Event Sourcing PHP 04

event-sourcing-php-04.php

<?php
class PriceChangeOverTimeProjection
{
    private array $priceChangeOverTime = [];

    public function registerPriceChange(PriceWasChanged $event): void
    {
        $lastPrice = end($this->priceChangeOverTime[$event->getProductId()]);
        $this->priceChangeOverTime[$event->getProductId()][] = new PriceChange($event->getPrice(), $event->getPrice() - $lastPrice->getPrice());
    }

    public function getPriceChangesFor(int $productId): array
    {
        if (!isset($this->priceChangeOverTime[$productId])) {
            return [];
        }

        return $this->priceChangeOverTime[$productId];
    }
}