ProtocolV2HookChain: Allow to create a chain of protocol V2 hooks

UploadPack only supports one protocol-v2 hook. There are already cases
where more than one is needed.

Offer a Chain class to compose ProtocolV2Hooks, as other hooks do. It
looks like a single hook but it calls all its members.

Change-Id: Idd173ca7df6672079ac0de03c67f77abac376538
Signed-off-by: Ivan Frade <ifrade@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV2HookChainTest.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2019, Google LLC.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.transport;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class ProtocolV2HookChainTest {
+
+	@Test
+	public void testDefaultIfEmpty() {
+		ProtocolV2Hook[] noHooks = {};
+		ProtocolV2Hook newChain = ProtocolV2HookChain
+				.newChain(Arrays.asList(noHooks));
+		assertEquals(newChain, ProtocolV2Hook.DEFAULT);
+	}
+
+	@Test
+	public void testFlattenChainIfOnlyOne() {
+		FakeProtocolV2Hook hook1 = new FakeProtocolV2Hook();
+		ProtocolV2Hook newChain = ProtocolV2HookChain
+				.newChain(Arrays.asList(ProtocolV2Hook.DEFAULT, hook1));
+		assertEquals(newChain, hook1);
+	}
+
+	@Test
+	public void testMultipleHooks() throws ServiceMayNotContinueException {
+		FakeProtocolV2Hook hook1 = new FakeProtocolV2Hook();
+		FakeProtocolV2Hook hook2 = new FakeProtocolV2Hook();
+
+		ProtocolV2Hook chained = ProtocolV2HookChain
+				.newChain(Arrays.asList(hook1, hook2));
+		chained.onLsRefs(LsRefsV2Request.builder().build());
+
+		assertTrue(hook1.wasInvoked());
+		assertTrue(hook2.wasInvoked());
+	}
+
+	private static final class FakeProtocolV2Hook implements ProtocolV2Hook {
+		boolean invoked;
+
+		@Override
+		public void onLsRefs(LsRefsV2Request req)
+				throws ServiceMayNotContinueException {
+			invoked = true;
+		}
+
+		@Override
+		public void onCapabilities(CapabilitiesV2Request req)
+				throws ServiceMayNotContinueException {
+			throw new UnsupportedOperationException();
+		}
+
+		@Override
+		public void onFetch(FetchV2Request req)
+				throws ServiceMayNotContinueException {
+			throw new UnsupportedOperationException();
+		}
+
+		public boolean wasInvoked() {
+			return invoked;
+		}
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/transport/ProtocolV2HookChain.java

@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2019, Google LLC.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.transport;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * {@link org.eclipse.jgit.transport.ProtocolV2Hook} that delegates to a list of
+ * other hooks.
+ * <p>
+ * Hooks are run in the order passed to the constructor. If running a method on
+ * one hook throws an exception, execution of remaining hook methods is aborted.
+ *
+ * @since 5.5
+ */
+public class ProtocolV2HookChain implements ProtocolV2Hook {
+	private final List<? extends ProtocolV2Hook> hooks;
+
+	/**
+	 * Create a new hook chaining the given hooks together.
+	 *
+	 * @param hooks
+	 *            hooks to execute, in order.
+	 * @return a new hook chain of the given hooks.
+	 */
+	public static ProtocolV2Hook newChain(
+			List<? extends ProtocolV2Hook> hooks) {
+		List<? extends ProtocolV2Hook> newHooks = hooks.stream()
+				.filter(hook -> !hook.equals(ProtocolV2Hook.DEFAULT))
+				.collect(Collectors.toList());
+
+		if (newHooks.isEmpty()) {
+			return ProtocolV2Hook.DEFAULT;
+		} else if (newHooks.size() == 1) {
+			return newHooks.get(0);
+		} else {
+			return new ProtocolV2HookChain(newHooks);
+		}
+	}
+
+	@Override
+	public void onCapabilities(CapabilitiesV2Request req)
+			throws ServiceMayNotContinueException {
+		for (ProtocolV2Hook hook : hooks) {
+			hook.onCapabilities(req);
+		}
+	}
+
+	@Override
+	public void onLsRefs(LsRefsV2Request req)
+			throws ServiceMayNotContinueException {
+		for (ProtocolV2Hook hook : hooks) {
+			hook.onLsRefs(req);
+		}
+	}
+
+	@Override
+	public void onFetch(FetchV2Request req)
+			throws ServiceMayNotContinueException {
+		for (ProtocolV2Hook hook : hooks) {
+			hook.onFetch(req);
+		}
+	}
+
+	private ProtocolV2HookChain(List<? extends ProtocolV2Hook> hooks) {
+		this.hooks = Collections.unmodifiableList(hooks);
+	}
+}