DMDirc-Plugins/scriptplugin/src/main/java/com/dmdirc/addons/scriptplugin/ScriptEngineWrapper.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.dmdirc.addons.scriptplugin;

import com.google.common.base.Preconditions;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static com.dmdirc.util.LogUtils.USER_ERROR;

/**
 * Class to create script engines!
 */
public class ScriptEngineWrapper {

    private static final Logger LOG = LoggerFactory.getLogger(ScriptEngineWrapper.class);
    /** The Script Engine this wrapper wraps */
    private ScriptEngine engine;
    /** The File this script is from */
    private final File file;
    /** Script-Local JS Helper */
    private final JavaScriptHelper localHelper = new JavaScriptHelper();
    /** Manager to get script engines. */
    private final ScriptEngineManager scriptEngineManager;

    /**
     * Create a new ScriptEngineWrapper
     *
     * @param scriptEngineManager Manager to get script engines
     * @param filename            Filename of script
     *
     * @throws ScriptException  If there was an error during creation
     */
    protected ScriptEngineWrapper(final ScriptEngineManager scriptEngineManager,
            final String filename) throws ScriptException {
        Preconditions.checkNotNull(filename, "File cannot be null");
        this.scriptEngineManager = scriptEngineManager;
        file = new File(filename);

        engine = createEngine();

        callFunction("onLoad");
    }

    /**
     * Get a reference to the ScriptEngine.
     *
     * @return a reference to the ScriptEngine
     */
    protected ScriptEngine getScriptEngine() {
        return engine;
    }

    /**
     * Get a reference to the JavaScriptHelper
     *
     * @return a reference to the JavaScriptHelper
     */
    protected JavaScriptHelper getJavaScriptHelper() {
        return localHelper;
    }

    /**
     * Get the file for this script
     *
     * @return The file for this script
     */
    protected File getFile() {
        return file;
    }

    /**
     * Create a new engine for this script
     *
     * @return Created script engine
     *
     * @throws ScriptException  If there was an error during creation
     */
    protected ScriptEngine createEngine() throws ScriptException {
        final ScriptEngine result = scriptEngineManager.getEngineByName("JavaScript");
        try (FileReader fr = new FileReader(file)) {
            result.eval(fr);
        } catch (IOException ex) {
            throw new ScriptException(ex);
        }

        result.put("localHelper", localHelper);
        result.put("thisEngine", this);

        return result;
    }

    /**
     * Call a function in this script.
     *
     * @param functionName Name of function
     * @param args         Arguments for function
     */
    protected void callFunction(final String functionName, final Object... args) {
        try {
            // Call Function
            final Invocable invEngine = (Invocable) engine;
            invEngine.invokeFunction(functionName, args);
        } catch (NoSuchMethodException nsme) {
            // There is no "methodExists" function, so we catch NoSuchMethodException
            // and do nothing rather that add an error every time a method is called
            // that doesn't exist (such as the action_* methods)
        } catch (ScriptException e) {
            LOG.info(USER_ERROR, "Error calling '{}' in '{}': {}",
                    functionName, file.getPath(), e.getMessage(), e);
        }
    }

    /**
     * Try to reload this script.
     *
     * @return True if script was reloaded
     */
    protected boolean reload() {
        // Tell the current engine that its about to be obliterated.
        callFunction("onPreRehash");

        try {
            // Try making a new engine
            engine = createEngine();
            // Tell it that it has been rehashed
            callFunction("onRehashSucess");
        } catch (ScriptException e) {
            LOG.info(USER_ERROR, "Reloading '{}' failed: {}", file.getPath(), e.getMessage(), e);
            // Tell it that its rehash failed
            callFunction("onRehashFailed", e);
            return false;
        }

        return true;
    }

}