#11 Rewrote, moved code to OrderManager

src/main/java/de/rwu/easydrop/service/processing/OrderManager.java

@@ -1,10 +1,88 @@
 package de.rwu.easydrop.service.processing;
 
-/**
- * Processes dropshipping orders.
- *
- * TODO implement
- */
-public class OrderManager {
+import java.util.List;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import de.rwu.easydrop.Main;
+import de.rwu.easydrop.exception.InvalidCatalogueException;
+import de.rwu.easydrop.model.Product;
+import de.rwu.easydrop.model.ProductCatalogue;
+import de.rwu.easydrop.model.ProductPair;
+import de.rwu.easydrop.util.FormattingUtil;
+
+/**
+ * Creates dropshipping orders based on price margin.
+ *
+ * @since 0.3.0
+ */
+public final class OrderManager {
+
+    /**
+     * Temporary logging instance.
+     */
+    private static final Logger LOGGER = LoggerFactory.getLogger(OrderManager.class);
+
+    /**
+     * Private constructor to prevent unwanted instantiation.
+     *
+     * @throws UnsupportedOperationException always
+     */
+    private OrderManager() throws UnsupportedOperationException {
+        throw new UnsupportedOperationException("This is a stateless class, don't instantiate it.");
+    }
+
+    /**
+     * Creates orders for products with sufficient margin.
+     *
+     * @param pCats Product Catalogues
+     */
+    public static void createOrders(final List<ProductCatalogue> pCats) {
+        for (ProductCatalogue pCat : pCats) {
+            ProductPair pair = getHighestMarginProducts(pCat);
+
+            // TODO: create actual orders/transactions, remove logger
+            double margin = pair.getProduct2().getCurrentPrice() -
+                    pair.getProduct1().getCurrentPrice();
+            String marginFormatted = FormattingUtil.formatEuro(margin);
+            LOGGER.info("{}: Margin {} ({} to {})",
+                    pCat.getProductName(),
+                    marginFormatted,
+                    pair.getProduct1().getDataOrigin(),
+                    pair.getProduct2().getDataOrigin());
+        }
+    }
+
+    /**
+     * Returns the cheapest and most expensive product of a catalogue to guarantee
+     * the biggest margin as a pair.
+     *
+     * @param pCat Product Catalogue
+     * @return Cheapest Product, Most Expensive Product as a Product Pair
+     */
+    public static ProductPair getHighestMarginProducts(final ProductCatalogue pCat) {
+        if (pCat.getProducts().size() < 2) {
+            throw new InvalidCatalogueException("Product Catalogue holds less than 2 products!");
+        }
+
+        // Initialize indexes
+        Product cheapestProduct = pCat.getProducts().get(0);
+        Product mostExpensiveProduct = pCat.getProducts().get(0);
+
+        for (Product product : pCat.getProducts()) {
+            if (product.getCurrentPrice() < cheapestProduct.getCurrentPrice()) {
+                cheapestProduct = product;
+            }
+            if (product.getCurrentPrice() > mostExpensiveProduct.getCurrentPrice()) {
+                mostExpensiveProduct = product;
+            }
+        }
+
+        if (cheapestProduct.getCurrentPrice() == mostExpensiveProduct.getCurrentPrice()) {
+            throw new InvalidCatalogueException("Price margin is zero!");
+        }
+
+        return new ProductPair(cheapestProduct, mostExpensiveProduct);
+    }
 }