import logging
from datetime import datetime
from threading import Thread, Event

import pytz
from requests import ReadTimeout
from requests.exceptions import ConnectionError, ConnectTimeout

from core.constants import HTTP_HEADERS
from core.url_data_cache import URLDataCache
from providers.callsigndata.callsign_data_provider import CallsignDataProvider


class FileDownloadCallsignDataProvider(CallsignDataProvider):
    """Generic static reference data provider class for providers that fetch their data from the web by downloading a
     file."""

    def __init__(self, name, provider_config, url, cache_file_path, poll_interval):
        """ Set up the provider, note poll_interval is in *days*."""
        super().__init__(name, provider_config)
        self._url = url
        self._cache_file_path = cache_file_path
        self._poll_interval = poll_interval
        self._thread = None
        self._stop_event = Event()
        self._url_data_cache = URLDataCache("callsigndata_" + name)

    def start(self):
        # Fire off the polling thread. It will poll immediately on startup, then sleep for poll_interval between
        # subsequent polls, so start() returns immediately and the application can continue starting.
        logging.info(
            "Set up query of " + self.name + " callsign reference data every " + str(self._poll_interval) + " days.")
        self._thread = Thread(target=self._run, daemon=True)
        self._thread.start()

    def stop(self):
        self._stop_event.set()

    def _run(self):
        while True:
            self._poll()
            if self._stop_event.wait(timeout=self._poll_interval * 60 * 60 * 24):
                break

    def _poll(self):
        try:
            # Request the file. Use the data cache (with a TTL of 1 day) here, not as the main mechanism for
            # caching, but just so continual restarts of the software during testing don't hammer the servers.
            logging.debug("Downloading " + self.name + " callsign reference data...")
            http_response = self._url_data_cache.get(self._url, headers=HTTP_HEADERS)
            # Check response code was good
            if http_response.ok:
                # Save the data to a local file
                with open(self._cache_file_path, "wb") as f:
                    f.write(http_response.content)
                    f.flush()
                    # Pass off to the subclass for processing
                    ok = self._handle_file(self._cache_file_path)
                    if ok:
                        self.status = "OK"
                        self.last_update_time = datetime.now(pytz.UTC)
                        logging.info("Updated callsign reference data from " + self.name)
                    else:
                        self.status = "Error"
                        logging.warning(f"Error updating callsign reference data from {self.name}.")

            else:
                self.status = "Error"
                logging.warning(f"HTTP {http_response.status_code} when downloading callsign reference data from {self.name}.")

        except ConnectionError:
            self.status = "Error"
            logging.warning(f"Connection error when downloading callsign reference data from {self.name}.")
        except (ConnectTimeout, ReadTimeout):
            self.status = "Error"
            logging.warning(f"Timeout when downloading callsign reference data from {self.name}.")
        except Exception:
            self.status = "Error"
            logging.exception("Exception in callsign reference data provider (" + self.name + ")")
            self._stop_event.wait(timeout=1)

    def _handle_file(self, path):
        """Handle an updated file downloaded from the server. Return true if successful, false otherwise."""

        raise NotImplementedError("Subclasses must implement this method")