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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package jdk.nashorn.api.scripting;

import static jdk.nashorn.internal.runtime.Source.sourceFor;

import java.io.IOException;
import java.io.Reader;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.Permissions;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.text.MessageFormat;
import java.util.Locale;
import java.util.Objects;
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.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 NashornScriptEngineFactory.getScriptEngine(). Note that this engine implements the Compilable and Invocable interfaces, allowing for efficient precompilation and repeated execution of scripts. 
See Also:
NashornScriptEngineFactory
Since:
1.8u40/**
 * 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
 *
 * @since 1.8u40
 */
public final class NashornScriptEngine extends AbstractScriptEngine implements Compilable, Invocable {
    
Key used to associate Nashorn global object mirror with arbitrary Bindings instance.
/**
     * 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;

    // 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);
        }
    }

    NashornScriptEngine(final NashornScriptEngineFactory factory, final String[] args, final ClassLoader appLoader, final ClassFilter classFilter) {
        assert args != null : "null argument array";
        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, classFilter);
                } 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();
        // 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();
    }

    // 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);
    }

    // Implementation only below this point

    private static Source makeSource(final Reader reader, final ScriptContext ctxt) throws ScriptException {
        try {
            return sourceFor(getScriptName(ctxt), reader);
        } catch (final IOException e) {
            throw new ScriptException(e);
        }
    }

    private static Source makeSource(final String src, final ScriptContext ctxt) {
        return sourceFor(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) {
        assert !(thiz instanceof ScriptObject) : "raw ScriptObject not expected here";

        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"));
            }
        }

        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!
        final 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();
        bindings.put(NASHORN_GLOBAL, mirror);
        // Since we created this global explicitly for the non-default script context we set the
        // current script context in global permanently so that invokes work as expected. See JDK-8150219
        mirror.getHomeGlobal().setInitScriptContext(ctxt);
        return mirror.getHomeGlobal();
    }

    // Retrieve nashorn Global object from a given ScriptObjectMirror
    private Global globalFromMirror(final ScriptObjectMirror mirror) {
        final 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 Global newGlobal = createNashornGlobal();
        return new ScriptObjectMirror(newGlobal, newGlobal);
    }

    // Create a new Nashorn Global object
    private Global createNashornGlobal() {
        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, this);

        return newGlobal;
    }

    private Object invokeImpl(final Object selfObject, final String name, final Object... args) throws ScriptException, NoSuchMethodException {
        Objects.requireNonNull(name);
        assert !(selfObject instanceof ScriptObject) : "raw ScriptObject not expected here";

        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 == null) {
            // selfObject is null => global function call
            final Global ctxtGlobal = getNashornGlobalFrom(context);
            invokeGlobal = ctxtGlobal;
            selfMirror = (ScriptObjectMirror)ScriptObjectMirror.wrap(ctxtGlobal, ctxtGlobal);
        }

        if (selfMirror != null) {
            try {
                return ScriptObjectMirror.translateUndefined(selfMirror.callMember(name, args));
            } catch (final Exception e) {
                final Throwable cause = e.getCause();
                if (cause instanceof NoSuchMethodException) {
                    throw (NoSuchMethodException)cause;
                }
                throwAsScriptException(e, invokeGlobal);
                throw new AssertionError("should not reach here");
            }
        }

        // Non-script object passed as selfObject
        throw new IllegalArgumentException(getMessage("interface.on.non.script.object"));
    }

    private Object evalImpl(final Source src, final ScriptContext ctxt) throws ScriptException {
        return evalImpl(compileImpl(src, ctxt), ctxt);
    }

    private Object evalImpl(final ScriptFunction script, final ScriptContext ctxt) throws ScriptException {
        return evalImpl(script, ctxt, getNashornGlobalFrom(ctxt));
    }

    private Object evalImpl(final Context.MultiGlobalCompiledScript mgcs, final ScriptContext ctxt, final Global ctxtGlobal) throws ScriptException {
        final Global oldGlobal = Context.getGlobal();
        final boolean globalChanged = (oldGlobal != ctxtGlobal);
        try {
            if (globalChanged) {
                Context.setGlobal(ctxtGlobal);
            }

            final ScriptFunction script = mgcs.getFunction(ctxtGlobal);
            final ScriptContext oldCtxt = ctxtGlobal.getScriptContext();
            ctxtGlobal.setScriptContext(ctxt);
            try {
                return ScriptObjectMirror.translateUndefined(ScriptObjectMirror.wrap(ScriptRuntime.apply(script, ctxtGlobal), ctxtGlobal));
            } finally {
                ctxtGlobal.setScriptContext(oldCtxt);
            }
        } catch (final Exception e) {
            throwAsScriptException(e, ctxtGlobal);
            throw new AssertionError("should not reach here");
        } finally {
            if (globalChanged) {
                Context.setGlobal(oldGlobal);
            }
        }
    }

    private Object evalImpl(final ScriptFunction script, final ScriptContext ctxt, final Global ctxtGlobal) throws ScriptException {
        if (script == null) {
            return null;
        }
        final Global oldGlobal = Context.getGlobal();
        final boolean globalChanged = (oldGlobal != ctxtGlobal);
        try {
            if (globalChanged) {
                Context.setGlobal(ctxtGlobal);
            }

            final ScriptContext oldCtxt = ctxtGlobal.getScriptContext();
            ctxtGlobal.setScriptContext(ctxt);
            try {
                return ScriptObjectMirror.translateUndefined(ScriptObjectMirror.wrap(ScriptRuntime.apply(script, ctxtGlobal), ctxtGlobal));
            } finally {
                ctxtGlobal.setScriptContext(oldCtxt);
            }
        } catch (final Exception e) {
            throwAsScriptException(e, ctxtGlobal);
            throw new AssertionError("should not reach here");
        } finally {
            if (globalChanged) {
                Context.setGlobal(oldGlobal);
            }
        }
    }

    private static void throwAsScriptException(final Exception e, final Global global) throws ScriptException {
        if (e instanceof ScriptException) {
            throw (ScriptException)e;
        } else if (e instanceof NashornException) {
            final NashornException ne = (NashornException)e;
            final ScriptException se = new ScriptException(
                ne.getMessage(), ne.getFileName(),
                ne.getLineNumber(), ne.getColumnNumber());
            ne.initEcmaError(global);
            se.initCause(e);
            throw se;
        } else if (e instanceof RuntimeException) {
            throw (RuntimeException)e;
        } else {
            // wrap any other exception as ScriptException
            throw new ScriptException(e);
        }
    }

    private CompiledScript asCompiledScript(final Source source) throws ScriptException {
        final Context.MultiGlobalCompiledScript mgcs;
        final ScriptFunction func;
        final Global oldGlobal = Context.getGlobal();
        final Global newGlobal = getNashornGlobalFrom(context);
        final boolean globalChanged = (oldGlobal != newGlobal);
        try {
            if (globalChanged) {
                Context.setGlobal(newGlobal);
            }

            mgcs = nashornContext.compileScript(source);
            func = mgcs.getFunction(newGlobal);
        } catch (final Exception e) {
            throwAsScriptException(e, newGlobal);
            throw new AssertionError("should not reach here");
        } finally {
            if (globalChanged) {
                Context.setGlobal(oldGlobal);
            }
        }

        return new CompiledScript() {
            @Override
            public Object eval(final ScriptContext ctxt) throws ScriptException {
                final Global globalObject = getNashornGlobalFrom(ctxt);
                // Are we running the script in the same global in which it was compiled?
                if (func.getScope() == globalObject) {
                    return evalImpl(func, ctxt, globalObject);
                }

                // different global
                return evalImpl(mgcs, ctxt, globalObject);
            }
            @Override
            public ScriptEngine getEngine() {
                return NashornScriptEngine.this;
            }
        };
    }

    private ScriptFunction compileImpl(final Source source, final ScriptContext ctxt) throws ScriptException {
        return compileImpl(source, getNashornGlobalFrom(ctxt));
    }

    private ScriptFunction compileImpl(final Source source, final Global newGlobal) throws ScriptException {
        final Global oldGlobal = Context.getGlobal();
        final boolean globalChanged = (oldGlobal != newGlobal);
        try {
            if (globalChanged) {
                Context.setGlobal(newGlobal);
            }

            return nashornContext.compileScript(source, newGlobal);
        } catch (final Exception e) {
            throwAsScriptException(e, newGlobal);
            throw new AssertionError("should not reach here");
        } finally {
            if (globalChanged) {
                Context.setGlobal(oldGlobal);
            }
        }
    }

    private static boolean isInterfaceImplemented(final Class<?> iface, final ScriptObject sobj) {
        for (final Method method : iface.getMethods()) {
            // ignore methods of java.lang.Object class
            if (method.getDeclaringClass() == Object.class) {
                continue;
            }

            // skip check for default methods - non-abstract, interface methods
            if (! Modifier.isAbstract(method.getModifiers())) {
                continue;
            }

            final Object obj = sobj.get(method.getName());
            if (! (obj instanceof ScriptFunction)) {
                return false;
            }
        }
        return true;
    }

    private static boolean isOfContext(final Global global, final Context context) {
        return global.isOfContext(context);
    }
}