from datetime import datetime, timedelta

import pytz

from core.config import SERVER_OWNER_CALLSIGN, MAX_ALERT_AGE
from core.constants import SOFTWARE_NAME, SOFTWARE_VERSION


# Generic alert provider class. Subclasses of this query the individual APIs for alerts.
class AlertProvider:

    # HTTP headers used for spot providers that use HTTP
    HTTP_HEADERS = { "User-Agent": SOFTWARE_NAME + " " + SOFTWARE_VERSION + " (operated by " + SERVER_OWNER_CALLSIGN + ")" }

    # Constructor
    def __init__(self, provider_config):
        self.name = provider_config["name"]
        self.enabled = provider_config["enabled"]
        self.last_update_time = datetime.min.replace(tzinfo=pytz.UTC)
        self.status = "Not Started" if self.enabled else "Disabled"
        self.alerts = None

    # Set up the provider, e.g. giving it the alert list to work from
    def setup(self, alerts):
        self.alerts = alerts

    # Start the provider. This should return immediately after spawning threads to access the remote resources
    def start(self):
        raise NotImplementedError("Subclasses must implement this method")

    # Submit a batch of alerts retrieved from the provider. There is no timestamp checking like there is for spots,
    # because alerts could be created at any point for any time in the future. Rely on hashcode-based id matching
    # to deal with duplicates.
    def submit_batch(self, alerts):
        for alert in alerts:
            # Fill in any blanks
            alert.infer_missing()
            # Add to the list, provided it heas not already expired.
            if not alert.expired():
                self.alerts.add(alert.id, alert, expire=MAX_ALERT_AGE)

    # Stop any threads and prepare for application shutdown
    def stop(self):
        raise NotImplementedError("Subclasses must implement this method")