const express = require('express');
const fs = require('fs');
const path = require('path');
const multer = require('multer');
const db = require('../db');
const asyncHandler = require('../middleware/asyncHandler');

const router = express.Router();

const ALLOWED_FILE_TYPES = {
    'application/pdf': ['.pdf'],
    'image/jpeg': ['.jpg', '.jpeg'],
    'image/png': ['.png'],
    'application/msword': ['.doc'],
    'application/vnd.openxmlformats-officedocument.wordprocessingml.document': ['.docx'],
};

function fileFilter(req, file, cb) {
    const allowedExtensions = Object.values(ALLOWED_FILE_TYPES).flat();
    const ext = path.extname(file.originalname).toLowerCase();
    if (allowedExtensions.includes(ext) && ALLOWED_FILE_TYPES[file.mimetype]) {
        cb(null, true);
    } else {
        cb(new Error(`Dateityp nicht erlaubt: ${ext}. Erlaubt sind: PDF, JPG, PNG, DOC, DOCX`), false);
    }
}

const storage = multer.diskStorage({
    destination: (req, file, cb) => cb(null, 'uploads/'),
    filename: (req, file, cb) => {
        const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1E9);
        cb(null, uniqueSuffix + path.extname(file.originalname));
    },
});

const upload = multer({ storage, fileFilter, limits: { fileSize: 10 * 1024 * 1024 } });

// Upload document for a schaltung (mounted as /api/schaltungen/:id/dokumente by server.js)
router.post('/schaltungen/:id/dokumente', upload.single('document'), asyncHandler(async (req, res) => {
    const schaltung_id = req.params.id;
    const file = req.file;
    if (!file) return res.status(400).json({ error: 'Keine Datei hochgeladen' });

    const cleanup = () => {
        fs.unlink(file.path, (e) => {
            if (e) console.error('Cleanup error:', e.message);
        });
    };

    const schaltung = await db.get('SELECT id FROM schaltungen WHERE id = ?', [schaltung_id]);
    if (!schaltung) {
        cleanup();
        return res.status(404).json({ error: 'Schaltung nicht gefunden' });
    }

    try {
        const result = await db.run(
            `INSERT INTO dokumente (schaltung_id, filename, original_filename, filepath, filesize, mimetype)
             VALUES (?, ?, ?, ?, ?, ?)`,
            [schaltung_id, file.filename, file.originalname, file.path, file.size, file.mimetype]
        );
        res.json({ id: result.lastID, message: 'Dokument erfolgreich hochgeladen', filename: file.originalname });
    } catch (err) {
        cleanup();
        throw err;
    }
}));

// List documents for a schaltung
router.get('/schaltungen/:id/dokumente', asyncHandler(async (req, res) => {
    const rows = await db.all('SELECT * FROM dokumente WHERE schaltung_id = ?', [req.params.id]);
    res.json(rows);
}));

// Download single document
router.get('/dokumente/:id/download', asyncHandler(async (req, res) => {
    const row = await db.get('SELECT * FROM dokumente WHERE id = ?', [req.params.id]);
    if (!row) return res.status(404).json({ error: 'Dokument nicht gefunden' });
    const filepath = req.app.locals.safeUploadPath(row.filepath);
    if (!filepath) {
        console.error(`Path traversal attempt or invalid path for document ${row.id}: ${row.filepath}`);
        return res.status(400).json({ error: 'Ungültiger Dateipfad' });
    }
    res.download(filepath, row.original_filename);
}));

// Delete document
router.delete('/dokumente/:id', asyncHandler(async (req, res) => {
    const row = await db.get('SELECT * FROM dokumente WHERE id = ?', [req.params.id]);
    if (!row) return res.status(404).json({ error: 'Dokument nicht gefunden' });

    await db.run('DELETE FROM dokumente WHERE id = ?', [req.params.id]);

    const filepath = req.app.locals.safeUploadPath(row.filepath);
    if (filepath) {
        fs.unlink(filepath, (err) => {
            if (err) console.error('Fehler beim Löschen der Datei:', err.message);
        });
    } else {
        console.error(`Skipping file delete - invalid path: ${row.filepath}`);
    }
    res.json({ message: 'Dokument erfolgreich gelöscht' });
}));

module.exports = router;