Examples for presentation.

sources/Example/Good/ApiClient.php

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+<?php
+
+namespace Example\Good;
+
+use GuzzleHttp\Client;
+
+class ApiClient
+{
+
+    private Client $client;
+
+    public function __construct(Client $client)
+    {
+        $this->client = $client;
+    }
+
+    /**
+     * @return Product[]
+     */
+    public function getProducts(string $filter): array
+    {
+        $response = $this->client->request('GET', 'api_endpoint/products', [
+            'query' => ['filter' => $filter]
+        ]);
+
+        $json = $response->getBody()->getContents();
+
+
+        $data = json_decode($json, true);
+
+        $products = [];
+        foreach ($data as $productArray) {
+            $products[] = (new Product())->setData($productArray);
+        }
+
+        return $products;
+    }
+}

sources/Example/Good/Controller.php

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+<?php
+
+namespace Example\Good;
+
+use Psr\Http\Message\RequestInterface;
+
+class Controller
+{
+    private ApiClient $apiClient;
+    private Repository $repository;
+    private VATCalculator $vatCalculator;
+
+    public function __construct(ApiClient $apiClient, Repository $repository, VATCalculator $vatCalculator)
+    {
+        $this->apiClient = $apiClient;
+        $this->repository = $repository;
+        $this->vatCalculator = $vatCalculator;
+    }
+
+
+    /**
+     * @return Product[]
+     */
+    public function getProducts(RequestInterface $request) : array {
+        $params = $request->getBody();
+
+        $products = $this->apiClient->getProducts($params);
+
+        $skus = [];
+        foreach ($products as $product) {
+            $skus[] = $product->sku;
+        }
+
+        $dbProducts = $this->repository->getProducts($skus);
+
+        Product::copyQuantities($dbProducts, $products);
+
+        $this->vatCalculator->applyVat($dbProducts);
+
+        return $dbProducts;
+    }
+
+}

sources/Example/Good/Product.php

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+<?php
+
+namespace Example\Good;
+
+class Product
+{
+    public string $sku = '';
+    public int $quantity = 0;
+    public float $price = 0;
+
+    public function setSku(string $sku): Product
+    {
+        $this->sku = $sku;
+        return $this;
+    }
+
+    public function setQuantity(int $quantity): Product
+    {
+        $this->quantity = $quantity;
+        return $this;
+    }
+
+    public function setPrice(float $price): Product
+    {
+        $this->price = $price;
+        return $this;
+    }
+
+
+    /**
+     * Instead of this better to use some DAO lib like JMSSerializer, or cuyz/valinor.
+     */
+    public function setData(array $data): Product {
+        $this->sku = $data['sku'] ?? '';
+        $this->quantity = $data['amount'] ?? 0;
+        $this->price = $data['price'] ?? 0;
+
+        return $this;
+    }
+
+    /**
+     * @param Product[] $destinationProducts
+     * @param Product[] $sourceProducts
+     */
+    public static function copyQuantities(array $destinationProducts, array $sourceProducts ) {
+        $indexedBySku = [];
+        foreach ($destinationProducts as $destinationProduct) {
+            $indexedBySku[$destinationProduct->sku] = $destinationProduct;
+        }
+
+        foreach ($sourceProducts as $sourceProduct) {
+            if ( !array_key_exists($sourceProduct->sku, $indexedBySku) ) {
+                continue;
+            }
+            $indexedBySku[$sourceProduct->sku]->setQuantity($sourceProduct->quantity);
+        }
+    }
+}

sources/Example/Good/Repository.php

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+<?php
+
+namespace Example\Good;
+
+use PDO;
+
+class Repository
+{
+    private PDO $pdo;
+
+    public function __construct(PDO $pdo)
+    {
+        $this->pdo = $pdo;
+    }
+
+    /**
+     * @return Product[]
+     */
+    public function getProducts($skus) : array{
+        $quotedSkus = [];
+        foreach($skus as $sku){
+            $quotedSkus[] = $this->pdo->quote($sku);
+        }
+        $skusStr = implode(',', $quotedSkus);
+        $sql = "SELECT * FROM products where id in ($skusStr)";
+
+        return $this->pdo->query($sql)->fetchAll(PDO::FETCH_CLASS, Product::class);
+    }
+}

sources/Example/Good/VATCalculator.php

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+<?php
+
+namespace Example\Good;
+
+class VATCalculator
+{
+    private float $vat;
+
+    /**
+     * @param float $vat
+     */
+    public function __construct(float $vat)
+    {
+        $this->vat = $vat;
+    }
+
+    /**
+     * @param Product[] $products
+     */
+    public function applyVat(array $products) : void {
+        foreach ($products as $product) {
+            $product->setPrice( $product->price * (1+$this->vat/100) );
+        }
+    }
+}