Centralize token generation and formats

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=135313726

javatests/google/registry/testing/DeterministicStringGenerator.java

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+// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
+//
+// 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 google.registry.testing;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.Lists.charactersOf;
+
+import com.google.common.collect.Iterators;
+import google.registry.util.RandomStringGenerator;
+import google.registry.util.StringGenerator;
+import java.util.Iterator;
+import javax.inject.Named;
+
+/**
+ * A string generator that produces strings using sequential characters in its alphabet. This is
+ * most useful in tests as a "fake" password generator (which would otherwise use
+ * {@link RandomStringGenerator}.
+ * 
+ * <p>Note that consecutive calls to createString will continue where the last call left off in
+ * the alphabet.
+ */
+public class DeterministicStringGenerator extends StringGenerator {
+
+  private Iterator<Character> iterator;
+  private final Rule rule;
+  private int counter = 0;
+
+  /** String generation rules. */
+  public enum Rule {
+
+    /**
+     * Simple string generation, cycling through sequential letters in the alphabet. May produce
+     * duplicates.
+     */
+    DEFAULT,
+
+    /**
+     * Same cyclical pattern as {@link Rule#DEFAULT}, prepending the iteration number and an
+     * underscore. Intended to avoid duplicates.
+     */
+    PREPEND_COUNTER
+  }
+
+  /**
+   * Generates a string using sequential characters in the generator's alphabet, cycling back to the
+   * beginning of the alphabet if necessary.
+   */
+  @Override
+  public String createString(int length) {
+    checkArgument(length > 0, "String length must be positive.");
+    String password = "";
+    for (int i = 0; i < length; i++) {
+      password += iterator.next();
+    }
+    switch (rule) {
+      case PREPEND_COUNTER:
+        return String.format("%04d_%s", counter++, password);
+      case DEFAULT:
+      default:
+        return password;
+    }
+  }
+
+  public DeterministicStringGenerator(@Named("alphabet") String alphabet, Rule rule) {
+    super(alphabet);
+    iterator = Iterators.cycle(charactersOf(alphabet));
+    this.rule = rule;
+  }
+
+  public DeterministicStringGenerator(@Named("alphabet") String alphabet) {
+    this(alphabet, Rule.DEFAULT);
+  }
+}