File Validation

Dropup provides comprehensive file validation to ensure only valid files are accepted.

Validation Options

Accept (File Types)

Specify which file types to accept:

// Accept only images
useDropup({ accept: 'image/*' });

// Accept specific types
useDropup({ accept: 'image/png, image/jpeg' });

// Accept by extension
useDropup({ accept: '.pdf, .doc, .docx' });

// Multiple categories
useDropup({ accept: ['image/*', 'application/pdf', '.txt'] });

Common Accept Patterns

Pattern	Description
image/*	All images
image/png, image/jpeg	Only PNG and JPEG
video/*	All videos
audio/*	All audio files
application/pdf	PDF files only
.doc, .docx	Word documents
*/*	All files (default)

File Size Limits

useDropup({
  maxSize: 10 * 1024 * 1024, // 10MB maximum
  minSize: 1024,              // 1KB minimum
});

File Count Limit

useDropup({
  maxFiles: 5, // Maximum 5 files
});

Image Dimension Limits

useDropup({
  accept: 'image/*',
  maxWidth: 4096,   // Max width in pixels
  maxHeight: 4096,  // Max height in pixels
  minWidth: 100,    // Min width in pixels
  minHeight: 100,   // Min height in pixels
});

Custom Validation Rules

Create custom validation logic:

useDropup({
  customRules: [
    // Rule 1: Check filename length
    (file) => {
      if (file.name.length > 100) {
        return 'Filename must be less than 100 characters';
      }
      return true;
    },

    // Rule 2: Check for specific content
    (file) => {
      if (file.name.includes('draft')) {
        return 'Draft files are not allowed';
      }
      return true;
    },

    // Rule 3: Async validation
    async (file) => {
      const hash = await calculateHash(file);
      const exists = await checkDuplicate(hash);
      if (exists) {
        return 'This file has already been uploaded';
      }
      return true;
    },
  ],
});

Rule Return Values

Return Value	Meaning
true	Validation passed
false	Validation failed (generic error)
string	Validation failed with custom message

Handling Validation Errors

Use the onValidationError callback:

useDropup({
  accept: 'image/*',
  maxSize: 5 * 1024 * 1024,
  onValidationError: (errors) => {
    errors.forEach(({ file, errors: fileErrors }) => {
      console.log(`${file.name} failed validation:`);
      fileErrors.forEach(error => console.log(`  - ${error}`));
    });

    // Show user-friendly message
    toast.error(`${errors.length} file(s) failed validation`);
  },
});

Validation Error Structure

interface ValidationError {
  file: File;              // The file that failed
  errors: string[];        // Array of error messages
}

Pre-built Validation Rules

Dropup includes common validation rules:

import { commonRules } from '@samithahansaka/dropup';

useDropup({
  customRules: [
    commonRules.noExecutables,     // Block .exe, .bat, etc.
    commonRules.noHiddenFiles,     // Block files starting with .
    commonRules.maxFilenameLength(50),
    commonRules.allowedExtensions(['.jpg', '.png', '.pdf']),
  ],
});

Drag Validation Feedback

Provide visual feedback during drag:

function DropZone() {
  const { getDropProps, state } = useDropup({
    accept: 'image/*',
  });

  // state.isDragAccept - files match accept criteria
  // state.isDragReject - files don't match

  return (
    <div
      {...getDropProps()}
      style={{
        borderColor: state.isDragAccept
          ? 'green'
          : state.isDragReject
          ? 'red'
          : 'gray',
      }}
    >
      {state.isDragReject && <p>File type not accepted!</p>}
    </div>
  );
}

Complete Validation Example

import { useDropup, commonRules } from '@samithahansaka/dropup';

function SecureUploader() {
  const { files, state, getDropProps, getInputProps } = useDropup({
    // File type
    accept: ['image/jpeg', 'image/png', 'application/pdf'],

    // Size limits
    maxSize: 10 * 1024 * 1024, // 10MB
    minSize: 100,              // 100 bytes (prevent empty files)

    // Count limit
    maxFiles: 10,

    // Image dimensions (for images only)
    maxWidth: 8000,
    maxHeight: 8000,

    // Custom rules
    customRules: [
      commonRules.noExecutables,
      commonRules.maxFilenameLength(100),

      // Custom: no files with spaces
      (file) => {
        if (file.name.includes(' ')) {
          return 'Filenames cannot contain spaces';
        }
        return true;
      },
    ],

    // Error handling
    onValidationError: (errors) => {
      errors.forEach(({ file, errors }) => {
        alert(`${file.name}: ${errors.join(', ')}`);
      });
    },
  });

  return (
    <div
      {...getDropProps()}
      className={`dropzone ${
        state.isDragReject ? 'reject' : state.isDragAccept ? 'accept' : ''
      }`}
    >
      <input {...getInputProps()} />
      {state.isDragReject ? (
        <p>❌ Some files will be rejected</p>
      ) : (
        <p>📁 Drop files here (JPEG, PNG, PDF only, max 10MB)</p>
      )}
    </div>
  );
}