/*
 * 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.tuscany.container.javascript.rhino;

import java.io.ByteArrayInputStream;

import javax.xml.stream.XMLStreamReader;

import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.impl.builder.StAXOMBuilder;
import org.apache.axiom.om.util.StAXUtils;
import org.apache.xmlbeans.XmlObject;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.ScriptableObject;
import org.mozilla.javascript.Wrapper;
import org.mozilla.javascript.xml.XMLObject;

/**
 * An invoker for a specific function in a JavaScript script
 */
public class RhinoFunctionInvoker {

    private Scriptable instanceScope;

    private Function function;

    private Class responseClass;

    public RhinoFunctionInvoker(Scriptable instanceScope, Function function, Class responseClass) {
        this.instanceScope = instanceScope;
        this.function = function;
        this.responseClass = responseClass;
    }

    public Object invoke(Object[] args) {
        Context cx = Context.enter();
        try {

            Object[] jsArgs = toJavaScript(args, instanceScope, cx);
            Object jsResponse = function.call(cx, instanceScope, instanceScope, jsArgs);
            Object response = fromJavaScript(jsResponse);
            return response;

        } catch ( Exception e ) {
            throw new RuntimeException(e);
        }
        finally {
            Context.exit();
        }
    }

    protected Object[] toJavaScript(Object[] arg, Scriptable scope, Context cx) throws RuntimeException {
        Object[] jsArgs;
        if (arg == null) {
            jsArgs = new Object[0];
        }  else if (arg.length == 1 && arg[0] instanceof OMElement) {
            try {
                XmlObject xmlObject = XmlObject.Factory.parse(arg[0].toString());
                Object jsXML = cx.getWrapFactory().wrap(cx, scope, xmlObject, XmlObject.class);
                jsArgs = new Object[] { cx.newObject(scope, "XML", new Object[] { jsXML }) };
            } catch ( Exception e ) {
                throw new RuntimeException(e);
            } 
        } else if (arg.length == 1 && arg[0] instanceof XmlObject) {
            Object jsXML = cx.getWrapFactory().wrap(cx, scope, (XmlObject)arg[0], XmlObject.class);
            jsArgs = new Object[] { cx.newObject(scope, "XML", new Object[] { jsXML }) };
        } else {
            jsArgs = new Object[arg.length];
            for (int i = 0; i < jsArgs.length; i++) {
                jsArgs[i] = Context.toObject(arg[i], scope);
            }
        }
        
        return jsArgs;
    }

    protected Object fromJavaScript(Object o) throws Exception {
        Object response;
        if (Context.getUndefinedValue().equals(o)) {
            response = null;
        } else if (o instanceof XMLObject) {
            // TODO: E4X Bug? Shouldn't need this copy, but without it the outer element gets lost???
            Scriptable jsXML = (Scriptable) ScriptableObject.callMethod((Scriptable) o, "copy", new Object[0]);
            Wrapper wrapper = (Wrapper) ScriptableObject.callMethod(jsXML, "getXmlObject", new Object[0]);
            response = wrapper.unwrap();
            
            XMLStreamReader xmlReader = 
                StAXUtils.createXMLStreamReader(new ByteArrayInputStream(response.toString().getBytes()));
            StAXOMBuilder staxOMBuilder = new StAXOMBuilder(OMAbstractFactory.getOMFactory(), xmlReader);
            response = staxOMBuilder.getDocumentElement();
            
        } else if (o instanceof Wrapper) {
            response = ((Wrapper) o).unwrap();
        } else {
            if (responseClass != null) {
                response = Context.jsToJava(o, responseClass);
            } else {
                response = Context.jsToJava(o, String.class);
            }
        }
        return response;
    }

}