from datetime import datetime

import pytz

from core.config import MAX_ALERT_AGE


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

    def __init__(self, provider_config):
        """Constructor"""

        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
        self.web_server = None

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

        self.alerts = alerts
        self.web_server = web_server

    def start(self):
        """Start the provider. This should return immediately after spawning threads to access the remote resources"""

        raise NotImplementedError("Subclasses must implement this method")

    def submit_batch(self, alerts):
        """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."""

        # Sort the batch so that earliest ones go in first. This helps keep the ordering correct when alerts are fired
        # off to SSE listeners.
        alerts = sorted(alerts, key=lambda alert: (alert.start_time if alert and alert.start_time else 0))
        for alert in alerts:
            # Fill in any blanks and add to the list
            alert.infer_missing()
            self.add_alert(alert)

    def add_alert(self, alert):
        if not alert.expired():
            self.alerts.add(alert.id, alert, expire=MAX_ALERT_AGE)
            # Ping the web server in case we have any SSE connections that need to see this immediately
            if self.web_server:
                self.web_server.notify_new_alert(alert)

    def stop(self):
        """Stop any threads and prepare for application shutdown"""

        raise NotImplementedError("Subclasses must implement this method")