/*
 * Copyright (c) 2002-2012 Alibaba Group Holding Limited.
 * All rights reserved.
 *
 * 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 com.alibaba.citrus.expr.composite;

import java.util.List;

import com.alibaba.citrus.expr.Expression;
import com.alibaba.citrus.expr.ExpressionContext;
import com.alibaba.citrus.expr.support.ExpressionSupport;

/**
 * 代表一个组合的表达式。
 *
 * @author Michael Zhou
 */
public class CompositeExpression extends ExpressionSupport {
    private String       expr;
    private Expression[] expressions;

    /**
     * 创建一个组合的表达式。
     *
     * @param expr        表达式字符串
     * @param expressions 表达式列表
     */
    public CompositeExpression(String expr, List<Expression> expressions) {
        this.expr = expr;
        this.expressions = expressions.toArray(new Expression[expressions.size()]);
    }

    /**
     * 取得表达式字符串表示。
     *
     * @return 表达式字符串表示
     */
    public String getExpressionText() {
        return expr;
    }

    /**
     * 在指定的上下文中计算表达式。
     *
     * @param context <code>ExpressionContext</code>上下文
     * @return 表达式的计算结果
     */
    public Object evaluate(ExpressionContext context) {
        StringBuffer buffer = new StringBuffer();

        for (Expression expression : expressions) {
            Object value = expression.evaluate(context);

            if (value != null) {
                buffer.append(value);
            }
        }

        return buffer.toString();
    }
}