feat: NBP service outline

src/main/java/eu/ztsh/wymiana/service/NbpService.java

@@ -0,0 +1,44 @@
+package eu.ztsh.wymiana.service;
+
+import eu.ztsh.wymiana.model.Rates;
+import org.assertj.core.util.VisibleForTesting;
+import org.springframework.stereotype.Service;
+
+import java.time.LocalDate;
+
+/**
+ * NBP exchange rates service
+ */
+@Service
+public class NbpService {
+
+    public double getSellRate(String currency) {
+        throw new UnsupportedOperationException("Not implemented yet");
+    }
+
+    public double getBuyRate(String currency) {
+        throw new UnsupportedOperationException("Not implemented yet");
+    }
+
+    /**
+     * Calculates date for data fetch.
+     * <p>
+     * Usually this would be today, but as rates are set only Mon-Fri, during weekends it is needed to fetch last friday rates.
+     *
+     * @return date for data fetch
+     */
+    @VisibleForTesting
+    LocalDate getFetchDate() {
+        throw new UnsupportedOperationException("Not implemented yet");
+    }
+
+    @VisibleForTesting
+    Rates fetchData(String date) {
+        throw new UnsupportedOperationException("Not implemented yet");
+    }
+
+    private record RatesCache(LocalDate date, double buy, double sell) {
+
+    }
+
+}