/*
    * Copyright 2018 SPF4J.
    *
    * 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 org.spf4j.base;
  
  import com.google.common.annotations.Beta;
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import gnu.trove.iterator.TLongIterator;
  import gnu.trove.list.array.TLongArrayList;
  import java.util.function.LongSupplier;
  import javax.annotation.Nonnull;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * @author Zoltan Farkas
   */
  @Beta
  public final class TestTimeSource implements LongSupplier {
  
    private static final Logger LOG = LoggerFactory.getLogger(TestTimeSource.class);
  
    public static final TLongIterator SYSTEM_NANO_TIME_STREAM = new TLongIterator() {
      @Override
      public long next() {
        return System.nanoTime();
      }
  
      @Override
      public boolean hasNext() {
        return true;
      }
  
      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }
    };
  
    private static volatile TLongIterator timeStream = SYSTEM_NANO_TIME_STREAM;
  
    public static void clear() {
      timeStream = SYSTEM_NANO_TIME_STREAM;
    }
  
    public static void setTimeStream(final TLongIterator stream) {
      timeStream = stream;
    }
  
    public static void setTimeStream(final long... times) {
      timeStream = new TLongArrayList(times).iterator();
    }
  
    public static long freezeTime() {
      long nanoTime = TimeSource.nanoTime();
      setTimeStream(new TLongIterator() {
        @Override
        public long next() {
          return nanoTime;
        }
  
        @Override
        public boolean hasNext() {
          return true;
        }
  
        @Override
        public void remove() {
          throw new UnsupportedOperationException();
        }
      });
      return nanoTime;
    }
  
  
    @Override
    @Nonnull
    @SuppressFBWarnings("CLI_CONSTANT_LIST_INDEX")
    public long getAsLong() {
      long nextTime;
      if (timeStream.hasNext()) {
        nextTime = timeStream.next();
      } else {
        StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
        throw new AssertionError("End of time reached at "
                + (stackTrace.length > 2 ? stackTrace[2] : "unknown"));
      }
     if (LOG.isTraceEnabled()) {
       StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
       LOG.trace("nanoTime = {} at {}", nextTime, stackTrace.length > 2 ? stackTrace[2] : "unknown");
     }
     return nextTime;
   }
 
 }