/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.scripting.support;

import java.io.IOException;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.scripting.ScriptCompilationException;
import org.springframework.scripting.ScriptFactory;
import org.springframework.scripting.ScriptSource;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.springframework.scripting.ScriptFactory} implementation based
 * on the JSR-223 script engine abstraction (as included in Java 6+).
 * Supports JavaScript, Groovy, JRuby, and other JSR-223 compliant engines.
 *
 * <p>Typically used in combination with a
 * {@link org.springframework.scripting.support.ScriptFactoryPostProcessor};
 * see the latter's javadoc for a configuration example.
 *
 * @author Juergen Hoeller
 * @since 4.2
 * @see ScriptFactoryPostProcessor
 */
public class StandardScriptFactory implements ScriptFactory, BeanClassLoaderAware {

        private final String scriptEngineName;

        private final String scriptSourceLocator;

        private final Class<?>[] scriptInterfaces;

        private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

        private volatile ScriptEngine scriptEngine;


        /**
         * Create a new StandardScriptFactory for the given script source.
         * @param scriptSourceLocator a locator that points to the source of the script.
         * Interpreted by the post-processor that actually creates the script.
         */
        public StandardScriptFactory(String scriptSourceLocator) {
                this(null, scriptSourceLocator, (Class<?>[]) null);
        }

        /**
         * Create a new StandardScriptFactory for the given script source.
         * @param scriptSourceLocator a locator that points to the source of the script.
         * Interpreted by the post-processor that actually creates the script.
         * @param scriptInterfaces the Java interfaces that the scripted object
         * is supposed to implement
         */
        public StandardScriptFactory(String scriptSourceLocator, Class<?>... scriptInterfaces) {
                this(null, scriptSourceLocator, scriptInterfaces);
        }

        /**
         * Create a new StandardScriptFactory for the given script source.
         * @param scriptEngineName the name of the JSR-223 ScriptEngine to use
         * (explicitly given instead of inferred from the script source)
         * @param scriptSourceLocator a locator that points to the source of the script.
         * Interpreted by the post-processor that actually creates the script.
         */
        public StandardScriptFactory(String scriptEngineName, String scriptSourceLocator) {
                this(scriptEngineName, scriptSourceLocator, (Class<?>[]) null);
        }

        /**
         * Create a new StandardScriptFactory for the given script source.
         * @param scriptEngineName the name of the JSR-223 ScriptEngine to use
         * (explicitly given instead of inferred from the script source)
         * @param scriptSourceLocator a locator that points to the source of the script.
         * Interpreted by the post-processor that actually creates the script.
         * @param scriptInterfaces the Java interfaces that the scripted object
         * is supposed to implement
         */
        public StandardScriptFactory(String scriptEngineName, String scriptSourceLocator, Class<?>... scriptInterfaces) {
                Assert.hasText(scriptSourceLocator, "'scriptSourceLocator' must not be empty");
                this.scriptEngineName = scriptEngineName;
                this.scriptSourceLocator = scriptSourceLocator;
                this.scriptInterfaces = scriptInterfaces;
        }


        @Override
        public void setBeanClassLoader(ClassLoader classLoader) {
                this.beanClassLoader = classLoader;
        }

        @Override
        public String getScriptSourceLocator() {
                return this.scriptSourceLocator;
        }

        @Override
        public Class<?>[] getScriptInterfaces() {
                return this.scriptInterfaces;
        }

        @Override
        public boolean requiresConfigInterface() {
                return false;
        }


        /**
         * Load and parse the script via JSR-223's ScriptEngine.
         */
        @Override
        public Object getScriptedObject(ScriptSource scriptSource, Class<?>... actualInterfaces)
                        throws IOException, ScriptCompilationException {

                Object script = evaluateScript(scriptSource);

                if (!ObjectUtils.isEmpty(actualInterfaces)) {
                        boolean adaptationRequired = false;
                        for (Class<?> requestedIfc : actualInterfaces) {
                                if (script instanceof Class ? !requestedIfc.isAssignableFrom((Class<?>) script) :
                                                !requestedIfc.isInstance(script)) {
                                        adaptationRequired = true;
                                        break;
                                }
                        }
                        if (adaptationRequired) {
                                script = adaptToInterfaces(script, scriptSource, actualInterfaces);
                        }
                }

                if (script instanceof Class) {
                        Class<?> scriptClass = (Class<?>) script;
                        try {
                                return scriptClass.newInstance();
                        }
                        catch (InstantiationException ex) {
                                throw new ScriptCompilationException(
                                                scriptSource, "Unable to instantiate script class: " + scriptClass.getName(), ex);
                        }
                        catch (IllegalAccessException ex) {
                                throw new ScriptCompilationException(
                                                scriptSource, "Could not access script constructor: " + scriptClass.getName(), ex);
                        }
                }

                return script;
        }

        protected Object evaluateScript(ScriptSource scriptSource) {
                try {
                        if (this.scriptEngine == null) {
                                this.scriptEngine = retrieveScriptEngine(scriptSource);
                                if (this.scriptEngine == null) {
                                        throw new IllegalStateException("Could not determine script engine for " + scriptSource);
                                }
                        }
                        return this.scriptEngine.eval(scriptSource.getScriptAsString());
                }
                catch (Exception ex) {
                        throw new ScriptCompilationException(scriptSource, ex);
                }
        }

        protected ScriptEngine retrieveScriptEngine(ScriptSource scriptSource) {
                ScriptEngineManager scriptEngineManager = new ScriptEngineManager(this.beanClassLoader);

                if (this.scriptEngineName != null) {
                        return StandardScriptUtils.retrieveEngineByName(scriptEngineManager, this.scriptEngineName);
                }

                if (scriptSource instanceof ResourceScriptSource) {
                        String filename = ((ResourceScriptSource) scriptSource).getResource().getFilename();
                        if (filename != null) {
                                String extension = StringUtils.getFilenameExtension(filename);
                                if (extension != null) {
                                        ScriptEngine engine = scriptEngineManager.getEngineByExtension(extension);
                                        if (engine != null) {
                                                return engine;
                                        }
                                }
                        }
                }

                return null;
        }

        protected Object adaptToInterfaces(Object script, ScriptSource scriptSource, Class<?>... actualInterfaces) {
                Class<?> adaptedIfc;
                if (actualInterfaces.length == 1) {
                        adaptedIfc = actualInterfaces[0];
                }
                else {
                        adaptedIfc = ClassUtils.createCompositeInterface(actualInterfaces, this.beanClassLoader);
                }

                if (adaptedIfc != null) {
                        if (!(this.scriptEngine instanceof Invocable)) {
                                throw new ScriptCompilationException(scriptSource,
                                                "ScriptEngine must implement Invocable in order to adapt it to an interface: " +
                                                                this.scriptEngine);
                        }
                        Invocable invocable = (Invocable) this.scriptEngine;
                        if (script != null) {
                                script = invocable.getInterface(script, adaptedIfc);
                        }
                        if (script == null) {
                                script = invocable.getInterface(adaptedIfc);
                                if (script == null) {
                                        throw new ScriptCompilationException(scriptSource,
                                                        "Could not adapt script to interface [" + adaptedIfc.getName() + "]");
                                }
                        }
                }

                return script;
        }

        @Override
        public Class<?> getScriptedObjectType(ScriptSource scriptSource)
                        throws IOException, ScriptCompilationException {

                return null;
        }

        @Override
        public boolean requiresScriptedObjectRefresh(ScriptSource scriptSource) {
                return scriptSource.isModified();
        }


        @Override
        public String toString() {
                return "StandardScriptFactory: script source locator [" + this.scriptSourceLocator + "]";
        }

}