'use client';

import { useEffect, useState, useCallback } from 'react';
import { ReminderSettings } from '@/lib/storage';

const LAST_NOTIFICATION_KEY = 'quittraq_last_notification_date';

export type NotificationPermission = 'default' | 'granted' | 'denied';

// Helper to convert VAPID key
function urlBase64ToUint8Array(base64String: string) {
  const padding = '='.repeat((4 - base64String.length % 4) % 4);
  const base64 = (base64String + padding)
    .replace(/-/g, '+')
    .replace(/_/g, '/');

  const rawData = window.atob(base64);
  const outputArray = new Uint8Array(rawData.length);

  for (let i = 0; i < rawData.length; ++i) {
    outputArray[i] = rawData.charCodeAt(i);
  }
  return outputArray;
}

export function useNotifications(reminderSettings: ReminderSettings) {
  const [permission, setPermission] = useState<NotificationPermission>('default');
  const [isSupported, setIsSupported] = useState(false);
  const [swRegistration, setSwRegistration] = useState<ServiceWorkerRegistration | null>(null);

  // Register Service Worker
  useEffect(() => {
    if (typeof window !== 'undefined' && 'serviceWorker' in navigator && 'PushManager' in window) {
      setIsSupported(true);
      setPermission(Notification.permission as NotificationPermission);

      navigator.serviceWorker.register('/sw.js')
        .then(registration => {
          console.log('Service Worker registered:', registration);
          setSwRegistration(registration);
        })
        .catch(error => {
          console.error('Service Worker registration failed:', error);
        });
    }
  }, []);

  const subscribeToPush = useCallback(async () => {
    try {
      const registration = await navigator.serviceWorker.ready;
      if (!registration) {
        throw new Error('Service Worker not ready');
      }

      const publicVapidKey = process.env.NEXT_PUBLIC_VAPID_PUBLIC_KEY;
      if (!publicVapidKey) {
        throw new Error('Missing VAPID key');
      }

      // 1. Ensure we have a subscription
      let subscription = await registration.pushManager.getSubscription();

      if (!subscription) {
        subscription = await registration.pushManager.subscribe({
          userVisibleOnly: true,
          applicationServerKey: urlBase64ToUint8Array(publicVapidKey)
        });
        console.log('New push notification subscribed');
      } else {
        console.log('Existing push subscription found, syncing with server...');
      }

      // 2. Refresh it on the backend (ALWAYS)
      const res = await fetch('/api/notifications/subscribe', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({ subscription }),
      });

      if (!res.ok) {
        const data = await res.json() as { error?: string };
        throw new Error(data.error || 'Failed to sync subscription to server');
      }

      // Success
      console.log('Subscription synced with server');
    } catch (error) {
      console.error('Failed to subscribe:', error);
      throw error; // Propagate to caller
    }
  }, []);

  // Request notification permission
  const requestPermission = useCallback(async () => {
    if (!isSupported) return 'denied';

    try {
      const result = await Notification.requestPermission();
      setPermission(result as NotificationPermission);

      if (result === 'granted') {
        // Verify we can subscribe and save to backend
        await subscribeToPush();
      }
      return result;
    } catch (error) {
      console.error('Error requesting notification permission:', error);
      alert('Error enabling notifications: ' + (error instanceof Error ? error.message : 'Unknown error'));
      return 'denied';
    }
  }, [isSupported, subscribeToPush]);

  // Send a notification
  const sendNotification = useCallback(
    (title: string, options?: NotificationOptions) => {
      if (!isSupported || permission !== 'granted') return;

      try {
        const notification = new Notification(title, {
          icon: '/icon-192.png',
          badge: '/icon-192.png',
          ...options,
        });

        notification.onclick = () => {
          window.focus();
          notification.close();
        };

        return notification;
      } catch (error) {
        console.error('Error sending notification:', error);
      }
    },
    [isSupported, permission]
  );

  // Play a "bubble pop" sound using Web Audio API
  const playNotificationSound = useCallback(() => {
    try {
      const AudioContext = window.AudioContext || (window as any).webkitAudioContext;
      if (!AudioContext) return;

      const ctx = new AudioContext();
      const oscillator = ctx.createOscillator();
      const gainNode = ctx.createGain();

      oscillator.connect(gainNode);
      gainNode.connect(ctx.destination);

      // Bubble 'pop' effect: sine wave with rapid frequency drop
      oscillator.type = 'sine';
      oscillator.frequency.setValueAtTime(800, ctx.currentTime);
      oscillator.frequency.exponentialRampToValueAtTime(100, ctx.currentTime + 0.1);

      // Envelope: quick attack, quick decay
      gainNode.gain.setValueAtTime(0, ctx.currentTime);
      gainNode.gain.linearRampToValueAtTime(0.3, ctx.currentTime + 0.01);
      gainNode.gain.exponentialRampToValueAtTime(0.01, ctx.currentTime + 0.1);

      oscillator.start();
      oscillator.stop(ctx.currentTime + 0.15);
    } catch (e) {
      console.error('Error playing notification sound:', e);
    }
  }, []);

  // Track previous settings to detect changes
  const [prevSettings, setPrevSettings] = useState(reminderSettings);

  // Check and send reminder
  const checkAndSendReminder = useCallback(() => {
    if (!reminderSettings.enabled || permission !== 'granted') return;

    const now = new Date();
    // 'en-CA' outputs YYYY-MM-DD in local timezone
    const today = now.toLocaleDateString('en-CA');

    if (reminderSettings.frequency === 'hourly') {
      const LAST_HOURLY_KEY = 'quittraq_last_hourly_notification';
      const lastNotifiedHour = localStorage.getItem(LAST_HOURLY_KEY);
      const currentHourKey = `${today}-${now.getHours()}`;

      if (lastNotifiedHour === currentHourKey) return; // Already notified this hour

      // Check active hours
      const startParts = (reminderSettings.hourlyStart || '09:00').split(':').map(Number);
      const endParts = (reminderSettings.hourlyEnd || '21:00').split(':').map(Number);

      const startMinutes = startParts[0] * 60 + startParts[1];
      const endMinutes = endParts[0] * 60 + endParts[1];
      const currentMinutes = now.getHours() * 60 + now.getMinutes();

      if (currentMinutes >= startMinutes && currentMinutes <= endMinutes) {
        playNotificationSound();
        sendNotification('QuitTraq Hourly Check-in', {
          body: "How are you doing? Log your status to stay on track!",
          tag: 'hourly-reminder',
          requireInteraction: true,
        });
        localStorage.setItem(LAST_HOURLY_KEY, currentHourKey);
      }

    } else {
      // Daily logic
      const lastNotified = localStorage.getItem(LAST_NOTIFICATION_KEY);

      if (lastNotified === today) return; // Already notified today

      const [hours, minutes] = reminderSettings.reminderTime.split(':').map(Number);
      const reminderTime = new Date();
      reminderTime.setHours(hours, minutes, 0, 0);

      // If current time is past the reminder time, send it
      if (now >= reminderTime) {
        playNotificationSound();
        sendNotification('QuitTraq Reminder', {
          body: "Time to log your daily usage! Every day counts on your journey.",
          tag: 'daily-reminder', // Tag ensures we don't stack multiple notifications
          requireInteraction: true, // Keep it visible until user interacts
        });
        localStorage.setItem(LAST_NOTIFICATION_KEY, today);
      }
    }
  }, [reminderSettings, permission, sendNotification, playNotificationSound]);

  // If settings change, we might need to reset notification history to allow "update and resend"
  // This effect MUST be after checkAndSendReminder is defined so we can call it immediately
  useEffect(() => {
    if (JSON.stringify(prevSettings) !== JSON.stringify(reminderSettings)) {
      // Only reset if time changed significantly or if toggled.
      // We can simply clear the 'last notified' date if the reminderTime changed.
      if (prevSettings.reminderTime !== reminderSettings.reminderTime && reminderSettings.frequency === 'daily') {
        localStorage.removeItem(LAST_NOTIFICATION_KEY);
        // Force immediate check
        checkAndSendReminder();
      }
      setPrevSettings(reminderSettings);
    }
  }, [reminderSettings, prevSettings, checkAndSendReminder]);

  // Set up interval to check for reminder time
  useEffect(() => {
    if (!reminderSettings.enabled || permission !== 'granted') return;

    // Check immediately
    checkAndSendReminder();

    // Check every minute
    const interval = setInterval(checkAndSendReminder, 60000);

    return () => clearInterval(interval);
  }, [reminderSettings, permission, checkAndSendReminder]);

  return {
    isSupported,
    permission,
    requestPermission,
    sendNotification,
  };
}