/*******************************************************************************
 *
 * Copyright (c) 2004-2010 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *
 *
 *******************************************************************************/ 

package hudson.util;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.io.Serializable;

/**
 * Visits files in a directory recursively.
 *
 * @since 1.343
 * @see DirScanner
 */
public abstract class FileVisitor {

    /**
     * Called for each file and directory that matches the criteria implied by
     * {@link DirScanner}
     *
     * @param f Either a file or a directory.
     * @param relativePath The file/directory name in question
     */
    public abstract void visit(File f, String relativePath) throws IOException;

    /**
     * Some visitors can handle symlinks as symlinks. Those visitors should
     * implement this method to provide a different handling for symlink. <p>
     * This method is invoked by those {@link DirScanner}s that can handle
     * symlinks as symlinks (not every {@link DirScanner}s are capable of doing
     * that, as proper symlink handling requires letting visitors decide whether
     * or not to descend into a symlink directory.
     */
    public void visitSymlink(File link, String target, String relativePath) throws IOException {
        visit(link, relativePath);
    }

    /**
     * Some visitors can handle symlinks as symlinks. Those visitors should
     * implement this method and return true to have callers invoke
     * {@link #visitSymlink(File, String, String)}
     */
    public boolean understandsSymlink() {
        return false;
    }

    /**
     * Decorates a visitor by a given filter.
     */
    public final FileVisitor with(FileFilter f) {
        if (f == null) {
            return this;
        }
        return new FilterFileVisitor(f, this);
    }

    private static final class FilterFileVisitor extends FileVisitor implements Serializable {

        private final FileFilter filter;
        private final FileVisitor visitor;

        private FilterFileVisitor(FileFilter filter, FileVisitor visitor) {
            this.filter = filter != null ? filter : PASS_THROUGH;
            this.visitor = visitor;
        }

        public void visit(File f, String relativePath) throws IOException {
            if (f.isDirectory() || filter.accept(f)) {
                visitor.visit(f, relativePath);
            }
        }
        private static final FileFilter PASS_THROUGH = new FileFilter() {
            public boolean accept(File pathname) {
                return true;
            }
        };
        private static final long serialVersionUID = 1L;
    }
}