# Product & Business Requirements

Core requirements and specifications for the Form Builder library.

## Product Overview

**Form Builder** transforms JSON schemas into dynamic, interactive web forms with real-time validation and structured data output. Designed as a framework-agnostic, zero-dependency library for easy integration.

**Primary Goal**: Provide a reusable form generation solution that eliminates custom form development overhead.

## Business Requirements

### Core Value Propositions

1. **Rapid Form Development**: Schema → Form in minutes, not hours
2. **Consistent UX**: Standardized form behavior across applications  
3. **Zero Dependencies**: No framework lock-in or bundle bloat
4. **File Upload Ready**: Built-in support for modern file workflows
5. **Deployment Flexibility**: CDN, NPM, or self-hosted options

### Target Users

- **Developers**: Need forms for SPA applications
- **Product Teams**: Require consistent form experiences
- **Startups**: Want rapid prototyping capabilities
- **Enterprise**: Need standardized form solutions

## Functional Requirements

### 1. Form Generation Engine

**MUST support field types:**
- `text` - Single line input with validation
- `textarea` - Multi-line text input  
- `number` - Numeric input with constraints
- `select` - Dropdown with options
- `file` - Single file upload with preview
- `files` - Multiple file upload with limits
- `group` - Nested objects with repeat support

```javascript
// Example schema
{
  "version": "0.3",
  "title": "Asset Upload",
  "elements": [
    {
      "type": "files",
      "key": "assets", 
      "label": "Images",
      "maxCount": 10,
      "accept": { "extensions": ["jpg", "png"] }
    }
  ]
}
```

### 2. Validation System

**MUST provide:**
- Real-time field validation
- Required field checking
- String length limits (minLength/maxLength)
- Numeric ranges (min/max)  
- Pattern matching (regex)
- File type restrictions
- Custom validation rules

**MUST support:**
- Form submission with full validation
- Draft saving without validation
- Field-level error display

### 3. File Upload System

**Upload Handler Requirements:**
```javascript
// Handler MUST return resource ID for download/submission
uploadHandler: async (file) => {
    // Upload logic...
    return resourceId; // NOT file URL
}
```

**MUST provide:**
- Visual file previews (thumbnails + icons)
- Upload progress indicators  
- Individual file removal
- Drag & drop support
- File metadata display (name, size, type)

### 4. Form Modes

**Submission Mode** (default):
- Full editing capabilities
- Real-time validation
- Submit button requires all validation to pass

**Read-Only Mode**:
- Display form data without editing
- Show file download links
- Disable all form interactions
- Support nested object display

**Draft Mode**:
- Save incomplete forms
- Skip required field validation
- Preserve user input
- Enable resume functionality

### 5. Integration Capabilities

**MUST support:**
- CDN via iframe embedding
- NPM package installation
- Direct HTML integration
- Schema loading via URL parameters
- Form data prefilling
- Event-based communication

```html
<!-- CDN Integration -->
<iframe src="https://picazru.github.io/form-builder/dist/index.html" 
        width="100%" height="600px"></iframe>
```

### 6. Styling System

**MUST use Tailwind CSS** for all styling:
- Consistent design system
- Responsive layouts  
- Dark/light theme support
- Custom CSS property integration
- Framework compatibility

## Technical Requirements

### 1. Architecture

**Core Stack:**
- HTML5 semantic markup
- CSS3 with custom properties
- Vanilla JavaScript (ES6+)
- Web APIs (FormData, PostMessage, Crypto)

**Performance:**
- Library size <500KB uncompressed
- Form rendering <2s for 1000 fields
- Real-time validation without UI blocking

### 2. Browser Support

**MUST support:**
- Chrome 80+, Firefox 75+, Safari 13+, Edge 80+
- Mobile browsers with touch interfaces
- Progressive enhancement for older browsers

### 3. Security

**MUST implement:**
- Input sanitization for all user data
- File type validation (MIME + extension)
- Secure resource ID generation
- CSP-compatible code (no inline scripts)
- Origin validation for iframe communication

### 4. Data Formats

**Schema Format (v0.3):**
```typescript
interface FormSchema {
  version: "0.3";
  title: string;
  elements: FormElement[];
}
```

**Output Format:**
```json
{
  "textField": "value",
  "fileField": "res_abc123",
  "multipleFiles": ["res_def456", "res_ghi789"],
  "nestedGroup": {
    "subField": "value"
  }
}
```

## Quality Requirements

### Performance Metrics
- **Form Rendering**: <2 seconds for 1000 fields
- **File Upload**: >95% success rate under size limits
- **Validation Speed**: <100ms per field
- **Memory Usage**: <50MB for large forms

### Reliability
- **Browser Compatibility**: >99% success rate on target browsers
- **Error Recovery**: Graceful fallback for all error conditions
- **Data Integrity**: No data loss during form interactions

### Usability
- **Accessibility**: WCAG 2.1 AA compliance
- **Mobile Support**: Touch-friendly interfaces
- **Error Messages**: Clear, actionable feedback
- **Loading States**: Visual feedback for all operations

## Deployment Requirements

### 1. CDN Distribution
- GitHub Pages hosting for global availability
- Versioned URLs for stable integration
- Automatic deployment on releases

### 2. NPM Package
- Published as `@dmitryvim/form-builder`
- ES6 module support
- CommonJS compatibility
- TypeScript definitions

### 3. Versioning
- Semantic versioning (SemVer)
- Backwards compatibility within major versions
- Migration guides for breaking changes

## Success Criteria

### Acceptance Criteria
- [ ] All field types render and validate correctly
- [ ] File uploads work with custom handlers
- [ ] Read-only mode displays data properly
- [ ] Draft saving works without validation
- [ ] Tailwind CSS styling applies correctly
- [ ] Cross-browser compatibility verified
- [ ] >80% test coverage achieved
- [ ] Performance benchmarks met

### Business Metrics
- **Developer Adoption**: Measurable NPM downloads
- **Integration Success**: Working implementations in production
- **Performance Goals**: Sub-2-second form rendering
- **Error Rates**: <1% form submission failures

## Constraints & Assumptions

### Technical Constraints
- No external dependencies allowed
- Must work in iframe sandboxes
- File handling delegated to integrating application
- Cannot make direct network requests (CORS limitations)

### Business Constraints  
- Open source MIT license
- Community-driven development
- GitHub-only deployment pipeline
- No specific backend requirements

### Assumptions
- Integrating applications handle file storage
- Modern browser environment (ES6+ support)
- Developers familiar with JSON Schema concepts
- Basic understanding of iframe communication

## Future Considerations

### Potential Enhancements
- Conditional field logic (show/hide based on values)
- Custom field type plugins
- Advanced file processing (image cropping, etc.)
- Internationalization support
- Real-time collaboration features

### Not In Scope
- Backend file storage implementation
- Database integration
- User authentication/authorization
- Advanced form analytics
- Multi-page form wizards

This requirements document defines the core functionality and quality standards for the Form Builder library, ensuring it meets both current needs and provides a foundation for future growth.