        if not self._log and self.cron:
            self._log = self.cron.log.for_program(self.command)
        return self._log

    @property
    def minute(self):
        """Return the minute slice"""
        return self.slices[0]

    @property
    def minutes(self):
        """Same as minute"""
        return self.minute

    @property
    def hour(self):
        """Return the hour slice"""
        return self.slices[1]

    @property
    def hours(self):
        """Same as hour"""
        return self.hour

    @property
    def day(self):
        """Return the day slice"""
        return self.dom

    @property
    def dom(self):
        """Return the day-of-the month slice"""
        return self.slices[2]

    @property
    def month(self):
        """Return the month slice"""
        return self.slices[3]

    @property
    def months(self):
        """Same as month"""
        return self.month

    @property
    def dow(self):
        """Return the day of the week slice"""
        return self.slices[4]

    def __repr__(self):
        return f"<CronItem '{self}'>"

    def __len__(self):
        return len(str(self))

    def __getitem__(self, key):
        return self.slices[key]

    def __lt__(self, value):
        return self.frequency() < CronSlices(value).frequency()

    def __gt__(self, value):
        return self.frequency() > CronSlices(value).frequency()

    def __str__(self):
        return self.render()


class Every:
    """Provide an interface to the job.every() method:
        Available Calls:
          minute, minutes, hour, hours, dom, doms, month, months, dow, dows

       Once run all units will be cleared (set to *) then proceeding units
       will be set to '0' and the target unit will be set as every x units.
    """
    def __init__(self, item, units):
        self.slices = item
        self.unit = units
        for (key, name) in enumerate(['minute', 'hour', 'dom', 'month', 'dow',
                                      'min', 'hour', 'day', 'moon', 'weekday']):
            setattr(self, name, self.set_attr(key % 5))
            setattr(self, name+'s', self.set_attr(key % 5))

    def set_attr(self, target):
        """Inner set target, returns function"""
        def innercall():
            """Returned inner call for setting slice targets"""
            self.slices.clear()
            # Day-of-week is actually a level 2 set, not level 4.
            for key in range(target == 4 and 2 or target):
                self.slices[key].on('<')
            self.slices[target].every(self.unit)
        return innercall

    def year(self):
        """Special every year target"""
        if self.unit > 1:
            raise ValueError(f"Invalid value '{self.unit}', outside 1 year")
        self.slices.setall('@yearly')


class CronSlices(list):
    """Controls a list of five time 'slices' which reprisent:
        minute frequency, hour frequency, day of month frequency,
        month requency and finally day of the week frequency.
     """
    def __init__(self, *args):
        super().__init__([CronSlice(info) for info in S_INFO])
        self.special = None
        self.setall(*args)
        self.is_valid = self.is_self_valid

    def is_self_valid(self, *args):
        """Object version of is_valid"""
        return CronSlices.is_valid(*(args or (self,)))

    @classmethod
    def is_valid(cls, *args): #pylint: disable=method-hidden
        """Returns true if the arguments are valid cron pattern"""
        try:
            return bool(cls(*args))
        except (ValueError, KeyError):
            return False

    def setall(self, *slices):
        """Parses the various ways date/time frequency can be specified"""
        self.clear()
        if len(slices) == 1:
            (slices, self.special) = self._parse_value(slices[0])
            if slices[0] == '@reboot':
                return
        if id(slices) == id(self):
            raise AssertionError("Can not set cron to itself!")
        for set_a, set_b in zip(self, slices):
            set_a.parse(set_b)

    @staticmethod
    def _parse_value(value):
        """Parse a single value into an array of slices"""
        if isinstance(value, str) and value:
            return CronSlices._parse_str(value)
        if isinstance(value, CronItem):
            return value.slices, None
        if isinstance(value, datetime):
            return [value.minute, value.hour, value.day, value.month, '*'], None
        if isinstance(value, time):
            return [value.minute, value.hour, '*', '*', '*'], None
        if isinstance(value, date):
            return [0, 0, value.day, value.month, '*'], None
            # It might be possible to later understand timedelta objects
            # but there's no convincing mathematics to do the conversion yet.
        if not isinstance(value, (list, tuple)):
            typ = type(value).__name__
            raise ValueError(f"Unknown type: {typ}")
        return value, None

    @staticmethod
    def _parse_str(value):
        """Parse a string which contains slice information"""
        key = value.lstrip('@').lower()
        if value.count(' ') == 4:
            return value.strip().split(' '), None
        if key in SPECIALS:
            return SPECIALS[key].split(' '), '@' + key
        if value.startswith('@'):
            raise ValueError(f"Unknown special '{value}'")
        return [value], None

    def clean_render(self):
        """Return just numbered parts of this crontab"""
        return ' '.join([str(s) for s in self])

    def render(self):
        "Return just the first part of a cron job (the numbers or special)"
        slices = self.clean_render()
        if self.special and SPECIALS_CONVERSION is not False:
            if self.special == '@reboot' or \
                    SPECIALS[self.special.strip('@')] == slices:
                return self.special
        if not SYSTEMV and SPECIALS_CONVERSION is True:
            for (name, value) in SPECIALS.items():
                if value == slices and name not in SPECIAL_IGNORE:
                    return f"@{name}"
        return slices

    def clear(self):
        """Clear the special and set values"""
        self.special = None
        for item in self:
            item.clear()

    def frequency(self, year=None):
        """Return frequence per year times frequency per day"""
        return self.frequency_per_year(year=year) * self.frequency_per_day()

    def frequency_per_year(self, year=None):
        """Returns the number of times this item will execute
           in a given year (default is this year)"""
        result = 0
        if not year:
            year = date.today().year

        weekdays = list(self[4])

        for month in self[3]:
            for day in self[2]:
                try:
                    if (date(year, month, day).weekday() + 1) % 7 in weekdays:
                        result += 1
                except ValueError:
                    continue
        return result

    def frequency_per_day(self):
        """Returns the number of times this item will execute in any day"""
        return len(self[0]) * len(self[1])

    def frequency_per_hour(self):
        """Returns the number of times this item will execute in any hour"""
        return len(self[0])

    def frequency_at_year(self, year=None):
        """Returns the number of /days/ this item will execute
           in a given year (default is this year)"""
        if not year:
            year = date.today().year

        total = 0
        for month in range(1, 13):
            total += self.frequency_at_month(year, month)
        return total

    def frequency_at_month(self, year=None, month=None):
        """Returns the number of times this item will execute in given month
        (default: current month)
        """
        if year is None and month is None:
            year = date.today().year
            month = date.today().month
        elif year is None or month is None:
            raise ValueError(
                f"One of more arguments undefined: year={year}, month={month}")

        total = 0
        if month in self[3]:
            # Calculate amount of days of specific month
            days = monthrange(year, month)[1]
            for day in range(1, days + 1):
                total += self.frequency_at_day(year, month, day)
        return total

    def frequency_at_day(self, year=None, month=None, day=None):
        """Returns the number of times this item will execute in a day
        (default: any executed day)
        """
        # If arguments provided, all needs to be provided
        test_none = [x is None for x in [year, month, day]]

        if all(test_none):
            return len(self[0]) * len(self[1])

        if any(test_none):
            raise ValueError(
                f"One of more arguments undefined: year={year}, month={month}, day={day}")

        total = 0
        if day in self[2]:
            for hour in range(24):
                total += self.frequency_at_hour(year, month, day, hour)
        return total

    def frequency_at_hour(self, year=None, month=None, day=None, hour=None):
        """Returns the number of times this item will execute in a hour
        (default: any executed hour)
        """
        # If arguments provided, all needs to be provided
        test_none = [x is None for x in [year, month, day, hour]]

        if all(test_none):
            return len(self[0])

        if any(test_none):
            raise ValueError(
                f"One of more arguments undefined: year={year}, month={month}, day={day}, hour={hour}")

        result = 0
        weekday = date(year, month, day).weekday()

        # Check if scheduled for execution at defined moment
        if hour in self[1] and \
           day in self[2] and \
           month in self[3] and \
           ((weekday + 1) % 7) in self[4]:
            result = len(self[0])

        return result

    def __str__(self):
        return self.render()

    def __eq__(self, arg):
        return self.render() == CronSlices(arg).render()


class SundayError(KeyError):
    """Sunday was specified as 7 instead of 0"""

class Also:
    """Link range values together (appending instead of replacing)"""
    def __init__(self, obj):
        self.obj = obj

    def every(self, *a):
        """Also every one of these"""
        return self.obj.every(*a, also=True)

    def on(self, *a):
        """Also on these"""
        return self.obj.on(*a, also=True)

    def during(self, *a):
        """Also during these"""
        return self.obj.during(*a, also=True)

class CronSlice:
    """Cron slice object which shows a time pattern"""
    def __init__(self, info, value=None):
        if isinstance(info, int):
            info = S_INFO[info]
        self.min = info.get('min', None)
        self.max = info.get('max', None)
        self.name = info.get('name', None)
        self.enum = info.get('enum', None)
        self.parts = []
        if value:
            self.parse(value)

    def __hash__(self):
        return hash(str(self))

    def parse(self, value):
        """Set values into the slice."""
        self.clear()
        if value is not None:
            for part in str(value).split(','):
                if part.find("/") > 0 or part.find("-") > 0 or part == '*':
                    self.parts += self.get_range(part)
                    continue
                self.parts.append(self.parse_value(part, sunday=0))

    def render(self, resolve=False):
        """Return the slice rendered as a crontab.

        resolve - return integer values instead of enums (default False)

        """
        if not self.parts:
            return '*'
        return _render_values(self.parts, ',', resolve)

    def __repr__(self):
        return f"<CronSlice '{self}'>"

    def __eq__(self, value):
        return str(self) == str(value)

    def __str__(self):
        return self.render()

    def every(self, n_value, also=False):
        """Set the every X units value"""
        n_value = self.test_value(n_value)
        if not also:
            self.clear()
        self.parts += self.get_range(int(n_value))
        return self.parts[-1]

    def on(self, *n_value, **opts):
        """Set the time values to the specified placements."""
        if not opts.get('also', False):
            self.clear()
        for set_a in n_value:
            self.parts += (self.parse_value(set_a, sunday=0),)
        return self.parts

    def during(self, vfrom, vto, also=False):
        """Set the During value, which sets a range"""
        if not also:
            self.clear()
        self.parts += self.get_range(str(vfrom) + '-' + str(vto))
        return self.parts[-1]

    @property
    def also(self):
        """Appends rather than replaces the new values"""
        return Also(self)

    def clear(self):
        """clear the slice ready for new vaues"""
        self.parts = []

    def get_range(self, *vrange):
        """Return a cron range for this slice"""
        ret = CronRange(self, *vrange)
        if ret.dangling is not None:
            return [ret.dangling, ret]
        return [ret]

    def __iter__(self):
        """Return the entire element as an iterable"""
        ret = {}
        # An empty part means '*' which is every(1)
        if not self.parts:
            self.every(1)
        for part in self.parts:
            if isinstance(part, CronRange):
                for bit in part.range():
                    ret[bit] = 1
            else:
                ret[int(part)] = 1
        for val in ret:
            yield val

    def __len__(self):
        """Returns the number of times this slice happens in it's range"""
        return len(list(self.__iter__()))

    def parse_value(self, val, sunday=None):
        """Parse the value of the cron slice and raise any errors needed"""
        if val == '>':
            val = self.max
        elif val == '<':
            val = self.min
        try:
            out = get_cronvalue(val, self.enum)
        except ValueError as err:
            raise ValueError(f"Unrecognised {self.name}: '{val}'") from err
        except KeyError as err:
            raise KeyError(f"No enumeration for {self.name}: '{val}'") from err
        return self.test_value(out, sunday=sunday)

    def test_value(self, value, sunday=None):
        """Test the value is within range for this slice"""
        if self.max == 6 and int(value) == 7:
            if sunday is not None:
                return sunday
            raise SundayError("Detected Sunday as 7 instead of 0!")

        if int(value) < self.min or int(value) > self.max:
            raise ValueError(f"'{value}', not in {self.min}-{self.max} for {self.name}")
        return value


def get_cronvalue(value, enums):
    """Returns a value as int (pass-through) or a special enum value"""
    if isinstance(value, int):
        return value
    if str(value).isdigit():
        return int(str(value))
    if not enums:
        raise KeyError("No enumeration allowed")
    return CronValue(str(value), enums)


class CronValue: # pylint: disable=too-few-public-methods
    """Represent a special value in the cron line"""
    def __init__(self, value, enums):
        self.text = value
        self.value = enums.index(value.lower())

    def __lt__(self, value):
        return self.value < int(value)

    def __repr__(self):
        return str(self)

    def __str__(self):
        return self.text

    def __int__(self):
        return self.value


def _render_values(values, sep=',', resolve=False):
    """Returns a rendered list, sorted and optionally resolved"""
    if len(values) > 1:
        values.sort()
    return sep.join([_render(val, resolve) for val in values])


def _render(value, resolve=False):
    """Return a single value rendered"""
    if isinstance(value, CronRange):
        return value.render(resolve)
    if resolve:
        return str(int(value))
    return str(f'{value:02d}' if ZERO_PAD else value)


class CronRange:
    """A range between one value and another for a time range."""
    def __init__(self, vslice, *vrange):
        # holds an extra dangling entry, for example sundays.
        self.dangling = None
        self.slice = vslice
        self.cron = None
        self.seq = 1

        if not vrange:
            self.all()
        elif isinstance(vrange[0], str):
            self.parse(vrange[0])
        elif isinstance(vrange[0], (int, CronValue)):
            if len(vrange) == 2:
                (self.vfrom, self.vto) = vrange
            else:
                self.seq = vrange[0]
                self.all()

    def parse(self, value):
        """Parse a ranged value in a cronjob"""
        if value.count('/') == 1:
            value, seq = value.split('/')
            try:
                self.seq = self.slice.parse_value(seq)
            except SundayError:
                self.seq = 1
                value = "0-0"
            if self.seq < 1 or self.seq > self.slice.max:
                raise ValueError("Sequence can not be divided by zero or max")
        if value.count('-') == 1:
            vfrom, vto = value.split('-')
            self.vfrom = self.slice.parse_value(vfrom, sunday=0)
            try:
                self.vto = self.slice.parse_value(vto)
            except SundayError:
                if self.vfrom == 1:
                    self.vfrom = 0
                else:
                    self.dangling = 0
                self.vto = self.slice.parse_value(vto, sunday=6)
            if self.vto < self.vfrom:
                raise ValueError(f"Bad range '{self.vfrom}-{self.vto}'")
        elif value == '*':
            self.all()
        else:
            raise ValueError(f'Unknown cron range value "{value}"')

    def all(self):
        """Set this slice to all units between the miniumum and maximum"""
        self.vfrom = self.slice.min
        self.vto = self.slice.max

    def render(self, resolve=False):
        """Render the ranged value for a cronjob"""
        value = '*'
        if int(self.vfrom) > self.slice.min or int(self.vto) < self.slice.max:
            if self.vfrom == self.vto:
                value = str(self.vfrom)
            else:
                value = _render_values([self.vfrom, self.vto], '-', resolve)
        if self.seq != 1:
            value += f"/{self.seq:d}"
        if value != '*' and SYSTEMV:
            value = ','.join([str(val) for val in self.range()])
        return value

    def range(self):
        """Returns the range of this cron slice as a iterable list"""
        return range(int(self.vfrom), int(self.vto)+1, self.seq)

    def every(self, value):
        """Set the sequence value for this range."""
        self.seq = int(value)

    def __lt__(self, value):
        return int(self.vfrom) < int(value)

    def __gt__(self, value):
        return int(self.vto) > int(value)

    def __int__(self):
        return int(self.vfrom)

    def __str__(self):
        return self.render()


class OrderedVariableList(OrderedDict):
    """An ordered dictionary with a linked list containing
    the previous OrderedVariableList which this list depends.

    Duplicates in this list are weeded out in favour of the previous
    list in the chain.

    This is all in aid of the ENV variables list which must exist one
    per job in the chain.
    """
    def __init__(self, *args, **kw):
        self.job = kw.pop('job', None)
        super().__init__(*args, **kw)

    @property
    def previous(self):
        """Returns the previous env in the list of jobs in the cron"""
        if self.job is not None and self.job.cron is not None:
            index = self.job.cron.crons.index(self.job)
            if index == 0:
                return self.job.cron.env
            return self.job.cron[index-1].env
        return None

    def all(self):
        """
        Returns the full dictionary, everything from this dictionary
        plus all those in the chain above us.
        """
        if self.job is not None:
            ret = self.previous.all().copy()
            ret.update(self)
            return ret
        return self.copy()

    def __getitem__(self, key):
        previous = self.previous
        if key in self:
            return super().__getitem__(key)
        if previous is not None:
            return previous.all()[key]
        raise KeyError(f"Environment Variable '{key}' not found.")

    def __str__(self):
        """Constructs to variable list output used in cron jobs"""
        ret = []
        for key, value in self.items():
            if self.previous:
                if self.previous.all().get(key, None) == value:
                    continue
            if ' ' in str(value) or value == '':
                value = f'"{value}"'
            ret.append(f"{key}={value}")
        ret.append('')
        return "\n".join(ret)