package com.atlassian.cache;
   
   import javax.annotation.Nonnull;
   
   import com.atlassian.util.concurrent.Supplier;
   
   import org.hamcrest.BaseMatcher;
   import org.hamcrest.Description;
   
  /**
   * Hamcrest matcher for statistics that recognizes the fact that they are optional.
   *
   * @since v2.4.0
   */
  public class StatisticMatcher extends BaseMatcher<Supplier<Long>>
  {
      public static StatisticMatcher stat(long expectedValue)
      {
          return new StatisticMatcher(expectedValue);
      }
  
      private final long expectedValue;
  
      private StatisticMatcher(long expectedValue)
      {
          this.expectedValue = expectedValue;
      }
  
      @Override
      public boolean matches(Object o)
      {
          return o instanceof Supplier ? matches((Supplier<?>)o) : (o == null);
      }
  
      private boolean matches(@Nonnull Supplier<?> supplier)
      {
          // Note: It is *not* okay for the supplier to return null!
          final Object value = supplier.get();
          return value instanceof Long && ((Long)value) == expectedValue;
      }
  
      @Override
      public void describeTo(Description description)
      {
          description.appendText("either null or a statistic with the value ").appendValue(expectedValue);
      }
  }