const express = require('express');
const { dbGet, dbAll } = require('../db');

const router = express.Router();

const requireAuth = (req, res, next) => {
  if (!req.session.user) return res.redirect('/login');
  next();
};

router.get('/login', (req, res) => {
  if (req.session.user) return res.redirect('/');
  res.render('login');
});

router.get('/', requireAuth, (req, res) => {
  res.render('index', { user: req.session.user });
});

router.get('/student/:id', requireAuth, (req, res) => {
  const student = dbGet('SELECT * FROM students WHERE id = ?', [req.params.id]);
  if (!student) return res.status(404).send('Ученик не найден');

  const results = dbAll(`
    SELECT er.*, s.name as subject_name, s.is_mandatory, s.code as subject_code
    FROM exam_results er
    JOIN subjects s ON s.code = er.subject_code
    WHERE er.student_id = ?
    ORDER BY s.is_mandatory DESC, s.name
  `, [req.params.id]);

  const mandatoryResults = results.filter(r => r.is_mandatory);
  const electiveResults = results.filter(r => !r.is_mandatory);
  const rusResult = mandatoryResults.find(r => r.subject_code === '01') || null;
  const mathResult = mandatoryResults.find(r => r.subject_code === '02') || null;

  res.render('student', {
    student,
    electiveResults,
    rusResult,
    mathResult,
    user: req.session.user
  });
});

router.get('/import', requireAuth, (req, res) => {
  res.render('import', { user: req.session.user });
});

router.get('/certificate/:id', requireAuth, (req, res) => {
  const { id } = req.params;
  const type = req.query.type || 'gia';
  const subjectCodes = req.query.subjects ? req.query.subjects.split(',') : [];

  const student = dbGet('SELECT * FROM students WHERE id = ?', [id]);
  if (!student) return res.status(404).send('Ученик не найден');

  const rusResult = dbGet(`
    SELECT er.*, s.name as subject_name
    FROM exam_results er JOIN subjects s ON s.code = er.subject_code
    WHERE er.student_id = ? AND er.subject_code = '01'
  `, [id]);

  const mathResult = dbGet(`
    SELECT er.*, s.name as subject_name
    FROM exam_results er JOIN subjects s ON s.code = er.subject_code
    WHERE er.student_id = ? AND er.subject_code = '02'
  `, [id]);

  let electives = [];
  if (type === 'gia' && subjectCodes.length > 0) {
    const placeholders = subjectCodes.map(() => '?').join(',');
    electives = dbAll(`
      SELECT er.*, s.name as subject_name
      FROM exam_results er JOIN subjects s ON s.code = er.subject_code
      WHERE er.student_id = ? AND er.subject_code IN (${placeholders})
    `, [id, ...subjectCodes]);
  }

  const today = new Date();
  const certNumber = `${today.getFullYear()}${String(id).padStart(4, '0')}`;
  const months = ['января', 'февраля', 'марта', 'апреля', 'мая', 'июня',
    'июля', 'августа', 'сентября', 'октября', 'ноября', 'декабря'];
  const dateStr = `«${String(today.getDate()).padStart(2, '0')}» ${months[today.getMonth()]} ${today.getFullYear()} года`;

  const gender = detectGender(student.patronymic);
  const fioDative = formatNameDative(student, gender);
  const verbEnding = gender === 'm' ? 'обучался' : 'обучалась';
  const verbEnding2 = gender === 'm' ? 'получил' : 'получила';

  res.render('certificate', {
    type,
    student: { ...student, fioDative, gender },
    certNumber,
    dateStr,
    verbEnding,
    verbEnding2,
    rusResult: rusResult || null,
    mathResult: mathResult || null,
    electives,
    allSubjects: type === 'gia'
      ? [
          rusResult || { subject_name: 'Русский язык', primary_score: null, grade: null },
          mathResult || { subject_name: 'Математика', primary_score: null, grade: null },
          ...electives
        ]
      : [
          rusResult || { subject_name: 'Русский язык', grade: null },
          mathResult || { subject_name: 'Математика', grade: null }
        ]
  });
});

function detectGender(patronymic) {
  if (!patronymic) return 'm';
  const last = patronymic.toLowerCase();
  if (/вна|чна|нична$/.test(last)) return 'f';
  return 'm';
}

function formatNameDative(student, gender) {
  const l = student.last_name || '';
  const f = student.first_name || '';
  const p = student.patronymic || '';
  if (gender === 'f') {
    return `${declineFemaleLast(l)} ${declineFemaleFirst(f)} ${declineFemalePatr(p)}`;
  }
  return `${declineMaleLast(l)} ${declineMaleFirst(f)} ${declineMalePatr(p)}`;
}

function declineFemaleLast(name) {
  if (!name) return '';
  if (name.endsWith('ая')) return name.slice(0, -2) + 'ой';
  if (name.endsWith('яя')) return name.slice(0, -2) + 'ей';
  if (name.endsWith('а')) return name.slice(0, -1) + 'ой';
  if (name.endsWith('я')) return name.slice(0, -1) + 'е';
  if (name.endsWith('ова') || name.endsWith('ева') || name.endsWith('ина')) return name.slice(0, -1) + 'ой';
  return name + 'ой';
}
function declineFemaleFirst(name) {
  if (!name) return '';
  if (name.endsWith('а') || name.endsWith('я')) return name.slice(0, -1) + 'е';
  return name + 'е';
}
function declineFemalePatr(name) {
  if (!name) return '';
  if (name.endsWith('на')) return name.slice(0, -1) + 'е';
  return name + 'е';
}

function declineMaleLast(name) {
  if (!name) return '';
  if (name.endsWith('ов') || name.endsWith('ев') || name.endsWith('ин') || name.endsWith('ёв')) return name + 'у';
  if (name.endsWith('ий') || name.endsWith('ый')) return name.slice(0, -2) + 'ому';
  if (name.endsWith('ой')) return name.slice(0, -2) + 'ому';
  return name + 'у';
}
function declineMaleFirst(name) {
  if (!name) return '';
  if (name.endsWith('й') || name.endsWith('ь')) return name.slice(0, -1) + 'ю';
  if (name.endsWith('а') || name.endsWith('я')) return name.slice(0, -1) + 'е';
  return name + 'у';
}
function declineMalePatr(name) {
  if (!name) return '';
  if (name.endsWith('ич')) return name + 'у';
  if (name.endsWith('на')) return name.slice(0, -1) + 'е';
  return name + 'у';
}

router.get('/batch-print', requireAuth, (req, res) => {
  const { class: cls, parallel, type } = req.query;

  let students;
  if (cls) {
    students = dbAll('SELECT * FROM students WHERE class = ? ORDER BY last_name, first_name', [cls]);
  } else if (parallel) {
    students = dbAll('SELECT * FROM students WHERE class LIKE ? ORDER BY class, last_name, first_name', [parallel + '%']);
  } else {
    students = dbAll('SELECT * FROM students ORDER BY class, last_name, first_name');
  }

  const today = new Date();
  const months = ['января', 'февраля', 'марта', 'апреля', 'мая', 'июня',
    'июля', 'августа', 'сентября', 'октября', 'ноября', 'декабря'];
  const dateStr = `«${String(today.getDate()).padStart(2, '0')}» ${months[today.getMonth()]} ${today.getFullYear()} года`;

  const studentData = students.map(st => {
    const results = dbAll(`
      SELECT er.*, s.name as subject_name, s.is_mandatory
      FROM exam_results er JOIN subjects s ON s.code = er.subject_code
      WHERE er.student_id = ?
    `, [st.id]);

    const rusResult = results.find(r => r.subject_code === '01') || null;
    const mathResult = results.find(r => r.subject_code === '02') || null;
    const electives = results.filter(r => !r.is_mandatory);

    // Автоопределение: элективы есть → ОГЭ, 1 предмет всего → второгодник ОГЭ, иначе ГВЭ
    const totalResults = results.length;
    const autoType = (electives.length > 0 || totalResults === 1) ? 'gia' : 'gve';
    const finalType = (type === 'gia' || type === 'gve') ? type : autoType;

    const gender = detectGender(st.patronymic);
    const fioDative = formatNameDative(st, gender);

    let allSubjects;
    if (finalType === 'gia') {
      allSubjects = [
        rusResult || { subject_name: 'Русский язык', primary_score: null, grade: null },
        mathResult || { subject_name: 'Математика', primary_score: null, grade: null },
        ...electives
      ];
    } else {
      allSubjects = [
        rusResult || { subject_name: 'Русский язык', grade: null },
        mathResult || { subject_name: 'Математика', grade: null }
      ];
    }

    return {
      student: { ...st, fioDative, gender },
      certNumber: `${today.getFullYear()}${String(st.id).padStart(4, '0')}`,
      dateStr,
      verbEnding: gender === 'm' ? 'обучался' : 'обучалась',
      verbEnding2: gender === 'm' ? 'получил' : 'получила',
      allSubjects,
      type: finalType
    };
  });

  res.render('batch-certificate', { students: studentData });
});

module.exports = router;