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                <?php namespace C4tech\RayEmitter\Event;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use C4tech\RayEmitter\Contracts\Domain\Event as EventInterface;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use C4tech\RayEmitter\Contracts\Event\Store as StoreInterface;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Illuminate\Support\Facades\Event as EventBus;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                use Illuminate\Database\Eloquent\Model;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                class Store extends Model implements StoreInterface  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected static $queue = [];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @inheritDoc  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected $table = 'event_store';  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @inheritDoc  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected $fillable = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'identifier',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'sequence',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'event',  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        'payload'  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    ];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @inheritDoc  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function getFor($identifier)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $events = new Collection;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $recorded_events = $this->newQuery()->forEntity($identifier)->get();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        foreach ($recorded_events as $record) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $events->append($this->restoreEvent($record));  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $events;  | 
            
                            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function replayAll()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $records = $this->all();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $records->each(function ($record) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            $event = $this->restoreEvent($record);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            EventBus::fire('replay:' . $record->event, [$event]); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        });  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Restore Event  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Unserialize saved record back into an Event.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  static         $record Event Store model record  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return EventInterface  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    protected function restoreEvent($record)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $class = $record->event;  | 
            
                            
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                        return $class::unserialize($record);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @inheritDoc  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function saveEvent(EventInterface $event)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $class = get_class($event);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        $record = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'event'      => $class,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'identifier' => $event->getId(),  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'payload'    => $event->serialize(),  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'sequence'   => $this->newQuery()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                                ->forEntity($event->getId())  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                                                ->count()  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        ];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        static::create($record);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        self::$queue[] = [  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'event' => $class,  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                            'payload' => [$event]  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        ];  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                        EventBus::fire('save:' . $class, [$event]); | 
            
            
                                                                        
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Save Queue  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * Persist all queued Events into Event Store.  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     * @return void  | 
            
            
                                                                        
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    public function publishQueue()  | 
            
            
                                                                        
                            
            
                                    
            
            
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                    { | 
            
            
                                                                        
                            
            
                                    
            
            
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                        foreach (static::$queue as $record) { | 
            
            
                                                                        
                            
            
                                    
            
            
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                            EventBus::fire('publish:' . $record['event'], $record['payload']); | 
            
            
                                                                        
                            
            
                                    
            
            
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                        }  | 
            
            
                                                                        
                            
            
                                    
            
            
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                        static::$queue = [];  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Scope: For Entity  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * Query scope for Entity identifier.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  Query  $query      Query Builder  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @param  string $identifier Entity identifier  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     * @return Query  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    public function scopeForEntity($query, $identifier)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                        return $query->where('identifier', '=', $identifier); | 
            
            
                                                                                                            
                            
            
                                    
            
            
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                    }  | 
            
            
                                                                                                            
                                                                
            
                                    
            
            
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                }  | 
            
            
                                                        
            
                                    
            
            
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.