const dayjs = require('dayjs');
const {
  Document,
  Employee,
  Vendor,
  User,
  SafetyBadge,
  GatePass,
  AlertLog
} = require('../models');
const { sendEmail, sendWhatsApp } = require('./notificationService');

async function ensureMandatoryDocuments(employeeId) {
  const rows = await Document.find({ employee_id: employeeId }, { type: 1, verified_by_hr: 1 }).lean();

  const hasAadhar = rows.some((r) => r.type === 'Aadhar');
  const hasUan = rows.some((r) => r.type === 'UAN');
  const hasEsi = rows.some((r) => r.type === 'ESI');
  const hasCompPolicy = rows.some((r) => r.type === 'Compensation_Policy');
  const hasPvc = rows.some((r) => r.type === 'PVC');

  return hasAadhar && hasUan && (hasEsi || hasCompPolicy) && hasPvc;
}

async function countVendorWorkers(vendorId) {
  return Employee.countDocuments({
    vendor_id: vendorId,
    is_active: true,
    status: { $in: ['Pending', 'HR_Approved', 'Safety_Approved', 'Active'] }
  });
}

async function findVendorContact(vendorId) {
  return User.findOne({ vendor_id: vendorId, role: 'Vendor', is_active: true }, { email: 1, phone: 1 }).lean();
}

async function sendAlert(alertType, table, refId, recipientEmail, recipientPhone, subject, message) {
  if (!recipientEmail) return;

  const existing = await AlertLog.findOne({
    alert_type: alertType,
    reference_table: table,
    reference_id: String(refId),
    recipient_email: recipientEmail,
    channel: 'Email'
  }).lean();

  if (!existing) {
    await sendEmail(recipientEmail, subject, message);
    await AlertLog.create({
      alert_type: alertType,
      reference_table: table,
      reference_id: String(refId),
      recipient_email: recipientEmail,
      channel: 'Email',
      message,
      sent_at: new Date()
    });
  }

  if (recipientPhone) {
    const existingWa = await AlertLog.findOne({
      alert_type: alertType,
      reference_table: table,
      reference_id: String(refId),
      recipient_email: recipientEmail,
      channel: 'WhatsApp'
    }).lean();

    if (!existingWa) {
      await sendWhatsApp(`whatsapp:${recipientPhone}`, message);
      await AlertLog.create({
        alert_type: alertType,
        reference_table: table,
        reference_id: String(refId),
        recipient_email: recipientEmail,
        channel: 'WhatsApp',
        message,
        sent_at: new Date()
      });
    }
  }
}

async function processBadgeAlerts(adminUsers) {
  const today = dayjs().startOf('day');
  const maxDate = today.add(30, 'day').endOf('day').toDate();

  const badges = await SafetyBadge.find({ expiry_date: { $lte: maxDate } })
    .populate({ path: 'employee_id', model: 'Employee', select: 'name vendor_id is_active' })
    .lean();

  for (const badge of badges) {
    const employee = badge.employee_id;
    if (!employee || !employee.is_active) continue;

    const vendor = await Vendor.findById(employee.vendor_id, { name: 1, is_active: 1 }).lean();
    if (!vendor || !vendor.is_active) continue;

    const daysToExpiry = dayjs(badge.expiry_date).startOf('day').diff(today, 'day');
    let alertType;
    let subject;

    if (daysToExpiry <= 0) {
      alertType = 'SAFETY_BADGE_EXPIRED';
      subject = `Safety Badge Expired - ${employee.name}`;
    } else if (daysToExpiry === 7) {
      alertType = 'SAFETY_BADGE_7_DAYS';
      subject = `Safety Badge Expires in 7 Days - ${employee.name}`;
    } else if (daysToExpiry === 30) {
      alertType = 'SAFETY_BADGE_30_DAYS';
      subject = `Safety Badge Expires in 30 Days - ${employee.name}`;
    } else {
      continue;
    }

    const message = `${employee.name} (${vendor.name}) safety badge due date: ${dayjs(badge.expiry_date).format('DD/MM/YYYY')}.`;

    const vendorUser = await findVendorContact(vendor._id);
    if (vendorUser) {
      await sendAlert(alertType, 'safety_badges', badge._id, vendorUser.email, vendorUser.phone, subject, message);
    }

    for (const adminUser of adminUsers) {
      await sendAlert(alertType, 'safety_badges', badge._id, adminUser.email, adminUser.phone, subject, message);
    }
  }
}

async function processGatePassAlerts(adminUsers) {
  const today = dayjs().startOf('day');
  const maxDate = today.add(30, 'day').endOf('day').toDate();

  const gatePasses = await GatePass.find({ expiry_date: { $lte: maxDate } })
    .populate({ path: 'employee_id', model: 'Employee', select: 'name vendor_id is_active' })
    .lean();

  for (const gatePass of gatePasses) {
    const employee = gatePass.employee_id;
    if (!employee || !employee.is_active) continue;

    const vendor = await Vendor.findById(employee.vendor_id, { name: 1, is_active: 1 }).lean();
    if (!vendor || !vendor.is_active) continue;

    const daysToExpiry = dayjs(gatePass.expiry_date).startOf('day').diff(today, 'day');
    let alertType;
    let subject;

    if (daysToExpiry <= 0) {
      alertType = 'GATE_PASS_EXPIRED';
      subject = `Gate Pass Expired - ${employee.name}`;
    } else if (daysToExpiry === 7) {
      alertType = 'GATE_PASS_7_DAYS';
      subject = `Gate Pass Expires in 7 Days - ${employee.name}`;
    } else if (daysToExpiry === 30) {
      alertType = 'GATE_PASS_30_DAYS';
      subject = `Gate Pass Expires in 30 Days - ${employee.name}`;
    } else {
      continue;
    }

    const message = `${employee.name} (${vendor.name}) gate pass due date: ${dayjs(gatePass.expiry_date).format('DD/MM/YYYY')}.`;

    const vendorUser = await findVendorContact(vendor._id);
    if (vendorUser) {
      await sendAlert(alertType, 'gate_passes', gatePass._id, vendorUser.email, vendorUser.phone, subject, message);
    }

    for (const adminUser of adminUsers) {
      await sendAlert(alertType, 'gate_passes', gatePass._id, adminUser.email, adminUser.phone, subject, message);
    }
  }
}

async function sendExpiryAlerts() {
  const adminUsers = await User.find({ role: 'Admin', is_active: true }, { email: 1, phone: 1 }).lean();

  await processBadgeAlerts(adminUsers);
  await processGatePassAlerts(adminUsers);

  await GatePass.updateMany(
    { expiry_date: { $lt: dayjs().startOf('day').toDate() }, status: { $ne: 'Expired' } },
    { $set: { status: 'Expired' } }
  );
}

module.exports = {
  ensureMandatoryDocuments,
  countVendorWorkers,
  sendExpiryAlerts
};