const express = require('express');
const multer = require('multer');
const cors = require('cors');
const path = require('path');
const fs = require('fs').promises;
const { v4: uuidv4 } = require('uuid');
const { validationResult } = require('express-validator');

// Import custom modules
const config = require('./config/config');
const logger = require('./config/logger');
const { 
    apiLimiter, 
    uploadLimiter, 
    securityHeaders, 
    fileValidation, 
    fileIdValidation, 
    searchValidation 
} = require('./config/security');
const STLDatabase = require('./database');

const app = express();

// Security middleware
app.use(securityHeaders);
app.use(cors({
    origin: config.nodeEnv === 'production' ? false : true,
    credentials: true
}));

// Rate limiting
app.use('/api/', apiLimiter);
app.use('/api/upload', uploadLimiter);

// Body parsing
app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ extended: true, limit: '10mb' }));

// Static files
app.use(express.static('public'));

const db = new STLDatabase(config.database.path, config.database.uploadDir);

// Enhanced file validation
const validateSTLFile = async (buffer) => {
    // Check if it's a valid STL file by looking for STL signatures
    const text = buffer.toString('utf8', 0, 80);
    const isBinarySTL = buffer.length > 80 && buffer.readUInt32LE(80) > 0;
    const isAsciiSTL = text.toLowerCase().includes('solid');
    
    return isBinarySTL || isAsciiSTL;
};

const storage = multer.diskStorage({
    destination: async (req, file, cb) => {
        const uploadPath = path.join(__dirname, config.upload.destination);
        try {
            await fs.access(uploadPath);
        } catch {
            await fs.mkdir(uploadPath, { recursive: true });
        }
        cb(null, uploadPath);
    },
    filename: (req, file, cb) => {
        // Sanitize filename
        const sanitizedName = file.originalname.replace(/[^a-zA-Z0-9.-]/g, '_');
        const uniqueName = `${uuidv4()}-${sanitizedName}`;
        cb(null, uniqueName);
    }
});

const fileFilter = async (req, file, cb) => {
    const fileExt = path.extname(file.originalname).toLowerCase();
    
    if (!config.upload.allowedExtensions.includes(fileExt)) {
        return cb(new Error('Only STL files are allowed'), false);
    }
    
    // Additional MIME type check
    const allowedMimeTypes = ['application/octet-stream', 'application/sla', 'text/plain'];
    if (file.mimetype && !allowedMimeTypes.includes(file.mimetype)) {
        return cb(new Error('Invalid file type'), false);
    }
    
    cb(null, true);
};

const upload = multer({
    storage: storage,
    fileFilter: fileFilter,
    limits: {
        fileSize: config.upload.maxFileSize,
        files: config.upload.maxFiles
    }
});

// Validation helper
const handleValidationErrors = (req, res, next) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({
            success: false,
            error: 'Validation failed',
            details: errors.array()
        });
    }
    next();
};

app.post('/api/upload', fileValidation, handleValidationErrors, upload.single('stlFile'), async (req, res) => {
    try {
        if (!req.file) {
            return res.status(400).json({ 
                success: false,
                error: 'No file uploaded' 
            });
        }

        // Additional file content validation
        const fileBuffer = await fs.readFile(req.file.path);
        if (!await validateSTLFile(fileBuffer)) {
            await fs.unlink(req.file.path);
            return res.status(400).json({
                success: false,
                error: 'Invalid STL file format'
            });
        }

        const fileData = {
            filename: req.file.filename,
            originalName: req.file.originalname,
            filePath: req.file.path,
            fileSize: req.file.size,
            description: req.body.description || null,
            tags: req.body.tags || null,
            printSettings: req.body.printSettings ? JSON.parse(req.body.printSettings) : null,
            dimensions: req.body.dimensions ? JSON.parse(req.body.dimensions) : null
        };

        const fileId = await db.addSTLFile(fileData);
        const savedFile = await db.getSTLFile(fileId);

        logger.info('File uploaded successfully', { 
            fileId, 
            filename: req.file.originalname,
            size: req.file.size,
            ip: req.ip 
        });

        res.json({
            success: true,
            message: 'File uploaded successfully',
            file: savedFile
        });
    } catch (error) {
        logger.error('Upload error', { error: error.message, stack: error.stack });
        
        if (req.file) {
            try {
                await fs.unlink(req.file.path);
            } catch (unlinkError) {
                logger.error('Error cleaning up file', { error: unlinkError.message });
            }
        }
        
        res.status(500).json({ 
            success: false,
            error: 'Upload failed',
            message: config.nodeEnv === 'development' ? error.message : 'Internal server error'
        });
    }
});

app.get('/api/files', searchValidation, handleValidationErrors, async (req, res) => {
    try {
        const limit = Math.min(parseInt(req.query.limit) || 50, 100);
        const offset = Math.max(parseInt(req.query.offset) || 0, 0);
        const search = req.query.search;

        let files;
        if (search) {
            files = await db.searchSTLFiles(search);
        } else {
            files = await db.getAllSTLFiles(limit, offset);
        }

        res.json({
            success: true,
            files: files,
            pagination: {
                limit: limit,
                offset: offset,
                hasMore: files.length === limit
            }
        });
    } catch (error) {
        logger.error('Get files error', { error: error.message, stack: error.stack });
        res.status(500).json({ 
            success: false,
            error: 'Failed to retrieve files',
            message: config.nodeEnv === 'development' ? error.message : 'Internal server error'
        });
    }
});

app.get('/api/files/:id', fileIdValidation, handleValidationErrors, async (req, res) => {
    try {
        const fileId = parseInt(req.params.id);
        const file = await db.getSTLFile(fileId);

        if (!file) {
            return res.status(404).json({ 
                success: false,
                error: 'File not found' 
            });
        }

        res.json({
            success: true,
            file: file
        });
    } catch (error) {
        logger.error('Get file error', { error: error.message, fileId: req.params.id });
        res.status(500).json({ 
            success: false,
            error: 'Failed to retrieve file',
            message: config.nodeEnv === 'development' ? error.message : 'Internal server error'
        });
    }
});

app.put('/api/files/:id', async (req, res) => {
    try {
        const fileId = parseInt(req.params.id);
        const updates = {};

        if (req.body.description !== undefined) updates.description = req.body.description;
        if (req.body.tags !== undefined) updates.tags = req.body.tags;
        if (req.body.printSettings !== undefined) updates.print_settings = req.body.printSettings;
        if (req.body.dimensions !== undefined) updates.dimensions = req.body.dimensions;

        const updated = await db.updateSTLFile(fileId, updates);

        if (!updated) {
            return res.status(404).json({ error: 'File not found' });
        }

        const updatedFile = await db.getSTLFile(fileId);
        res.json({
            success: true,
            message: 'File updated successfully',
            file: updatedFile
        });
    } catch (error) {
        console.error('Update file error:', error);
        res.status(500).json({ 
            error: 'Failed to update file',
            message: error.message 
        });
    }
});

app.delete('/api/files/:id', async (req, res) => {
    try {
        const fileId = parseInt(req.params.id);
        const deleted = await db.deleteSTLFile(fileId);

        if (!deleted) {
            return res.status(404).json({ error: 'File not found' });
        }

        res.json({
            success: true,
            message: 'File deleted successfully'
        });
    } catch (error) {
        console.error('Delete file error:', error);
        res.status(500).json({ 
            error: 'Failed to delete file',
            message: error.message 
        });
    }
});

app.get('/api/files/:id/download', async (req, res) => {
    try {
        const fileId = parseInt(req.params.id);
        const file = await db.getSTLFile(fileId);

        if (!file) {
            return res.status(404).json({ error: 'File not found' });
        }

        try {
            await fs.access(file.file_path);
        } catch {
            return res.status(404).json({ error: 'Physical file not found' });
        }

        res.download(file.file_path, file.original_name);
    } catch (error) {
        console.error('Download error:', error);
        res.status(500).json({ 
            error: 'Failed to download file',
            message: error.message 
        });
    }
});

app.use('/uploads', express.static(path.join(__dirname, 'uploads'), {
    setHeaders: (res, filePath) => {
        if (path.extname(filePath).toLowerCase() === '.stl') {
            res.setHeader('Content-Type', 'application/octet-stream');
            res.setHeader('Access-Control-Allow-Origin', '*');
        }
    }
}));

app.use((error, req, res, next) => {
    if (error instanceof multer.MulterError) {
        if (error.code === 'LIMIT_FILE_SIZE') {
            return res.status(400).json({ error: 'File too large (max 100MB)' });
        }
    }
    
    console.error('Unhandled error:', error);
    res.status(500).json({ 
        error: 'Internal server error',
        message: error.message 
    });
});

async function startServer() {
    try {
        await db.initialize();
        logger.info('Database initialized successfully');
        
        app.listen(config.port, config.host, () => {
            logger.info('STL Storage server started', {
                host: config.host,
                port: config.port,
                nodeEnv: config.nodeEnv
            });
            console.log(`🚀 STL Storage server running on ${config.host}:${config.port}`);
            console.log(`📁 Upload endpoint: http://${config.host}:${config.port}/api/upload`);
            console.log(`🔍 Browse files: http://${config.host}:${config.port}/api/files`);
        });
    } catch (error) {
        logger.error('Failed to start server', { error: error.message, stack: error.stack });
        console.error('❌ Failed to start server:', error);
        process.exit(1);
    }
}

process.on('SIGINT', async () => {
    console.log('\n🛑 Shutting down server...');
    await db.close();
    process.exit(0);
});

if (require.main === module) {
    startServer();
}

module.exports = app;