TypeSafeWrappingMatcher.java

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 * Copyright (C) 2020 wcm.io
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 *
 *      http://www.apache.org/licenses/LICENSE-2.0
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package io.wcm.qa.glnm.hamcrest;

import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;

import com.google.common.base.Optional;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;


/**
 * <p>Abstract TypeSafeWrappingMatcher class.</p>
 *
 * @since 5.0.0
 */
public abstract class TypeSafeWrappingMatcher<T, M> extends TypeSafeMatcher<T> {

  private Matcher<M> internalMatcher;
  private final CacheLoader<T, Optional<M>> loader = new CacheLoader<T, Optional<M>>() {
    @Override
    public Optional<M> load(T key) throws Exception {
      return Optional.fromNullable(map(key));
    };
  };
  private final LoadingCache<T, Optional<M>> mappedItems = CacheBuilder.newBuilder().build(loader);

  protected TypeSafeWrappingMatcher(Matcher<M> matcher) {
    setInternalMatcher(matcher);
  }

  /** {@inheritDoc} */
  @Override
  public void describeTo(Description description) {
    getInternalMatcher().describeTo(description);
  }

  private M mapped(T item) {
    Optional<M> optional = mappedItems.getIfPresent(item);
    if (optional != null && optional.isPresent()) {
      return optional.get();
    }
    return null;
  }

  @Override
  protected void describeMismatchSafely(T item, Description mismatchDescription) {
    getInternalMatcher().describeMismatch(mapped(item), mismatchDescription);
  }

  protected Matcher<M> getInternalMatcher() {
    return internalMatcher;
  }

  protected abstract M map(T item);

  @Override
  protected boolean matchesSafely(T item) {
    mappedItems.refresh(item);
    return getInternalMatcher().matches(mapped(item));
  }

  protected void setInternalMatcher(Matcher<M> internalMatcher) {
    this.internalMatcher = internalMatcher;
  }

}