import { useState, useEffect, useCallback } from 'react';
import { apiClient } from '../api/client';

interface PushPreferences {
  reminder_enabled: boolean;
  reminder_time: string; // "HH:MM" in UTC
}

function urlBase64ToUint8Array(base64String: string): Uint8Array {
  const padding = '='.repeat((4 - (base64String.length % 4)) % 4);
  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/');
  const raw = atob(base64);
  const arr = new Uint8Array(raw.length);
  for (let i = 0; i < raw.length; i++) {
    arr[i] = raw.charCodeAt(i);
  }
  return arr;
}

export function localTimeToUtc(localTime: string): string {
  const [hours, minutes] = localTime.split(':').map(Number);
  const now = new Date();
  now.setHours(hours, minutes, 0, 0);
  const utcH = now.getUTCHours().toString().padStart(2, '0');
  const utcM = now.getUTCMinutes().toString().padStart(2, '0');
  return `${utcH}:${utcM}`;
}

export function utcTimeToLocal(utcTime: string): string {
  const [hours, minutes] = utcTime.split(':').map(Number);
  const now = new Date();
  now.setUTCHours(hours, minutes, 0, 0);
  const localH = now.getHours().toString().padStart(2, '0');
  const localM = now.getMinutes().toString().padStart(2, '0');
  return `${localH}:${localM}`;
}

export function usePushNotifications() {
  const [permission, setPermission] = useState<NotificationPermission>(
    typeof window !== 'undefined' && 'Notification' in window
      ? Notification.permission
      : 'denied',
  );
  const [preferences, setPreferences] = useState<PushPreferences | null>(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    apiClient
      .get<PushPreferences>('/api/push/preferences')
      .then(setPreferences)
      .catch(() => {})
      .finally(() => setLoading(false));
  }, []);

  const subscribe = useCallback(async () => {
    if (!('Notification' in window) || !('serviceWorker' in navigator)) return;

    const perm = await Notification.requestPermission();
    setPermission(perm);
    if (perm !== 'granted') return;

    const { vapid_public_key } = await apiClient.get<{ vapid_public_key: string }>(
      '/api/push/vapid-key',
    );

    const applicationServerKey = urlBase64ToUint8Array(vapid_public_key);

    const registration = await navigator.serviceWorker.ready;
    const subscription = await registration.pushManager.subscribe({
      userVisibleOnly: true,
      applicationServerKey: applicationServerKey.buffer as ArrayBuffer,
    });

    const json = subscription.toJSON();
    await apiClient.post('/api/push/subscribe', {
      endpoint: json.endpoint,
      p256dh: json.keys?.p256dh,
      auth: json.keys?.auth,
    });
  }, []);

  const unsubscribe = useCallback(async () => {
    if (!('serviceWorker' in navigator)) return;

    try {
      const registration = await navigator.serviceWorker.ready;
      const subscription = await registration.pushManager.getSubscription();
      if (subscription) {
        await subscription.unsubscribe();
      }
    } catch {
      // ignore errors
    }
    await apiClient.delete('/api/push/subscribe');
  }, []);

  const updatePreferences = useCallback(async (prefs: PushPreferences) => {
    await apiClient.put('/api/push/preferences', prefs);
    setPreferences(prefs);
  }, []);

  return { permission, preferences, loading, subscribe, unsubscribe, updatePreferences };
}