# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
#
# 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 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""Run command on a remote, (i.e. a remote [user@]host)."""

import os
from pathlib import Path
from posix import WIFSIGNALED
import shlex
from shlex import quote
import signal

# CODACY ISSUE:
#   Consider possible security implications associated with Popen module.
# REASON IGNORED:
#   Subprocess is needed, but we use it with security in mind.
from subprocess import (
    DEVNULL,
    PIPE,
    Popen,
)
import sys
from time import (
    sleep,
    time,
)
from typing import (
    Any,
    Dict,
    List,
    Literal,
    Optional,
    Tuple,
    Union,
    overload,
)

from cylc.flow import (
    LOG,
    __version__ as CYLC_VERSION,
)
import cylc.flow.flags
from cylc.flow.log_level import verbosity_to_opts
from cylc.flow.platforms import (
    get_host_from_platform,
    get_platform,
)
from cylc.flow.util import format_cmd


def get_proc_ancestors():
    """Return list of parent PIDs back to init."""
    pid = os.getpid()
    ancestors = []
    while True:
        p = Popen(  # nosec
            ["ps", "-p", str(pid), "-oppid="],
            stdout=PIPE,
            stderr=PIPE,
            text=True
        )
        # * there is no untrusted output
        ppid = p.communicate()[0].strip()
        if not ppid:
            return ancestors
        ancestors.append(ppid)
        pid = ppid


def watch_and_kill(proc):
    """Kill proc if my PPID (etc.) changed - e.g. ssh connection dropped."""
    gpa = get_proc_ancestors()
    ps_interval = 60  # secs
    last_ps_time = time()
    while True:
        if proc.poll() is not None:
            break
        if time() - last_ps_time > ps_interval:
            # Run ps command
            if get_proc_ancestors() != gpa:
                sleep(1)
                os.kill(proc.pid, signal.SIGTERM)
                break
            last_ps_time = time()
        sleep(1)


def run_cmd(
    command,
    stdin=None,
    stdin_str=None,
    capture_process=False,
    capture_status=False,
    manage=False,
    text=True,
):
    """Run a given cylc command on another host.

    Arguments:
        command (list):
            command inclusive of all opts and args required to run via ssh.
        stdin (file):
            If specified, it should be a readable file object.
            If None, DEVNULL is set if output is to be captured.
        stdin_str (str):
            A string to be passed to stdin.
            Implies `stdin=PIPE`.
        capture_process (boolean):
            If True, set stdout=PIPE and return the Popen object.
        capture_status (boolean):
            If True, and the remote command is unsuccessful, return the
            associated exit code instead of exiting with an error.
        manage (boolean):
            If True, watch ancestor processes and kill command if they change
            (e.g. kill tail-follow commands when parent ssh connection dies).
        text (boolean):
            If True, use string mode instead of bytes for communicating
            with subprocess.

    Return:
        * If capture_process=True: the Popen[str|bytes] object if created
          successfully.
        * Else if capture_status=True: the remote command exit code.
        * Else if the remote command is executed successfully: 0.
        * Else exits with an error message instead of returning.

    Exits with code 1 in the event of certain command errors.

    """
    # CODACY ISSUE:
    #   subprocess call - check for execution of untrusted input.
    # REASON IGNORED:
    #   The command is read from the site/user global config file, but we check
    #   above that it ends in 'cylc', and in any case the user could execute
    #   any such command directly via ssh.
    stdout = None
    stderr = None
    if capture_process:
        stdout = PIPE
        stderr = PIPE
        if stdin is None:
            stdin = DEVNULL
    if stdin_str:
        read, write = os.pipe()
        os.write(write, stdin_str.encode())
        os.close(write)
        stdin = read

    try:
        LOG.debug(f'running command:\n$ {format_cmd(command)}')
        proc = Popen(  # nosec
            command,
            stdin=stdin,
            stdout=stdout,
            stderr=stderr,
            text=text
        )
        # * this see CODACY ISSUE comment above
    except OSError as exc:
        sys.exit(r'ERROR: %s: %s' % (
            exc, ' '.join(quote(item) for item in command)))

    if capture_process:
        return proc
    if manage:
        watch_and_kill(proc)
    res = proc.wait()
    if WIFSIGNALED(res):
        sys.exit(
            r'ERROR: command terminated by signal %d: %s'
            % (res, ' '.join(quote(item) for item in command))
        )
    if capture_status or not res:
        return res
    sys.exit(
        r'ERROR: command returns %d: %s'
        % (res, ' '.join(quote(item) for item in command))
    )


def get_includes_to_rsync(rsync_includes=None):
    """Returns list of configured dirs/files for remote file installation."""

    configured_includes = []

    if rsync_includes is not None:
        for include in rsync_includes:
            if include.endswith("/"):  # item is a directory
                configured_includes.append("/" + include + "***")
            else:  # item is a file
                configured_includes.append("/" + include)

    return configured_includes


DEFAULT_RSYNC_OPTS = [
    '-a',
    '--checksum',
    '--out-format=%o %n%L',
    '--no-t'
]
# %o: the operation (send or del.)
# %n: filename
# %L: "-> symlink_target" if applicable

DEFAULT_INCLUDES = [
    '/ana/***',  # Rose ana analysis modules
    '/app/***',  # Rose applications
    '/bin/***',  # Cylc bin directory (added to PATH)
    '/etc/***',  # Miscellaneous resources
    '/lib/***',  # Cylc lib directory (lib/python added to PYTHONPATH for
                 # workflow config)
]


def construct_rsync_over_ssh_cmd(
    src_path: str, dst_path: str, platform: Dict[str, Any],
    rsync_includes=None, bad_hosts=None
) -> Tuple[List[str], str]:
    """Constructs the rsync command used for remote file installation.

    Includes as standard the directories: app, bin, etc, lib; and the server
    key, used for ZMQ authentication.

    Args:
        src_path: source path
        dst_path: path of target
        platform: contains info relating to platform
        rsync_includes: files and directories to be included in the rsync

    Raises:
        NoHostsError:
            If there are no hosts available for the requested platform.

    Developer Warning:
        The Cylc Subprocess Pool method ``rsync_255_fail`` relies on
        ``rsync_cmd[0] == 'rsync'``. Please check that changes to this function
        do not break ``rsync_255_fail``.
    """
    dst_path = dst_path.replace('$HOME/', '')
    dst_host = get_host_from_platform(platform, bad_hosts=bad_hosts)
    ssh_cmd = platform['ssh command']
    command = platform['rsync command']
    rsync_cmd = shlex.split(command)
    rsync_options = [
        "--delete",
        "--rsh=" + ssh_cmd,
        "--include=/.service/",
        "--include=/.service/server.key"
    ] + DEFAULT_RSYNC_OPTS
    # Note to future devs - be wary of changing the order of the following
    # rsync options, rsync is very particular about order of in/ex-cludes.
    rsync_cmd.extend(rsync_options)
    for exclude in ['/log', '/share', '/work']:
        rsync_cmd.append(f"--exclude={exclude}")
    for include in DEFAULT_INCLUDES:
        rsync_cmd.append(f"--include={include}")
    for include in get_includes_to_rsync(rsync_includes):
        rsync_cmd.append(f"--include={include}")
    # The following excludes are required in case these are added to the
    rsync_cmd.append("--exclude=*")  # exclude everything else
    rsync_cmd.append(f"{src_path}/")
    rsync_cmd.append(f"{dst_host}:{dst_path}/")
    return rsync_cmd, dst_host


def construct_ssh_cmd(
    raw_cmd,
    platform,
    host,
    forward_x11=False,
    stdin=False,
    set_UTC=False,
    set_verbosity=False,
    timeout=None,
):
    """Build an SSH command for execution on a remote platform hosts.

    Arguments:
        raw_cmd (list):
            primitive command to run remotely.
        platform (dict):
            The Cylc job "platform" to run the command on. This is used
            to determine the settings used e.g. "ssh command".
        host (string):
            remote host name. Use 'localhost' if not specified.
        forward_x11 (boolean):
            If True, use 'ssh -Y' to enable X11 forwarding, else just 'ssh'.
        stdin:
            If None, the `-n` option will be added to the SSH command line.
        set_UTC (boolean):
            If True, check UTC mode and specify if set to True (non-default).
        set_verbosity (boolean):
            If True apply -q, -v opts to match cylc.flow.flags.verbosity.
        timeout (str):
            String for bash timeout command.

    Returns:
        list - A list containing a chosen command including all arguments and
        options necessary to directly execute the bare command on a given host
        via ssh.

    """
    command = shlex.split(platform['ssh command'])

    if forward_x11:
        command.append('-Y')
    if stdin is None:
        command.append('-n')

    command.append(host)

    # Pass CYLC_VERSION and optionally, CYLC_CONF_PATH & CYLC_UTC through.
    command += ['env', quote(r'CYLC_VERSION=%s' % CYLC_VERSION)]

    for envvar in [
        'CYLC_CONF_PATH',
        'CYLC_COVERAGE',
        'CLIENT_COMMS_METH',
        'CYLC_ENV_NAME',
        *platform['ssh forward environment variables'],
    ]:
        if envvar in os.environ:
            command.append(
                quote(f'{envvar}={os.environ[envvar]}')
            )

    if set_UTC and os.getenv('CYLC_UTC') in ["True", "true"]:
        command.append(quote(r'CYLC_UTC=True'))
        command.append(quote(r'TZ=UTC'))

    # Use bash -l?
    ssh_login_shell = platform['use login shell']
    if ssh_login_shell:
        # A login shell will always source /etc/profile and the user's bash
        # profile file. To avoid having to quote the entire remote command
        # it is passed as arguments to the bash script.
        command += ['bash', '--login', '-c', quote(r'exec "$0" "$@"')]

    if timeout:
        command += ['timeout', timeout]

    # 'cylc' on the remote host
    remote_cylc_path = platform['cylc path']
    if remote_cylc_path:
        cylc_cmd = str(Path(remote_cylc_path) / 'cylc')
    else:
        cylc_cmd = 'cylc'
    command.append(cylc_cmd)

    # Insert core raw command after ssh, but before its own, command options.
    command += raw_cmd

    if set_verbosity:
        command.extend(verbosity_to_opts(cylc.flow.flags.verbosity))

    return command


def construct_cylc_server_ssh_cmd(
    cmd,
    host,
    **kwargs,
):
    """Convenience function to building SSH commands for remote Cylc servers.

    Build an SSH command that connects to the specified host using the
    localhost platform config.

    * To run commands on job platforms use construct_ssh_cmd.
    * Use this interface to connect to:
      * Cylc servers (i.e. `[scheduler][run hosts]available`).
      * The host `cylc play` was run on, use this interface.

    This assumes the host you are connecting to shares the $HOME filesystem
    with the localhost platform.

    For arguments and returns see construct_ssh_cmd.
    """
    return construct_ssh_cmd(
        cmd,
        get_platform(),  # use localhost settings
        host,
        **kwargs,
    )


def remote_cylc_cmd(
    cmd,
    platform,
    bad_hosts=None,
    host=None,
    stdin=None,
    stdin_str=None,
    ssh_login_shell=None,
    ssh_cmd=None,
    remote_cylc_path=None,
    capture_process=False,
    manage=False,
    text=True,
):
    """Execute a Cylc command on a remote platform.

    Uses the provided platform configuration to construct the command.

    For arguments and returns see construct_ssh_cmd and run_cmd.

    Raises:
        NoHostsError: If the platform is not contactable.

    Exits with code 1 in the event of certain command errors.

    """
    if not host:
        # no host selected => perform host selection from platform config
        host = get_host_from_platform(platform, bad_hosts=bad_hosts)

    return run_cmd(
        construct_ssh_cmd(
            cmd,
            platform,
            host=host,
            stdin=True if stdin_str else stdin,
        ),
        stdin=stdin,
        stdin_str=stdin_str,
        capture_process=capture_process,
        capture_status=True,
        manage=manage,
        text=text
    )


@overload
def cylc_server_cmd(
    cmd,
    host: Optional[str] = None,
    *,
    capture_process: 'Literal[False]' = False,
    **kwargs,
) -> int:
    ...


@overload
def cylc_server_cmd(
    cmd,
    host: Optional[str] = None,
    *,
    capture_process: 'Literal[True]',
    **kwargs,
) -> Popen:
    ...


@overload
def cylc_server_cmd(
    cmd,
    host: Optional[str] = None,
    *,
    capture_process: bool,
    **kwargs,
) -> Union[int, Popen]:
    ...


def cylc_server_cmd(
    cmd,
    host: Optional[str] = None,
    *,
    capture_process: bool = False,
    **kwargs,
) -> Union[int, Popen]:
    """Convenience function for running commands on remote Cylc servers.

    Executes a Cylc command on the specified host using localhost platform
    config.

    * To run commands on job platforms use remote_cylc_cmd.
    * Use this interface to run commands on:
      * Cylc servers (i.e. `[scheduler][run hosts]available`).
      * The host `cylc play` was run on.

    Runs a command via SSH using the configuration for the localhost platform.
    This assumes the host you are connecting to shares the $HOME filesystem
    with the localhost platform.

    For arguments and returns see construct_ssh_cmd and run_cmd.

    Raises:
        NoHostsError: If the platform is not contactable.

    Exits with code 1 in the event of certain command errors.

    """
    return remote_cylc_cmd(
        cmd,
        get_platform(),  # use localhost settings
        host=host,
        capture_process=capture_process,
        **kwargs,
    )
