/*

 * 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

 * questions.

 */

package jdk.nashorn.api.scripting;

import static jdk.nashorn.internal.runtime.ECMAErrors.referenceError;

import static jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.Reader;

import java.lang.invoke.MethodHandles;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.net.URL;

import java.nio.charset.Charset;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.Permissions;

import java.security.PrivilegedAction;

import java.security.PrivilegedActionException;

import java.security.PrivilegedExceptionAction;

import java.security.ProtectionDomain;

import java.text.MessageFormat;

import java.util.Locale;

import java.util.ResourceBundle;

import javax.script.AbstractScriptEngine;

import javax.script.Bindings;

import javax.script.Compilable;

import javax.script.CompiledScript;

import javax.script.Invocable;

import javax.script.ScriptContext;

import javax.script.ScriptEngine;

import javax.script.ScriptEngineFactory;

import javax.script.ScriptException;

import javax.script.SimpleBindings;

import jdk.nashorn.internal.objects.Global;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.ErrorManager;

import jdk.nashorn.internal.runtime.Property;

import jdk.nashorn.internal.runtime.ScriptEnvironment;

import jdk.nashorn.internal.runtime.ScriptFunction;

import jdk.nashorn.internal.runtime.ScriptObject;

import jdk.nashorn.internal.runtime.ScriptRuntime;

import jdk.nashorn.internal.runtime.Source;

import jdk.nashorn.internal.runtime.linker.JavaAdapterFactory;

import jdk.nashorn.internal.runtime.options.Options;

/**

 * JSR-223 compliant script engine for Nashorn. Instances are not created directly, but rather returned through

 * {@link NashornScriptEngineFactory#getScriptEngine()}. Note that this engine implements the {@link Compilable} and

 * {@link Invocable} interfaces, allowing for efficient precompilation and repeated execution of scripts.

 * @see NashornScriptEngineFactory

 */

public final class NashornScriptEngine extends AbstractScriptEngine implements Compilable, Invocable {

    /**

     * Key used to associate Nashorn global object mirror with arbitrary Bindings instance.

     */

    public static final String NASHORN_GLOBAL = "nashorn.global";

    // commonly used access control context objects

    private static AccessControlContext createPermAccCtxt(final String permName) {

        final Permissions perms = new Permissions();

        perms.add(new RuntimePermission(permName));

        return new AccessControlContext(new ProtectionDomain[] { new ProtectionDomain(null, perms) });

    }

    private static final AccessControlContext CREATE_CONTEXT_ACC_CTXT = createPermAccCtxt(Context.NASHORN_CREATE_CONTEXT);

    private static final AccessControlContext CREATE_GLOBAL_ACC_CTXT  = createPermAccCtxt(Context.NASHORN_CREATE_GLOBAL);

    // the factory that created this engine

    private final ScriptEngineFactory factory;

    // underlying nashorn Context - 1:1 with engine instance

    private final Context             nashornContext;

    // do we want to share single Nashorn global instance across ENGINE_SCOPEs?

    private final boolean             _global_per_engine;

    // This is the initial default Nashorn global object.

    // This is used as "shared" global if above option is true.

    private final Global              global;

    // initialized bit late to be made 'final'.

    // Property object for "context" property of global object.

    private volatile Property         contextProperty;

    // default options passed to Nashorn Options object

    private static final String[] DEFAULT_OPTIONS = new String[] { "-doe" };

    // Nashorn script engine error message management

    private static final String MESSAGES_RESOURCE = "jdk.nashorn.api.scripting.resources.Messages";

    private static final ResourceBundle MESSAGES_BUNDLE;

    static {

        MESSAGES_BUNDLE = ResourceBundle.getBundle(MESSAGES_RESOURCE, Locale.getDefault());

    }

    // helper to get Nashorn script engine error message

    private static String getMessage(final String msgId, final String... args) {

        try {

            return new MessageFormat(MESSAGES_BUNDLE.getString(msgId)).format(args);

        } catch (final java.util.MissingResourceException e) {

            throw new RuntimeException("no message resource found for message id: "+ msgId);

        }

    }

    // load engine.js and return content as a char[]

    @SuppressWarnings("resource")

    private static char[] loadEngineJSSource() {

        final String script = "resources/engine.js";

        try {

            final InputStream is = AccessController.doPrivileged(

                    new PrivilegedExceptionAction<InputStream>() {

                        @Override

                        public InputStream run() throws Exception {

                            final URL url = NashornScriptEngine.class.getResource(script);

                            return url.openStream();

                        }

                    });

            return Source.readFully(new InputStreamReader(is));

        } catch (final PrivilegedActionException | IOException e) {

            if (Context.DEBUG) {

                e.printStackTrace();

            }

            throw new RuntimeException(e);

        }

    }

    // Source object for engine.js

    private static final Source ENGINE_SCRIPT_SRC = new Source(NashornException.ENGINE_SCRIPT_SOURCE_NAME, loadEngineJSSource());

    NashornScriptEngine(final NashornScriptEngineFactory factory, final ClassLoader appLoader) {

        this(factory, DEFAULT_OPTIONS, appLoader);

    }

    NashornScriptEngine(final NashornScriptEngineFactory factory, final String[] args, final ClassLoader appLoader) {

        this.factory = factory;

        final Options options = new Options("nashorn");

        options.process(args);

        // throw ParseException on first error from script

        final ErrorManager errMgr = new Context.ThrowErrorManager();

        // create new Nashorn Context

        this.nashornContext = AccessController.doPrivileged(new PrivilegedAction<Context>() {

            @Override

            public Context run() {

                try {

                    return new Context(options, errMgr, appLoader);

                } catch (final RuntimeException e) {

                    if (Context.DEBUG) {

                        e.printStackTrace();

                    }

                    throw e;

                }

            }

        }, CREATE_CONTEXT_ACC_CTXT);

        // cache this option that is used often

        this._global_per_engine = nashornContext.getEnv()._global_per_engine;

        // create new global object

        this.global = createNashornGlobal(context);

        // set the default ENGINE_SCOPE object for the default context

        context.setBindings(new ScriptObjectMirror(global, global), ScriptContext.ENGINE_SCOPE);

    }

    @Override

    public Object eval(final Reader reader, final ScriptContext ctxt) throws ScriptException {

        return evalImpl(makeSource(reader, ctxt), ctxt);

    }

    @Override

    public Object eval(final String script, final ScriptContext ctxt) throws ScriptException {

        return evalImpl(makeSource(script, ctxt), ctxt);

    }

    @Override

    public ScriptEngineFactory getFactory() {

        return factory;

    }

    @Override

    public Bindings createBindings() {

        if (_global_per_engine) {

            // just create normal SimpleBindings.

            // We use same 'global' for all Bindings.

            return new SimpleBindings();

        }

        return createGlobalMirror(null);

    }

    // Compilable methods

    @Override

    public CompiledScript compile(final Reader reader) throws ScriptException {

        return asCompiledScript(makeSource(reader, context));

    }

    @Override

    public CompiledScript compile(final String str) throws ScriptException {

        return asCompiledScript(makeSource(str, context));

    }

    // Invocable methods

    @Override

    public Object invokeFunction(final String name, final Object... args)

            throws ScriptException, NoSuchMethodException {

        return invokeImpl(null, name, args);

    }

    @Override

    public Object invokeMethod(final Object thiz, final String name, final Object... args)

            throws ScriptException, NoSuchMethodException {

        if (thiz == null) {

            throw new IllegalArgumentException(getMessage("thiz.cannot.be.null"));

        }

        return invokeImpl(thiz, name, args);

    }

    @Override

    public <T> T getInterface(final Class<T> clazz) {

        return getInterfaceInner(null, clazz);

    }

    @Override

    public <T> T getInterface(final Object thiz, final Class<T> clazz) {

        if (thiz == null) {

            throw new IllegalArgumentException(getMessage("thiz.cannot.be.null"));

        }

        return getInterfaceInner(thiz, clazz);

    }

    // These are called from the "engine.js" script

    /**

     * This hook is used to search js global variables exposed from Java code.

     *

     * @param self 'this' passed from the script

     * @param ctxt current ScriptContext in which name is searched

     * @param name name of the variable searched

     * @return the value of the named variable

     */

    public Object __noSuchProperty__(final Object self, final ScriptContext ctxt, final String name) {

        if (ctxt != null) {

            final int scope = ctxt.getAttributesScope(name);

            final Global ctxtGlobal = getNashornGlobalFrom(ctxt);

            if (scope != -1) {

                return ScriptObjectMirror.unwrap(ctxt.getAttribute(name, scope), ctxtGlobal);

            }

            if (self == UNDEFINED) {

                // scope access and so throw ReferenceError

                throw referenceError(ctxtGlobal, "not.defined", name);

            }

        }

        return UNDEFINED;

    }

    // Implementation only below this point

    private static Source makeSource(final Reader reader, final ScriptContext ctxt) throws ScriptException {

        try {

            if (reader instanceof URLReader) {

                final URL url = ((URLReader)reader).getURL();

                final Charset cs = ((URLReader)reader).getCharset();

                return new Source(url.toString(), url, cs);

            }

            return new Source(getScriptName(ctxt), Source.readFully(reader));

        } catch (final IOException e) {

            throw new ScriptException(e);

        }

    }

    private static Source makeSource(final String src, final ScriptContext ctxt) {

        return new Source(getScriptName(ctxt), src);

    }

    private static String getScriptName(final ScriptContext ctxt) {

        final Object val = ctxt.getAttribute(ScriptEngine.FILENAME);

        return (val != null) ? val.toString() : "<eval>";

    }

    private <T> T getInterfaceInner(final Object thiz, final Class<T> clazz) {

        if (clazz == null || !clazz.isInterface()) {

            throw new IllegalArgumentException(getMessage("interface.class.expected"));

        }

        // perform security access check as early as possible

        final SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            if (! Modifier.isPublic(clazz.getModifiers())) {

                throw new SecurityException(getMessage("implementing.non.public.interface", clazz.getName()));

            }

            Context.checkPackageAccess(clazz);

        }

        ScriptObject realSelf = null;

        Global realGlobal = null;

        if(thiz == null) {

            // making interface out of global functions

            realSelf = realGlobal = getNashornGlobalFrom(context);

        } else if (thiz instanceof ScriptObjectMirror) {

            final ScriptObjectMirror mirror = (ScriptObjectMirror)thiz;

            realSelf = mirror.getScriptObject();

            realGlobal = mirror.getHomeGlobal();

            if (! isOfContext(realGlobal, nashornContext)) {

                throw new IllegalArgumentException(getMessage("script.object.from.another.engine"));

            }

        } else if (thiz instanceof ScriptObject) {

            // called from script code.

            realSelf = (ScriptObject)thiz;

            realGlobal = Context.getGlobal();

            if (realGlobal == null) {

                throw new IllegalArgumentException(getMessage("no.current.nashorn.global"));

            }

            if (! isOfContext(realGlobal, nashornContext)) {

                throw new IllegalArgumentException(getMessage("script.object.from.another.engine"));

            }

        }

        if (realSelf == null) {

            throw new IllegalArgumentException(getMessage("interface.on.non.script.object"));

        }

        try {

            final Global oldGlobal = Context.getGlobal();

            final boolean globalChanged = (oldGlobal != realGlobal);

            try {

                if (globalChanged) {

                    Context.setGlobal(realGlobal);

                }

                if (! isInterfaceImplemented(clazz, realSelf)) {

                    return null;

                }

                return clazz.cast(JavaAdapterFactory.getConstructor(realSelf.getClass(), clazz,

                        MethodHandles.publicLookup()).invoke(realSelf));

            } finally {

                if (globalChanged) {

                    Context.setGlobal(oldGlobal);

                }

            }

        } catch(final RuntimeException|Error e) {

            throw e;

        } catch(final Throwable t) {

            throw new RuntimeException(t);

        }

    }

    // Retrieve nashorn Global object for a given ScriptContext object

    private Global getNashornGlobalFrom(final ScriptContext ctxt) {

        if (_global_per_engine) {

            // shared single global object for all ENGINE_SCOPE Bindings

            return global;

        }

        final Bindings bindings = ctxt.getBindings(ScriptContext.ENGINE_SCOPE);

        // is this Nashorn's own Bindings implementation?

        if (bindings instanceof ScriptObjectMirror) {

            final Global glob = globalFromMirror((ScriptObjectMirror)bindings);

            if (glob != null) {

                return glob;

            }

        }

        // Arbitrary user Bindings implementation. Look for NASHORN_GLOBAL in it!

        Object scope = bindings.get(NASHORN_GLOBAL);

        if (scope instanceof ScriptObjectMirror) {

            final Global glob = globalFromMirror((ScriptObjectMirror)scope);

            if (glob != null) {

                return glob;

            }

        }

        // We didn't find associated nashorn global mirror in the Bindings given!

        // Create new global instance mirror and associate with the Bindings.

        final ScriptObjectMirror mirror = createGlobalMirror(ctxt);

        bindings.put(NASHORN_GLOBAL, mirror);

        return mirror.getHomeGlobal();

    }

    // Retrieve nashorn Global object from a given ScriptObjectMirror

    private Global globalFromMirror(final ScriptObjectMirror mirror) {

        ScriptObject sobj = mirror.getScriptObject();

        if (sobj instanceof Global && isOfContext((Global)sobj, nashornContext)) {

            return (Global)sobj;

        }

        return null;

    }

    // Create a new ScriptObjectMirror wrapping a newly created Nashorn Global object

    private ScriptObjectMirror createGlobalMirror(final ScriptContext ctxt) {

        final Global newGlobal = createNashornGlobal(ctxt);

        return new ScriptObjectMirror(newGlobal, newGlobal);

    }

    // Create a new Nashorn Global object

    private Global createNashornGlobal(final ScriptContext ctxt) {

        final Global newGlobal = AccessController.doPrivileged(new PrivilegedAction<Global>() {

            @Override

            public Global run() {

                try {

                    return nashornContext.newGlobal();

                } catch (final RuntimeException e) {

                    if (Context.DEBUG) {

                        e.printStackTrace();

                    }

                    throw e;

                }

            }

        }, CREATE_GLOBAL_ACC_CTXT);

        nashornContext.initGlobal(newGlobal);

        final int NON_ENUMERABLE_CONSTANT = Property.NOT_ENUMERABLE | Property.NOT_CONFIGURABLE | Property.NOT_WRITABLE;

        // current ScriptContext exposed as "context"

        // "context" is non-writable from script - but script engine still

        // needs to set it and so save the context Property object

        contextProperty = newGlobal.addOwnProperty("context", NON_ENUMERABLE_CONSTANT, ctxt);

        // current ScriptEngine instance exposed as "engine". We added @SuppressWarnings("LeakingThisInConstructor") as

        // NetBeans identifies this assignment as such a leak - this is a false positive as we're setting this property

        // in the Global of a Context we just created - both the Context and the Global were just created and can not be

        // seen from another thread outside of this constructor.

        newGlobal.addOwnProperty("engine", NON_ENUMERABLE_CONSTANT, this);

        // global script arguments with undefined value

        newGlobal.addOwnProperty("arguments", Property.NOT_ENUMERABLE, UNDEFINED);

        // file name default is null

        newGlobal.addOwnProperty(ScriptEngine.FILENAME, Property.NOT_ENUMERABLE, null);

        // evaluate engine.js initialization script this new global object

        try {

            evalImpl(compileImpl(ENGINE_SCRIPT_SRC, newGlobal), ctxt, newGlobal);

        } catch (final ScriptException exp) {

            throw new RuntimeException(exp);

        }

        return newGlobal;

    }

    // scripts should see "context" and "engine" as variables in the given global object

    private void setContextVariables(final Global ctxtGlobal, final ScriptContext ctxt) {

        // set "context" global variable via contextProperty - because this

        // property is non-writable

        contextProperty.setValue(ctxtGlobal, ctxtGlobal, ctxt, false);

        Object args = ScriptObjectMirror.unwrap(ctxt.getAttribute("arguments"), ctxtGlobal);

        if (args == null || args == UNDEFINED) {

            args = ScriptRuntime.EMPTY_ARRAY;

        }

        // if no arguments passed, expose it

        if (! (args instanceof ScriptObject)) {

            args = ctxtGlobal.wrapAsObject(args);

            ctxtGlobal.set("arguments", args, false);

        }

    }

    private Object invokeImpl(final Object selfObject, final String name, final Object... args) throws ScriptException, NoSuchMethodException {

        name.getClass(); // null check

        Global invokeGlobal = null;

        ScriptObjectMirror selfMirror = null;

        if (selfObject instanceof ScriptObjectMirror) {

            selfMirror = (ScriptObjectMirror)selfObject;

            if (! isOfContext(selfMirror.getHomeGlobal(), nashornContext)) {

                throw new IllegalArgumentException(getMessage("script.object.from.another.engine"));

            }

            invokeGlobal = selfMirror.getHomeGlobal();

        } else if (selfObject instanceof ScriptObject) {

            // invokeMethod called from script code - in which case we may get 'naked' ScriptObject

            // Wrap it with oldGlobal to make a ScriptObjectMirror for the same.

            final Global oldGlobal = Context.getGlobal();

            invokeGlobal = oldGlobal;