# Quick Reference Guide - New Improvements

## 🚀 How to Use New Features

### 1. Validation Service

#### Import and inject:
```typescript
import { ValidationService } from '../../services/validation.service';

constructor(private validationService: ValidationService) {}
```

#### Validate a single field:
```typescript
onFieldChange(field: string, value: any) {
  const errors = this.validationService.validateItem({ [field]: value });
  
  if (errors[field]) {
    this.snackBar.open(`Error: ${errors[field]}`, 'Close', { duration: 3000 });
    return;
  }
  
  // Proceed with save
}
```

#### Validate entire object:
```typescript
onSubmit() {
  const errors = this.validationService.validateItem(this.item);
  
  if (Object.keys(errors).length > 0) {
    const errorMsg = Object.values(errors).join(', ');
    this.snackBar.open(`Validation failed: ${errorMsg}`, 'Close', { duration: 4000 });
    return;
  }
  
  // Proceed with API call
  this.apiService.createItem(...);
}
```

#### Available validators:
- `validateRequired(value)` - Checks for empty values
- `validateNumber(value, min?, max?)` - Validates numeric input
- `validatePrice(value)` - Ensures price >= 0
- `validateQuantity(value)` - Validates integer >= 0
- `validateUrl(value)` - Checks URL format
- `validateImageUrl(value)` - Validates image extensions
- `validateId(value)` - Ensures URL-safe ID (2-50 chars)
- `validatePriority(value)` - Validates 0-9999
- `validateCurrency(value)` - USD, EUR, RUB, GBP, UAH
- `validateArrayNotEmpty(arr)` - Ensures non-empty array

---

### 2. Toast Notification Service

#### Import and inject:
```typescript
import { ToastService } from '../../services/toast.service';

constructor(private toast: ToastService) {}
```

#### Show notifications:
```typescript
// Success (green, 2s)
this.toast.success('Item saved successfully!');

// Error (red, 4s)
this.toast.error('Failed to save item');

// Warning (orange, 3s)
this.toast.warning('This action will delete all items');

// Info (blue, 2s)
this.toast.info('Loading data...');

// Custom duration
this.toast.success('Saved!', 5000); // 5 seconds
```

#### Best practices:
- Use `success()` for completed operations
- Use `error()` for failures with specific message
- Use `warning()` before dangerous actions
- Use `info()` for status updates

---

### 3. Loading Skeleton Component

#### Import in component:
```typescript
import { LoadingSkeletonComponent } from '../../components/loading-skeleton/loading-skeleton.component';

@Component({
  imports: [
    // ... other imports
    LoadingSkeletonComponent
  ]
})
```

#### Use in template:
```html
<!-- For tree/sidebar -->
@if (loading()) {
  <app-loading-skeleton type="tree"></app-loading-skeleton>
} @else {
  <!-- Your tree content -->
}

<!-- For card layouts -->
@if (loading()) {
  <app-loading-skeleton type="card"></app-loading-skeleton>
} @else {
  <!-- Your card content -->
}

<!-- For list views -->
@if (loading()) {
  <app-loading-skeleton type="list"></app-loading-skeleton>
} @else {
  <!-- Your list content -->
}

<!-- For forms -->
@if (loading()) {
  <app-loading-skeleton type="form"></app-loading-skeleton>
} @else {
  <!-- Your form content -->
}
```

#### Available types:
- `tree` - Nested hierarchy with indentation (sidebar)
- `card` - Grid of rectangular cards
- `list` - Vertical list of items
- `form` - Form fields with labels

---

### 4. Enhanced Error Handling

The API service now provides detailed error messages automatically:

#### Error codes and messages:
- **400** - "Invalid request data"
- **401** - "Unauthorized - please log in"
- **403** - "You don't have permission to perform this action"
- **404** - "Resource not found"
- **409** - "Conflict - resource already exists"
- **422** - "Validation failed"
- **500** - "Internal server error"
- **503** - "Service temporarily unavailable"

#### Example usage:
```typescript
this.apiService.createItem(item).subscribe({
  next: (created) => {
    this.toast.success('Item created!');
  },
  error: (err) => {
    // err.message already contains user-friendly message
    this.toast.error(err.message || 'Failed to create item');
  }
});
```

---

### 5. Enhanced Confirmation Dialogs

#### Example with count information:
```typescript
deleteCategory(node: CategoryNode) {
  const subCount = node.children?.length || 0;
  const message = subCount > 0 
    ? `Are you sure you want to delete "${node.name}"? This will also delete ${subCount} subcategory(ies) and all their items. This action cannot be undone.`
    : `Are you sure you want to delete "${node.name}"? This action cannot be undone.`;
  
  const dialogRef = this.dialog.open(ConfirmDialogComponent, {
    data: {
      title: 'Delete Category',
      message: message,
      confirmText: 'Delete',
      cancelText: 'Cancel',
      dangerous: true  // Shows red confirm button
    }
  });
  
  dialogRef.afterClosed().subscribe(result => {
    if (result) {
      // User confirmed, proceed with deletion
    }
  });
}
```

#### Dialog options:
- `title` - Dialog header
- `message` - Description text (can include HTML)
- `confirmText` - Confirm button label (default: "Confirm")
- `cancelText` - Cancel button label (default: "Cancel")
- `dangerous` - Makes confirm button red (for destructive actions)

---

## 🎨 Styling Tips

### Toast colors are automatic:
```typescript
// Green background
this.toast.success('...');

// Red background
this.toast.error('...');

// Orange background
this.toast.warning('...');

// Blue background
this.toast.info('...');
```

### Loading skeletons animate automatically:
- Shimmer effect from left to right
- Gray placeholders that match content structure
- No additional CSS needed

---

## 📋 Component Integration Checklist

When adding these features to a new component:

### For validation:
- [ ] Import `ValidationService`
- [ ] Inject in constructor
- [ ] Call validation before API calls
- [ ] Display errors via toast or inline

### For loading states:
- [ ] Import `LoadingSkeletonComponent`
- [ ] Add to `imports` array
- [ ] Add `loading` signal
- [ ] Wrap content with `@if (loading()) { skeleton } @else { content }`

### For toasts:
- [ ] Import `ToastService`
- [ ] Inject in constructor
- [ ] Replace MatSnackBar calls with toast methods
- [ ] Use appropriate type (success/error/warning/info)

### For error handling:
- [ ] Handle `error` callback in subscribe
- [ ] Use `err.message` for user-friendly message
- [ ] Display via toast service
- [ ] Consider retry logic for critical operations

---

## 🐛 Common Patterns

### Pattern 1: Form submission with validation
```typescript
onSubmit() {
  // Validate
  const errors = this.validationService.validateItem(this.item());
  if (Object.keys(errors).length > 0) {
    const errorMsg = Object.values(errors).join(', ');
    this.toast.error(`Validation failed: ${errorMsg}`);
    return;
  }
  
  // Save
  this.saving.set(true);
  this.apiService.updateItem(this.itemId(), this.item()).subscribe({
    next: (updated) => {
      this.item.set(updated);
      this.toast.success('Item saved successfully!');
      this.saving.set(false);
    },
    error: (err) => {
      this.toast.error(err.message || 'Failed to save item');
      this.saving.set(false);
    }
  });
}
```

### Pattern 2: Loading data with skeleton
```typescript
// Component
loading = signal(true);

ngOnInit() {
  this.loadData();
}

loadData() {
  this.loading.set(true);
  this.apiService.getData().subscribe({
    next: (data) => {
      this.data.set(data);
      this.loading.set(false);
    },
    error: (err) => {
      this.toast.error(err.message || 'Failed to load data');
      this.loading.set(false);
    }
  });
}

// Template
@if (loading()) {
  <app-loading-skeleton type="list"></app-loading-skeleton>
} @else {
  @for (item of data(); track item.id) {
    <div>{{ item.name }}</div>
  }
}
```

### Pattern 3: Destructive action with confirmation
```typescript
deleteItem() {
  const dialogRef = this.dialog.open(ConfirmDialogComponent, {
    data: {
      title: 'Delete Item',
      message: `Are you sure you want to delete "${this.item().name}"? This action cannot be undone.`,
      confirmText: 'Delete',
      cancelText: 'Cancel',
      dangerous: true
    }
  });
  
  dialogRef.afterClosed().subscribe(result => {
    if (result) {
      this.apiService.deleteItem(this.itemId()).subscribe({
        next: () => {
          this.toast.success('Item deleted successfully');
          this.router.navigate(['/items']);
        },
        error: (err) => {
          this.toast.error(err.message || 'Failed to delete item');
        }
      });
    }
  });
}
```

---

## ✅ Testing Your Implementation

### Test validation:
1. Try submitting empty form → Should show "Name is required"
2. Try negative price → Should show "Price must be at least 0"
3. Try invalid quantity → Should show "Quantity must be a non-negative integer"

### Test toasts:
1. Success action → Should show green toast
2. Failed action → Should show red toast
3. Multiple toasts → Should queue properly

### Test loading skeletons:
1. Slow network → Should show skeleton first
2. Fast network → Should briefly show skeleton
3. Skeleton should match content structure

### Test error handling:
1. Network error → Should show user-friendly message
2. 404 error → Should show "Resource not found"
3. 500 error → Should show "Internal server error"

---

## 🎯 Migration Guide

### Replace old MatSnackBar:
```typescript
// OLD
this.snackBar.open('Saved!', 'Close', { duration: 2000 });
this.snackBar.open('Error!', 'Close', { duration: 3000 });

// NEW
this.toast.success('Saved!');
this.toast.error('Error!');
```

### Replace old spinners:
```html
<!-- OLD -->
@if (loading()) {
  <mat-spinner></mat-spinner>
}

<!-- NEW -->
@if (loading()) {
  <app-loading-skeleton type="list"></app-loading-skeleton>
}
```

### Add validation to existing forms:
```typescript
// Before API call, add:
const errors = this.validationService.validateItem(this.item);
if (Object.keys(errors).length > 0) {
  this.toast.error(`Validation errors: ${Object.values(errors).join(', ')}`);
  return;
}
```

---

## 📚 Additional Resources

- **IMPROVEMENTS.md** - Full improvement roadmap
- **URGENT-IMPROVEMENTS-COMPLETED.md** - Implementation details
- **API.md** - API documentation

For questions or issues, check the implementation in:
- `src/app/pages/project-view/` - Reference implementation
- `src/app/pages/item-editor/` - Validation examples
- `src/app/services/` - Service documentation