# Copyright: (c) 2018 Ansible Project
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)

from __future__ import annotations

import re

from ansible import constants as C
from ansible.errors import AnsibleError
from ansible.utils.display import Display
from ansible.utils.plugin_docs import get_versioned_doclink

_FALLBACK_INTERPRETER = '/usr/bin/python3'

display = Display()
foundre = re.compile(r'FOUND(.*)ENDFOUND', flags=re.DOTALL)


class InterpreterDiscoveryRequiredError(Exception):
    def __init__(self, message, interpreter_name, discovery_mode):
        super(InterpreterDiscoveryRequiredError, self).__init__(message)
        self.interpreter_name = interpreter_name
        self.discovery_mode = discovery_mode


def discover_interpreter(action, interpreter_name, discovery_mode, task_vars):
    """Probe the target host for a Python interpreter from the `INTERPRETER_PYTHON_FALLBACK` list, returning the first found or `/usr/bin/python3` if none."""
    host = task_vars.get('inventory_hostname', 'unknown')
    res = None
    found_interpreters = [_FALLBACK_INTERPRETER]  # fallback value
    is_silent = discovery_mode.endswith('_silent')

    try:
        bootstrap_python_list = C.config.get_config_value('INTERPRETER_PYTHON_FALLBACK', variables=task_vars)

        display.vvv(msg=f"Attempting {interpreter_name} interpreter discovery.", host=host)

        # not all command -v impls accept a list of commands, so we have to call it once per python
        command_list = ["command -v '%s'" % py for py in bootstrap_python_list]
        shell_bootstrap = "echo FOUND; {0}; echo ENDFOUND".format('; '.join(command_list))

        # FUTURE: in most cases we probably don't want to use become, but maybe sometimes we do?
        res = action._low_level_execute_command(shell_bootstrap, sudoable=False)

        raw_stdout = res.get('stdout', u'')

        match = foundre.match(raw_stdout)

        if not match:
            display.debug(u'raw interpreter discovery output: {0}'.format(raw_stdout), host=host)
            raise ValueError('unexpected output from Python interpreter discovery')

        found_interpreters = [interp.strip() for interp in match.groups()[0].splitlines() if interp.startswith('/')]

        display.debug(u"found interpreters: {0}".format(found_interpreters), host=host)

        if not found_interpreters:
            if not is_silent:
                display.warning(msg=f'No python interpreters found for host {host!r} (tried {bootstrap_python_list!r}).')

            # this is lame, but returning None or throwing an exception is uglier
            return _FALLBACK_INTERPRETER
    except AnsibleError:
        raise
    except Exception as ex:
        if not is_silent:
            display.error_as_warning(msg=f'Unhandled error in Python interpreter discovery for host {host!r}.', exception=ex)

            if res and res.get('stderr'):  # the current ssh plugin implementation always has stderr, making coverage of the false case difficult
                display.vvv(msg=f"Interpreter discovery remote stderr:\n{res.get('stderr')}", host=host)

    if not is_silent:
        display.warning(
            msg=(
                f"Host {host!r} is using the discovered Python interpreter at {found_interpreters[0]!r}, "
                "but future installation of another Python interpreter could cause a different interpreter to be discovered."
            ),
            help_text=f"See {get_versioned_doclink('reference_appendices/interpreter_discovery.html')} for more information.",
        )

    return found_interpreters[0]
