# LiveComponents End-to-End Guide

**Complete guide to building LiveComponents from scratch to production.**

This guide walks you through creating, testing, and deploying LiveComponents with all features.

---

## Table of Contents

1. [Quick Start (5 Minutes)](#quick-start-5-minutes)
2. [Component Basics](#component-basics)
3. [State Management](#state-management)
4. [Actions & Events](#actions--events)
5. [Advanced Features](#advanced-features)
6. [Performance Optimization](#performance-optimization)
7. [Real-World Examples](#real-world-examples)

---

## Quick Start (5 Minutes)

### Step 1: Create Component Class

```php
<?php

declare(strict_types=1);

namespace App\Application\LiveComponents\Counter;

use App\Framework\LiveComponents\Attributes\Action;
use App\Framework\LiveComponents\Attributes\LiveComponent;
use App\Framework\LiveComponents\Contracts\LiveComponentContract;
use App\Framework\LiveComponents\ValueObjects\ComponentId;
use App\Framework\LiveComponents\ValueObjects\ComponentRenderData;

#[LiveComponent('counter')]
final readonly class CounterComponent implements LiveComponentContract
{
    public function __construct(
        public ComponentId $id,
        public CounterState $state
    ) {
    }

    public function getRenderData(): ComponentRenderData
    {
        return new ComponentRenderData(
            templatePath: 'livecomponent-counter',
            data: [
                'componentId' => $this->id->toString(),
                'count' => $this->state->count,
            ]
        );
    }

    #[Action]
    public function increment(): CounterState
    {
        return $this->state->increment();
    }
}
```

### Step 2: Create State Value Object

```php
<?php

declare(strict_types=1);

namespace App\Application\LiveComponents\Counter;

use App\Framework\LiveComponents\ValueObjects\ComponentState;

final readonly class CounterState extends ComponentState
{
    public function __construct(
        public int $count = 0
    ) {
    }

    public function increment(): self
    {
        return new self(count: $this->count + 1);
    }

    public static function empty(): self
    {
        return new self();
    }

    public static function fromArray(array $data): self
    {
        return new self(
            count: $data['count'] ?? 0
        );
    }

    public function toArray(): array
    {
        return [
            'count' => $this->count,
        ];
    }
}
```

### Step 3: Create Template

**File**: `resources/templates/livecomponent-counter.view.php`

```html
<div data-component-id="{componentId}">
    <h2>Counter: {count}</h2>
    <button data-live-action="increment">Increment</button>
</div>
```

### Step 4: Use in Template

```html
<x-counter id="demo" />
```

**That's it!** Your component is ready to use.

---

## Component Basics

### Component Structure

Every LiveComponent consists of:

1. **Component Class** - Implements `LiveComponentContract`
2. **State Value Object** - Extends `ComponentState`
3. **Template** - HTML template with placeholders
4. **Actions** - Methods marked with `#[Action]`

### Component ID

Components are identified by a `ComponentId` consisting of:
- **Name**: Component name from `#[LiveComponent]` attribute
- **Instance ID**: Unique identifier (e.g., 'demo', 'user-123')

```php
ComponentId::create('counter', 'demo')  // counter:demo
ComponentId::create('user-profile', '123')  // user-profile:123
```

### RenderData

`getRenderData()` returns template path and data:

```php
public function getRenderData(): ComponentRenderData
{
    return new ComponentRenderData(
        templatePath: 'livecomponent-counter',
        data: [
            'componentId' => $this->id->toString(),
            'count' => $this->state->count,
            'lastUpdate' => $this->state->lastUpdate,
        ]
    );
}
```

---

## State Management

### State Value Objects

State is managed through immutable Value Objects:

```php
final readonly class CounterState extends ComponentState
{
    public function __construct(
        public int $count = 0,
        public ?string $lastUpdate = null
    ) {
    }

    // Factory methods
    public static function empty(): self
    {
        return new self();
    }

    public static function fromArray(array $data): self
    {
        return new self(
            count: $data['count'] ?? 0,
            lastUpdate: $data['lastUpdate'] ?? null
        );
    }

    // Transformation methods (return new instance)
    public function increment(): self
    {
        return new self(
            count: $this->count + 1,
            lastUpdate: date('H:i:s')
        );
    }

    public function reset(): self
    {
        return new self(
            count: 0,
            lastUpdate: date('H:i:s')
        );
    }

    // Serialization
    public function toArray(): array
    {
        return [
            'count' => $this->count,
            'lastUpdate' => $this->lastUpdate,
        ];
    }
}
```

### State Updates

Actions return new State instances:

```php
#[Action]
public function increment(): CounterState
{
    return $this->state->increment();
}

#[Action]
public function addAmount(int $amount): CounterState
{
    return $this->state->addAmount($amount);
}
```

---

## Actions & Events

### Actions

Actions are public methods marked with `#[Action]`:

```php
#[Action]
public function increment(): CounterState
{
    return $this->state->increment();
}

#[Action(rateLimit: 10, idempotencyTTL: 60)]
public function expensiveOperation(): CounterState
{
    // Rate limited to 10 calls per minute
    // Idempotent for 60 seconds
    return $this->state->performExpensiveOperation();
}
```

### Action Parameters

Actions can accept parameters:

```php
#[Action]
public function addAmount(int $amount): CounterState
{
    return $this->state->addAmount($amount);
}
```

**Client-side**:
```html
<button data-live-action="addAmount" data-amount="5">
    Add 5
</button>
```

### Events

Dispatch events from actions:

```php
#[Action]
public function increment(?ComponentEventDispatcher $events = null): CounterState
{
    $newState = $this->state->increment();
    
    $events?->dispatch('counter:changed', EventPayload::fromArray([
        'old_value' => $this->state->count,
        'new_value' => $newState->count,
    ]));
    
    return $newState;
}
```

**Client-side**:
```javascript
document.addEventListener('livecomponent:event', (e) => {
    if (e.detail.name === 'counter:changed') {
        console.log('Counter changed:', e.detail.data);
    }
});
```

---

## Advanced Features

### Caching

Implement `Cacheable` interface:

```php
#[LiveComponent('user-stats')]
final readonly class UserStatsComponent implements LiveComponentContract, Cacheable
{
    public function getCacheKey(): string
    {
        return 'user-stats:' . $this->state->userId;
    }

    public function getCacheTTL(): Duration
    {
        return Duration::fromMinutes(5);
    }

    public function shouldCache(): bool
    {
        return true;
    }

    public function getCacheTags(): array
    {
        return ['user-stats', 'user:' . $this->state->userId];
    }

    public function getVaryBy(): ?VaryBy
    {
        return VaryBy::userId();
    }

    public function getStaleWhileRevalidate(): ?Duration
    {
        return Duration::fromHours(1);
    }
}
```

### Polling

Implement `Pollable` interface:

```php
#[LiveComponent('live-feed')]
final readonly class LiveFeedComponent implements LiveComponentContract, Pollable
{
    public function poll(): LiveComponentState
    {
        // Fetch latest data
        $newItems = $this->feedService->getLatest();
        
        return $this->state->withItems($newItems);
    }

    public function getPollInterval(): int
    {
        return 5000; // Poll every 5 seconds
    }
}
```

### File Uploads

Implement `SupportsFileUpload` interface:

```php
#[LiveComponent('image-uploader')]
final readonly class ImageUploaderComponent implements LiveComponentContract, SupportsFileUpload
{
    public function handleUpload(
        UploadedFile $file,
        ?ComponentEventDispatcher $events = null
    ): LiveComponentState {
        // Process upload
        $path = $this->storage->store($file);
        
        $events?->dispatch('file:uploaded', EventPayload::fromArray([
            'path' => $path,
            'size' => $file->getSize(),
        ]));
        
        return $this->state->withUploadedFile($path);
    }

    public function validateUpload(UploadedFile $file): array
    {
        $errors = [];
        
        if (!in_array($file->getMimeType(), ['image/jpeg', 'image/png'])) {
            $errors[] = 'Only JPEG and PNG images are allowed';
        }
        
        if ($file->getSize() > 5 * 1024 * 1024) {
            $errors[] = 'File size must be less than 5MB';
        }
        
        return $errors;
    }

    public function getAllowedMimeTypes(): array
    {
        return ['image/jpeg', 'image/png'];
    }

    public function getMaxFileSize(): int
    {
        return 5 * 1024 * 1024; // 5MB
    }
}
```

### Fragments

Use fragments for partial updates:

**Template**:
```html
<div data-lc-fragment="counter-display">
    <h2>Count: {count}</h2>
</div>

<div data-lc-fragment="actions">
    <button data-live-action="increment" data-lc-fragments="counter-display">
        Increment
    </button>
</div>
```

**Client-side**: Only `counter-display` fragment is updated, not the entire component.

### Slots

Implement `SupportsSlots` for flexible component composition:

```php
#[LiveComponent('card')]
final readonly class CardComponent implements LiveComponentContract, SupportsSlots
{
    public function getSlotDefinitions(): array
    {
        return [
            SlotDefinition::named('header'),
            SlotDefinition::default('<p>Default content</p>'),
            SlotDefinition::named('footer'),
        ];
    }

    public function getSlotContext(string $slotName): SlotContext
    {
        return SlotContext::create([
            'card_title' => $this->state->title,
        ]);
    }

    public function processSlotContent(SlotContent $content): SlotContent
    {
        return $content; // No processing needed
    }

    public function validateSlots(array $providedSlots): array
    {
        return []; // No validation errors
    }
}
```

**Usage**:
```html
<x-card id="demo" title="My Card">
    <slot name="header">
        <h1>Custom Header</h1>
    </slot>
    
    <slot>
        <p>Main content</p>
    </slot>
</x-card>
```

### Islands

Use `#[Island]` for isolated rendering:

```php
#[LiveComponent('heavy-widget')]
#[Island(isolated: true, lazy: true, placeholder: 'Loading widget...')]
final readonly class HeavyWidgetComponent implements LiveComponentContract
{
    // Component implementation
}
```

---

## Performance Optimization

### Caching Strategies

**Global Cache**:
```php
public function getVaryBy(): ?VaryBy
{
    return VaryBy::none(); // Same for all users
}
```

**Per-User Cache**:
```php
public function getVaryBy(): ?VaryBy
{
    return VaryBy::userId(); // Different cache per user
}
```

**Per-User Per-Locale Cache**:
```php
public function getVaryBy(): ?VaryBy
{
    return VaryBy::userAndLocale(); // Different cache per user and locale
}
```

**With Feature Flags**:
```php
public function getVaryBy(): ?VaryBy
{
    return VaryBy::userId()
        ->withFeatureFlags(['new-ui', 'dark-mode']);
}
```

### Stale-While-Revalidate

Serve stale content while refreshing:

```php
public function getCacheTTL(): Duration
{
    return Duration::fromMinutes(5); // Fresh for 5 minutes
}

public function getStaleWhileRevalidate(): ?Duration
{
    return Duration::fromHours(1); // Serve stale for 1 hour while refreshing
}
```

### Request Batching

Batch multiple operations:

```javascript
// Client-side
const response = await LiveComponent.executeBatch([
    {
        componentId: 'counter:demo',
        method: 'increment',
        params: { amount: 5 },
        fragments: ['counter-display']
    },
    {
        componentId: 'stats:user-123',
        method: 'refresh'
    }
]);
```

### Lazy Loading

Load components when entering viewport:

```php
// In template
{{ lazy_component('notification-center:user-123', [
    'priority' => 'high',
    'threshold' => '0.1',
    'placeholder' => 'Loading notifications...'
]) }}
```

---

## Real-World Examples

### Example 1: User Profile Component

```php
#[LiveComponent('user-profile')]
#[Island(isolated: true, lazy: true)]
final readonly class UserProfileComponent implements LiveComponentContract, Cacheable
{
    public function __construct(
        public ComponentId $id,
        public UserProfileState $state
    ) {
    }

    public function getRenderData(): ComponentRenderData
    {
        return new ComponentRenderData(
            templatePath: 'livecomponent-user-profile',
            data: [
                'componentId' => $this->id->toString(),
                'user' => $this->state->user,
                'stats' => $this->state->stats,
            ]
        );
    }

    #[Action]
    public function updateProfile(array $data, ?ComponentEventDispatcher $events = null): UserProfileState
    {
        $updatedUser = $this->userService->update($this->state->user->id, $data);
        
        $events?->dispatch('profile:updated', EventPayload::fromArray([
            'user_id' => $updatedUser->id,
        ]));
        
        return $this->state->withUser($updatedUser);
    }

    // Cacheable implementation
    public function getCacheKey(): string
    {
        return 'user-profile:' . $this->state->user->id;
    }

    public function getCacheTTL(): Duration
    {
        return Duration::fromMinutes(10);
    }

    public function shouldCache(): bool
    {
        return true;
    }

    public function getCacheTags(): array
    {
        return ['user-profile', 'user:' . $this->state->user->id];
    }

    public function getVaryBy(): ?VaryBy
    {
        return VaryBy::userId();
    }

    public function getStaleWhileRevalidate(): ?Duration
    {
        return null; // No SWR for user profiles
    }
}
```

### Example 2: Search Component with Debouncing

```php
#[LiveComponent('search')]
final readonly class SearchComponent implements LiveComponentContract
{
    #[Action(rateLimit: 20)] // Allow 20 searches per minute
    public function search(string $query, ?ComponentEventDispatcher $events = null): SearchState
    {
        if (strlen($query) < 3) {
            return $this->state->withResults([]);
        }
        
        $results = $this->searchService->search($query);
        
        $events?->dispatch('search:completed', EventPayload::fromArray([
            'query' => $query,
            'result_count' => count($results),
        ]));
        
        return $this->state->withQuery($query)->withResults($results);
    }
}
```

**Client-side debouncing**:
```javascript
let searchTimeout;
const searchInput = document.querySelector('[data-live-action="search"]');

searchInput.addEventListener('input', (e) => {
    clearTimeout(searchTimeout);
    searchTimeout = setTimeout(() => {
        LiveComponent.executeAction('search:demo', 'search', {
            query: e.target.value
        });
    }, 300); // 300ms debounce
});
```

### Example 3: Dashboard with Multiple Components

```php
// Dashboard page template
<div class="dashboard">
    <!-- Heavy widget - lazy loaded -->
    <x-analytics-dashboard id="main" />
    
    <!-- User stats - cached -->
    <x-user-stats id="current-user" />
    
    <!-- Live feed - polled -->
    <x-live-feed id="feed" />
</div>
```

---

## Testing

### Using LiveComponentTestCase

```php
class CounterComponentTest extends LiveComponentTestCase
{
    public function test_increments_counter(): void
    {
        $this->mount('counter:test', ['count' => 5])
            ->call('increment')
            ->seeStateKey('count', 6)
            ->seeHtmlHas('Count: 6');
    }

    public function test_resets_counter(): void
    {
        $this->mount('counter:test', ['count' => 10])
            ->call('reset')
            ->seeStateKey('count', 0)
            ->seeHtmlHas('Count: 0');
    }

    public function test_dispatches_event_on_increment(): void
    {
        $this->mount('counter:test', ['count' => 5])
            ->call('increment')
            ->seeEventDispatched('counter:changed', [
                'old_value' => 5,
                'new_value' => 6,
            ]);
    }
}
```

### Snapshot Testing

```php
public function test_renders_counter_correctly(): void
{
    $component = mountComponent('counter:test', ['count' => 5]);
    
    expect($component['html'])->toMatchSnapshot('counter-initial-state');
}
```

---

## Best Practices

### 1. Immutable State

Always return new State instances:

```php
// ✅ CORRECT
public function increment(): CounterState
{
    return new CounterState(count: $this->state->count + 1);
}

// ❌ WRONG (won't work with readonly)
public function increment(): void
{
    $this->state->count++; // Error: Cannot modify readonly property
}
```

### 2. Type-Safe State

Use Value Objects instead of arrays:

```php
// ✅ CORRECT
public function __construct(
    public CounterState $state
) {}

// ❌ WRONG
public function __construct(
    public array $state
) {}
```

### 3. Action Validation

Validate inputs in actions:

```php
#[Action]
public function addAmount(int $amount): CounterState
{
    if ($amount < 0) {
        throw new \InvalidArgumentException('Amount must be positive');
    }
    
    return $this->state->addAmount($amount);
}
```

### 4. Error Handling

Handle errors gracefully:

```php
#[Action]
public function performOperation(): CounterState
{
    try {
        return $this->state->performOperation();
    } catch (\Exception $e) {
        // Log error
        error_log("Operation failed: " . $e->getMessage());
        
        // Return unchanged state or error state
        return $this->state->withError($e->getMessage());
    }
}
```

### 5. Performance

- Use caching for expensive operations
- Use fragments for partial updates
- Use lazy loading for below-the-fold content
- Use Islands for heavy components
- Batch multiple operations

---

## Next Steps

- [Security Guide](security-guide-complete.md) - CSRF, Rate Limiting, Authorization
- [Performance Guide](performance-guide-complete.md) - Caching, Batching, Optimization
- [Upload Guide](upload-guide-complete.md) - File Uploads, Validation, Chunking
- [API Reference](api-reference-complete.md) - Complete API documentation