package jalview.io;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;

public class BackupFilenameFilter implements FilenameFilter
{

  public String base;

  public String template;

  public int digits;

  public String extension;

  public BackupFilenameFilter(String base, String template, int digits,
          String extension)
  {
    this.base = base;
    this.template = template;
    this.digits = digits;
    this.extension = extension;
  }

  @Override
  public boolean accept(File dir, String filename)
  {
    boolean ret = false;
    try
    {
      File file = new File(
              dir.getCanonicalPath() + File.separatorChar + filename);
      if (file.isDirectory())
      {
        // backup files aren't dirs!
        return false;
      }
    } catch (IOException e)
    {
      System.out.println("IOException when checking file '" + filename
              + "' is a backupfile");
    }

    BackupFilenameParts bffp = new BackupFilenameParts(filename, base,
            template, digits, extension);
    ret = bffp.isBackupFile();
    return ret;
  }

}

class BackupFilenameParts
{
  String base;

  String templateStart;

  int num;

  int digits;

  String templateEnd;

  String extension;

  boolean isBackupFile;

  public BackupFilenameParts(File file, String base, String template, int digits,
          String extension)
  {
    this(file.getName(), base, template, digits, extension);
  }

  public BackupFilenameParts(String filename, String base, String template,
          int digits, String extension)
  {
    this.isBackupFile = false;

    // calculate minimum length of a backup filename
    int minlength = base.length() + template.length()
            - BackupFiles.NUM_PLACEHOLDER.length() + digits
            + extension.length();

    if (!(filename.startsWith(base) && filename.endsWith(extension)
            && filename.length() >= minlength))
    {
      // non-starter
      return;
    }

    int numcharstart = template.indexOf(BackupFiles.NUM_PLACEHOLDER);
    String templateStart = template;
    String templateEnd = "";
    if (numcharstart > -1)
    {
      templateStart = template.substring(0, numcharstart);
      templateEnd = template.substring(numcharstart + BackupFiles.NUM_PLACEHOLDER.length());
    }
    
    int startLength = base.length() + templateStart.length();
    int endLength = templateEnd.length() + extension.length();
    String numString = filename.substring(startLength,
            filename.length() - endLength);

    if (filename.length() >= startLength + digits + endLength
            && filename.startsWith(base + templateStart)
            && filename.endsWith(templateEnd + extension)
            && numString.matches("[0-9]+"))
    {
      this.base = base;
      this.templateStart = templateStart;
      this.num = Integer.parseInt(numString);
      this.digits = digits;
      this.templateStart = templateStart;
      this.templateEnd = templateEnd;
      this.isBackupFile = true;
    }
    
  }

  public static String getBackupFilename(int index, String base,
          String template,
          int digits, String extension)
  {
    String numString = String.format("%0" + digits + "d", index);
    String backupSuffix = template.replaceAll(BackupFiles.NUM_PLACEHOLDER,
            numString);
    String backupfilename = base + backupSuffix + extension;
    return backupfilename;
  }

  public boolean isBackupFile()
  {
    return this.isBackupFile;
  }

  public int indexNum()
  {
    return this.num;
  }
}