package jalview.io;

import java.io.File;

public class BackupFilenameParts
{
  String base;

  String templateStart;

  int num;

  int digits;

  String templateEnd;

  boolean isBackupFile;

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

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

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

    if (!(filename.startsWith(base) && 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();
    String numString = filename.substring(startLength,
            filename.length() - endLength);

    if (filename.length() >= startLength + digits + endLength
            && filename.startsWith(base + templateStart)
            && filename.endsWith(templateEnd)
            && 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 boolean isBackupFile()
  {
    return this.isBackupFile;
  }

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