001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase;
019
020import java.util.function.Supplier;
021import org.apache.yetus.audience.InterfaceAudience;
022import org.hamcrest.Description;
023import org.hamcrest.Matcher;
024import org.hamcrest.StringDescription;
025
026/**
027 * An implementation of {@link Waiter.ExplainingPredicate} that uses Hamcrest {@link Matcher} for
028 * both predicate evaluation and explanation.
029 * @param <T> The type of value to be evaluated via {@link Matcher}.
030 */
031@InterfaceAudience.Private
032public class MatcherPredicate<T> implements Waiter.ExplainingPredicate<RuntimeException> {
033
034  private final String reason;
035  private final Supplier<T> supplier;
036  private final Matcher<? super T> matcher;
037  private T currentValue;
038
039  public MatcherPredicate(final Supplier<T> supplier, final Matcher<? super T> matcher) {
040    this("", supplier, matcher);
041  }
042
043  public MatcherPredicate(final String reason, final Supplier<T> supplier,
044    final Matcher<? super T> matcher) {
045    this.reason = reason;
046    this.supplier = supplier;
047    this.matcher = matcher;
048    this.currentValue = null;
049  }
050
051  @Override
052  public boolean evaluate() {
053    currentValue = supplier.get();
054    return matcher.matches(currentValue);
055  }
056
057  @Override
058  public String explainFailure() {
059    final Description description = new StringDescription().appendText(reason)
060      .appendText("\nExpected: ").appendDescriptionOf(matcher).appendText("\n     but: ");
061    matcher.describeMismatch(currentValue, description);
062    return description.toString();
063  }
064}