import {
  collection,
  query,
  orderBy,
  onSnapshot,
  addDoc,
  getDocs,
  doc,
  updateDoc,
  deleteDoc,
  writeBatch,
  serverTimestamp,
  Timestamp,
} from 'firebase/firestore';
import { db } from './firebase.js';

const donorsRef = collection(db, 'donors');
let unsubscribe = null;

export function subscribeToDonors(callback) {
  const q = query(donorsRef, orderBy('date', 'desc'));
  unsubscribe = onSnapshot(
    q,
    (snapshot) => {
      const donors = [];
      snapshot.forEach((doc) => {
        donors.push({ id: doc.id, ...doc.data() });
      });
      callback(donors);
    },
    (error) => {
      console.error('Error fetching donors:', error);
      callback([]);
    }
  );
  return unsubscribe;
}

export async function addDonor({ name, amount, classYear, message, anonymous }) {
  return addDoc(donorsRef, {
    name: anonymous ? 'Anonymous' : name,
    amount: Number(amount),
    classYear: classYear || '',
    message: message || '',
    anonymous: !!anonymous,
    date: serverTimestamp(),
  });
}

export function calculateTotal(donors) {
  return donors.reduce((sum, d) => sum + (d.amount || 0), 0);
}

// ===== Admin Operations =====

export async function getDonors() {
  const q = query(donorsRef, orderBy('date', 'desc'));
  const snapshot = await getDocs(q);
  const donors = [];
  snapshot.forEach((d) => donors.push({ id: d.id, ...d.data() }));
  return donors;
}

export async function addDonorWithDate({ name, amount, classYear, message, anonymous, date }) {
  const dateValue = date ? Timestamp.fromDate(new Date(date)) : serverTimestamp();
  return addDoc(donorsRef, {
    name: anonymous ? 'Anonymous' : name,
    amount: Number(amount),
    classYear: classYear || '',
    message: message || '',
    anonymous: !!anonymous,
    date: dateValue,
  });
}

export async function updateDonor(id, fields) {
  return updateDoc(doc(db, 'donors', id), fields);
}

export async function deleteDonor(id) {
  return deleteDoc(doc(db, 'donors', id));
}

export async function addDonorsBatch(donorsArray) {
  const chunks = [];
  for (let i = 0; i < donorsArray.length; i += 500) {
    chunks.push(donorsArray.slice(i, i + 500));
  }
  let imported = 0;
  for (const chunk of chunks) {
    const batch = writeBatch(db);
    for (const d of chunk) {
      const ref = doc(collection(db, 'donors'));
      const dateValue = d.date ? Timestamp.fromDate(new Date(d.date)) : serverTimestamp();
      batch.set(ref, {
        name: d.anonymous ? 'Anonymous' : (d.name || 'Anonymous'),
        amount: Number(d.amount) || 0,
        classYear: d.classYear || '',
        message: d.message || '',
        anonymous: !!d.anonymous,
        date: dateValue,
      });
    }
    await batch.commit();
    imported += chunk.length;
  }
  return imported;
}

export function sortDonors(donors, sortBy) {
  const sorted = [...donors];
  if (sortBy === 'amount') {
    sorted.sort((a, b) => (b.amount || 0) - (a.amount || 0));
  } else {
    sorted.sort((a, b) => {
      const dateA = a.date?.toMillis?.() || 0;
      const dateB = b.date?.toMillis?.() || 0;
      return dateB - dateA;
    });
  }
  return sorted;
}