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/*
 * Copyright 2003-2012 the original author or authors.
 *
 * 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.codehaus.groovy.jsr223;

import groovy.lang.Binding;

import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
import java.io.Reader;
import java.util.Map;
import java.util.Set;

/**
 * This class defines new Java 6 specific groovy methods which extend the normal
 * JDK classes inside the Groovy environment. Static methods are used with the
 * first parameter the destination class.
 */
public class ScriptExtensions {
    /**
     * Executes the specified script.  The default ScriptContext for the ScriptEngine
     * is used. Variables from a Groovy Binding are made available in the default scope of the
     * Bindings of the ScriptEngine. Resulting variables in the Bindings
     * are returned back to the Groovy Binding.
     *
     * @param self A ScriptEngine
     * @param script The script language source to be executed
     * @param binding A Groovy binding
     * @return The value returned from the execution of the script (if supported by the Script engine)
     * @throws javax.script.ScriptException if error occurs in script
     * @throws NullPointerException if the argument is null
     * @see #eval(javax.script.ScriptEngine, java.io.Reader, groovy.lang.Binding)
     * @since 1.7.3
     */
    public static Object eval(ScriptEngine self, String script, Binding binding) throws ScriptException {
        storeBindingVars(self, binding);
        Object result = self.eval(script);
        retrieveBindingVars(self, binding);
        return result;
    }

    /**
     * Same as eval(ScriptEngine, Reader, Binding) except that the
     * source of the script is provided as a Reader
     *
     * @param self A ScriptEngine
     * @param reader The source of the script
     * @param binding A Groovy binding
     * @return The value returned by the script
     * @throws javax.script.ScriptException if an error occurs in script
     * @throws NullPointerException if the argument is null
     * @see #eval(javax.script.ScriptEngine, java.lang.String, groovy.lang.Binding)
     * @since 1.7.3
     */
    public static Object eval(ScriptEngine self, Reader reader, Binding binding) throws ScriptException {
        storeBindingVars(self, binding);
        Object result = self.eval(reader);
        retrieveBindingVars(self, binding);
        return result;
    }

    private static void retrieveBindingVars(ScriptEngine self, Binding binding) {
        Set> returnVars = self.getBindings(ScriptContext.ENGINE_SCOPE).entrySet();
        for (Map.Entry me : returnVars) {
            binding.setVariable(me.getKey(), me.getValue());
        }
    }

    @SuppressWarnings("unchecked")
    private static void storeBindingVars(ScriptEngine self, Binding binding) {
        Set vars = binding.getVariables().entrySet();
        for (Map.Entry me : vars) {
            self.put(me.getKey().toString(), me.getValue());
        }
    }

}