Class Switch

basex-core/src/main/java/org/basex/query/expr/Switch.java:26–313

Switch expression. @author BaseX Team, BSD License @author Christian Gruen

 * @author Christian Gruen
 */
public final class Switch extends ParseExpr {
  /** Condition. */
  private Expr cond;
  /** Case groups. */
  private SwitchGroup[] groups;

  /**
   * Constructor.
   * @param info input info (can be {@code null})
   * @param cond condition
   * @param groups case groups (last one is default case)
   */
  public Switch(final InputInfo info, final Expr cond, final SwitchGroup[] groups) {
    super(info, Types.ITEM_ZM);
    this.cond = cond;
    this.groups = groups;
  }

  @Override
  public void checkUp() throws QueryException {
    checkNoUp(cond);
    for(final SwitchGroup group : groups) group.checkUp();
    // check if none or all return expressions are updating
    final ExprList rtrns = new ExprList(groups.length);
    for(final SwitchGroup group : groups) rtrns.add(group.rtrn());
    checkAllUp(rtrns.finish());
  }

  @Override
  public Expr compile(final CompileContext cc) throws QueryException {
    cond = cond.compile(cc);
    for(final SwitchGroup group : groups) group.compile(cc);
    return optimize(cc);
  }

  @Override
  public Expr optimize(final CompileContext cc) throws QueryException {
    cond = cond.simplifyFor(Simplify.STRING, cc);

    // check if expression can be pre-evaluated
    final Expr expr = opt(cc);
    if(expr != this) return cc.replaceWith(this, expr);

    // combine types of return expressions
    exprType.assign(SeqType.union(groups, true)).data(groups);

    return this;
  }

  @Override
  public Expr simplifyFor(final Simplify mode, final CompileContext cc) throws QueryException {
    boolean changed = false;
    for(final SwitchGroup group : groups) {
      changed |= group.simplifyFor(mode, cc) == null;
    }
    return changed ? optimize(cc) : super.simplifyFor(mode, cc);
  }