/*
 * 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.apache.myfaces.extensions.scripting.core.api;

import org.apache.myfaces.extensions.scripting.core.api.eventhandling.WeavingEvent;
import org.apache.myfaces.extensions.scripting.core.api.eventhandling.WeavingEventListener;
import org.apache.myfaces.extensions.scripting.core.api.eventhandling.events.BeginCompiling;
import org.apache.myfaces.extensions.scripting.core.api.eventhandling.events.EndCompiling;
import org.apache.myfaces.extensions.scripting.core.common.util.ClassUtils;
import org.apache.myfaces.extensions.scripting.core.common.util.ReflectUtil;
import org.apache.myfaces.extensions.scripting.core.engine.FactoryEngines;
import org.apache.myfaces.extensions.scripting.core.engine.ThrowAwayClassloader;
import org.apache.myfaces.extensions.scripting.core.engine.api.ClassScanner;
import org.apache.myfaces.extensions.scripting.core.engine.api.CompilationResult;
import org.apache.myfaces.extensions.scripting.core.engine.api.ScriptingEngine;
import org.apache.myfaces.extensions.scripting.core.monitor.ClassResource;
import org.apache.myfaces.extensions.scripting.core.monitor.WatchedResource;
import org.apache.myfaces.extensions.scripting.core.reloading.GlobalReloadingStrategy;
import org.apache.myfaces.extensions.scripting.core.reloading.MethodLevelReloadingHandler;

import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.logging.Logger;

/**
 * @author Werner Punz (latest modification by $Author$)
 * @version $Revision$ $Date$
 *          <p/>
 *          Central weaving context
 */

public class WeavingContext
{
    static final Logger log = Logger.getLogger(WeavingContext.class.getName());

    /**
     * lock var which can be used for recompilation
     */
    public AtomicBoolean recompileLock = new AtomicBoolean(false);
    /**
     * configuration which stores all external configuration entries
     */
    protected Configuration configuration = new Configuration();

    //ClassDependencies _dependencyMap = new ClassDependencies();
    /**
     * Service provider for the implementation under which this extension
     * runs
     */
    volatile ImplementationService _implementation = null;
    /**
     * the collection of reloading strategies depending on their artifact type
     */
    GlobalReloadingStrategy _reloadingStrategy = new GlobalReloadingStrategy();
    /**
     * the annotation scanning reference
     */
    ClassScanner _annotationScanner = null;

    /**
     * true only if the startup has performed without errors
     */
    boolean _scriptingEnabled = true;

    /**
     * holder for various operations within our lifecycle
     */
    ConcurrentHashMap<String, Long> lifecycleRegistry = new ConcurrentHashMap<String, Long>();

    WeakHashMap<WeavingEventListener, String> _listeners = new WeakHashMap<WeavingEventListener, String>();


    /**
     * This is a log which keeps track of the taints
     * over time, we need that mostly for bean refreshes
     * in multiuser surroundings, because only tainted beans need
     * to be refreshed.
     * Now if a user misses multiple updates he has to get a full
     * set of changed classes to be able to drop all personal scoped beans tainted
     * since the he refreshed last! Hence we have to move away from our
     * two dimensional &lt;class, taint&gt; to a three dimensional &lt;class, taint, time&gt;
     * view of things
     */
    private List<TaintingHistoryEntry> _taintLog = Collections.synchronizedList(new LinkedList<TaintingHistoryEntry>());

    /**
     * compilation results holder for the compiler listeners (components etc...)
     */
    private static final Map<Integer, CompilationResult> _compilationResults = new ConcurrentHashMap<Integer, CompilationResult>();

    /**
     * we keep a 10 minutes timeout period to keep the performance in place
     */
    private final long TAINT_HISTORY_TIMEOUT = 10 * 60 * 1000;

    /**
     * internal class used by our own history log
     */
    static class TaintingHistoryEntry
    {
        long _timestamp;
        ClassResource _data;

        public TaintingHistoryEntry(ClassResource data)
        {
            _data = data;
            _timestamp = System.currentTimeMillis();
        }

        public long getTimestamp()
        {
            return _timestamp;
        }

        public ClassResource getData()
        {
            return _data;
        }
    }

    
    public void addListener(WeavingEventListener listener) {
        if(!_listeners.containsKey(listener)) {
            _listeners.put(listener,"");
        }
    }
    
    public void removeListener(WeavingEventListener listener) {
        _listeners.remove(listener);
    }
    
    public void sendWeavingEvent(WeavingEvent evt) {
        for(WeavingEventListener listener: _listeners.keySet()) {
            listener.onEvent(evt);
        }
    }
    
    public void initEngines() throws IOException
    {
        FactoryEngines.getInstance().init();
        initScanner();
    }

    public void initScanner()
    {
        try
        {
            Class scanner = ClassUtils.getContextClassLoader().loadClass("org.apache.myfaces.extensions.scripting.jsf.annotation.GenericAnnotationScanner");
            this._annotationScanner = (ClassScanner) ReflectUtil.instantiate(scanner);

        }
        catch (ClassNotFoundException e)
        {
            //we do nothing here
            //generic annotation scanner can be missing in jsf 1.2 environments
            //_logger.log(Level.FINER, "", e);
        }
    }

    public Collection<ScriptingEngine> getEngines()
    {
        return FactoryEngines.getInstance().getEngines();
    }

    public ScriptingEngine getEngine(int engineType)
    {
        return FactoryEngines.getInstance().getEngine(engineType);
    }

    public ScriptingEngine getAssociatedEngine(Object artifact) {
        for(ScriptingEngine engine : getEngines()) {
            if(engine.isArtifactOfEngine(artifact)) return engine;
        }
        return null;
    }
    
    
    /**
     * returns the mitable watche resource maps for the various engines
     *
     * @return
     */
    public Map<Integer, Map<String, ClassResource>> getWatchedResources()
    {
        Map<Integer, Map<String, ClassResource>> ret = new HashMap<Integer, Map<String, ClassResource>>();
        for (ScriptingEngine engine : getEngines())
        {
            ret.put(engine.getEngineType(), engine.getWatchedResources());
        }
        return ret;
    }

    /**
     * @return a map of all watched resources over all engines
     */
    public Map<String, ClassResource> getAllWatchedResources()
    {
        Map<String, ClassResource> ret = new HashMap<String, ClassResource>();
        for (ScriptingEngine engine : getEngines())
        {
            Map<String, ClassResource> watchedResourceMap = engine.getWatchedResources();
            for (Map.Entry<String, ClassResource> entry : watchedResourceMap.entrySet())
            {
                ret.put(entry.getKey(), entry.getValue());
            }
        }
        return ret;
    }

    /**
     * @param key the watched resource classname
     * @return the watched resource from the given key or null
     */
    public ClassResource getWatchedResource(String key)
    {
        for (ScriptingEngine engine : getEngines())
        {
            if (!engine.getWatchedResources().containsKey(key)) continue;
            return engine.getWatchedResources().get(key);
        }
        return null;
    }

    public Collection<ClassResource> getTaintedClasses(int scriptingEngine) {
            Map<String, ClassResource> watchedResources = getEngine(scriptingEngine).getWatchedResources();
            List<ClassResource> res = new LinkedList<ClassResource>();
            for(Map.Entry<String, ClassResource> entry: watchedResources.entrySet()) {
                if(entry.getValue().isTainted()) {
                    res.add(entry.getValue());
                }
            }
            return res;
        }


    public Collection<ClassResource> getTaintedClasses() {
        Map<String, ClassResource> watchedResources = getAllWatchedResources();
        List<ClassResource> res = new LinkedList<ClassResource>();
        for(Map.Entry<String, ClassResource> entry: watchedResources.entrySet()) {
            if(entry.getValue().isTainted()) {
                res.add(entry.getValue());
            }
        }
        return res;
    }
    
    /**
     * checks if a resource idenified by key is tainted
     *
     * @param key the identifier for the resource
     * @return true in case of being tainted
     */
    public boolean isTainted(String key)
    {
        ClassResource res = getWatchedResource(key);
        if (res == null) return false;
        return res.isTainted();
    }

    public Set<String> loadPossibleDynamicClasses()
    {
        return getAllWatchedResources().keySet();
    }

    public Configuration getConfiguration()
    {
        return configuration;
    }

    public void setConfiguration(Configuration configuration)
    {
        this.configuration = configuration;
    }

    public boolean needsRecompile()
    {
        for (ScriptingEngine engine : getEngines())
        {
            //log.info("[EXT-SCRIPTING] scanning " + engine.getEngineType() + " files");
            if (engine.needsRecompile()) return true;
            //log.info("[EXT-SCRIPTING] scanning " + engine.getEngineType() + " files done");
        }
        return false;
    }

    public void fullScan()
    {
        for (ScriptingEngine engine : getEngines())
        {
            engine.scanForAddedDeleted();
        }
        //the scanner scans only the tainted classes
        //hence this should work whatever happens

    }

    public void annotationScan()
    {
        if (_annotationScanner != null)
            _annotationScanner.scanPaths();
    }

    public boolean compile()
    {
        boolean compile = false;
        for (ScriptingEngine engine : getEngines())
        {
            if (!engine.needsRecompile()) continue;
            sendWeavingEvent(new BeginCompiling());

            compile = true;
            log.info("[EXT-SCRIPTING] compiling " + engine.getEngineTypeAsStr() + " files");
            CompilationResult result = engine.compile();
            if(result != null) {
                WeavingContext.getInstance().setCompilationResult(engine.getEngineType(), result);
            }
            sendWeavingEvent(new EndCompiling());
            log.info("[EXT-SCRIPTING] compiling " + engine.getEngineTypeAsStr() + " files done");
        }
        return compile;
    }

    public void scanDependencies()
    {
        for (ScriptingEngine engine : getEngines())
        {
            if (engine.isTainted())
            {
                log.info("[EXT-SCRIPTING] scanning " + engine.getEngineTypeAsStr() + " dependencies");
                engine.scanDependencies();
                log.info("[EXT-SCRIPTING] scanning " + engine.getEngineTypeAsStr() + " dependencies end");
            }
        }
    }

    public void markTaintedDependends()
    {
        for (ScriptingEngine engine : getEngines())
        {
            engine.markTaintedDependencies();
        }
    }

    public WatchedResource getResource(String className)
    {
        WatchedResource ret = null;
        for (ScriptingEngine engine : getEngines())
        {
            ret = engine.getWatchedResources().get(className);
            if (ret != null) return ret;
        }
        return ret;
    }

    public boolean isDynamic(Class clazz)
    {
        return (clazz.getClassLoader() instanceof ThrowAwayClassloader)/*<> || (clazz.getClassLoader() instanceof
            ScannerClassloader))*/;
    }

    /**
     * we create a proxy to an existing object
     * which does reloading of the internal class
     * on method level
     * <p/>
     * this works only on classes which implement contractual interfaces
     * it cannot work on things like the navigation handler
     * which rely on base classes
     *
     * @param o            the source object to be proxied
     * @param theInterface the proxying interface
     * @param artifactType the artifact type to be reloaded
     * @return a proxied reloading object of type theInterface
     */
    public Object createMethodReloadingProxyFromObject(Object o, Class theInterface, int artifactType)
    {
        //if (!isScriptingEnabled()) {
        //    return o;
        //}
        return Proxy.newProxyInstance(o.getClass().getClassLoader(),
                new Class[]{theInterface},
                new MethodLevelReloadingHandler(o, artifactType));
    }

    public Class forName(String name) {
        return _implementation.forName(name);
    }
    
    /**
     * reload the class dynamically
     */
    public Class reload(Class clazz)
    {
        if (!isDynamic(clazz)) return clazz;
        ClassResource resource = (ClassResource) getResource(clazz.getName());
        if (resource == null) return clazz;
        if (resource.isTainted() || resource.getAClass() == null)
        {
            clazz = _implementation.forName(clazz.getName());
            //TODO not needed anymore, done by the forName now
            resource.setAClass(clazz);
        }
        return clazz;
    }

    public Object reload(Object instance,  int strategyType)
    {
        int engineType = getAssociatedEngine(instance).getEngineType();

        return _reloadingStrategy.reload(instance, engineType, strategyType);
    }

    /**
     * we create a proxy to an existing object
     * which does reloading of the internal class
     * on newInstance level
     *
     * @param o            the original object
     * @param theInterface the proxy interface
     * @param artifactType the artifact type to be handled
     * @return the proxy of the object if scripting is enabled, the original one otherwise
     */
    @SuppressWarnings("unused")
    public static Object createConstructorReloadingProxyFromObject(Object o, Class theInterface, int artifactType)
    {
        //if (!isScriptingEnabled()) {
        //    return o;
        //}
        return Proxy.newProxyInstance(o.getClass().getClassLoader(),
                new Class[]{theInterface},
                new MethodLevelReloadingHandler(o, artifactType));
    }

    /**
     * un-mapping of a proxied object
     *
     * @param o the proxied object
     * @return the un-proxied object
     */
    public static Object getDelegateFromProxy(Object o)
    {
        if (o == null)
        {
            return null;
        }
        if (o instanceof Decorated)
            return ((Decorated) o).getDelegate();

        if (!Proxy.isProxyClass(o.getClass())) return o;
        InvocationHandler handler = Proxy.getInvocationHandler(o);
        if (handler instanceof Decorated)
        {
            return ((Decorated) handler).getDelegate();
        }
        return o;
    }

    public void addDependency(int engineType, String fromClass, String toClass)
    {
        //TODO implement this tomorrow
    }

    protected ImplementationService getImplementationSPI() {
        return ServiceLoader.load(ImplementationService.class).iterator().next(); //MyFacesSPI.getInstance();
    }

    //----------------------------------------------------------------------
    //lifecycle related tasks
    public boolean isPostInit()
    {
        return (lifecycleRegistry.get("LIFECYCLE_POST_INIT") != null);
    }

    public void markPostInit()
    {
        lifecycleRegistry.put("LIFECYCLE_POST_INIT", System.currentTimeMillis());
    }

    public void markLastTaint()
    {
        lifecycleRegistry.put("LIFECYCLE_LAST_TAINTED", System.currentTimeMillis());
    }

    /**
     * @return the time value of the last taint happening
     */
    public long getLastTaint()
    {
        Long lastTainted = lifecycleRegistry.get("LIFECYCLE_LAST_TAINTED");
        lastTainted = (lastTainted != null) ? lastTainted : -1L;
        return lastTainted;
    }

    /**
     * marks the last annotation scan
     */
    public void markLastAnnotationScan()
    {
        lifecycleRegistry.put("LIFECYCLE_LAST_ANN_SCAN", System.currentTimeMillis());
    }

    /**
     * @return a the time value of the last annotation scan
     */
    public long getLastAnnotationScan()
    {
        Long lastTainted = lifecycleRegistry.get("LIFECYCLE_LAST_ANN_SCAN");
        lastTainted = (lastTainted != null) ? lastTainted : -1L;
        return lastTainted;
    }

    //------------------------------ tainting history entries -----------------------

    /**
     * adds a new entry into our taint log
     * which allows us to access tainting data
     * from a given point in time
     *
     * @param data the tainting data to be added
     */
    public void addTaintLogEntry(ClassResource data)
    {
        _taintLog.add(new TaintingHistoryEntry(data));
    }

    /**
     * garbage collects our tainting data
     * and removes all entries which are not
     * present anymore due to timeout
     * this gc code is called asynchronously
     * from our tainting thread to keep the
     * performance intact
     */
    public void gcTaintLog()
    {
        long timeoutTimestamp = System.currentTimeMillis() - TAINT_HISTORY_TIMEOUT;
        Iterator<TaintingHistoryEntry> it = _taintLog.iterator();

        while (it.hasNext())
        {
            TaintingHistoryEntry entry = it.next();
            if (entry.getTimestamp() < timeoutTimestamp)
            {
                it.remove();
            }
        }
    }

    /**
     * returns the last noOfEntries entries in the taint history
     *
     * @param noOfEntries the number of entries to be delivered
     * @return a collection of the last &lt;noOfEntries&gt; entries
     */
    public Collection<ClassResource> getLastTainted(int noOfEntries)
    {
        Iterator<TaintingHistoryEntry> it = _taintLog.subList(Math.max(_taintLog.size() - noOfEntries, 0), _taintLog.size()).iterator();
        List<ClassResource> retVal = new LinkedList<ClassResource>();
        while (it.hasNext())
        {
            TaintingHistoryEntry entry = it.next();
            retVal.add(entry.getData());
        }
        return retVal;
    }

    /**
     * Returns a set of tainting data from a given point in time up until now
     *
     * @param timestamp the point in time from which the tainting data has to be derived from
     * @return a set of entries which are a union of all points in time beginning from timestamp
     */
    public Collection<ClassResource> getTaintHistory(long timestamp)
    {
        List<ClassResource> retVal = new LinkedList<ClassResource>();
        Iterator<TaintingHistoryEntry> it = _taintLog.iterator();

        while (it.hasNext())
        {
            TaintingHistoryEntry entry = it.next();
            if (entry.getTimestamp() >= timestamp)
            {
                retVal.add(entry.getData());
            }
        }
        return retVal;
    }

    /**
     * Returns a set of tainted classes from a given point in time up until now
     *
     * @param timestamp the point in time from which the tainting data has to be derived from
     * @return a set of classnames which are a union of all points in time beginning from timestamp
     */
    public Set<String> getTaintHistoryClasses(long timestamp)
    {
        Set<String> retVal = new HashSet<String>();
        Iterator<TaintingHistoryEntry> it = _taintLog.iterator();

        while (it.hasNext())
        {
            TaintingHistoryEntry entry = it.next();
            if (entry.getTimestamp() >= timestamp)
            {
                if (entry.getData() instanceof ClassResource)
                {
                    retVal.add(((ClassResource) entry.getData()).getAClass().getName());
                } else
                {
                    retVal.add(entry.getData().getFile().getAbsolutePath());
                }
            }
        }
        return retVal;
    }

    protected static WeavingContext _instance = new WeavingContext();

    public static WeavingContext getInstance()
    {
        return _instance;
    }

    public ImplementationService getImplementation()
    {
        if(_implementation == null) {
            _implementation = getImplementationSPI();
        }
        return _implementation;
    }

    public void setImplementation(ImplementationService implementation)
    {
        _implementation = implementation;
    }

    public boolean isScriptingEnabled()
    {
        return _scriptingEnabled;
    }

    public void setScriptingEnabled(boolean scriptingEnabled)
    {
        _scriptingEnabled = scriptingEnabled;
    }

    public CompilationResult getCompilationResult(Integer scriptingEngine)
    {
        return _compilationResults.get(scriptingEngine);
    }

    public void setCompilationResult(Integer scriptingEngine, CompilationResult result)
    {
        _compilationResults.put(scriptingEngine, result);
    }

}