/*
 * Copyright 2009 Fedora Commons
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.mulgara.sparql.parser.cst;

import java.util.LinkedList;
import java.util.List;


/**
 * Represents the assignment of a variable.
 *
 * @created July 2, 2009
 * @author Paula Gearon
 * @copyright © 2008 <a href="http://www.fedora-commons.org/">Fedora Commons</a>
 * @licence <a href="{@docRoot}/../LICENCE.txt">Apache License, Version 2.0</a>
 */
public class VarAssign extends BasicGraphPattern {

  /** The main pattern */
  GroupGraphPattern main;

  /** The variable to be assigned */
  Variable var;

  /** The expression to assign to the variable */
  Expression expr;

  /**
   * Build an optional join out of two GroupGraphPatterns.
   * @param main The main pattern to be matched
   * @param optional The pattern to be optionally matched
   */
  public VarAssign(GroupGraphPattern main, Variable var, Expression expr) {
    this.main = main;
    this.var = var;
    this.expr = expr;
  }

  /**
   * @return the main pattern
   */
  public GroupGraphPattern getMain() {
    return main;
  }

  /**
   * @return the variable
   */
  public Variable getVar() {
    return var;
  }

  /**
   * @return the expression
   */
  public Expression getExpression() {
    return expr;
  }

  /**
   * @see org.mulgara.sparql.parser.cst.BasicGraphPattern#getElements()
   */
  @Override
  public List<GroupGraphPattern> getElements() {
    List<GroupGraphPattern> result = new LinkedList<GroupGraphPattern>();
    result.add(main);
    return result;
  }

  /**
   * @see org.mulgara.sparql.parser.cst.BasicGraphPattern#getImage()
   */
  @Override
  public String getImage() {
    return addPatterns(main.getImage() + " LET ( " + var.getImage() + " := " + expr.getImage() + " )");
  }

}