import java.io.*;

public class BackupJob implements Runnable {

    private File startDir;
    private File destDir;
    private Filter filter;

    public BackupJob(File s, File d){
        this(s, d, null);
    }

    public BackupJob(File s, File d, Filter f){
        startDir = s;
        destDir = d;
        filter = f;
    }

    @Override
    public void run() {
        try {
            validateDirectory(startDir);
            validateDirectory(destDir);

            File[] contents = startDir.listFiles();

            for (int i = 0; i < contents.length; i++){
                recurse(contents[i]);
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private void recurse(File file){
        if (!filter.isAcceptable(file))
            return;

        File dest = new File (destDir, getRelPath(file, startDir));

        if (file.isDirectory()){
            if(!dest.exists()){
                dest.mkdirs();
                File [] contents = file.listFiles();

                for (int i = 0; i < contents.length; i++){
                    recurse(contents[i]);
                }
            }
        } else {
            if(dest.exists() && dest.lastModified() >= file.lastModified()
                    && dest.length() == file.length()){
                System.out.println("File exists, not copied.");
            } else {
                dest.getParentFile().mkdirs();
                CopyJob cj = new CopyJob(file, dest);
                //TODO: get job to pool
            }
        }
    }

    //returns the path of f relative to the given root directory
    private String getRelPath (File f, File root){
        String p = f.getAbsolutePath();
        return p.replace(f.getParent(), "");
    }

    /**
     * Directory is valid if it exists, does not represent a file, and can be read.
     */
     private void validateDirectory (File aDirectory) throws FileNotFoundException {
       if (aDirectory == null) {
         throw new IllegalArgumentException("Directory should not be null.");
       }
       if (!aDirectory.exists()) {
         throw new FileNotFoundException("Directory does not exist: " + aDirectory);
       }
       if (!aDirectory.isDirectory()) {
         throw new IllegalArgumentException("Is not a directory: " + aDirectory);
       }
       if (!aDirectory.canRead()) {
         throw new IllegalArgumentException("Directory cannot be read: " + aDirectory);
       }
     }
}