#!/usr/bin/python
# Copyright (c) 2019, Saranya Sridharan
# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
# SPDX-License-Identifier: GPL-3.0-or-later

from __future__ import annotations

DOCUMENTATION = r"""
module: pids
description: "Retrieves a list of PIDs of given process name in Ansible controller/controlled machines. Returns an empty list
  if no process in that name exists."
short_description: Retrieves process IDs list if the process is running otherwise return empty list
author:
  - Saranya Sridharan (@saranyasridharan)
requirements:
  - psutil(python module)
extends_documentation_fragment:
  - community.general.attributes
attributes:
  check_mode:
    support: full
  diff_mode:
    support: none
options:
  name:
    description: The name of the process(es) you want to get PID(s) for.
    type: str
  pattern:
    description: The pattern (regular expression) to match the process(es) you want to get PID(s) for.
    type: str
    version_added: 3.0.0
  ignore_case:
    description: Ignore case in pattern if using the O(pattern) option.
    type: bool
    default: false
    version_added: 3.0.0
"""

EXAMPLES = r"""
# Pass the process name
- name: Getting process IDs of the process
  community.general.pids:
    name: python
  register: pids_of_python

- name: Printing the process IDs obtained
  ansible.builtin.debug:
    msg: "PIDS of python:{{pids_of_python.pids|join(',')}}"

- name: Getting process IDs of processes matching pattern
  community.general.pids:
    pattern: python(2(\.7)?|3(\.6)?)?\s+myapp\.py
  register: myapp_pids
"""

RETURN = r"""
pids:
  description: Process IDs of the given process.
  returned: list of none, one, or more process IDs
  type: list
  sample: [100, 200]
"""

import abc
import re
from os.path import basename

from ansible.module_utils.basic import AnsibleModule
from ansible_collections.community.general.plugins.module_utils import deps
from ansible.module_utils.common.text.converters import to_native

from ansible_collections.community.general.plugins.module_utils.version import LooseVersion

with deps.declare("psutil"):
    import psutil


class PSAdapterError(Exception):
    pass


class PSAdapter(metaclass=abc.ABCMeta):
    NAME_ATTRS = ("name", "cmdline")
    PATTERN_ATTRS = ("name", "exe", "cmdline")

    def __init__(self, psutil):
        self._psutil = psutil

    @staticmethod
    def from_package(psutil):
        version = LooseVersion(psutil.__version__)
        if version < LooseVersion("2.0.0"):
            return PSAdapter100(psutil)
        elif version < LooseVersion("5.3.0"):
            return PSAdapter200(psutil)
        else:
            return PSAdapter530(psutil)

    def get_pids_by_name(self, name):
        return [p.pid for p in self._process_iter(*self.NAME_ATTRS) if self._has_name(p, name)]

    def _process_iter(self, *attrs):
        return self._psutil.process_iter()

    def _has_name(self, proc, name):
        attributes = self._get_proc_attributes(proc, *self.NAME_ATTRS)
        return (
            compare_lower(attributes["name"], name)
            or attributes["cmdline"]
            and compare_lower(attributes["cmdline"][0], name)
        )

    def _get_proc_attributes(self, proc, *attributes):
        return {attribute: self._get_attribute_from_proc(proc, attribute) for attribute in attributes}

    @staticmethod
    @abc.abstractmethod
    def _get_attribute_from_proc(proc, attribute):
        pass

    def get_pids_by_pattern(self, pattern, ignore_case):
        flags = 0
        if ignore_case:
            flags |= re.I

        try:
            regex = re.compile(pattern, flags)
        except re.error as e:
            raise PSAdapterError(f"'{pattern}' is not a valid regular expression: {e}")

        return [p.pid for p in self._process_iter(*self.PATTERN_ATTRS) if self._matches_regex(p, regex)]

    def _matches_regex(self, proc, regex):
        # See https://psutil.readthedocs.io/en/latest/#find-process-by-name for more information
        attributes = self._get_proc_attributes(proc, *self.PATTERN_ATTRS)
        matches_name = regex.search(to_native(attributes["name"]))
        matches_exe = attributes["exe"] and regex.search(basename(to_native(attributes["exe"])))
        matches_cmd = attributes["cmdline"] and regex.search(to_native(" ".join(attributes["cmdline"])))

        return any([matches_name, matches_exe, matches_cmd])


class PSAdapter100(PSAdapter):
    def __init__(self, psutil):
        super().__init__(psutil)

    @staticmethod
    def _get_attribute_from_proc(proc, attribute):
        return getattr(proc, attribute)


class PSAdapter200(PSAdapter):
    def __init__(self, psutil):
        super().__init__(psutil)

    @staticmethod
    def _get_attribute_from_proc(proc, attribute):
        method = getattr(proc, attribute)
        return method()


class PSAdapter530(PSAdapter):
    def __init__(self, psutil):
        super().__init__(psutil)

    def _process_iter(self, *attrs):
        return self._psutil.process_iter(attrs=attrs)

    @staticmethod
    def _get_attribute_from_proc(proc, attribute):
        return proc.info[attribute]


def compare_lower(a, b):
    if a is None or b is None:
        # this could just be "return False" but would lead to surprising behavior if both a and b are None
        return a == b

    return a.lower() == b.lower()


class Pids:
    def __init__(self, module):
        deps.validate(module)

        self._ps = PSAdapter.from_package(psutil)

        self._module = module
        self._name = module.params["name"]
        self._pattern = module.params["pattern"]
        self._ignore_case = module.params["ignore_case"]

        self._pids = []

    def execute(self):
        if self._name is not None:
            self._pids = self._ps.get_pids_by_name(self._name)
        else:
            try:
                self._pids = self._ps.get_pids_by_pattern(self._pattern, self._ignore_case)
            except PSAdapterError as e:
                self._module.fail_json(msg=to_native(e))

        return self._module.exit_json(**self.result)

    @property
    def result(self):
        return {
            "pids": self._pids,
        }


def main():
    module = AnsibleModule(
        argument_spec=dict(
            name=dict(type="str"),
            pattern=dict(type="str"),
            ignore_case=dict(type="bool", default=False),
        ),
        required_one_of=[("name", "pattern")],
        mutually_exclusive=[("name", "pattern")],
        supports_check_mode=True,
    )

    Pids(module).execute()


if __name__ == "__main__":
    main()
