/*
 * (C) Copyright 2006-2008 Nuxeo SAS (http://nuxeo.com/) and contributors.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser General Public License
 * (LGPL) version 2.1 which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl.html
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * Contributors:
 *     bstefanescu
 *
 * $Id$
 */

package org.nuxeo.ecm.webengine.scripting;

import groovy.lang.GroovyRuntimeException;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;
import javax.script.SimpleScriptContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.nuxeo.ecm.webengine.loader.WebLoader;

/**
 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
 */
public class Scripting {

    private static final Log log = LogFactory.getLog(Scripting.class);

    private final ConcurrentMap<File, Entry> cache = new ConcurrentHashMap<File, Entry>();

    // this will be lazy initialized
    private ScriptEngineManager scriptMgr;

    private final WebLoader loader;

    public Scripting(WebLoader loader) {
        this.loader = loader;
    }

    public static CompiledScript compileScript(ScriptEngine engine, File file) throws ScriptException {
        if (engine instanceof Compilable) {
            Compilable comp = (Compilable) engine;
            try {
                Reader reader = new FileReader(file);
                try {
                    return comp.compile(reader);
                } finally {
                    reader.close();
                }
            } catch (IOException e) {
                throw new ScriptException(e);
            }
        } else {
            return null;
        }
    }

    /**
     * Lazy init scripting manager to avoid loading script engines when no scripting is used.
     * <p>
     * Javax Scripting is not used by default in WebWengine, we are using directly the Groovy engine. This also fixes an
     * annoying pb on Mac in java5 due to AppleScripting which is failing to register.
     *
     * @return the scriptMgr
     */
    public ScriptEngineManager getEngineManager() {
        if (scriptMgr == null) {
            scriptMgr = new ScriptEngineManager();
        }
        return scriptMgr;
    }

    public boolean isScript(String ext) {
        return getEngineManager().getEngineByExtension(ext) != null;
    }

    public Object runScript(ScriptFile script) throws ScriptException {
        return runScript(script, null);
    }

    public Object runScript(ScriptFile script, Map<String, Object> args) throws ScriptException {
        if (log.isDebugEnabled()) {
            log.debug("## Running Script: " + script.getFile());
        }
        if ("groovy".equals(script.getExtension())) {
            try {
                return loader.getGroovyScripting().eval(script.file, args);
            } catch (GroovyRuntimeException e) {
                throw new ScriptException(e);
            }
        } else {
            return _runScript(script, args);
        }
    }

    // TODO: add an output stream to use as arg?
    protected Object _runScript(ScriptFile script, Map<String, Object> args) throws ScriptException {
        SimpleBindings bindings = new SimpleBindings();
        if (args != null) {
            bindings.putAll(args);
        }
        String ext = script.getExtension();
        // check for a script engine
        ScriptEngine engine = getEngineManager().getEngineByExtension(ext);
        if (engine != null) {
            ScriptContext ctx = new SimpleScriptContext();
            ctx.setBindings(bindings, ScriptContext.ENGINE_SCOPE);
            CompiledScript comp = getCompiledScript(engine, script.getFile()); // use cache for compiled scripts
            if (comp != null) {
                return comp.eval(ctx);
            } // compilation not supported - eval it on the fly
            try {
                Reader reader = new FileReader(script.getFile());
                try { // TODO use __result__ to pass return value for engine that doesn't returns like jython
                    Object result = engine.eval(reader, ctx);
                    if (result == null) {
                        result = bindings.get("__result__");
                    }
                    return result;
                } finally {
                    reader.close();
                }
            } catch (IOException e) {
                throw new ScriptException(e);
            }
        }
        return null;
    }

    public CompiledScript getCompiledScript(ScriptEngine engine, File file) throws ScriptException {
        Entry entry = cache.get(file);
        long tm = file.lastModified();
        if (entry != null) {
            if (entry.lastModified < tm) { // recompile
                entry.script = compileScript(engine, file);
                entry.lastModified = tm;
            }
            return entry.script;
        }
        CompiledScript script = compileScript(engine, file);
        if (script != null) {
            cache.putIfAbsent(file, new Entry(script, tm));
            return script;
        }
        return null;
    }

    class Entry {
        public CompiledScript script;

        public long lastModified;

        Entry(CompiledScript script, long lastModified) {
            this.lastModified = lastModified;
            this.script = script;
        }
    }

}