const path = require('path');
const Degree = require('../models/degree');
const Department = require('../models/department');
const Level = require('../models/level');
const writeAuditLog = require('../audit/writeAuditLog');
const AUDIT_ACTIONS = require('../constants/auditAction');

// Helper: store only filename, served via /secure-files/ route
function normalizePath(filePath) {
  if (!filePath) return undefined;
  return path.basename(filePath.replace(/\\/g, '/'));
}

// GET /admin/degree
exports.index = async (req, res) => {
  try {
    const { search, type, department, level, status } = req.query;
    const filter = {};
    if (search) {
      filter.$or = [
        { qualification_number: { $regex: search, $options: 'i' } },
        { certification_number: { $regex: search, $options: 'i' } },
        { student_name: { $regex: search, $options: 'i' } }
      ];
    }
    if (type) filter.type = type;
    if (department) filter.department = department;
    if (level) filter.level = level;
    if (status) filter.status = status;

    const [degrees, departments, levels] = await Promise.all([
      Degree.find(filter).populate('department level').sort({ createdAt: -1 }),
      Department.find(),
      Level.find()
    ]);

    res.render('admin/degree/index', {
      degrees, departments, levels,
      query: req.query,
      user: req.session.user,
      layout: 'layouts/admin',
      title: 'Quản lý Văn bằng'
    });
  } catch (err) {
    console.error('degreeController.index error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi tải danh sách văn bằng');
    res.redirect('/admin/dashboard');
  }
};

// GET /admin/degree/create
exports.createForm = async (req, res) => {
  try {
    const [departments, levels] = await Promise.all([Department.find(), Level.find()]);
    res.render('admin/degree/create', {
      departments, levels,
      user: req.session.user,
      layout: 'layouts/admin',
      title: 'Tạo Văn bằng mới'
    });
  } catch (err) {
    console.error('degreeController.createForm error:', err);
    req.flash('error', 'Đã xảy ra lỗi');
    res.redirect('/admin/degree');
  }
};

// POST /admin/degree/create
exports.create = async (req, res) => {
  try {
    const degreeData = { ...req.body };
    const degreeImagePath = req.files?.degree_image?.[0]?.path;
    const certificateImagePath = req.files?.certificate_image?.[0]?.path;
    if (degreeImagePath) degreeData.degree_image = normalizePath(degreeImagePath);
    if (certificateImagePath) degreeData.certificate_image = normalizePath(certificateImagePath);

    const degree = new Degree(degreeData);
    await degree.save();

    await writeAuditLog({
      model: 'Degree', documentId: degree._id,
      action: AUDIT_ACTIONS.CREATE_DEGREE,
      before: null, after: degree.toObject(), req
    });

    req.flash('success', 'Degree created');
    res.redirect('/admin/degree');
  } catch (err) {
    console.error('degreeController.create error:', err);
    try {
      const [departments, levels] = await Promise.all([Department.find(), Level.find()]);
      res.render('admin/degree/create', {
        error: err.message, formData: req.body,
        departments, levels,
        user: req.session.user,
        layout: 'layouts/admin',
        title: 'Tạo Văn bằng mới'
      });
    } catch (renderErr) {
      req.flash('error', err.message);
      res.redirect('/admin/degree');
    }
  }
};

// GET /admin/degree/:id/edit
exports.editForm = async (req, res) => {
  try {
    const degree = await Degree.findById(req.params.id).populate('department level');
    if (!degree) {
      req.flash('error', 'Degree not found');
      return res.redirect('/admin/degree');
    }
    const [departments, levels] = await Promise.all([Department.find(), Level.find()]);
    res.render('admin/degree/edit', {
      degree, departments, levels,
      user: req.session.user,
      layout: 'layouts/admin',
      title: 'Chỉnh sửa Văn bằng'
    });
  } catch (err) {
    console.error('degreeController.editForm error:', err);
    req.flash('error', 'Đã xảy ra lỗi');
    res.redirect('/admin/degree');
  }
};

// POST /admin/degree/:id/edit
exports.update = async (req, res) => {
  try {
    const degree = await Degree.findById(req.params.id);
    if (!degree) {
      req.flash('error', 'Degree not found');
      return res.redirect('/admin/degree');
    }
    const beforeData = degree.toObject();
    const fields = [
      'qualification_number', 'certification_number', 'student_name', 'program_name',
      'type', 'department', 'level', 'issued_date', 'status',
      'passport_number', 'address', 'topic_name', 'topic_short_desc'
    ];
    fields.forEach(field => { if (req.body[field] !== undefined) degree[field] = req.body[field]; });

    const degreeImagePath = req.files?.degree_image?.[0]?.path;
    const certificateImagePath = req.files?.certificate_image?.[0]?.path;
    if (degreeImagePath) degree.degree_image = normalizePath(degreeImagePath);
    if (certificateImagePath) degree.certificate_image = normalizePath(certificateImagePath);

    await degree.save();
    await writeAuditLog({
      model: 'Degree', documentId: degree._id,
      action: AUDIT_ACTIONS.UPDATE_DEGREE,
      before: beforeData, after: degree.toObject(), req
    });

    req.flash('success', 'Degree updated');
    res.redirect('/admin/degree');
  } catch (err) {
    console.error('degreeController.update error:', err);
    req.flash('error', err.message);
    res.redirect('back');
  }
};

// POST /admin/degree/:id/delete
exports.destroy = async (req, res) => {
  try {
    const degree = await Degree.findById(req.params.id);
    if (!degree) {
      req.flash('error', 'Degree not found');
      return res.redirect('/admin/degree');
    }
    await writeAuditLog({
      model: 'Degree', documentId: degree._id,
      action: AUDIT_ACTIONS.DELETE_DEGREE,
      before: degree.toObject(), after: null, req
    });
    await degree.deleteOne();
    req.flash('success', 'Degree deleted');
    res.redirect('/admin/degree');
  } catch (err) {
    console.error('degreeController.destroy error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi xóa văn bằng');
    res.redirect('/admin/degree');
  }
};

// ─── Public API ───────────────────────────────────────────────────────────────

function buildSecureUrl(req, filename) {
  if (!filename) return undefined;
  const baseUrl = process.env.BACKEND_URL ?? `${req.protocol}://${req.get('host')}`;
  const name = path.basename(filename);
  return `${baseUrl}/secure-files/${name}?api_key=${req.query.api_key}`;
}

// GET /api/verify-degree/:degree_id?api_key=xxx
// Lookup by qualification_number — returns degree fields + topic_name if PhD
exports.apiGetByQualification = async (req, res) => {
  try {
    const degree = await Degree.findOne({
      qualification_number: { $regex: new RegExp('^' + req.params.degree_id + '$', 'i') }
    }).populate('department level');

    if (!degree) return res.status(404).json({ error: 'Degree not found' });
    if (degree.status === 'revoked') return res.status(404).json({ error: 'Degree has been revoked' });

    const imageUrl = buildSecureUrl(req, degree.degree_image);

    const response = {
      full_name: degree.student_name,
      program_name: degree.program_name,
      degree_id: degree.qualification_number,
    };

    if (degree.passport_number) response.passport_number = degree.passport_number;
    if (degree.address) response.address = degree.address;
    if (imageUrl) response.degree_image = [imageUrl];

    // topic_name present → PhD view; absent → MBA/Master view
    if (degree.topic_name) {
      response.topic_name = degree.topic_name;
      if (degree.topic_short_desc) response.topic_short_desc = degree.topic_short_desc;
    }

    return res.json(response);
  } catch (err) {
    console.error('apiGetByQualification error:', err);
    return res.status(500).json({ error: 'Internal server error' });
  }
};

// GET /api/verify-certificate/:cert_id?api_key=xxx
// Lookup by certification_number — returns certificate fields (no topic_name)
exports.apiGetByCertification = async (req, res) => {
  try {
    const degree = await Degree.findOne({
      certification_number: { $regex: new RegExp('^' + req.params.cert_id + '$', 'i') }
    }).populate('department level');

    if (!degree) return res.status(404).json({ error: 'Certificate not found' });
    if (degree.status === 'revoked') return res.status(404).json({ error: 'Certificate has been revoked' });

    const imageUrl = buildSecureUrl(req, degree.certificate_image);

    const response = {
      full_name: degree.student_name,
      certification_title: degree.program_name,
      certificate_id: degree.certification_number,
    };

    if (degree.passport_number) response.passport_number = degree.passport_number;
    if (degree.address) response.address = degree.address;
    if (imageUrl) response.certificate_image = [imageUrl];

    return res.json(response);
  } catch (err) {
    console.error('apiGetByCertification error:', err);
    return res.status(500).json({ error: 'Internal server error' });
  }
};