package org.webslinger.commons.vfs;

 import java.util.concurrent.atomic.AtomicBoolean;

 import java.util.concurrent.atomic.AtomicInteger;

 import java.util.concurrent.atomic.AtomicMarkableReference;

 import java.util.concurrent.atomic.AtomicReference;

 import org.apache.commons.vfs.FileName;

 import org.apache.commons.vfs.FileObject;

 import org.apache.commons.vfs.FileSystemException;

 import org.apache.commons.vfs.FileSystemOptions;

 import org.apache.commons.vfs.FileType;

 import org.apache.commons.vfs.NameScope;

 import org.webslinger.commons.vfs.VFSUtil;

 import org.webslinger.util.TTLObject;

 public abstract class GenerationalFileSystem<N extends FileName, F extends GenerationalFileObject<N, F, R, S>, R extends GenerationalFileSystem.Resolution<N, F, R, S>, S extends GenerationalFileSystem<N, F, R, S>> extends LayeredFileSystem<N, F, S> {

     protected AtomicInteger generation = new AtomicInteger();

     public GenerationalFileSystem(N name, FileObject root, FileSystemOptions options) throws FileSystemException {

         super(name, root, options);

     }

     protected R resolve(F genFile, R resolution, boolean create) throws FileSystemException {

         int generation = this.generation();

         if (resolution != null && resolution.generation == generation && !resolution.isOutOfDate(create)) return resolution;

         return newResolution(generation, genFile);

     }

     protected R getResolution(F other, boolean create) throws FileSystemException {

         return other.getResolution(create);

     }

     public int generation() {

         return generation.get();

     }

     protected int newGeneration() {

         return generation.incrementAndGet();

     }

     protected abstract R newResolution(int generation, F file) throws FileSystemException;

     protected abstract F[] newArray(int length);

     public abstract static class Resolution<N extends FileName, F extends GenerationalFileObject<N, F, R, S>, R extends GenerationalFileSystem.Resolution<N, F, R, S>, S extends GenerationalFileSystem<N, F, R, S>> {

         public final int generation;

         public final F file;

         private final AtomicReference<FoundFile> foundFile = new AtomicReference<FoundFile>();

         protected Resolution(int generation, F file) {

             this.generation = generation;

             this.file = file;

         }

         private void refreshLocal() {

             foundFile.set(null);

         }

         protected boolean refresh() throws FileSystemException {

             refreshLocal();

             return false;

         }

         protected FileObject getFile(boolean create) throws FileSystemException {

             FoundFile oldFoundFile, newFoundFile;

             do {

                 oldFoundFile = foundFile.get();

                 if (oldFoundFile != null && (oldFoundFile.create == create || !create)) return oldFoundFile.file;

                 newFoundFile = new FoundFile(doGetFile(create), create);

             } while (!foundFile.compareAndSet(oldFoundFile, newFoundFile));

             return newFoundFile.file;

         }

         protected void delete() throws FileSystemException {

             doDelete();

             refreshLocal();

         }

         protected abstract boolean isWriteable() throws FileSystemException;

         protected abstract FileObject doGetFile(boolean create) throws FileSystemException;

         protected abstract boolean isOutOfDate(boolean create) throws FileSystemException;

         protected abstract void doDelete() throws FileSystemException;

         protected abstract String[] getChildNames() throws FileSystemException;

         protected void injectType(FileType newType) throws FileSystemException {

             refreshLocal();

         }

         protected final class FoundFile {

             public final boolean create;

             public final FileObject file;

             protected FoundFile(FileObject file, boolean create) {

                 this.file = file;

                 this.create = create;

             }

         }

     }

 }