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/*******************************************************************************
 * Copyright (C) 2009, 2015, Danilo Pianini and contributors
 * listed in the project's build.gradle or pom.xml file.
 *
 * This file is distributed under the terms of the Apache License, version 2.0
 *******************************************************************************/
package org.danilopianini.io;

import java.io.File;

/**
 * This abstract class represents a Runnable able to recursively scan the
 * filesystem. For each File and Directory found, an abstract method is called.
 * Implement it to give the FileScanner the behavior you want.
 * 
 * 
 */
public abstract class AbstractFileScanner implements Runnable {

    private final File file;
    private final boolean followH;

    /**
     * @param f
     *            the file or directory to start with
     */
    public AbstractFileScanner(final File f) {
        this(f, true);
    }

    /**
     * @param f
     *            the file or directory to start with
     * @param followHidden
     *            true if the scanner should walk through hidden folders
     */
    public AbstractFileScanner(final File f, final boolean followHidden) {
        this.file = f;
        this.followH = followHidden;
    }

    /**
     * This method is called as soon as the scanning ends.
     */
    protected abstract void finish();

    /**
     * This method is called each time a directory is found.
     * 
     * @param directory the directory which has been found
     */
    protected abstract void foundDirectory(File directory);

    /**
     * This method is called each time a new file is found.
     * 
     * @param f the file which has been found
     */
    protected abstract void foundFile(File f);

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Runnable#run()
     */
    @Override
    public void run() {
        setup();
        scan(file);
        finish();
    }

    /**
     * This recursive method scans the filesystem.
     * 
     * @param f
     *            The directory or file to start with
     */
    protected void scan(final File f) {
        if (f.isDirectory() && (followH || !f.isHidden())) {
            foundDirectory(f);
            final File[] list = f.listFiles();
            if (list != null) {
                for (final File s : list) {
                    scan(s);
                }
            }
            exitDirectory(f);
        } else {
            foundFile(f);
        }
    }

    /**
     * Called every time the scanner exits a directory.
     * 
     * @param directory the directory which has been scanned
     */
    protected abstract void exitDirectory(File directory);

    /**
     * This method is called before starting the scanning.
     */
    protected abstract void setup();

}