package jalview.datamodel;

import java.util.Iterator;
import java.util.List;

/**
 * A local iterator which iterates over hidden column regions in a range.
 * Intended for use ONLY within the HiddenColumns class, because it works
 * directly with the hiddenColumns collection without locking (callers should
 * lock hiddenColumns).
 */
public class RegionsIterator implements Iterator<int[]>
{
  // start position to iterate from
  private int start;

  // end position to iterate to
  private int end;

  // current index in hiddenColumns
  private int currentPosition = 0;

  // current column in hiddenColumns
  private int[] nextRegion = null;

  private int[] currentRegion = null;

  private int removedIndex = -1;

  private final List<int[]> hiddenColumns;

  // Constructor with bounds
  RegionsIterator(int lowerBound, int upperBound, List<int[]> hiddenCols,
          HiddenColumnsCursor cursor)
  {
    start = lowerBound;
    end = upperBound;
    hiddenColumns = hiddenCols;

    if (hiddenColumns != null)
    {
      // TODO remove whole class?
      // commented out to compile
      // currentPosition = cursor.findRegionForColumn(start);

      if (currentPosition < hiddenColumns.size())
      {
        nextRegion = hiddenColumns.get(currentPosition);
      }
    }
  }

  @Override
  public boolean hasNext()
  {
    return (hiddenColumns != null) && (nextRegion != null)
            && (nextRegion[0] <= end);
  }

  @Override
  public int[] next()
  {
    currentRegion = nextRegion;
    currentPosition++;
    if (currentPosition < hiddenColumns.size())
    {
      nextRegion = hiddenColumns.get(currentPosition);
    }
    else
    {
      nextRegion = null;
    }
    return currentRegion;
  }

  @Override
  public void remove()
  {
    if ((currentRegion != null) && (removedIndex != currentPosition))
    {
      currentPosition--;
      hiddenColumns.subList(currentPosition, currentPosition + 1).clear();
      removedIndex = currentPosition;
    }
    else
    {
      // already removed element last returned by next()
      // or next() has not yet been called
      throw new IllegalStateException();
    }
  }

}