[sync] Upstream the Android ProfileSyncService

chrome/android/java/src/org/chromium/chrome/browser/identity/UniqueIdentificationGeneratorFactory.java

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.identity;
+
+import com.google.common.annotations.VisibleForTesting;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Factory for setting and retrieving instances of {@link UniqueIdentificationGenerator}s.
+ * <p/>
+ * A generator must always be set for a generator type before it is asked for. A generator type
+ * is any string you want to use for your generator. It is typically defined as a public static
+ * field in the generator itself.
+ */
+public final class UniqueIdentificationGeneratorFactory {
+    private static final Object LOCK = new Object();
+    private static final Map<String, UniqueIdentificationGenerator> GENERATOR_MAP =
+            new HashMap<String, UniqueIdentificationGenerator>();
+
+    private UniqueIdentificationGeneratorFactory() {
+    }
+
+    /**
+     * Returns a UniqueIdentificationGenerator if it exists, else throws IllegalArgumentException.
+     *
+     * @param generatorType the generator type you want
+     * @return a unique ID generator
+     */
+    public static UniqueIdentificationGenerator getInstance(String generatorType) {
+        synchronized (LOCK) {
+            if (!GENERATOR_MAP.containsKey(generatorType)) {
+                throw new IllegalArgumentException("Unknown generator type " + generatorType);
+            }
+            return GENERATOR_MAP.get(generatorType);
+        }
+    }
+
+    /**
+     * During startup of the application, and before any calls to
+     * {@link #getInstance(String)} you must add all supported generators
+     * to this factory.
+     *
+     * @param generatorType the type of generator this is. Must be a unique string.
+     * @param gen           the generator.
+     * @param force         if set to true, will override any existing generator for this type. Else
+     *                      discards calls where a generator exists.
+     */
+    @VisibleForTesting
+    public static void registerGenerator(String generatorType, UniqueIdentificationGenerator gen,
+                                         boolean force) {
+        synchronized (LOCK) {
+            if (GENERATOR_MAP.containsKey(generatorType) && !force) {
+                return;
+            }
+            GENERATOR_MAP.put(generatorType, gen);
+        }
+    }
+
+    @VisibleForTesting
+    public static void clearGeneratorMapForTest() {
+        synchronized (LOCK) {
+            GENERATOR_MAP.clear();
+        }
+    }
+}