import * as Notifications from 'expo-notifications';
import { SchedulableTriggerInputTypes } from 'expo-notifications';
import type { Event, Journey, ReminderSettings } from '@timetoleave/core';

// Register for push notification permissions
Notifications.setNotificationHandler({
  handleNotification: async () => ({
    shouldShowAlert: true,
    shouldPlaySound: true,
    shouldSetBadge: false,
    shouldShowBanner: true,
    shouldShowList: true,
  }),
});

/**
 * Calculate leave-by time from event time and journey data.
 * Uses earliest real departure time if journeys exist, otherwise event time minus buffer.
 *
 * @param event - The event to calculate leave-by time for
 * @param journeys - Journey data for this event
 * @param arrivalBufferMinutes - How many minutes before the event to arrive
 * @param bufferMinutes - How many minutes before leaving to be reminded
 */
export function calculateLeaveByTime(
  event: Event,
  journeys: Journey[],
  arrivalBufferMinutes: number,
  bufferMinutes: number
): Date {
  // Calculate target arrival time (event time minus arrival buffer)
  const targetArrivalTime = new Date(event.eventTime);
  targetArrivalTime.setMinutes(targetArrivalTime.getMinutes() - arrivalBufferMinutes);

  // If we have journeys, use the earliest non-cancelled real departure
  if (journeys.length > 0) {
    const best = journeys
      .filter((j) => !j.cancelled)
      .sort((a, b) => a.rD.getTime() - b.rD.getTime())[0];

    if (best) {
      // Leave by time = target arrival time - buffer minutes
      return new Date(targetArrivalTime.getTime() - bufferMinutes * 60 * 1000);
    }
  }

  // Fallback: event time minus arrival buffer minus buffer (no journey data)
  return new Date(targetArrivalTime.getTime() - bufferMinutes * 60 * 1000);
}

/**
 * Schedule notifications for an event
 *
 * @param event - The event to schedule notifications for
 * @param journeys - Journey data for this event (optional)
 * @param settings - Notification settings
 */
export async function scheduleNotificationsForEvent(
  event: Event,
  journeys: Journey[] = [],
  settings: ReminderSettings
): Promise<void> {
  // Don't schedule if notifications are disabled
  if (!settings.enabled) {
    return;
  }

  // Calculate leave-by time (when user should actually leave)
  const leaveByTime = calculateLeaveByTime(event, journeys, settings.arrivalBufferMinutes, settings.bufferMinutes);

  // Cancel existing notifications for this event - cancel one by one
    const existing = await Notifications.getAllScheduledNotificationsAsync();
    const toCancel = existing.filter(n => n.content.data?.eventId === event.id);
    if (toCancel.length > 0) {
      for (const notif of toCancel) {
        await Notifications.cancelScheduledNotificationAsync(notif.identifier);
      }
    }

  // Default reminders: 30min, 10min, and at leave-by time
  // But respect the buffer time - we want reminders relative to when they should leave
  const defaultReminders = [30, 10, 0];

  // Schedule notifications
  for (const minutesBefore of defaultReminders) {
    const triggerTime = new Date(leaveByTime.getTime() - minutesBefore * 60 * 1000);

    // Skip if trigger time is in the past
    if (triggerTime <= new Date()) {
      continue;
    }

    // Skip if this would be before the event actually starts (add some safety margin)
    if (triggerTime < new Date(event.eventTime.getTime() - 2 * 60 * 60 * 1000)) {
      continue;
    }

    // Use Date trigger with time property
    await Notifications.scheduleNotificationAsync({
      content: {
        title: `🚆 ${event.title}`,
        body: minutesBefore === 0
          ? 'Zeit zu gehen!'
          : `${minutesBefore} Minuten bis du losmusst`,
        data: { eventId: event.id },
      },
      trigger: { type: SchedulableTriggerInputTypes.DATE, date: triggerTime },
    });
  }
}

/**
 * Reschedule notifications for all events
 * Use this when origin station changes or notification settings are updated
 */
export async function rescheduleAllNotifications(
  events: Event[],
  journeysMap: Record<string, Journey[]>,  // eventId -> journeys
  settings: ReminderSettings
): Promise<void> {
  // Cancel ALL existing notifications first
  await Notifications.cancelAllScheduledNotificationsAsync();

  // Schedule new notifications for each event
  for (const event of events) {
    const eventJourneys = journeysMap[event.id] || [];
    await scheduleNotificationsForEvent(event, eventJourneys, settings);
  }
}

// Request permissions if not already granted
let permissionsRequested = false;

export async function requestNotificationPermissions(): Promise<boolean> {
  if (permissionsRequested) {
    return true;
  }

  permissionsRequested = true;
  const { status } = await Notifications.requestPermissionsAsync();
  return status === 'granted';
}

// Request permissions automatically when app starts (for Android)
// This is called in App.tsx

export function setupNotifications() {
  Notifications.setNotificationHandler({
    handleNotification: async () => ({
      shouldShowAlert: true,
      shouldPlaySound: true,
      shouldSetBadge: false,
      shouldShowBanner: true,
      shouldShowList: true,
    }),
  });
}