// /components/payments/paymentService.js
'use strict';

const Payment = require('./paymentModel');
const AppError = require('../../utils/AppError');
const eventEmitter = require('../../events/eventEmitter');
const EVENT_NAMES = require('../../constants/eventNames');
const { calculateMeta } = require('../../utils/pagination');

const getAllPayments = async (query) => {
  const page = parseInt(query.page) || 1;
  const limit = Math.min(parseInt(query.limit) || 20, 200);
  const skip = (page - 1) * limit;

  const filter = {};
  if (query.userId) filter.user = query.userId;
  if (query.status) filter.status = query.status;

  const [items, total] = await Promise.all([
    Payment.find(filter)
      .populate({ path: 'user', select: 'name' })
      .populate({ path: 'classes', select: 'name' })
      .populate({ path: 'course', select: 'title' })
      .skip(skip).limit(limit).sort({ createdAt: -1 }).lean(),
    Payment.countDocuments(filter)
  ]);

  return { data: items, meta: calculateMeta(total, page, limit) };
};

const getPaymentById = async (id) => {
  const payment = await Payment.findById(id)
    .populate({ path: 'user', select: 'name phoneNumber' })
    .populate({ path: 'classes', select: 'name tuitionFee' })
    .populate({ path: 'course', select: 'title price' })
    .lean();
  if (!payment) throw new AppError('PAYMENT_NOT_FOUND');
  return payment;
};

const createPayment = async (body, actorId = null) => {
  const payment = await Payment.create({
    ...body,
    paidAmount: body.paidAmount || 0
  });

  if (actorId) {
    eventEmitter.emit(EVENT_NAMES.PAYMENT_CREATED, {
      paymentId: payment._id,
      userId: payment.user,
      actorId
    });
  }

  return getPaymentById(payment._id);
};

const updatePayment = async (id, body, actorId = null) => {
  const payment = await Payment.findById(id);
  if (!payment) throw new AppError('PAYMENT_NOT_FOUND');

  const previousStatus = payment.status;
  Object.assign(payment, body);
  await payment.save();

  if (body.status && body.status !== previousStatus) {
    eventEmitter.emit(EVENT_NAMES.PAYMENT_STATUS_CHANGED, {
      paymentId: payment._id,
      userId: payment.user,
      oldStatus: previousStatus,
      newStatus: payment.status,
      actorId
    });
  }

  return getPaymentById(payment._id);
};

const deletePayment = async (id) => {
  const payment = await Payment.findByIdAndDelete(id);
  if (!payment) throw new AppError('PAYMENT_NOT_FOUND');
  return null;
};

const searchPayments = async (query) => getAllPayments(query);

const addTransaction = async (paymentId, trxData, actorId = null) => {
  const payment = await Payment.findById(paymentId);
  if (!payment) throw new AppError('PAYMENT_NOT_FOUND');

  payment.transactions.push({
    ...trxData,
    recordedBy: actorId || trxData.recordedBy,
    date: trxData.date || new Date()
  });
  payment.paidAmount = payment.transactions.reduce((sum, t) => sum + (t.amount || 0), 0);
  await payment.save();
  return getPaymentById(paymentId);
};

const getMyPayments = async (userId, query = {}) => {
  return getAllPayments({ ...query, userId });
};

module.exports = {
  getAllPayments,
  getPaymentById,
  createPayment,
  updatePayment,
  deletePayment,
  searchPayments,
  addTransaction,
  getMyPayments,
  // Aliases for older call sites
  getAll: getAllPayments,
  getOne: getPaymentById,
  create: createPayment,
  recordTransaction: addTransaction,
  remove: deletePayment
};