# 🎯 Accordion Component Design
**Senior Rust Staff Engineer Review - September 20, 2025**

## 📋 Component Overview

The **Accordion** component provides a vertically stacked set of collapsible content sections. Each section can be expanded or collapsed independently, allowing users to focus on specific content while keeping the interface clean and organized.

### **Current Status**
- **File Size**: 287 lines (default.rs) - ✅ **COMPLIANT**
- **Test Coverage**: 3 test files - ✅ **MODERATE**
- **Priority**: **P2** - Medium Priority

---

## 🎨 Design Principles

### **1. Accessibility First**
- **ARIA Support**: Full ARIA attributes for screen readers
- **Keyboard Navigation**: Arrow keys, Enter, Space, Tab navigation
- **Focus Management**: Clear focus indicators and logical tab order
- **Screen Reader Support**: Proper announcements for state changes

### **2. Performance Optimized**
- **Lazy Loading**: Content loaded only when expanded
- **Memory Management**: Proper cleanup of event listeners
- **Signal Management**: Efficient reactive state updates
- **Bundle Size**: Minimal impact on application bundle

### **3. Developer Experience**
- **Type Safety**: Full TypeScript support with proper prop types
- **Composable**: Easy to extend and customize
- **Consistent API**: Follows established patterns
- **Documentation**: Comprehensive examples and guides

---

## 🏗️ Architecture

### **Core Components**
```rust
// Main accordion container
pub struct Accordion {
    pub value: Option<String>,
    pub on_value_change: Option<Callback<String>>,
    pub collapsible: bool,
    pub class: Option<String>,
    pub children: Children,
}

// Individual accordion item
pub struct AccordionItem {
    pub value: String,
    pub disabled: bool,
    pub class: Option<String>,
    pub children: Children,
}

// Accordion trigger (header)
pub struct AccordionTrigger {
    pub class: Option<String>,
    pub children: Children,
}

// Accordion content (body)
pub struct AccordionContent {
    pub class: Option<String>,
    pub children: Children,
}
```

### **State Management**
```rust
// Accordion state
pub struct AccordionState {
    pub open_items: RwSignal<HashSet<String>>,
    pub focused_item: RwSignal<Option<String>>,
    pub keyboard_navigation: RwSignal<bool>,
}

// Accordion item state
pub struct AccordionItemState {
    pub is_open: RwSignal<bool>,
    pub is_focused: RwSignal<bool>,
    pub is_disabled: RwSignal<bool>,
}
```

---

## 🎯 API Design

### **Accordion Props**
```rust
pub struct AccordionProps {
    // Core functionality
    pub value: Option<String>,                    // Currently open item
    pub on_value_change: Option<Callback<String>>, // Value change callback
    pub collapsible: bool,                        // Allow all items to be closed
    
    // Styling
    pub class: Option<String>,                    // Custom CSS classes
    pub variant: AccordionVariant,               // Visual variant
    
    // Accessibility
    pub aria_label: Option<String>,              // ARIA label
    pub aria_labelledby: Option<String>,         // ARIA labelledby
    
    // Children
    pub children: Children,                      // Accordion items
}
```

### **AccordionItem Props**
```rust
pub struct AccordionItemProps {
    // Core functionality
    pub value: String,                           // Unique identifier
    pub disabled: bool,                          // Disabled state
    
    // Styling
    pub class: Option<String>,                   // Custom CSS classes
    
    // Children
    pub children: Children,                     // Trigger and content
}
```

### **AccordionTrigger Props**
```rust
pub struct AccordionTriggerProps {
    // Styling
    pub class: Option<String>,                   // Custom CSS classes
    
    // Children
    pub children: Children,                     // Trigger content
}
```

### **AccordionContent Props**
```rust
pub struct AccordionContentProps {
    // Styling
    pub class: Option<String>,                   // Custom CSS classes
    
    // Children
    pub children: Children,                     // Content
}
```

---

## 🎨 Visual Design

### **Variants**
```rust
pub enum AccordionVariant {
    Default,    // Standard accordion
    Bordered,   // With borders between items
    Filled,     // Filled background
    Ghost,      // Transparent background
}
```

### **Sizes**
```rust
pub enum AccordionSize {
    Small,      // Compact spacing
    Medium,     // Standard spacing
    Large,      // Generous spacing
}
```

### **States**
- **Closed**: Collapsed state with trigger visible
- **Open**: Expanded state with content visible
- **Disabled**: Non-interactive state
- **Focused**: Keyboard focus state
- **Hover**: Mouse hover state

---

## 🧪 Testing Strategy

### **Unit Tests**
- [ ] **Basic Rendering**: Component renders without errors
- [ ] **Props Handling**: All props are properly applied
- [ ] **State Management**: Open/close state works correctly
- [ ] **Event Handling**: Click and keyboard events work
- [ ] **Accessibility**: ARIA attributes are correct

### **Integration Tests**
- [ ] **Multiple Items**: Multiple accordion items work together
- [ ] **Collapsible Behavior**: Collapsible prop works correctly
- [ ] **Value Changes**: on_value_change callback fires
- [ ] **Keyboard Navigation**: Arrow keys, Enter, Space work
- [ ] **Focus Management**: Focus moves correctly

### **Accessibility Tests**
- [ ] **Screen Reader**: Content is announced correctly
- [ ] **Keyboard Navigation**: All interactions work with keyboard
- [ ] **Focus Indicators**: Focus is clearly visible
- [ ] **ARIA Attributes**: Proper ARIA implementation

### **Performance Tests**
- [ ] **Rendering Performance**: Fast initial render
- [ ] **Memory Usage**: No memory leaks
- [ ] **Bundle Size**: Minimal impact on bundle
- [ ] **Signal Updates**: Efficient reactive updates

---

## 🚀 Implementation Plan

### **Phase 1: Core Implementation (Week 1)**
- [ ] **Basic Structure**: Create core component files
- [ ] **Props Definition**: Define all prop types
- [ ] **State Management**: Implement reactive state
- [ ] **Basic Rendering**: Simple accordion functionality

### **Phase 2: Advanced Features (Week 2)**
- [ ] **Keyboard Navigation**: Arrow keys, Enter, Space
- [ ] **Accessibility**: ARIA attributes and screen reader support
- [ ] **Styling**: Variants and size options
- [ ] **Event Handling**: Click and keyboard events

### **Phase 3: Testing & Documentation (Week 3)**
- [ ] **Unit Tests**: Comprehensive test coverage
- [ ] **Integration Tests**: Multi-item scenarios
- [ ] **Accessibility Tests**: Screen reader and keyboard
- [ ] **Documentation**: Examples and guides

### **Phase 4: Optimization (Week 4)**
- [ ] **Performance**: Optimize rendering and memory
- [ ] **Bundle Size**: Minimize impact on bundle
- [ ] **Signal Management**: Efficient reactive updates
- [ ] **Final Testing**: End-to-end validation

---

## 📊 Success Metrics

### **Functionality**
- [ ] **Basic Accordion**: Open/close functionality works
- [ ] **Multiple Items**: Multiple items work together
- [ ] **Collapsible**: All items can be closed
- [ ] **Value Changes**: Callbacks fire correctly

### **Accessibility**
- [ ] **Screen Reader**: Content is announced correctly
- [ ] **Keyboard Navigation**: All interactions work with keyboard
- [ ] **Focus Management**: Focus moves correctly
- [ ] **ARIA Compliance**: Meets WCAG 2.1 AA standards

### **Performance**
- [ ] **Rendering**: Fast initial render (< 16ms)
- [ ] **Memory**: No memory leaks
- [ ] **Bundle Size**: Minimal impact (< 5KB)
- [ ] **Updates**: Efficient reactive updates

### **Developer Experience**
- [ ] **Type Safety**: Full TypeScript support
- [ ] **Documentation**: Comprehensive examples
- [ ] **API Consistency**: Follows established patterns
- [ ] **Error Handling**: Clear error messages

---

## 🎯 Conclusion

The **Accordion** component is a **medium priority** component that requires **moderate test coverage improvements** and **file size optimization**. The component follows **accessibility-first design principles** with **comprehensive keyboard navigation** and **screen reader support**.

**Key Focus Areas:**
1. **Test Coverage**: Expand from 3 to 5+ test files
2. **File Size**: Ensure all files under 300 lines
3. **Accessibility**: Comprehensive ARIA support
4. **Performance**: Optimize rendering and memory usage

**Expected Outcome:**
A **production-ready, fully-accessible, well-tested** accordion component that meets enterprise standards.

---

*Accordion Component Design created: September 20, 2025*  
*Next review: October 20, 2025*
