From 8832cdec8828365e7ca9a65c6f6798a33dfb8bcb Mon Sep 17 00:00:00 2001
From: gotty <gotty@hedgecode.org>
Date: Sun, 12 Jan 2020 03:30:29 +0300
Subject: [PATCH] [LIB-13] Add service provider interface registry

---
 .../chess/scanner/spi/ServiceRegistry.java         | 57 ++++++++++++++++++++++
 .../scanner/spi/ServiceRegistryException.java      | 30 ++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistry.java
 create mode 100644 src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistryException.java

diff --git a/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistry.java b/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistry.java
new file mode 100644
index 0000000..cb955bd
--- /dev/null
+++ b/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistry.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2019-2020. Developed by Hedgecode.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.hedgecode.chess.scanner.spi;
+
+import java.util.Iterator;
+import java.util.ServiceLoader;
+
+/**
+ * Service Provider Interface (SPI) Registry.
+ *
+ * @author Dmitry Samoshin aka gotty
+ */
+public final class ServiceRegistry {
+
+    private ServiceRegistry() {
+    }
+
+    public static <ServiceType> ServiceType singleProvider(Class<ServiceType> serviceClass) {
+        final Iterator<ServiceType> providers = providers(serviceClass);
+
+        ServiceType provider = providers.next();
+        if (providers.hasNext()) {
+            throw new ServiceRegistryException(
+                    String.format("Too many service providers for: %s", serviceClass.getName())
+            );
+        }
+
+        return provider;
+    }
+
+    private static <ServiceType> Iterator<ServiceType> providers(Class<ServiceType> serviceClass) {
+        final Iterator<ServiceType> providers = ServiceLoader.load(serviceClass).iterator();
+
+        if (!providers.hasNext()) {
+            throw new ServiceRegistryException(
+                    String.format("Service provider not found for: %s", serviceClass.getName())
+            );
+        }
+
+        return providers;
+    }
+
+}
diff --git a/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistryException.java b/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistryException.java
new file mode 100644
index 0000000..16fa341
--- /dev/null
+++ b/src/main/java/org/hedgecode/chess/scanner/spi/ServiceRegistryException.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2019-2020. Developed by Hedgecode.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.hedgecode.chess.scanner.spi;
+
+/**
+ * Service Provider Interface (SPI) Registry Exception.
+ *
+ * @author Dmitry Samoshin aka gotty
+ */
+public class ServiceRegistryException extends RuntimeException {
+
+    ServiceRegistryException(String message) {
+        super(message);
+    }
+
+}
-- 
2.10.0