const { body, param } = require('express-validator');
const { v4: uuidv4 } = require('uuid');
const dayjs = require('dayjs');
const {
  Employee,
  Vendor,
  Document,
  SafetyBadge,
  GatePass,
  RenewRequest,
  SafetyInduction
} = require('../models');
const validate = require('../utils/validation');
const { toValidObjectIdStrings } = require('../utils/objectId');
const { ensureMandatoryDocuments } = require('../services/workflowService');

const verifyDocumentValidators = [
  param('id').isMongoId().withMessage('valid employee id is required'),
  body('types').isArray({ min: 1 }).withMessage('types array is required'),
  validate
];

const reviewDocumentValidators = [
  param('id').isMongoId().withMessage('valid document id is required'),
  body('action').isIn(['Approve', 'Reject']).withMessage('action must be Approve or Reject'),
  body('remarks').optional({ nullable: true }).isLength({ max: 255 }).withMessage('remarks must be at most 255 characters'),
  body('pvc_validity_date')
    .optional({ nullable: true })
    .isDate()
    .withMessage('pvc_validity_date must be a valid date'),
  validate
];

const approveEmployeeValidators = [
  param('id').isMongoId().withMessage('valid employee id is required'),
  validate
];

const createGatePassValidators = [
  param('id').isMongoId().withMessage('valid employee id is required'),
  body('issue_date').isDate().withMessage('issue_date must be valid'),
  body('fee_paid').isBoolean().withMessage('fee_paid must be boolean'),
  body('fee_amount').optional().isFloat({ min: 0 }).withMessage('fee_amount must be valid number'),
  validate
];

const renewGatePassValidators = [
  param('id').isMongoId().withMessage('valid gate pass id is required'),
  body('issue_date').isDate().withMessage('issue_date is required'),
  body('fee_paid').isBoolean().withMessage('fee_paid must be boolean'),
  validate
];

const processRenewRequestValidators = [
  param('id').isMongoId().withMessage('valid renewal request id is required'),
  body('fee_paid').isBoolean().withMessage('fee_paid must be boolean'),
  body('issue_date').optional().isDate().withMessage('issue_date must be valid'),
  validate
];

function latestByEmployee(rows) {
  const map = new Map();
  for (const row of rows) {
    const key = String(row.employee_id);
    if (!map.has(key)) map.set(key, row);
  }
  return map;
}

async function getPendingVerification(req, res, next) {
  try {
    const employees = await Employee.find({ status: 'Pending', is_active: true })
      .sort({ created_at: -1 })
      .lean();

    const vendorIds = toValidObjectIdStrings(employees.map((e) => e.vendor_id));
    const vendors = vendorIds.length
      ? await Vendor.find({ _id: { $in: vendorIds }, is_active: true }, { name: 1 }).lean()
      : [];
    const vendorMap = new Map(vendors.map((v) => [String(v._id), v]));

    const filteredEmployees = employees.filter((e) => vendorMap.has(String(e.vendor_id)));
    const employeeIds = filteredEmployees.map((e) => e._id);

    const docs = await Document.find({ employee_id: { $in: employeeIds } }).sort({ uploaded_at: -1 }).lean();
    const badges = await SafetyBadge.find({ employee_id: { $in: employeeIds } }, { employee_id: 1, expiry_date: 1 }).lean();
    const passes = await GatePass.find({ employee_id: { $in: employeeIds } }).sort({ created_at: -1 }).lean();

    const badgeMap = new Map(badges.map((b) => [String(b.employee_id), b]));
    const passMap = latestByEmployee(passes);

    const docsByEmployee = new Map();
    for (const doc of docs) {
      const key = String(doc.employee_id);
      if (!docsByEmployee.has(key)) docsByEmployee.set(key, []);
      docsByEmployee.get(key).push(doc);
    }

    const rows = [];
    for (const employee of filteredEmployees) {
      const key = String(employee._id);
      const vendor = vendorMap.get(String(employee.vendor_id));
      const employeeDocs = docsByEmployee.get(key) || [];
      const badge = badgeMap.get(key);
      const pass = passMap.get(key);

      if (employeeDocs.length === 0) {
        rows.push({
          employee_id: key,
          employee_code: employee.employee_code,
          employee_name: employee.name,
          status: employee.status,
          vendor_name: vendor?.name || 'N/A',
          profile_photo_path: employee.profile_photo_path,
          document_id: null,
          type: null,
          file_path: null,
          verified_by_hr: false,
          hr_status: null,
          hr_remarks: null,
          pvc_validity_date: null,
          hse_due_date: badge?.expiry_date || null,
          pass_due_date: pass?.expiry_date || null,
          pass_status: pass?.status || null
        });
        continue;
      }

      for (const doc of employeeDocs) {
        rows.push({
          employee_id: key,
          employee_code: employee.employee_code,
          employee_name: employee.name,
          status: employee.status,
          vendor_name: vendor?.name || 'N/A',
          profile_photo_path: employee.profile_photo_path,
          document_id: String(doc._id),
          type: doc.type,
          file_path: doc.file_path,
          pvc_validity_date: doc.pvc_validity_date,
          verified_by_hr: doc.verified_by_hr,
          hr_status: doc.hr_status,
          hr_remarks: doc.hr_remarks,
          uploaded_at: doc.uploaded_at,
          hse_due_date: badge?.expiry_date || null,
          pass_due_date: pass?.expiry_date || null,
          pass_status: pass?.status || null
        });
      }
    }

    return res.json(rows);
  } catch (error) {
    return next(error);
  }
}

async function verifyDocuments(req, res, next) {
  try {
    const employeeId = req.params.id;
    const { types } = req.body;

    if (!Array.isArray(types) || types.length === 0) {
      return res.status(400).json({ message: 'types array is required' });
    }

    if (types.includes('PVC')) {
      const pvcDoc = await Document.findOne({ employee_id: employeeId, type: 'PVC' }, { pvc_validity_date: 1 }).lean();
      if (!pvcDoc?.pvc_validity_date) {
        return res.status(400).json({ message: 'PVC validity date is required before approving PVC document' });
      }
    }

    await Document.updateMany(
      { employee_id: employeeId, type: { $in: types } },
      {
        $set: {
          verified_by_hr: true,
          verified_at: new Date(),
          hr_status: 'Approved',
          hr_remarks: null,
          reviewed_at: new Date(),
          reviewed_by: req.user.id
        }
      }
    );

    return res.json({ message: 'Selected documents marked as verified' });
  } catch (error) {
    return next(error);
  }
}

async function reviewDocument(req, res, next) {
  try {
    const documentId = req.params.id;
    const { action, remarks, pvc_validity_date } = req.body;
    const cleanRemarks = String(remarks || '').trim();

    const doc = await Document.findById(documentId);
    if (!doc) {
      return res.status(404).json({ message: 'Document not found' });
    }

    if (action === 'Approve') {
      if (doc.type === 'PVC') {
        const nextPvcDate = pvc_validity_date ? new Date(pvc_validity_date) : doc.pvc_validity_date;
        if (!nextPvcDate || Number.isNaN(new Date(nextPvcDate).getTime())) {
          return res.status(400).json({ message: 'PVC validity date is required before approving PVC document' });
        }
        doc.pvc_validity_date = nextPvcDate;
      }
      doc.verified_by_hr = true;
      doc.verified_at = new Date();
      doc.hr_status = 'Approved';
      doc.hr_remarks = null;
      doc.reviewed_at = new Date();
      doc.reviewed_by = req.user.id;
      await doc.save();
      return res.json({ message: 'Document approved' });
    }

    doc.verified_by_hr = false;
    doc.verified_at = null;
    doc.hr_status = 'Rejected';
    doc.hr_remarks = cleanRemarks || null;
    doc.reviewed_at = new Date();
    doc.reviewed_by = req.user.id;
    await doc.save();

    return res.json({ message: 'Document rejected' });
  } catch (error) {
    return next(error);
  }
}

async function approveForSafety(req, res, next) {
  try {
    const employeeId = req.params.id;
    const mandatoryDocsExist = await ensureMandatoryDocuments(employeeId);
    if (!mandatoryDocsExist) {
      return res.status(400).json({ message: 'Mandatory document set is incomplete' });
    }

    const docs = await Document.find({ employee_id: employeeId }, { type: 1, verified_by_hr: 1 }).lean();

    const isVerified = (type) => docs.some((d) => d.type === type && d.verified_by_hr === true);
    const hasAadhar = isVerified('Aadhar');
    const hasUan = isVerified('UAN');
    const hasAlt = isVerified('ESI') || isVerified('Compensation_Policy');
    const hasPvc = isVerified('PVC');

    if (!(hasAadhar && hasUan && hasAlt && hasPvc)) {
      return res.status(400).json({ message: 'HR verification is incomplete for mandatory docs' });
    }

    const employee = await Employee.findById(employeeId);
    if (!employee) {
      return res.status(404).json({ message: 'Employee not found' });
    }

    const vendor = await Vendor.findById(employee.vendor_id, { is_active: 1 }).lean();
    if (!employee.is_active || !vendor?.is_active) {
      return res.status(400).json({ message: 'Employee or vendor is inactive' });
    }

    employee.status = 'HR_Approved';
    employee.hr_approved_at = new Date();
    await employee.save();

    return res.json({ message: 'Employee approved for Safety induction' });
  } catch (error) {
    return next(error);
  }
}

async function generateGatePass(req, res, next) {
  try {
    const employeeId = req.params.id;
    const { issue_date, fee_paid, fee_amount } = req.body;

    if (!fee_paid) {
      return res.status(400).json({ message: 'Gate pass can be generated only after fee is marked as paid' });
    }

    const employee = await Employee.findById(employeeId);
    if (!employee) {
      return res.status(404).json({ message: 'Employee not found' });
    }

    const vendor = await Vendor.findById(employee.vendor_id, { is_active: 1 }).lean();
    if (!employee.is_active || !vendor?.is_active) {
      return res.status(400).json({ message: 'Employee or vendor is inactive' });
    }

    if (!['Safety_Approved', 'Active'].includes(employee.status)) {
      return res.status(400).json({ message: 'Employee must complete safety induction before pass issuance' });
    }

    const gatePass = await GatePass.create({
      employee_id: employeeId,
      issue_date: new Date(issue_date),
      fee_paid,
      fee_amount: fee_amount || 100,
      barcode: `DSS-${employeeId}-${uuidv4().slice(0, 8).toUpperCase()}`,
      status: 'Active',
      issued_by: req.user.id
    });

    employee.status = 'Active';
    employee.due_date = gatePass.expiry_date;
    await employee.save();

    return res.status(201).json({
      id: String(gatePass._id),
      employee_id: String(gatePass.employee_id),
      issue_date: gatePass.issue_date,
      expiry_date: gatePass.expiry_date,
      fee_paid: gatePass.fee_paid,
      fee_amount: gatePass.fee_amount,
      barcode: gatePass.barcode,
      status: gatePass.status
    });
  } catch (error) {
    return next(error);
  }
}

async function renewGatePass(req, res, next) {
  try {
    const gatePassId = req.params.id;
    const { issue_date, fee_paid } = req.body;

    if (!fee_paid) {
      return res.status(400).json({ message: 'Renewal can be processed only after fee is paid' });
    }

    const previousPass = await GatePass.findById(gatePassId).lean();
    if (!previousPass) {
      return res.status(404).json({ message: 'Gate pass not found' });
    }

    const employee = await Employee.findById(previousPass.employee_id);
    if (!employee) {
      return res.status(404).json({ message: 'Employee not found' });
    }

    const vendor = await Vendor.findById(employee.vendor_id, { is_active: 1 }).lean();
    if (!employee.is_active || !vendor?.is_active) {
      return res.status(400).json({ message: 'Employee or vendor is inactive' });
    }

    if (new Date(previousPass.expiry_date) >= new Date()) {
      return res.status(400).json({ message: 'Pass is not expired yet, renewal is not allowed' });
    }

    const newPass = await GatePass.create({
      employee_id: previousPass.employee_id,
      issue_date: new Date(issue_date),
      fee_paid,
      fee_amount: 100,
      barcode: `DSS-${previousPass.employee_id}-${uuidv4().slice(0, 8).toUpperCase()}`,
      status: 'Active',
      issued_by: req.user.id
    });

    employee.status = 'Active';
    employee.due_date = newPass.expiry_date;
    await employee.save();

    return res.status(201).json({
      message: 'Pass renewed successfully',
      new_gate_pass_id: String(newPass._id),
      barcode: newPass.barcode
    });
  } catch (error) {
    return next(error);
  }
}

async function listRenewRequests(req, res, next) {
  try {
    const requests = await RenewRequest.find({ status: 'Requested' })
      .sort({ created_at: -1 })
      .lean();

    const employeeIds = toValidObjectIdStrings(requests.map((r) => r.employee_id));
    const vendorIds = toValidObjectIdStrings(requests.map((r) => r.vendor_id));
    const gatePassIds = toValidObjectIdStrings(requests.map((r) => r.gate_pass_id));

    const employees = employeeIds.length
      ? await Employee.find({ _id: { $in: employeeIds }, is_active: true }, { name: 1, vendor_id: 1 }).lean()
      : [];
    const vendors = vendorIds.length
      ? await Vendor.find({ _id: { $in: vendorIds }, is_active: true }, { name: 1 }).lean()
      : [];
    const gatePasses = gatePassIds.length
      ? await GatePass.find({ _id: { $in: gatePassIds } }, { expiry_date: 1 }).lean()
      : [];

    const employeeMap = new Map(employees.map((e) => [String(e._id), e]));
    const vendorMap = new Map(vendors.map((v) => [String(v._id), v]));
    const gatePassMap = new Map(gatePasses.map((g) => [String(g._id), g]));

    const rows = requests
      .filter((reqRow) => employeeMap.has(String(reqRow.employee_id)) && vendorMap.has(String(reqRow.vendor_id)))
      .map((reqRow) => {
        const employee = employeeMap.get(String(reqRow.employee_id));
        const vendor = vendorMap.get(String(reqRow.vendor_id));
        const gatePass = gatePassMap.get(String(reqRow.gate_pass_id));
        return {
          id: String(reqRow._id),
          gate_pass_id: String(reqRow.gate_pass_id),
          employee_id: String(reqRow.employee_id),
          vendor_id: String(reqRow.vendor_id),
          requested_issue_date: reqRow.requested_issue_date,
          status: reqRow.status,
          remarks: reqRow.remarks,
          employee_name: employee?.name || 'N/A',
          vendor_name: vendor?.name || 'N/A',
          previous_expiry_date: gatePass?.expiry_date || null
        };
      });

    return res.json(rows);
  } catch (error) {
    return next(error);
  }
}

async function processRenewRequest(req, res, next) {
  try {
    const requestId = req.params.id;
    const { fee_paid, issue_date } = req.body;

    if (!fee_paid) {
      return res.status(400).json({ message: 'Renewal request can be processed only after fee is paid' });
    }

    const renewRequest = await RenewRequest.findById(requestId);
    if (!renewRequest) {
      return res.status(404).json({ message: 'Renewal request not found' });
    }

    if (renewRequest.status !== 'Requested') {
      return res.status(400).json({ message: 'Renewal request already processed' });
    }

    const previousPass = await GatePass.findById(renewRequest.gate_pass_id).lean();
    if (!previousPass) {
      return res.status(404).json({ message: 'Previous gate pass not found' });
    }

    const employee = await Employee.findById(renewRequest.employee_id);
    if (!employee) {
      return res.status(404).json({ message: 'Employee not found' });
    }

    const vendor = await Vendor.findById(renewRequest.vendor_id, { is_active: 1 }).lean();
    if (!employee.is_active || !vendor?.is_active) {
      return res.status(400).json({ message: 'Employee or vendor is inactive' });
    }

    if (new Date(previousPass.expiry_date) >= new Date()) {
      return res.status(400).json({ message: 'Previous pass has not expired' });
    }

    const effectiveIssueDate = issue_date || dayjs(renewRequest.requested_issue_date).format('YYYY-MM-DD');
    const newPass = await GatePass.create({
      employee_id: renewRequest.employee_id,
      issue_date: new Date(effectiveIssueDate),
      fee_paid,
      fee_amount: 100,
      barcode: `DSS-${renewRequest.employee_id}-${uuidv4().slice(0, 8).toUpperCase()}`,
      status: 'Active',
      issued_by: req.user.id
    });

    renewRequest.status = 'Processed';
    renewRequest.remarks = 'Processed and activated';
    await renewRequest.save();

    employee.status = 'Active';
    employee.due_date = newPass.expiry_date;
    await employee.save();

    return res.json({
      message: 'Renewal request processed successfully',
      gate_pass_id: String(newPass._id),
      barcode: newPass.barcode
    });
  } catch (error) {
    return next(error);
  }
}

module.exports = {
  verifyDocumentValidators,
  reviewDocumentValidators,
  approveEmployeeValidators,
  createGatePassValidators,
  renewGatePassValidators,
  processRenewRequestValidators,
  getPendingVerification,
  verifyDocuments,
  reviewDocument,
  approveForSafety,
  generateGatePass,
  renewGatePass,
  listRenewRequests,
  processRenewRequest
};