import * as Notifications from 'expo-notifications';
import * as Device from 'expo-device';
import { Platform } from 'react-native';
import { API_BASE } from './types';
import { getSessionId } from './storage';

// Configure how notifications appear when the app is in the foreground
Notifications.setNotificationHandler({
  handleNotification: async () => ({
    shouldShowAlert: true,
    shouldPlaySound: true,
    shouldSetBadge: true,
  }),
});

export async function registerForPushNotifications(): Promise<string | null> {
  if (!Device.isDevice) {
    // Push notifications don't work in simulators
    return null;
  }

  // Check / request permission
  const { status: existing } = await Notifications.getPermissionsAsync();
  let finalStatus = existing;
  if (existing !== 'granted') {
    const { status } = await Notifications.requestPermissionsAsync();
    finalStatus = status;
  }
  if (finalStatus !== 'granted') return null;

  // Android needs a notification channel
  if (Platform.OS === 'android') {
    await Notifications.setNotificationChannelAsync('default', {
      name: 'EventFlow',
      importance: Notifications.AndroidImportance.MAX,
      vibrationPattern: [0, 250, 250, 250],
      lightColor: '#f97316',
    });
  }

  // Get Expo push token
  const tokenData = await Notifications.getExpoPushTokenAsync();
  const token = tokenData.data;

  // Register token with backend
  const sid = await getSessionId();
  await fetch(`${API_BASE}/push/register`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ token, context: 'participant', context_id: sid }),
  }).catch(() => {}); // silently fail — non-critical

  return token;
}