/* An instance of this class is a tree that represents a compound expression,
** meaning one involving at least one operator.
**
** Authors: R. McCloskey and < STUDENT's NAME >
** Date: Feb. 2022
** Collaborated with: ...
** Known Defects: ...
*/
public class ExprTreeCompound extends ExprTree {

   // instance variables
   // ------------------

   private String operator;  // the represented expression's (binary) operator
   private ExprTree first;   // the represented expression's first operand
   private ExprTree second;  // the represented expression's second operand


   // constructor
   // -----------

   /* Establishes this tree as one that represents an expression that
   ** is composed of the given operator together with its two operands
   ** (which are themselves given in the form of expression trees).
   */
   public ExprTreeCompound(ExprTree first, String op, ExprTree second) {
      super();
      this.first = first;
      this.second = second;
      this.operator = op;
   }


   // observers
   // ---------

   /* Returns the value of the expression represented by this tree, 
   ** which is obtained by applying its operator to the values of its 
   ** two operands.
   */
   public int valueOf() {
      return 0;  // STUB
   }


   /* Returns the expression-string describing the expression represented
   ** by this tree in the form specified by the given parameter, which is
   ** expected to be one of the inherited "print mode" values.  If it is not,
   ** an IllegalArgumentException is thrown.
   */
   @Override
   public String toString(int mode) {
      if (mode == PrefixMode) { return toStringPrefix(); }
      else if (mode == InfixMode) { return toStringInfix(); }
      else if (mode == PostfixMode) { return toStringPostfix(); }
      else {
         String errorMessage = " is not a legal mode";
         throw new IllegalArgumentException(mode + errorMessage);
      }
   }


   // private methods
   // ---------------

   /* Returns the prefix form expression-string corresponding to this tree.
   */
   private String toStringPrefix() {
      return "Gris";   // STUB!
   }

   /* Returns the postfix form expression-string corresponding to this tree.
   */
   private String toStringPostfix() {
      return "Grop";   // STUB!
   }

   /* Returns the (fully-parenthesized) infix form expression-string
   ** corresponding to this tree.
   */
   private String toStringInfix() {
      return "( " + first.toString(InfixMode) + 
             ' ' + operator + ' ' +
             second.toString(InfixMode) + " )";
   }

}