import fs from 'node:fs';
import path from 'node:path';
import crypto from 'node:crypto';
import multer from 'multer';
import { env } from '../config/env.js';

const ALLOWED_MIME = new Set([
  'application/pdf',
  'image/png',
  'image/jpeg',
  'image/webp',
  'application/msword',
  'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  'application/vnd.ms-excel',
  'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
  'text/plain',
  'text/markdown',
  'application/zip',
]);

// El navegador no manda un mimetype confiable para .md (varia segun SO: text/markdown,
// application/octet-stream, vacio...) -- se normaliza por extension para no rechazar
// documentos validos ni depender de esa adivinanza.
const MARKDOWN_EXTENSIONS = new Set(['.md', '.markdown']);

const uploadsDir = path.join(env.storageRoot, 'attachments');
fs.mkdirSync(uploadsDir, { recursive: true });

const storage = multer.diskStorage({
  destination: (req, file, cb) => cb(null, uploadsDir),
  // Nombre generado por el servidor: evita path traversal y colisiones.
  filename: (req, file, cb) => {
    const ext = path.extname(file.originalname).slice(0, 10);
    cb(null, `${Date.now()}-${crypto.randomBytes(8).toString('hex')}${ext}`);
  },
});

export const upload = multer({
  storage,
  limits: { fileSize: 15 * 1024 * 1024 },
  fileFilter: (req, file, cb) => {
    if (MARKDOWN_EXTENSIONS.has(path.extname(file.originalname).toLowerCase())) {
      file.mimetype = 'text/markdown';
      return cb(null, true);
    }
    if (!ALLOWED_MIME.has(file.mimetype)) {
      return cb(new Error('Tipo de archivo no permitido'));
    }
    cb(null, true);
  },
});

export { uploadsDir };