import { initializeApp, getApps, getApp } from "firebase/app";
import { getAuth } from "firebase/auth";
import { getDatabase } from "firebase/database";

// As variáveis de ambiente devem ser configuradas no Vercel e no ficheiro .env.local
const firebaseConfig = {
  apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
  authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
  projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
  storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
  messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
  appId: process.env.NEXT_PUBLIC_FIREBASE_APP_ID,
  databaseURL: process.env.NEXT_PUBLIC_FIREBASE_DATABASE_URL || "https://namesa-429c1-default-rtdb.firebaseio.com"
};

// Validate that all required environment variables are present
const requiredEnvVars = [
  "NEXT_PUBLIC_FIREBASE_API_KEY",
  "NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN",
  "NEXT_PUBLIC_FIREBASE_PROJECT_ID",
  "NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET",
  "NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID",
  "NEXT_PUBLIC_FIREBASE_APP_ID",
];

const missingVars = requiredEnvVars.filter(
  (key) => !process.env[key]
);

if (missingVars.length > 0) {
  console.error(
    "[Firebase] Missing environment variables:",
    missingVars.join(", "),
    "\nPlease ensure all Firebase environment variables are set in .env.local or your hosting platform."
  );
}

// Initialize Firebase only once — prevents duplicate app errors in development (HMR) and SSR
let app;
try {
  app = getApps().length === 0 ? initializeApp(firebaseConfig) : getApp();
} catch (error: any) {
  if (error?.code === "app/duplicate-app") {
    app = getApp();
  } else {
    throw new Error(
      `[Firebase] Failed to initialize: ${error?.message || "Unknown error"}. Check your environment variables.`
    );
  }
}

export const auth = getAuth(app);
export const db = getDatabase(app);
export default app;