content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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.apache.calcite.util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.slf4j.helpers.MessageFormatter;
  
  /**
   * Callback to be called when a test for validity succeeds or fails.
   */
  public interface Litmus {
    /** Implementation of {@link org.apache.calcite.util.Litmus} that throws
     * an {@link java.lang.AssertionError} on failure. */
    Litmus THROW = (message, args) -> {
      final String s = message == null
          ? null : MessageFormatter.arrayFormat(message, args).getMessage();
      throw new AssertionError(s);
    };
  
    /** Implementation of {@link org.apache.calcite.util.Litmus} that returns
     * a status code but does not throw. */
    Litmus IGNORE = new Litmus() {
      @Override public boolean fail(@Nullable String message, @Nullable Object... args) {
        return false;
      }
  
      @Override public boolean check(boolean condition, @Nullable String message,
          @Nullable Object... args) {
        return condition;
      }
  
      @Override public Litmus withMessageArgs(@Nullable String message,
          @Nullable Object... args) {
        // IGNORE never throws, so don't bother remembering message and args.
        return this;
      }
    };
  
    /** Called when test fails. Returns false or throws.
     *
     * @param message Message
     * @param args Arguments
     */
    boolean fail(@Nullable String message, @Nullable Object... args);
  
    /** Called when test succeeds. Returns true. */
    default boolean succeed() {
      return true;
    }
  
    /** Checks a condition.
     *
     * <p>If the condition is true, calls {@link #succeed};
     * if the condition is false, calls {@link #fail},
     * converting {@code info} into a string message.
     */
    default boolean check(boolean condition, @Nullable String message,
        @Nullable Object... args) {
      if (condition) {
        return succeed();
      } else {
        return fail(message, args);
      }
    }
  
    /** Creates a Litmus that, if it fails, will use the given arguments. */
    default Litmus withMessageArgs(@Nullable String message,
        @Nullable Object... args) {
      final Litmus delegate = this;
      return (message1, args1) -> delegate.fail(message, args);
    }
  }
  