/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.openjpa.kernel.exps;

import org.apache.openjpa.kernel.StoreContext;

/**
 * Trims leading, trailing, or both charactes from a String.
 *
 * @author Marc Prud'hommeaux
 */
class Trim
    extends Val {

    private final Val _val;
    private final Val _trimChar;
    private final Boolean _where;

    /**
     * Constructor. Provide value to upper-case.
     */
    public Trim(Val val, Val trimChar, Boolean where) {
        _val = val;
        _trimChar = trimChar;
        _where = where;
    }

    public Class getType() {
        return String.class;
    }

    public void setImplicitType(Class type) {
    }

    protected Object eval(Object candidate, Object orig,
        StoreContext ctx, Object[] params) {
        Object eval = _val.eval(candidate, orig, ctx, params);
        if (eval == null)
            return null;

        String toTrim = _trimChar.eval(candidate, orig, ctx, params).
            toString();
        String str = eval.toString();

        // null indicates both, TRUE indicates leading
        if (_where == null || Boolean.TRUE.equals(_where)) {
            while (str.startsWith(toTrim))
                str = str.substring(toTrim.length());
        }

        // null indicates both, FALSE indicates trailing
        if (_where == null || Boolean.FALSE.equals(_where)) {
            while (str.endsWith(toTrim))
                str = str.substring(0, str.length() - toTrim.length());
        }
        return str;
    }

    public void acceptVisit(ExpressionVisitor visitor) {
        visitor.enter(this);
        _val.acceptVisit(visitor);
        _trimChar.acceptVisit(visitor);
        visitor.exit(this);
    }
}