package jalview.datamodel;

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

/**
 * An iterator which iterates over hidden column regions in a range. Works with
 * a copy of the hidden columns collection. Intended to be used by callers
 * OUTSIDE of HiddenColumns.
 */
public class HiddenColsIterator implements Iterator<int[]>
{
  // current index in hiddenColumns
  private int currentPosition = 0;

  // current column in hiddenColumns
  private int[] currentRegion;

  // local copy or reference to hiddenColumns
  private List<int[]> localHidden;

  /**
   * Unbounded constructor
   */
  HiddenColsIterator(List<int[]> hiddenColumns)
  {
    if (!hiddenColumns.isEmpty())
    {
      int last = hiddenColumns.get(hiddenColumns.size() - 1)[1];
      init(0, last, hiddenColumns);
    }
    else
    {
      init(0, 0, hiddenColumns);
    }
  }

  /**
   * Construct an iterator over hiddenColums bounded at [lowerBound,upperBound]
   * 
   * @param lowerBound
   *          lower bound to iterate from
   * @param upperBound
   *          upper bound to iterate to
   */
  HiddenColsIterator(int lowerBound, int upperBound,
          List<int[]> hiddenColumns)
  {
    init(lowerBound, upperBound, hiddenColumns);
  }

  /**
   * Construct an iterator over hiddenColums bounded at [lowerBound,upperBound]
   * 
   * @param lowerBound
   *          lower bound to iterate from
   * @param upperBound
   *          upper bound to iterate to
   */
  private void init(int lowerBound, int upperBound,
          List<int[]> hiddenColumns)
  {
    int start = lowerBound;
    int end = upperBound;

    if (hiddenColumns != null)
    {
      localHidden = new ArrayList<>();

      // iterate until a region overlaps with [start,end]
      int i = 0;
      while ((i < hiddenColumns.size())
              && (hiddenColumns.get(i)[1] < start))
      {
        i++;
      }

      // iterate from start to end, adding each hidden region. Positions are
      // absolute, and all regions which *overlap* [start,end] are added.
      while (i < hiddenColumns.size() && (hiddenColumns.get(i)[0] <= end))
      {
        int[] rh = hiddenColumns.get(i);
        int[] cp = new int[2];
        System.arraycopy(rh, 0, cp, 0, rh.length);
        localHidden.add(cp);
        i++;
      }
    }
  }

  @Override
  public boolean hasNext()
  {
    return (localHidden != null) && (currentPosition < localHidden.size());
  }

  @Override
  public int[] next()
  {
    currentRegion = localHidden.get(currentPosition);
    currentPosition++;
    return currentRegion;
  }
}