package dods.dap.Server;

import java.util.*;
import java.io.*;
import dods.dap.BaseType;

/** Represents a clause containing a simple value. If the value is
 *  an constant value such as "2.0", the clause's isConstant() method
 *  will return true; if it is a variable of the dataset, isConstant() will
 *  return false. 
 * @see ClauseFactory
 *  @author Joe Wielgosz (joew@cola.iges.org) */
public class ValueClause 
    extends AbstractClause
    implements SubClause {
    
    /** Creates a new ValueClause.
     * @param value The BaseType represented by this clause. This can 
     * be either a BaseType taken from the DDS of a dataset, or a BaseType
     * object created to hold a constant value.
     * @param constant Should be set to false if the value parameter is
     * from the DDS of a dataset, and true if the value parameter is a
     * constant value.
     */
    protected ValueClause(BaseType value, 
			  boolean constant) {
	this.value = value;
	this.constant = constant;
	this.defined = constant;
	this.children = new ArrayList();
    }

    /** Returns the BaseType represented by this clause. */
    public BaseType getValue() {
	return value;
    }

    /** Returns the BaseType represented by this clause. Equivalent to 
     *  getValue(), except that
     *  calling this method flags this clause as "defined". 
     * @exception SDODSException Not thrown by this type of clause. */
    public BaseType evaluate() {
	defined = true;
	return value;
    }

    public Clause getParent() {
	return parent;
    }

    public void setParent(Clause parent) {
	this.parent = parent;
    }

    /** Prints the original string representation of this clause.
     *  For use in debugging.
     */
    public String toString() {
	if (constant) {
	    StringWriter w = new StringWriter();
	    value.printVal(new PrintWriter(w), "",false);
	    return w.toString();
	} else {
	    return value.getName();
	}
    }

    protected BaseType value;
    protected Clause parent;

}