/*

 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package jdk.nashorn.api.scripting;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineFactory;

import jdk.nashorn.internal.runtime.Version;

import sun.reflect.Reflection;

/**

 * JSR-223 compliant script engine factory for Nashorn. The engine answers for:

 * <ul>

 * <li>names {@code "nashorn"}, {@code "Nashorn"}, {@code "js"}, {@code "JS"}, {@code "JavaScript"},

 * {@code "javascript"}, {@code "ECMAScript"}, and {@code "ecmascript"};</li>

 * <li>MIME types {@code "application/javascript"}, {@code "application/ecmascript"}, {@code "text/javascript"}, and

 * {@code "text/ecmascript"};</li>

 * <li>as well as for the extension {@code "js"}.</li>

 * </ul>

 * Programs executing in engines created using {@link #getScriptEngine(String[])} will have the passed arguments

 * accessible as a global variable named {@code "arguments"}.

 */

public final class NashornScriptEngineFactory implements ScriptEngineFactory {

    @Override

    public String getEngineName() {

        return (String) getParameter(ScriptEngine.ENGINE);

    }

    @Override

    public String getEngineVersion() {

        return (String) getParameter(ScriptEngine.ENGINE_VERSION);

    }

    @Override

    public List<String> getExtensions() {

        return Collections.unmodifiableList(extensions);

    }

    @Override

    public String getLanguageName() {

        return (String) getParameter(ScriptEngine.LANGUAGE);

    }

    @Override

    public String getLanguageVersion() {

        return (String) getParameter(ScriptEngine.LANGUAGE_VERSION);

    }

    @Override

    public String getMethodCallSyntax(final String obj, final String method, final String... args) {

        final StringBuilder sb = new StringBuilder().append(obj).append('.').append(method).append('(');

        final int len = args.length;

        if (len > 0) {

            sb.append(args[0]);

        }

        for (int i = 1; i < len; i++) {

            sb.append(',').append(args[i]);

        }

        sb.append(')');

        return sb.toString();

    }

    @Override

    public List<String> getMimeTypes() {

        return Collections.unmodifiableList(mimeTypes);

    }

    @Override

    public List<String> getNames() {

        return Collections.unmodifiableList(names);

    }

    @Override

    public String getOutputStatement(final String toDisplay) {

        return "print(" + toDisplay + ")";

    }

    @Override

    public Object getParameter(final String key) {

        switch (key) {

        case ScriptEngine.NAME:

            return "javascript";

        case ScriptEngine.ENGINE:

            return "Oracle Nashorn";

        case ScriptEngine.ENGINE_VERSION:

            return Version.version();

        case ScriptEngine.LANGUAGE:

            return "ECMAScript";

        case ScriptEngine.LANGUAGE_VERSION:

            return "ECMA - 262 Edition 5.1";

        case "THREADING":

            // The engine implementation is not thread-safe. Can't be

            // used to execute scripts concurrently on multiple threads.

            return null;

        default:

            throw new IllegalArgumentException("Invalid key");

        }

    }

    @Override

    public String getProgram(final String... statements) {

        final StringBuilder sb = new StringBuilder();

        for (final String statement : statements) {

            sb.append(statement).append(';');

        }

        return sb.toString();

    }

    @Override

    public ScriptEngine getScriptEngine() {

        return new NashornScriptEngine(this, getAppClassLoader());

    }

    /**

     * Create a new Script engine initialized by given class loader.

     *

     * @param appLoader class loader to be used as script "app" class loader.

     * @return newly created script engine.

     */

    public ScriptEngine getScriptEngine(final ClassLoader appLoader) {

        return new NashornScriptEngine(this, appLoader);

    }

    /**

     * Create a new Script engine initialized by given arguments.

     *

     * @param args arguments array passed to script engine.

     * @return newly created script engine.

     */

    public ScriptEngine getScriptEngine(final String[] args) {

        return new NashornScriptEngine(this, args, getAppClassLoader());

    }

    /**

     * Create a new Script engine initialized by given arguments.

     *

     * @param args arguments array passed to script engine.

     * @param appLoader class loader to be used as script "app" class loader.

     * @return newly created script engine.

     */

    public ScriptEngine getScriptEngine(final String[] args, final ClassLoader appLoader) {

        return new NashornScriptEngine(this, args, appLoader);

    }

    // -- Internals only below this point

    private static final List<String> names;

    private static final List<String> mimeTypes;

    private static final List<String> extensions;

    static {

        names = immutableList(

                    "nashorn", "Nashorn",

                    "js", "JS",

                    "JavaScript", "javascript",

                    "ECMAScript", "ecmascript"

                );

        mimeTypes = immutableList(

                        "application/javascript",

                        "application/ecmascript",

                        "text/javascript",

                        "text/ecmascript"

                    );

        extensions = immutableList("js");

    }

    private static List<String> immutableList(final String... elements) {

        return Collections.unmodifiableList(Arrays.asList(elements));

    }

    private static ClassLoader getAppClassLoader() {

        if (System.getSecurityManager() == null) {

            return Thread.currentThread().getContextClassLoader();

        }

        // Try to determine the caller class loader. Use that if it can be

        // found. If not, use the class loader of nashorn itself as the

        // "application" class loader for scripts.

        // User could have called ScriptEngineFactory.getScriptEngine()

        //

        // <caller>

        //  <factory.getScriptEngine()>

        //   <factory.getAppClassLoader()>

        //    <Reflection.getCallerClass()>

        //

        // or used one of the getEngineByABC methods of ScriptEngineManager.

        //

        // <caller>

        //  <ScriptEngineManager.getEngineByName()>

        //   <factory.getScriptEngine()>

        //    <factory.getAppClassLoader()>

        //     <Reflection.getCallerClass()>

        // So, stack depth is 3 or 4 (recall it is zero based). We try

        // stack depths 3, 4 and look for non-bootstrap caller.

        Class<?> caller = null;

        for (int depth = 3; depth < 5; depth++) {

            caller = Reflection.getCallerClass(depth);

            if (caller != null && caller.getClassLoader() != null) {

                // found a non-bootstrap caller

                break;

            }

        }

        final ClassLoader ccl = (caller == null)? null : caller.getClassLoader();

        // if caller loader is null, then use nashorn's own loader

        return (ccl == null)? NashornScriptEngineFactory.class.getClassLoader() : ccl;

    }

}