/*
 * 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.commons.scxml2;

import java.util.Map;

/**
 * A Context or &quot;scope&quot; for storing variables; usually tied to
 * a SCXML root or State object.
 */
public interface Context {

    /**
     * Current namespaces are saved under this key in the context.
     */
    String NAMESPACES_KEY = "_ALL_NAMESPACES";

    /**
     * Assigns a new value to an existing variable or creates a new one.
     * The method searches the chain of parent Contexts for variable
     * existence.
     *
     * @param name The variable name
     * @param value The variable value
     */
    void set(String name, Object value);

    /**
     * Assigns a new value to an existing variable or creates a new one.
     * The method allows to shaddow a variable of the same name up the
     * Context chain.
     *
     * @param name The variable name
     * @param value The variable value
     */
    void setLocal(String name, Object value);

    /**
     * Get the value of this variable; delegating to parent.
     *
     * @param name The name of the variable
     * @return The value (or null)
     */
    Object get(String name);

    /**
     * Check if this variable exists, delegating to parent.
     *
     * @param name The name of the variable
     * @return Whether a variable with the name exists in this Context
     */
    boolean has(String name);

    /**
     * Check if this variable exists, only checking this Context
     *
     * @param name The name of the variable
     * @return Whether a variable with the name exists in this Context
     */
    boolean hasLocal(String name);

    /**
     * Get the Map of all variables in this Context.
     *
     * @return Local variable entries Map
     * To get variables in parent Context, call getParent().getVars().
     * @see #getParent()
     */
    Map<String, Object> getVars();

    /**
     * Clear this Context.
     */
    void reset();

    /**
     * Get the parent Context, may be null.
     *
     * @return The parent Context in a chained Context environment
     */
    Context getParent();

    /**
     * Get the SCXMLSystemContext for this Context, should not be null unless this is the root Context
     *
     * @return The SCXMLSystemContext in a chained Context environment
     */
    SCXMLSystemContext getSystemContext();

}