# zabbix_utils
#
# Copyright (C) 2001-2023 Zabbix SIA
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies
# of the Software, and to permit persons to whom the Software
# is furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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import ssl
import socket
import asyncio
import logging
from typing import Callable, Optional

from .logger import EmptyHandler
from .types import AgentResponse
from .common import ZabbixProtocol
from .exceptions import ProcessingError

log = logging.getLogger(__name__)
log.addHandler(EmptyHandler())


class AsyncGetter():
    """Zabbix get asynchronous implementation.

    Args:
        host (str, optional): Zabbix agent address. Defaults to `'127.0.0.1'`.

        port (int, optional): Zabbix agent port. Defaults to `10050`.

        timeout (int, optional): Connection timeout value. Defaults to `10`.

        source_ip (str, optional): IP from which to establish connection. Defaults to `None`.

        ssl_context (Callable, optional): Func(), returned prepared ssl.SSLContext. \
Defaults to `None`.
    """

    def __init__(self, host: str = '127.0.0.1', port: int = 10050, timeout: int = 10,
                 source_ip: Optional[str] = None, ssl_context: Optional[Callable] = None):
        self.host = host
        self.port = port
        self.timeout = timeout
        self.source_ip = source_ip

        self.ssl_context = ssl_context
        if self.ssl_context:
            if not isinstance(self.ssl_context, Callable):
                raise TypeError('Value "ssl_context" should be a function.')

    async def __get_response(self, reader: asyncio.StreamReader) -> Optional[str]:
        result = await ZabbixProtocol.parse_async_packet(reader, log, ProcessingError)

        log.debug('Received data: %s', result)

        return result

    async def get(self, key: str) -> Optional[str]:
        """Gets item value from Zabbix agent by specified key.

        Args:
            key (str): Zabbix item key.

        Returns:
            str: Value from Zabbix agent for specified key.
        """

        packet = ZabbixProtocol.create_packet(key, log)

        connection_params = {
            "host": self.host,
            "port": self.port
        }

        if self.source_ip:
            connection_params['local_addr'] = (self.source_ip, 0)

        if self.ssl_context:
            connection_params['ssl'] = self.ssl_context()
            if not isinstance(connection_params['ssl'], ssl.SSLContext):
                raise TypeError(
                    'Function "ssl_context" must return "ssl.SSLContext".') from None

        connection = asyncio.open_connection(**connection_params)

        try:
            reader, writer = await asyncio.wait_for(connection, timeout=self.timeout)
            writer.write(packet)
            await writer.drain()
        except asyncio.TimeoutError as err:
            log.error(
                'The connection to %s timed out after %d seconds',
                f"{self.host}:{self.port}",
                self.timeout
            )
            raise err
        except (ConnectionRefusedError, socket.gaierror) as err:
            log.error(
                'An error occurred while trying to connect to %s: %s',
                f"{self.host}:{self.port}",
                getattr(err, 'msg', str(err))
            )
            raise err
        except (OSError, socket.error) as err:
            log.warning(
                'An error occurred while trying to send to %s: %s',
                f"{self.host}:{self.port}",
                getattr(err, 'msg', str(err))
            )
            raise err

        try:
            response = await self.__get_response(reader)
        except (ConnectionResetError, asyncio.exceptions.IncompleteReadError) as err:
            log.debug('Get value error: %s', err)
            log.warning('Check access restrictions in Zabbix agent configuration.')
            raise err
        log.debug('Response from [%s:%s]: %s', self.host, self.port, response)

        writer.close()
        await writer.wait_closed()

        return AgentResponse(response)