/*
 * Copyright (c) 2006 The Visigoth Software Society. All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Visigoth Software Society (http://www.visigoths.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the 
 *    project contributors may be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact visigoths@visigoths.org.
 *
 * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
 *    nor may "FreeMarker" or "Visigoth" appear in their names
 *    without prior written permission of the Visigoth Software Society.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Visigoth Software Society. For more
 * information on the Visigoth Software Society, please see
 * http://www.visigoths.org/
 */

package freemarker.core;


import freemarker.template.*;

class DefaultToExpression extends Expression {
	
    private static final TemplateCollectionModel EMPTY_COLLECTION = new SimpleCollection(new java.util.ArrayList(0));
    
	static private class EmptyStringAndSequence 
	  implements TemplateScalarModel, TemplateSequenceModel, TemplateHashModelEx {
		public String getAsString() {
			return "";
		}
		public TemplateModel get(int i) {
			return null;
		}
		public TemplateModel get(String s) {
			return null;
		}
		public int size() {
			return 0;
		}
		public boolean isEmpty() {
			return true;
		}
		public TemplateCollectionModel keys() {
			return EMPTY_COLLECTION;
		}
		public TemplateCollectionModel values() {
			return EMPTY_COLLECTION;
		}
		
	}
	
	static final TemplateModel EMPTY_STRING_AND_SEQUENCE = new EmptyStringAndSequence();
	
	private Expression lhs, rhs;
	
	DefaultToExpression(Expression lhs, Expression rhs) {
		this.lhs = lhs;
		this.rhs = rhs;
	}

	TemplateModel _getAsTemplateModel(Environment env) throws TemplateException {
		TemplateModel left = null;		
		try {
			left = lhs.getAsTemplateModel(env);
		} catch (InvalidReferenceException ire) {
			if (!(lhs instanceof ParentheticalExpression)) {
				throw ire;
			}
		}
		if (left != null) return left;
		if (rhs == null) return EMPTY_STRING_AND_SEQUENCE;
		return rhs.getAsTemplateModel(env);
	}

	boolean isLiteral() {
		return false;
	}

	Expression _deepClone(String name, Expression subst) {
		if (rhs == null) {
			return new DefaultToExpression(lhs.deepClone(name, subst), null);
		}
		return new DefaultToExpression(lhs.deepClone(name, subst), rhs.deepClone(name, subst));
	}

	public String getCanonicalForm() {
		if (rhs == null) {
			return lhs.getCanonicalForm() + "!";
		}
		return lhs.getCanonicalForm() + "!" + rhs.getCanonicalForm();
	}
}
