package jalview.datamodel;

/**
 * An immutable object representing one or more residue and corresponding
 * alignment column positions for a sequence
 */
public class SequenceCursor
{
  /**
   * the aligned sequence this cursor applies to
   */
  public final SequenceI sequence;

  /**
   * residue position in sequence (start...), 0 if undefined
   */
  public final int residuePosition;

  /**
   * column position (1...) corresponding to residuePosition, or 0 if undefined
   */
  public final int columnPosition;

  /**
   * a token which may be used to check whether this cursor is still valid for
   * its sequence (allowing it to be ignored if the sequence has changed)
   */
  public final int token;

  /**
   * Constructor
   * 
   * @param seq
   *          sequence this cursor applies to
   * @param resPos
   *          residue position in sequence (start..)
   * @param column
   *          column position in alignment (1..)
   * @param tok
   *          a token that may be validated by the sequence to check the cursor
   *          is not stale
   */
  public SequenceCursor(SequenceI seq, int resPos, int column, int tok)
  {
    sequence = seq;
    residuePosition = resPos;
    columnPosition = column;
    token = tok;
  }

  @Override
  public int hashCode()
  {
    int hash = 31 * residuePosition;
    hash = 31 * hash + columnPosition;
    hash = 31 * hash + token;
    if (sequence != null)
    {
      hash += sequence.hashCode();
    }
    return hash;
  }

  /**
   * Two cursors are equal if they refer to the same sequence object and have
   * the same residue position, column position and token value
   */
  @Override
  public boolean equals(Object obj)
  {
    if (!(obj instanceof SequenceCursor))
    {
      return false;
    }
    SequenceCursor sc = (SequenceCursor) obj;
    return sequence == sc.sequence && residuePosition == sc.residuePosition
            && columnPosition == sc.columnPosition && token == sc.token;
  }

  @Override
  public String toString()
  {
    return (sequence == null ? "" : sequence.getName()) + ":Pos"
            + residuePosition + ":Col" + columnPosition + ":tok" + token;
  }
}