const multer = require('multer');
const path = require('path');
const fs = require('fs');
const { v4: uuidv4 } = require('uuid');

// Ensure upload directories exist
const ensureUploadDirs = () => {
  const dirs = [
    'uploads/documents',
    'uploads/avatars',
    'uploads/kyc',
    'uploads/temp'
  ];
  
  dirs.forEach(dir => {
    if (!fs.existsSync(dir)) {
      fs.mkdirSync(dir, { recursive: true });
    }
  });
};

ensureUploadDirs();

// File filter function
const fileFilter = (allowedTypes) => {
  return (req, file, cb) => {
    const fileExtension = path.extname(file.originalname).toLowerCase();
    const allowedExtensions = allowedTypes.map(type => `.${type}`);
    
    if (allowedExtensions.includes(fileExtension)) {
      cb(null, true);
    } else {
      cb(new Error(`File type not allowed. Allowed types: ${allowedTypes.join(', ')}`), false);
    }
  };
};

// Storage configuration
const createStorage = (uploadPath) => {
  return multer.diskStorage({
    destination: (req, file, cb) => {
      cb(null, uploadPath);
    },
    filename: (req, file, cb) => {
      const uniqueSuffix = uuidv4();
      const fileExtension = path.extname(file.originalname);
      cb(null, `${uniqueSuffix}${fileExtension}`);
    }
  });
};

// Document upload (KYC, contracts, etc.)
const documentUpload = multer({
  storage: createStorage('uploads/documents'),
  limits: {
    fileSize: parseInt(process.env.MAX_FILE_SIZE) || 5 * 1024 * 1024, // 5MB
    files: 10
  },
  fileFilter: fileFilter(['pdf', 'doc', 'docx', 'jpg', 'jpeg', 'png'])
});

// Avatar upload
const avatarUpload = multer({
  storage: createStorage('uploads/avatars'),
  limits: {
    fileSize: 2 * 1024 * 1024, // 2MB
    files: 1
  },
  fileFilter: fileFilter(['jpg', 'jpeg', 'png', 'gif'])
});

// KYC document upload
const kycUpload = multer({
  storage: createStorage('uploads/kyc'),
  limits: {
    fileSize: parseInt(process.env.MAX_FILE_SIZE) || 5 * 1024 * 1024, // 5MB
    files: 5
  },
  fileFilter: fileFilter(['pdf', 'jpg', 'jpeg', 'png'])
});

// Generic file upload
const genericUpload = multer({
  storage: createStorage('uploads/temp'),
  limits: {
    fileSize: parseInt(process.env.MAX_FILE_SIZE) || 5 * 1024 * 1024, // 5MB
    files: 5
  },
  fileFilter: fileFilter(['pdf', 'doc', 'docx', 'jpg', 'jpeg', 'png', 'txt', 'csv', 'xlsx'])
});

// File validation middleware
const validateFile = (req, res, next) => {
  if (!req.file && !req.files) {
    return res.status(400).json({
      success: false,
      message: 'No file uploaded'
    });
  }
  next();
};

// File cleanup utility
const cleanupFile = (filePath) => {
  try {
    if (fs.existsSync(filePath)) {
      fs.unlinkSync(filePath);
      console.log(`File deleted: ${filePath}`);
    }
  } catch (error) {
    console.error(`Error deleting file ${filePath}:`, error);
  }
};

// File info extractor
const extractFileInfo = (file) => {
  return {
    originalName: file.originalname,
    filename: file.filename,
    path: file.path,
    size: file.size,
    mimetype: file.mimetype,
    uploadedAt: new Date()
  };
};

// Multiple file info extractor
const extractMultipleFileInfo = (files) => {
  if (Array.isArray(files)) {
    return files.map(extractFileInfo);
  }
  
  // Handle multer's field-based file object
  const result = {};
  Object.keys(files).forEach(fieldName => {
    result[fieldName] = files[fieldName].map(extractFileInfo);
  });
  return result;
};

module.exports = {
  documentUpload,
  avatarUpload,
  kycUpload,
  genericUpload,
  validateFile,
  cleanupFile,
  extractFileInfo,
  extractMultipleFileInfo,
  ensureUploadDirs
};