const fs = require('fs');
const path = require('path');
const XLSX = require('xlsx');
const { getCompressedDefaultImage } = require('../function/GetImageDefaault');
const { parse } = require('csv-parse/sync');
const { pool } = require('../database');
const dayjs = require('dayjs');
const customParseFormat = require('dayjs/plugin/customParseFormat');
dayjs.extend(customParseFormat);

// ---------- Fonctions utilitaires ----------
function fixEncoding(str) {
  if (typeof str !== 'string') return str;
  return str
    .replace(/├®/g, 'é')
    .replace(/├à/g, 'à')
    .replace(/├©/g, 'é')
    .replace(/├ô/g, 'ô')
    .replace(/├ù/g, 'ù')
    .replace(/’/g, "'")
    .replace(/â€/g, '…')
    .replace(/â€/g, '-');
}

function convertToISODate(input) {
  if (!input) return null;

  if (input instanceof Date && !isNaN(input)) {
    return dayjs(input).format('YYYY-MM-DD');
  }

  if (typeof input === 'number') {
    return dayjs(new Date((input - 25569) * 86400 * 1000)).format('YYYY-MM-DD');
  }

  if (typeof input === 'string') {
    const cleanInput = input.trim();
    const versMatch = cleanInput.match(/vers\s*(\d{4})/i);
    if (versMatch) return `${versMatch[1]}-01-01`;

    const formats = [
      'DD/MM/YYYY', 'D/M/YYYY',
      'YYYY-MM-DD',
      'DD-MM-YYYY', 'D-M-YYYY',
      'MM/DD/YYYY', 'M/D/YYYY',
      'MM-DD-YYYY', 'M-D-YYYY',
      'DD/MM/YY', 'D/M/YY',
      'MM/DD/YY', 'M/D/YY',
      'DD-MM-YY', 'D-M-YY',
      'MM-DD-YY', 'M-D-YY'
    ];

    for (const fmt of formats) {
      const parsed = dayjs(cleanInput, fmt, true);
      if (parsed.isValid()) return parsed.format('YYYY-MM-DD');
    }

    const freeParse = dayjs(cleanInput);
    if (freeParse.isValid()) return freeParse.format('YYYY-MM-DD');
  }

  return null;
}

// Vérifie année bissextile
function isLeapYear(year) {
  return (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
}

// ---------- UPDATE étudiant ----------
async function updateEtudiant(row) {
  const fields = [];
  const params = [];

  function addFieldIfValue(field, value) {
    if (value !== undefined && value !== null && value !== '') {
      fields.push(`${field} = ?`);
      params.push(value);
    }
  }

  addFieldIfValue('nom', row.nom);
  addFieldIfValue('prenom', row.prenom);
  addFieldIfValue('date_de_naissances', convertToISODate(row.date_naissance));
  addFieldIfValue('niveau', row.niveau);
  addFieldIfValue('annee_scolaire', row.annee_scolaire);
  addFieldIfValue('status', row.code_redoublement);
  addFieldIfValue('mention_id', row.mention);
  addFieldIfValue('num_inscription', row.num_inscription?.toString());
  addFieldIfValue('sexe', row.sexe);
  addFieldIfValue('date_delivrance', convertToISODate(row.date_de_delivrance));
  addFieldIfValue('nationalite', row.nationaliter);
  addFieldIfValue('annee_bacc', parseInt(row.annee_baccalaureat, 10));
  addFieldIfValue('serie', row.serie);
  addFieldIfValue('boursier', row.boursier);
  addFieldIfValue('domaine', fixEncoding(row.domaine));
  addFieldIfValue('contact', row.contact);

  if (fields.length === 0) return { success: false, error: 'Aucun champ valide à mettre à jour' };

  let sql, whereParams;

  if (row.cin && row.cin.toString().trim() !== '') {
    sql = `UPDATE etudiants SET ${fields.join(', ')} WHERE cin = ?`;
    whereParams = [row.cin];
  } else {
    sql = `UPDATE etudiants SET ${fields.join(', ')} WHERE LOWER(TRIM(nom)) = ? AND LOWER(TRIM(prenom)) = ?`;
    whereParams = [row.nom.toLowerCase().trim(), row.prenom.toLowerCase().trim()];
  }

  try {
    const [result] = await pool.query(sql, [...params, ...whereParams]);
    return { success: true, affectedRows: result.affectedRows };
  } catch (error) {
    return { success: false, error: error.message };
  }
}

// ---------- INSERT multiple étudiants ----------
async function insertMultipleEtudiants(etudiants) {
  if (!etudiants || etudiants.length === 0) return { success: true, affectedRows: 0 };

  const sql = `
    INSERT INTO etudiants (
      nom, prenom, photos, date_de_naissances, niveau, annee_scolaire, status,
      mention_id, num_inscription, sexe, cin, date_delivrance, nationalite,
      annee_bacc, serie, boursier, domaine, contact, parcours
    ) VALUES ?
  `;

  const values = etudiants.map(row => [
    row.nom,
    row.prenom,
    getCompressedDefaultImage(),
    convertToISODate(row.date_naissance),
    row.niveau,
    row.annee_scolaire,
    row.code_redoublement,
    row.mention,
    row.num_inscription.toString(),
    row.sexe,
    row.cin || null,
    convertToISODate(row.date_de_delivrance),
    row.nationaliter,
    parseInt(row.annee_baccalaureat, 10),
    row.serie,
    row.boursier,
    fixEncoding(row.domaine),
    row.contact,
    null
  ]);

  try {
    const [result] = await pool.query(sql, [values]);
    return { success: true, affectedRows: result.affectedRows };
  } catch (error) {
    return { success: false, error: error.message };
  }
}

// ---------- IMPORT fichier ----------
async function importFileToDatabase(filePath) {
  let records;
  const ext = path.extname(filePath).toLowerCase();

  if (ext === '.xlsx') {
    const workbook = XLSX.readFile(filePath);
    const worksheet = workbook.Sheets[workbook.SheetNames[0]];
    records = XLSX.utils.sheet_to_json(worksheet, { defval: '' });
  } else if (ext === '.csv') {
    const content = fs.readFileSync(filePath, 'utf8');
    records = parse(content, { columns: true, skip_empty_lines: true });
  } else {
    return { error: true, message: 'Format de fichier non supporté' };
  }

  // Vérifier champs obligatoires
  const requiredFields = [
    'nom', 'date_naissance', 'niveau', 'annee_scolaire',
    'mention', 'num_inscription', 'nationaliter', 'sexe',
    'annee_baccalaureat', 'serie', 'code_redoublement',
    'boursier', 'domaine'
  ];

  for (const [i, row] of records.entries()) {
    for (const f of requiredFields) {
      if (!row[f]) return { error: true, message: `Le champ '${f}' est manquant à la ligne ${i + 2}` };
    }
  }

  const [mentionRows] = await pool.query('SELECT * FROM mentions');
  const [statusRows] = await pool.query('SELECT * FROM status');

  const etudiantsToInsert = [];
  const doublons = [];

  for (const row of records) {
    row.date_naissance = convertToISODate(row.date_naissance);

    // Mapping mention
    const matchedMention = mentionRows.find(
      m => m.nom.toUpperCase() === row.mention.toUpperCase() || m.uniter.toUpperCase() === row.mention.toUpperCase()
    );
    if (matchedMention) row.mention = matchedMention.id;

    // Mapping status
    row.code_redoublement = (row.code_redoublement ? row.code_redoublement.trim().substring(0, 1) : 'N');
    const statusMatch = statusRows.find(s => s.nom.toLowerCase().startsWith(row.code_redoublement.toLowerCase()));
    if (statusMatch) row.code_redoublement = statusMatch.id;

    // Détection doublons (ignorer CIN vide)
    let existing;
    if (row.cin && row.cin.toString().trim() !== '') {
      [existing] = await pool.query('SELECT * FROM etudiants WHERE cin = ?', [row.cin]);
    } else {
      [existing] = await pool.query(
        'SELECT * FROM etudiants WHERE LOWER(TRIM(nom)) = ? AND LOWER(TRIM(prenom)) = ?',
        [row.nom.toLowerCase().trim(), row.prenom.toLowerCase().trim()]
      );
    }

    if (existing.length > 0) {
      doublons.push({ nom: row.nom, prenom: row.prenom, cin: row.cin });
      const updateResult = await updateEtudiant(row);
      if (!updateResult.success) return { error: true, message: `Erreur update ${row.nom} ${row.prenom}: ${updateResult.error}` };
    } else {
      etudiantsToInsert.push(row);
    }
  }

  console.log('✅ Nouveaux à insérer :', etudiantsToInsert.map(e => e.nom + ' ' + e.prenom));
  console.log('🔄 Étudiants mis à jour :', doublons.map(e => e.nom + ' ' + e.prenom));

  const insertResult = await insertMultipleEtudiants(etudiantsToInsert);
  if (!insertResult.success) return { error: true, message: insertResult.error };

  return { error: false, message: `Importation réussie. ${etudiantsToInsert.length} nouvel(le)(s) inséré(s), ${doublons.length} mis à jour.` };
}

module.exports = { importFileToDatabase };