src/main/java/org/apache/commons/scxml2/Evaluator.java

/*
 * 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
 *
 *     https://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.commons.scxml2;

/**
 * Interface for a component that may be used by the SCXML engines to
 * evaluate the expressions within the SCXML document.
 */
public interface Evaluator {

    /** SCXML 1.0 Null Data Model name **/
    String NULL_DATA_MODEL = "null";

    /** SCXML 1.0 ECMAScript Data Model name **/
    String ECMASCRIPT_DATA_MODEL = "ecmascript";

    /** Default Data Model name **/
    String DEFAULT_DATA_MODEL = "";

    /**
     * @param data data to be cloned
     * @return A deep clone of the data
     */
    Object cloneData(Object data);

    /**
     * Evaluate an expression returning a data value
     *
     * @param ctx variable context
     * @param expr expression
     * @return the result of the evaluation
     * @throws SCXMLExpressionException A malformed expression exception
     */
    Object eval(Context ctx, String expr)
    throws SCXMLExpressionException;

    /**
     * Assigns data to a location
     *
     * @param ctx variable context
     * @param location location expression
     * @param data the data to assign.
     * @throws SCXMLExpressionException A malformed expression exception
     */
    void evalAssign(Context ctx, String location, Object data)
            throws SCXMLExpressionException;

    /**
     * Evaluate a condition.
     * Manifests as "cond" attributes of <transition>,
     * <if> and <elseif> elements.
     *
     * @param ctx variable context
     * @param expr expression
     * @return true/false
     * @throws SCXMLExpressionException A malformed expression exception
     */
    Boolean evalCond(Context ctx, String expr)
    throws SCXMLExpressionException;

    /**
     * Evaluate a script.
     * Manifests as <script> element.
     *
     * @param ctx variable context
     * @param script The script
     * @return The result of the script execution.
     * @throws SCXMLExpressionException A malformed script
     */
    Object evalScript(Context ctx, String script)
    throws SCXMLExpressionException;

    /**
     * Gets the datamodel type supported by this Evaluator
     *
     * @return The supported datamodel type
     */
    String getSupportedDatamodel();

    /**
     * Create a new child context.
     *
     * @param parent parent context
     * @return new child context
     */
    Context newContext(Context parent);

    /**
     * If this Evaluator only supports a global context.
     *
     * @return true if this Evaluator only support a global context
     */
    boolean requiresGlobalContext();

}