/*
 * The initial contribution was derived from the reference implementation
 * developed by Sun in consultation with the Groovy community. The reference
 * implementation had the following license header:
 *
 *  Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 *  Use is subject to license terms.
 *
 *  Redistribution and use in source and binary forms, with or without modification, are
 *  permitted provided that the following conditions are met: Redistributions of source code
 *  must retain the above copyright notice, this list of conditions and the following disclaimer.
 *  Redistributions in binary form must reproduce the above copyright notice, this list of
 *  conditions and the following disclaimer in the documentation and/or other materials
 *  provided with the distribution. Neither the name of the Sun Microsystems nor the names of
 *  is contributors may be used to endorse or promote products derived from this software
 *  without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS
 *  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 *  AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 *  OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 *  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 *  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 *  OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *
 * Subsequent modifications by the Groovy community have been done under the Apache License v2:
 *
 *  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.codehaus.groovy.jsr223;

import groovy.lang.Binding;
import groovy.lang.Closure;
import groovy.lang.DelegatingMetaClass;
import groovy.lang.GroovyClassLoader;
import groovy.lang.MetaClass;
import groovy.lang.MissingMethodException;
import groovy.lang.MissingPropertyException;
import groovy.lang.Script;
import groovy.lang.Tuple;
import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.control.CompilerConfiguration;
import org.codehaus.groovy.runtime.InvokerHelper;
import org.codehaus.groovy.runtime.MetaClassHelper;
import org.codehaus.groovy.runtime.MethodClosure;
import org.codehaus.groovy.util.ManagedConcurrentValueMap;
import org.codehaus.groovy.util.ReferenceBundle;

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 java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * JSR-223 Engine implementation.
 *
 * Adapted from original by Mike Grogan and A. Sundararajan
 */
public class GroovyScriptEngineImpl extends AbstractScriptEngine implements Compilable, Invocable {

    private static boolean debug = false;

    // script-string-to-generated Class map
    private final ManagedConcurrentValueMap<String, Class<?>> classMap = new ManagedConcurrentValueMap<>(ReferenceBundle.getSoftBundle());
    // global closures map - this is used to simulate a single
    // global functions namespace
    private final ManagedConcurrentValueMap<String, Closure<?>> globalClosures = new ManagedConcurrentValueMap<>(ReferenceBundle.getHardBundle());
    // class loader for Groovy generated classes
    private GroovyClassLoader loader;
    // lazily initialized factory
    private volatile GroovyScriptEngineFactory factory;

    // counter used to generate unique global Script class names
    private static int counter;

    static {
        counter = 0;
    }

    public GroovyScriptEngineImpl() {
        this(AccessController.doPrivileged(new PrivilegedAction<GroovyClassLoader>() {
            @Override
            public GroovyClassLoader run() {
                return new GroovyClassLoader(getParentLoader(), new CompilerConfiguration(CompilerConfiguration.DEFAULT));
            }
        }));
    }

    public GroovyScriptEngineImpl(GroovyClassLoader classLoader) {
        if (classLoader == null) throw new IllegalArgumentException("GroovyClassLoader is null");
        this.loader = classLoader;
    }

    GroovyScriptEngineImpl(GroovyScriptEngineFactory factory) {
        this();
        this.factory = factory;
    }

    @Override
    public Object eval(Reader reader, ScriptContext ctx)
            throws ScriptException {
        return eval(readFully(reader), ctx);
    }

    @Override
    public Object eval(String script, ScriptContext ctx)
            throws ScriptException {
        try {
            String val = (String) ctx.getAttribute("#jsr223.groovy.engine.keep.globals", ScriptContext.ENGINE_SCOPE);
            ReferenceBundle bundle = ReferenceBundle.getHardBundle();
            if (val != null && val.length() > 0) {
                if (val.equalsIgnoreCase("soft")) {
                    bundle = ReferenceBundle.getSoftBundle();
                } else if (val.equalsIgnoreCase("weak")) {
                    bundle = ReferenceBundle.getWeakBundle();
                } else if (val.equalsIgnoreCase("phantom")) {
                    bundle = ReferenceBundle.getPhantomBundle();
                }
            }
            globalClosures.setBundle(bundle);
        } catch (ClassCastException cce) { /*ignore.*/ }

        try {
            Class<?> clazz = getScriptClass(script, ctx);
            if (clazz == null) throw new ScriptException("Script class is null");
            return eval(clazz, ctx);
        } catch (Exception e) {
            if (debug) e.printStackTrace();
            throw new ScriptException(e);
        }
    }

    @Override
    public Bindings createBindings() {
        return new SimpleBindings();
    }

    @Override
    public ScriptEngineFactory getFactory() {
        if (factory == null) {
            synchronized (this) {
                if (factory == null) {
                    factory = new GroovyScriptEngineFactory();
                }
            }
        }
        return factory;
    }

    // javax.script.Compilable methods
    @Override
    public CompiledScript compile(String scriptSource) throws ScriptException {
        try {
            return new GroovyCompiledScript(this,
                    getScriptClass(scriptSource, context));
        } catch (CompilationFailedException ee) {
            throw new ScriptException(ee);
        }
    }

    @Override
    public CompiledScript compile(Reader reader) throws ScriptException {
        return compile(readFully(reader));
    }

    // javax.script.Invokable methods.
    @Override
    public Object invokeFunction(String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        return invokeImpl(null, name, args);
    }

    @Override
    public Object invokeMethod(Object thiz, String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        if (thiz == null) {
            throw new IllegalArgumentException("script object is null");
        }
        return invokeImpl(thiz, name, args);
    }

    @Override
    public <T> T getInterface(Class<T> clazz) {
        return makeInterface(null, clazz);
    }

    @Override
    public <T> T getInterface(Object thiz, Class<T> clazz) {
        if (thiz == null) {
            throw new IllegalArgumentException("script object is null");
        }
        return makeInterface(thiz, clazz);
    }

    // package-privates
    Object eval(Class<?> scriptClass, final ScriptContext ctx) throws ScriptException {
        /*
         * We use the following Binding instance so that global variable lookup
         * will be done in the current ScriptContext instance.
         */
        Binding binding = new Binding(ctx.getBindings(ScriptContext.ENGINE_SCOPE)) {
            @Override
            public Object getVariable(String name) {
                synchronized (ctx) {
                    int scope = ctx.getAttributesScope(name);
                    if (scope != -1) {
                        return ctx.getAttribute(name, scope);
                    }
                    // Redirect script output to context writer, if out var is not already provided
                    if ("out".equals(name)) {
                        Writer writer = ctx.getWriter();
                        if (writer != null) {
                            return (writer instanceof PrintWriter) ?
                                    (PrintWriter) writer :
                                    new PrintWriter(writer, true);
                        }
                    }
                    // Provide access to engine context, if context var is not already provided
                    if ("context".equals(name)) {
                        return ctx;
                    }
                }
                throw new MissingPropertyException(name, getClass());
            }

            @Override
            public void setVariable(String name, Object value) {
                synchronized (ctx) {
                    int scope = ctx.getAttributesScope(name);
                    if (scope == -1) {
                        scope = ScriptContext.ENGINE_SCOPE;
                    }
                    ctx.setAttribute(name, value, scope);
                }
            }
        };

        try {
            // if this class is not an instance of Script, it's a full-blown class
            // then simply return that class
            if (!Script.class.isAssignableFrom(scriptClass)) {
                return scriptClass;
            } else {
                // it's a script
                Script scriptObject = InvokerHelper.createScript(scriptClass, binding);

                // save all current closures into global closures map
                Method[] methods = scriptClass.getMethods();
                for (Method m : methods) {
                    String name = m.getName();
                    globalClosures.put(name, new MethodClosure(scriptObject, name));
                }

                MetaClass oldMetaClass = scriptObject.getMetaClass();

                /*
                * We override the MetaClass of this script object so that we can
                * forward calls to global closures (of previous or future "eval" calls)
                * This gives the illusion of working on the same "global" scope.
                */
                scriptObject.setMetaClass(new DelegatingMetaClass(oldMetaClass) {
                    @Override
                    public Object invokeMethod(Object object, String name, Object args) {
                        if (args == null) {
                            return invokeMethod(object, name, MetaClassHelper.EMPTY_ARRAY);
                        }
                        if (args instanceof Tuple) {
                            return invokeMethod(object, name, ((Tuple) args).toArray());
                        }
                        if (args instanceof Object[]) {
                            return invokeMethod(object, name, (Object[]) args);
                        } else {
                            return invokeMethod(object, name, new Object[]{args});
                        }
                    }

                    @Override
                    public Object invokeMethod(Object object, String name, Object[] args) {
                        try {
                            return super.invokeMethod(object, name, args);
                        } catch (MissingMethodException mme) {
                            return callGlobal(name, args, ctx);
                        }
                    }

                    @Override
                    public Object invokeStaticMethod(Object object, String name, Object[] args) {
                        try {
                            return super.invokeStaticMethod(object, name, args);
                        } catch (MissingMethodException mme) {
                            return callGlobal(name, args, ctx);
                        }
                    }
                });

                return scriptObject.run();
            }
        } catch (Exception e) {
            throw new ScriptException(e);
        }
    }

    Class<?> getScriptClass(String script)
            throws CompilationFailedException {
        return getScriptClass(script, null);
    }

    Class<?> getScriptClass(String script, ScriptContext context)
            throws CompilationFailedException {
        Class<?> clazz = classMap.get(script);
        if (clazz != null) {
            return clazz;
        }

        clazz = loader.parseClass(script, generateScriptName(context));
        classMap.put(script, clazz);
        return clazz;
    }

    public void setClassLoader(GroovyClassLoader classLoader) {
        this.loader = classLoader;
    }

    public GroovyClassLoader getClassLoader() {
        return this.loader;
    }

    //-- Internals only below this point

    // invokes the specified method/function on the given object.
    private Object invokeImpl(Object thiz, String name, Object... args)
            throws ScriptException, NoSuchMethodException {
        if (name == null) {
            throw new NullPointerException("method name is null");
        }

        try {
            if (thiz != null) {
                return InvokerHelper.invokeMethod(thiz, name, args);
            } else {
                return callGlobal(name, args);
            }
        } catch (MissingMethodException mme) {
            throw new NoSuchMethodException(mme.getMessage());
        } catch (Exception e) {
            throw new ScriptException(e);
        }
    }

    private Object invokeImplSafe(Object thiz, String name, Object... args) {
        if (name == null) {
            throw new NullPointerException("method name is null");
        }

        try {
            if (thiz != null) {
                return InvokerHelper.invokeMethod(thiz, name, args);
            } else {
                return callGlobal(name, args);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    // call the script global function of the given name
    private Object callGlobal(String name, Object[] args) {
        return callGlobal(name, args, context);
    }

    private Object callGlobal(String name, Object[] args, ScriptContext ctx) {
        Closure<?> closure = globalClosures.get(name);
        if (closure != null) {
            return closure.call(args);
        } else {
            // Look for closure valued variable in the
            // given ScriptContext. If available, call it.
            Object value = ctx.getAttribute(name);
            if (value instanceof Closure) {
                return ((Closure) value).call(args);
            } // else fall thru..
        }
        throw new MissingMethodException(name, getClass(), args);
    }

    // generate a unique name for top-level Script classes
    private static synchronized String generateScriptName(ScriptContext	context) {
        // If context is available, and contains FILENAME,
        // use it as script name
        if (context != null) {
            Object filename = context.getAttribute(ScriptEngine.FILENAME);
            if (filename != null) {
                return filename.toString();
            }
        }
        return "Script" + (++counter) + ".groovy";
    }

    @SuppressWarnings("unchecked")
    private <T> T makeInterface(Object obj, Class<T> clazz) {
        final Object thiz = obj;
        if (clazz == null || !clazz.isInterface()) {
            throw new IllegalArgumentException("interface Class expected");
        }
        return (T) Proxy.newProxyInstance(
                clazz.getClassLoader(),
                new Class<?>[]{clazz},
                (proxy, m, args) -> invokeImplSafe(thiz, m.getName(), args));
    }

    // determine appropriate class loader to serve as parent loader
    // for GroovyClassLoader instance
    private static ClassLoader getParentLoader() {
        // check whether thread context loader can "see" Groovy Script class
        ClassLoader ctxtLoader = Thread.currentThread().getContextClassLoader();
        try {
            Class<?> c = ctxtLoader.loadClass(Script.class.getName());
            if (c == Script.class) {
                return ctxtLoader;
            }
        } catch (ClassNotFoundException cnfe) {
            /* ignore */
        }
        // exception was thrown or we get wrong class
        return Script.class.getClassLoader();
    }

    private static String readFully(Reader reader) throws ScriptException {
        char[] arr = new char[8 * 1024]; // 8K at a time
        StringBuilder buf = new StringBuilder();
        int numChars;
        try {
            while ((numChars = reader.read(arr, 0, arr.length)) > 0) {
                buf.append(arr, 0, numChars);
            }
        } catch (IOException exp) {
            throw new ScriptException(exp);
        }
        return buf.toString();
    }
}
