/**
    * 
    */
   package org.treetank.revisioning;
   
   import static com.google.common.base.Objects.toStringHelper;
   import static com.google.common.base.Preconditions.checkArgument;
   
   import org.treetank.bucket.DataBucket;
  import org.treetank.io.LogValue;
  
  /**
   * Sliding Snapshot versioning of {@link DataBucket}s.
   * 
   * @author Sebastian Graf, University of Konstanz
   * 
   */
  public class SlidingSnapshot implements IRevisioning {
  
      /**
       * {@inheritDoc}
       */
      @Override
      public DataBucket combineBuckets(final DataBucket[] pBuckets) {
          checkArgument(pBuckets.length > 0, "At least one DataBucket must be provided");
          // create entire bucket..
          final DataBucket returnVal = new DataBucket(pBuckets[0].getBucketKey(), pBuckets[0].getLastBucketPointer());
          // ...iterate through the datas and check if it is stored..
          for (int i = 0; i < pBuckets[0].getDatas().length; i++) {
              boolean bucketSkip = false;
              // ... form the newest version to the oldest one..
              for (int j = 0; !bucketSkip && j < pBuckets.length; j++) {
                  // if the data is not set yet but existing in the current version..
                  if (pBuckets[j].getData(i) != null) {
                      // ...break out the loop the next time and..
                      bucketSkip = true;
                      // ...set it
                      returnVal.setData(i, pBuckets[j].getData(i));
                  }
  
              }
          }
          return returnVal;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public LogValue combineBucketsForModification(int pRevisionsToRestore, long pNewBucketKey, DataBucket[] pBuckets,
          boolean pFullDump) {
          checkArgument(pBuckets.length > 0, "At least one DataBucket must be provided");
          // create buckets for container..
          final DataBucket[] returnVal =
              {
                  new DataBucket(pBuckets[0].getBucketKey(), pBuckets[0].getLastBucketPointer()),
                  new DataBucket(pNewBucketKey, pBuckets[0].getBucketKey())
              };
          // ...iterate through the datas and check if it is stored..
          for (int i = 0; i < pBuckets[0].getDatas().length; i++) {
              boolean continueVal = true;
              // ... form the newest version to the oldest one..
              for (int j = 0; j < pBuckets.length && continueVal; j++) {
                  // check if the data is not set..
                  if (returnVal[0].getData(i) == null && pBuckets[j].getData(i) != null) {
                      // ...set it to the read-cache and..
                      returnVal[0].setData(i, pBuckets[j].getData(i));
                      // ..if we receive the oldest version where the data was not set yet, then copy it by hand
                      if (pBuckets.length >= pRevisionsToRestore && j == pBuckets.length - 1) {
                          returnVal[1].setData(i, pBuckets[j].getData(i));
                      }
                      // escape this loop since val was set
                      continueVal = false;
                  }
              }
          }
          // return the container
          return new LogValue(returnVal[0], returnVal[1]);
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public String toString() {
          return toStringHelper(this).toString();
      }
  
  }