Event Sourcing PHP Example 06

event-sourcing-php-06.php

<?php
#[Projection("price_change_over_time", Product::class)] // 1
class PriceChangeOverTimeProjection
{
    /** @var PriceChange[][] */
    private array $priceChangeOverTime = [];

    /**
     * @return PriceChange[]
     */
    #[QueryHandler("product.getPriceChange")] // 2
    public function getPriceChangesFor(int $productId): array
    {
        if (!isset($this->priceChangeOverTime[$productId])) {
            return [];
        }

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

    #[EventHandler] // 3
    public function registerPrice(ProductWasRegistered $event): void
    {
        $this->priceChangeOverTime[$event->getProductId()][] = new PriceChange($event->getPrice(), 0);
    }

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