1 files changed, 66 insertions, 0 deletions
diff --git a/gerrit-index/src/main/java/com/google/gerrit/index/SchemaDefinitions.java b/gerrit-index/src/main/java/com/google/gerrit/index/SchemaDefinitions.java
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+++ b/gerrit-index/src/main/java/com/google/gerrit/index/SchemaDefinitions.java
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+// Copyright (C) 2016 The Android Open Source Project
+//
+// 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 com.google.gerrit.index;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.collect.ImmutableSortedMap;
+import com.google.common.collect.Iterables;
+import com.google.gerrit.common.Nullable;
+
+/**
+ * Definitions of the various schema versions over a given Gerrit data type.
+ *
+ * <p>A <em>schema</em> is a description of the fields that are indexed over the given data type.
+ * This class contains all the versions of a schema defined over its data type, exposed as a map of
+ * version number to schema definition. If you are interested in the classes responsible for
+ * backend-specific runtime implementations, see the implementations of {@link IndexDefinition}.
+ */
+public abstract class SchemaDefinitions<V> {
+  private final String name;
+  private final ImmutableSortedMap<Integer, Schema<V>> schemas;
+
+  protected SchemaDefinitions(String name, Class<V> valueClass) {
+    this.name = checkNotNull(name);
+    this.schemas = SchemaUtil.schemasFromClass(getClass(), valueClass);
+  }
+
+  public final String getName() {
+    return name;
+  }
+
+  public final ImmutableSortedMap<Integer, Schema<V>> getSchemas() {
+    return schemas;
+  }
+
+  public final Schema<V> get(int version) {
+    Schema<V> schema = schemas.get(version);
+    checkArgument(schema != null, "Unrecognized %s schema version: %s", name, version);
+    return schema;
+  }
+
+  public final Schema<V> getLatest() {
+    return schemas.lastEntry().getValue();
+  }
+
+  @Nullable
+  public final Schema<V> getPrevious() {
+    if (schemas.size() <= 1) {
+      return null;
+    }
+    return Iterables.get(schemas.descendingMap().values(), 1);
+  }
+}