import multer from 'multer';
import path from 'path';
import fs from 'fs';
import crypto from 'crypto';
import { Request } from 'express';

// Use /tmp for uploads in production environments (like Hugging Face Spaces)
// This ensures we have write permissions
const uploadsDir = process.env.NODE_ENV === 'production' 
  ? path.join('/tmp', 'uploads')
  : path.join(process.cwd(), 'uploads');

// Safely create uploads directory with error handling
try {
  if (!fs.existsSync(uploadsDir)) {
    fs.mkdirSync(uploadsDir, { recursive: true });
    console.log(`✅ Created uploads directory: ${uploadsDir}`);
  } else {
    console.log(`✅ Uploads directory exists: ${uploadsDir}`);
  }
  
  // Test write permissions
  const testFile = path.join(uploadsDir, 'test-permissions.txt');
  fs.writeFileSync(testFile, 'test');
  fs.unlinkSync(testFile);
  console.log(`✅ Upload directory is writable: ${uploadsDir}`);
  
} catch (error) {
  console.warn(`❌ Failed to create or write to uploads directory at ${uploadsDir}:`, error);
  console.log('File uploads may not work properly');
}

// Configure multer for file uploads
const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    try {
      // Create subdirectories by date for organization
      const dateDir = new Date().toISOString().split('T')[0];
      const fullPath = path.join(uploadsDir, dateDir);
      
      console.log(`Creating upload destination: ${fullPath} for file: ${file.originalname}`);
      
      if (!fs.existsSync(fullPath)) {
        fs.mkdirSync(fullPath, { recursive: true });
        console.log(`Created upload subdirectory: ${fullPath}`);
      }
      
      cb(null, fullPath);
    } catch (error) {
      console.error('Failed to create upload directory:', error);
      console.log(`Falling back to base directory: ${uploadsDir}`);
      // Fallback to base uploads directory
      cb(null, uploadsDir);
    }
  },
  filename: (req, file, cb) => {
    // Generate unique filename with timestamp and random string
    const timestamp = Date.now();
    const randomString = crypto.randomBytes(8).toString('hex');
    const ext = path.extname(file.originalname);
    const baseName = path.basename(file.originalname, ext);
    
    // Sanitize filename
    const sanitizedBaseName = baseName.replace(/[^a-zA-Z0-9-_]/g, '_');
    const filename = `${timestamp}_${randomString}_${sanitizedBaseName}${ext}`;
    
    cb(null, filename);
  }
});

// File filter to accept specific file types
const fileFilter = (req: Request, file: Express.Multer.File, cb: multer.FileFilterCallback) => {
  const allowedMimeTypes = [
    'application/pdf',
    'image/jpeg',
    'image/jpg', 
    'image/png',
    'image/gif',
    'image/webp',
    'text/plain',
    'text/markdown',
    'application/msword',
    'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    'application/json'
  ];

  if (allowedMimeTypes.includes(file.mimetype)) {
    cb(null, true);
  } else {
    cb(new Error(`Unsupported file type: ${file.mimetype}. Allowed types: PDF, images (JPEG, PNG, GIF, WebP), text files, Word documents, JSON`));
  }
};

// Configure multer with size limits
export const upload = multer({
  storage,
  fileFilter,
  limits: {
    fileSize: 50 * 1024 * 1024, // 50MB limit
    files: 10 // Maximum 10 files per upload
  }
});

// File processing utilities
export class FileProcessor {
  static async getFileInfo(filePath: string): Promise<{
    size: number;
    mimeType: string;
    exists: boolean;
  }> {
    try {
      const stats = await fs.promises.stat(filePath);
      return {
        size: stats.size,
        mimeType: await this.getMimeType(filePath),
        exists: true
      };
    } catch (error) {
      return {
        size: 0,
        mimeType: '',
        exists: false
      };
    }
  }

  static async getMimeType(filePath: string): Promise<string> {
    const ext = path.extname(filePath).toLowerCase();
    const mimeTypes: Record<string, string> = {
      '.pdf': 'application/pdf',
      '.jpg': 'image/jpeg',
      '.jpeg': 'image/jpeg',
      '.png': 'image/png',
      '.gif': 'image/gif',
      '.webp': 'image/webp',
      '.txt': 'text/plain',
      '.md': 'text/markdown',
      '.doc': 'application/msword',
      '.docx': 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
      '.json': 'application/json'
    };
    
    return mimeTypes[ext] || 'application/octet-stream';
  }

  static async readTextFile(filePath: string): Promise<string> {
    try {
      const content = await fs.promises.readFile(filePath, 'utf-8');
      return content;
    } catch (error) {
      throw new Error(`Failed to read text file: ${error}`);
    }
  }

  static async deleteFile(filePath: string): Promise<boolean> {
    try {
      await fs.promises.unlink(filePath);
      return true;
    } catch (error) {
      console.error(`Failed to delete file ${filePath}:`, error);
      return false;
    }
  }

  static isTextFile(mimeType: string): boolean {
    return mimeType.startsWith('text/') || 
           mimeType === 'application/json' ||
           mimeType.includes('document');
  }

  static isImageFile(mimeType: string): boolean {
    return mimeType.startsWith('image/');
  }

  static isPdfFile(mimeType: string): boolean {
    return mimeType === 'application/pdf';
  }

  static requiresOCR(mimeType: string): boolean {
    return this.isImageFile(mimeType) || this.isPdfFile(mimeType);
  }
}

// Upload validation middleware
export const validateUpload = (req: Request, res: any, next: any) => {
  if (!req.files || (Array.isArray(req.files) && req.files.length === 0)) {
    return res.status(400).json({
      error: 'No files uploaded',
      message: 'Please select at least one file to upload'
    });
  }

  next();
};

export default upload;