const prisma = require('../config/db');
const { safeErrorMessage } = require('../utils/errorUtils');

// Shared building blocks for the per-dashboard stats endpoints below. Each dashboard
// (staff/supervisor/admin) gets exactly one endpoint that returns only what it renders,
// computed with aggregate queries — never a full payments/events list shipped to the
// client just to be reduced down to a couple of numbers.

async function computeScanStats(userId) {
  const startOfDay = new Date();
  startOfDay.setHours(0, 0, 0, 0);
  const whereBase = { scannedAt: { gte: startOfDay } };

  const [totalToday, myToday, lastHour, byStaffRaw] = await Promise.all([
    prisma.ticketUsage.count({ where: whereBase }),
    prisma.ticketUsage.count({ where: { ...whereBase, scannedById: userId } }),
    prisma.ticketUsage.count({ where: { scannedAt: { gte: new Date(Date.now() - 60 * 60 * 1000) } } }),
    prisma.ticketUsage.groupBy({ by: ['scannedById'], where: whereBase, _count: { _all: true } }),
  ]);

  const staffIds = byStaffRaw.map((b) => b.scannedById);
  const staffUsers = staffIds.length > 0
    ? await prisma.user.findMany({ where: { id: { in: staffIds } }, select: { id: true, name: true } })
    : [];
  const nameMap = Object.fromEntries(staffUsers.map((u) => [u.id, u.name]));

  return {
    totalToday,
    myToday,
    lastHour,
    byStaff: byStaffRaw.map((b) => ({ scannedById: b.scannedById, name: nameMap[b.scannedById] || 'Staff', count: b._count._all })),
  };
}

function getRecentScans(limit = 10) {
  return prisma.ticketUsage.findMany({
    orderBy: { scannedAt: 'desc' },
    take: limit,
    select: {
      id: true,
      scannedAt: true,
      quantityRedeemed: true,
      scannedBy: { select: { id: true, name: true } },
      ticket: {
        select: {
          id: true,
          event: { select: { title: true } },
          registrationOption: { select: { eventOption: { select: { name: true } } } },
        },
      },
    },
  });
}

function getActiveEventsCount() {
  return prisma.event.count({ where: { isActive: true, endDate: { gte: new Date() } } });
}

async function computePaymentStats({ includeWeekMonth }) {
  const startOfDay = new Date(new Date().setHours(0, 0, 0, 0));

  const queries = [
    prisma.payment.aggregate({ _sum: { amount: true }, where: { createdAt: { gte: startOfDay } } }),
    prisma.payment.count({ where: { isDonation: true, createdAt: { gte: startOfDay } } }),
  ];
  if (includeWeekMonth) {
    const lastWeek = new Date(startOfDay.getTime() - 7 * 24 * 60 * 60 * 1000);
    const lastMonth = new Date(startOfDay.getTime() - 30 * 24 * 60 * 60 * 1000);
    queries.push(
      prisma.payment.aggregate({ _sum: { amount: true }, where: { createdAt: { gte: lastWeek } } }),
      prisma.payment.aggregate({ _sum: { amount: true }, where: { createdAt: { gte: lastMonth } } }),
    );
  }

  const [totalToday, donationsToday, totalWeek, totalMonth] = await Promise.all(queries);

  const stats = {
    totalToday: totalToday._sum.amount || 0,
    donationsToday,
  };
  if (includeWeekMonth) {
    stats.totalWeek = totalWeek._sum.amount || 0;
    stats.totalMonth = totalMonth._sum.amount || 0;
  }
  return stats;
}

// @desc    All stats the staff dashboard needs, in one call
// @route   GET /api/stats/staff
// @access  Private/Staff+
const getStaffDashboardStats = async (req, res) => {
  try {
    const [scanStats, recentScans] = await Promise.all([
      computeScanStats(req.user.id),
      getRecentScans(10),
    ]);
    res.json({ scanStats, recentScans });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    All stats the supervisor dashboard needs, in one call
// @route   GET /api/stats/supervisor
// @access  Private/Supervisor+
const getSupervisorDashboardStats = async (req, res) => {
  try {
    const [scanStats, recentScans, paymentStats, activeEventsCount] = await Promise.all([
      computeScanStats(req.user.id),
      getRecentScans(10),
      computePaymentStats({ includeWeekMonth: false }),
      getActiveEventsCount(),
    ]);
    res.json({ scanStats, recentScans, paymentStats, activeEventsCount });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    All stats the admin dashboard needs, in one call
// @route   GET /api/stats/admin
// @access  Private/Admin
const getAdminDashboardStats = async (req, res) => {
  try {
    const [scanStats, recentScans, paymentStats, activeEventsCount] = await Promise.all([
      computeScanStats(req.user.id),
      getRecentScans(10),
      computePaymentStats({ includeWeekMonth: true }),
      getActiveEventsCount(),
    ]);
    res.json({ scanStats, recentScans, paymentStats, activeEventsCount });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

module.exports = {
  getStaffDashboardStats,
  getSupervisorDashboardStats,
  getAdminDashboardStats,
};