package jalview.datamodel;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * Iterator over the visible *columns* (not regions) as determined by the set of
 * hidden columns. Uses a local copy of hidden columns.
 * 
 * @author kmourao
 *
 */
public class VisibleColsIterator implements Iterator<Integer>
{
  private int last;

  private int current;

  private int next;

  private List<int[]> localHidden = new ArrayList<>();

  private int nexthiddenregion;

  VisibleColsIterator(int firstcol, int lastcol, List<int[]> hiddenColumns)
  {
    last = lastcol;
    current = firstcol;
    next = firstcol;
    nexthiddenregion = 0;

    if (hiddenColumns != null)
    {
      int i = 0;
      for (i = 0; i < hiddenColumns.size()
              && (current <= hiddenColumns.get(i)[0]); ++i)
      {
        if (current >= hiddenColumns.get(i)[0]
                && current <= hiddenColumns.get(i)[1])
        {
          // current is hidden, move to right
          current = hiddenColumns.get(i)[1] + 1;
          next = current;
          nexthiddenregion = i + 1;
        }
      }

      for (i = hiddenColumns.size() - 1; i >= 0
              && (last >= hiddenColumns.get(i)[1]); --i)
      {
        if (last >= hiddenColumns.get(i)[0]
                && last <= hiddenColumns.get(i)[1])
        {
          // last is hidden, move to left
          last = hiddenColumns.get(i)[0] - 1;
        }
      }

      // make a local copy of the bit we need
      i = nexthiddenregion;
      while (i < hiddenColumns.size() && hiddenColumns.get(i)[0] <= last)
      {
        int[] region = new int[] { hiddenColumns.get(i)[0],
            hiddenColumns.get(i)[1] };
        localHidden.add(region);
        i++;
      }
    }
  }

  @Override
  public boolean hasNext()
  {
    return next <= last;
  }

  @Override
  public Integer next()
  {
    if (next > last)
    {
      throw new NoSuchElementException();
    }
    current = next;
    if ((localHidden != null) && (nexthiddenregion < localHidden.size()))
    {
      // still some more hidden regions
      if (next + 1 < localHidden.get(nexthiddenregion)[0])
      {
        // next+1 is still before the next hidden region
        next++;
      }
      else if ((next + 1 >= localHidden.get(nexthiddenregion)[0])
              && (next + 1 <= localHidden.get(nexthiddenregion)[1]))
      {
        // next + 1 is in the next hidden region
        next = localHidden.get(nexthiddenregion)[1] + 1;
        nexthiddenregion++;
      }
    }
    else
    {
      // finished with hidden regions, just increment normally
      next++;
    }
    return current;
  }

  @Override
  public void remove()
  {
    throw new UnsupportedOperationException();
  }
}