LibrarySystem {
 (@
   
   public void Add_It (User us) {       /* Add User to the list of users */
     if(get_users() != null ) 
       get_users().set_first(new Nonempty_User_List ( us, get_users().get_first()));
     else 
       set_users( new User_List (new Nonempty_User_List( us , null )));
   }

   public void Add_It (Staff sf) {  /* Add Staff to the list of staff personell */
     if(get_staff() != null ) 
       get_staff().set_first(new Nonempty_Staff_List( sf, get_staff().get_first()));
     else 
       set_staff( new Staff_List ( new Nonempty_Staff_List ( sf, null )));
   }

  public void Add_It (BookEntry be , Integer num) { /* Add book entry */
    Copy_List list = new Copy_List();
    list.set_first( generate_list(num) );
    Book newbook = new Book( be, list ); 
    if(get_books() != null) {
      Nonempty_Book_List newlist = new
        Nonempty_Book_List ( newbook , get_books().get_first());
      get_books().set_first( newlist );
    }
    else {
      Nonempty_Book_List newlist = new Nonempty_Book_List ( newbook, null);
      set_books( new Book_List (newlist) );
    }
  } 
 
  private Nonempty_Copy_List generate_list (Integer  i) { /* service procedure */
    if (i.intValue() == 1) 
      return  new Nonempty_Copy_List ( new Copy (i,(User) null, new Boolean(true) ), null );
    else 
      return new Nonempty_Copy_List ( new Copy (i,(User) null, new Boolean(true)), 
                                      generate_list ( new Integer(i.intValue() - 1)) );
  }
        
 @)

 traversal PrintUsers (PrintingVisitor pv) {
   bypassing Book_List to-stop  User; }

 traversal Add_Copy (AddingVisitor av) {
   bypassing User_List to-stop Book; }

 traversal SearchBook (SearchingVisitorB svB) {
   bypassing User_List to-stop Book; } 
 
 traversal FindBook (SearchingVisitorISBN svISBN) {
   bypassing User_List to-stop Book; }

 traversal SearchUser (SearchingVisitorU svU) {
   bypassing Book_List to-stop User; }      

 traversal SearchStaff (SearchingVisitorS svS) {
   to-stop Staff; } 

} 

Book_List {

  traversal PrintBooks (PrintingVisitor pv) {
    to-stop { BookEntry, Copy }; }
}

Book {
  (@
    public Copy get_copy(Integer number) {
      Nonempty_Copy_List copy = get_copies().get_first();
      while(copy.get_it().get_number().equals(number) == false) 
        copy = copy.get_next();
      return copy.get_it();
    }
  
  @)
}
 
User {
  (@
    public void AddCheckOut(CheckedOut item) { /* Insert a book into the list of checked books */
      if(get_books() != null)
        try {
          Nonempty_CheckedOut_List current_item = get_books().get_first();
          do {
            if(current_item.get_it().get_entry().get_isbn().equals(item.get_entry().get_isbn()))
              throw new Exception("consistency violation");
            if( current_item.get_next() != null ) current_item = current_item.get_next();
          } while(current_item.get_next() != null);
          if(current_item.get_it().get_entry().get_isbn().equals(item.get_entry().get_isbn()))
              throw new Exception("consistency violation");
          item.get_copy().set_status( new Boolean(false) );  
          current_item.set_next( new Nonempty_CheckedOut_List ( item, null));
        } catch (Exception e) { System.out.println("can't check out this book - user has a copy of it");}
      else {
        item.get_copy().set_status( new Boolean(false) ); 
        set_books( new CheckedOut_List( new Nonempty_CheckedOut_List (item,null)));
      }
    }

    public void RemoveCheckOut(Ident isbn) { /* Removes book from the list of cheked out books */
      Nonempty_CheckedOut_List current = get_books().get_first();
      if(current.get_it().get_entry().get_isbn().equals(isbn))
        get_books().set_first(current.get_next());
      else {
       while (current.get_next().get_it().get_entry().get_isbn().equals(isbn) == false) 
         current = current.get_next();
       current.set_next(current.get_next().get_next());
      }
      set_nbooks( new Integer ( get_nbooks().intValue() -1 ));
    }
  @)

  traversal PrintCheckedOut(PrintingVisitor pv) {
      bypassing Copy to-stop BookEntry; }
}
  
ListOfCommands  {
  (@
    void Do_It(ActionVisitor av)  {
      try {
        this.AllCommands(new GuardingVisitor(av), av);
      } catch (Exception e) {
        av.set_lsystem(av.get_store());
      } 
      System.out.println(" ");
  
    }
  @)
  traversal AllCommands(GuardingVisitor gv, ActionVisitor av) {
      to  * ; }
}

ActionVisitor {                        
                     
  before Nonempty_Command_List (@
    System.out.println(" ");
  @)

  after Nonempty_Command_List (@
    set_store(get_lsystem());
  @)
  
  before UserType (@
    get_lsystem().Add_It(new User(host.get_name(),host.get_quota(),null,new Integer(0)));
    System.out.println (" Creating user account - USER:"+  host.get_name()+" ...");
  @)

  before StaffType (@
    get_lsystem().Add_It(new Staff(host.get_name(),host.get_password()));
    System.out.println (" Creating staff account - STAFF:"+ host.get_name()+" ...");
  @)

  before ListUsers (@             /* List Users Command */ 
    System.out.println (" Printing users ");
    System.out.println (" ------------------------ ");
    PrintingVisitor pv  = new PrintingVisitor();
    get_lsystem().PrintUsers(pv); 
  @)    

  before AddBook (@              /* Add Book Command   */
    get_lsystem().Add_It( host.get_entry() , host.get_number());
    System.out.println (" Adding book entry - Book:  "+ host.get_entry().get_title()+" ...");
  @)

  before AddCopy (@              /* Add additional copy of existing book */ 
    get_lsystem().Add_Copy(new AddingVisitor(host.get_isbn()));   
    System.out.println (" Adding copy of book - ISBN: "+ host.get_isbn()+" ..." );
  @)
      
  before ListBooks (@           /* Printing the list of books */
    System.out.println(" Printing books... ");
    get_lsystem().get_books().PrintBooks( new PrintingVisitor() );
  @)

  before AuthorSearch (@        /* Search book by author */
    SearchingVisitorB svB = new SearchingVisitorB (host.get_author(),null,null);
    get_lsystem().SearchBook(svB);
    System.out.println(" Looking for book by " + host.get_author() + "...");
    svB.get_books().PrintBooks( new PrintingVisitor() );    
  @)

  before SubjectSearch (@        /* Search book by subject */
    SearchingVisitorB svB = new SearchingVisitorB(null,host.get_subject(),null );
    get_lsystem().SearchBook(svB);
    System.out.println(" Looking for book about " + host.get_subject() + "...");
    svB.get_books().PrintBooks( new PrintingVisitor() );    
  @)

  before CheckOut (@		 /* Check out a copy of the book */
    SearchingVisitorISBN svISBN = new SearchingVisitorISBN (host.get_isbn(), null);
    get_lsystem().FindBook(svISBN);
    Copy copy = svISBN.get_book().get_copy(host.get_number());
    if(copy.get_status().equals(new Boolean(true))) {
      SearchingVisitorU svU = new SearchingVisitorU ( new User(host.get_name(),null,null,null));
      get_lsystem().SearchUser(svU);
      if(svU.get_user().get_nbooks().intValue() < svU.get_user().get_quota().intValue()) {
        svU.get_user().set_nbooks( new Integer(svU.get_user().get_nbooks().intValue() + 1 ));
        copy.set_borrower(svU.get_user());
        System.out.println(" Checking out book - ISBN:" + host.get_isbn() + " copy#" + 
                           host.get_number() + " for user:" + host.get_name() + " ...");
        svU.get_user().AddCheckOut(new CheckedOut(svISBN.get_book().get_entry(),copy));
      }
      else System.out.println(" can't exceed quota ");
    } 
    else System.out.println(" copy is not available "); 
  @)  

  before Return (@              /* Returning a copy of a book */
    SearchingVisitorISBN svISBN = new SearchingVisitorISBN (host.get_isbn(),null);
    get_lsystem().FindBook(svISBN);
    Copy copy = svISBN.get_book().get_copy(host.get_number());
    copy.set_status(new Boolean(true));
    copy.get_borrower().RemoveCheckOut(host.get_isbn());
    System.out.println(" Checking in book - ISBN:" + host.get_isbn()+" COPY#" +host.get_number());
  @)

  before ShowStatus (@        /* Show books borrowed by  user */
    SearchingVisitorU svU = new SearchingVisitorU(new User(host.get_name(),null,null,null)); 
    get_lsystem().SearchUser(svU);
    System.out.println(" Books borrowed by user " + host.get_name()+":"); 
    svU.get_user().PrintCheckedOut(new PrintingVisitor());
  @)

  before UserStatus (@      /* Show books borrowed by user - user version */
    SearchingVisitorU svU = new SearchingVisitorU(new User(get_user(),null,null,null)); 
    get_lsystem().SearchUser(svU);
    System.out.println(" Books borrowed by user " + get_user()+":"); 
    svU.get_user().PrintCheckedOut(new PrintingVisitor());
  @)

  before LastUser (@   /* Find out the user who checkes this book last */
    SearchingVisitorISBN svISBN = new SearchingVisitorISBN (host.get_isbn(),null);
    get_lsystem().FindBook(svISBN);
    System.out.println(" Book - ISBN:"+host.get_isbn()+" COPY#" + host.get_number() +
      "  has been last checked out by USER:" + 
      svISBN.get_book().get_copy(host.get_number()).get_borrower().get_name());
  @)

  before StartC  (@ /* Execute a sequence of commands from file specified */
    ListOfCommands commands = null;
    try {
      commands = ListOfCommands.parse(new FileInputStream(host.get_file().toString()));
    } catch (Exception e) { System.out.println("File not found");}   
    commands.Do_It(this);
  @)

  before UserMode (@ /* Switch to the User Mode */
    set_mode(new Integer(1));
    set_user(host.get_name());
    System.out.println(" user mode - USER:"+host.get_name());
  @)

  before StaffMode (@ /* Switch to the Staff Mode */
    SearchingVisitorS svS = new SearchingVisitorS(new Staff(host.get_name(), null));
    get_lsystem().SearchStaff(svS);
    if(svS.get_staff().get_password().equals(host.get_password())) {
      set_mode(new Integer(2));
      set_user(host.get_name());
      System.out.println(" staff mode - STAFF:" + host.get_name());
    }
    else 
      System.out.println(" error: check name and password and try again");
  @)

  before Logout (@
    System.out.println(" logging out ...");
    set_mode(new Integer(0));
  @)
 
}
	
GuardingVisitor {

  before StaffCommand (@
    if (get_av().get_mode().intValue() < 2 ) {
      System.out.println("permission denied - this command for staff use only");
      get_av().set_lsystem(null);
    }
  @)

  before UserCommand (@
    if (get_av().get_mode().intValue() < 1) {
      System.out.println("register as a user first...");
      get_av().set_lsystem(null);
    }
  @) 
}

SearchingVisitorB {

  before Book (@
    if ( host.get_entry().get_author().equals(get_author())  ||
         host.get_entry().get_subject().equals(get_subject()))
      if ( get_books() != null ) 
        get_books().set_first( new Nonempty_Book_List ( host , get_books().get_first()) );
      else 
        set_books(new Book_List (  new Nonempty_Book_List (host , null) ));
  @)
}

SearchingVisitorU {
  
  before User (@
    if ( host.get_name().equals(get_user().get_name()) )
       set_user(host);
  @)
}

SearchingVisitorS {

  before Staff (@
    if (host.get_name().equals(get_staff().get_name()) )
       set_staff(host);
  @)
}

SearchingVisitorISBN {

  before Book (@
    if ( host.get_entry().get_isbn().equals(get_isbn()) )
      set_book(host); 
  @)
} 

PrintingVisitor {             
  
  before User (@
    System.out.println (" USER:" + host.get_name() + "  QUOTA:" +host.get_quota() );
  @)
 
  before BookEntry (@
    System.out.println ("----------------------------------------");
    System.out.println ( "Book:  title:" + host.get_title()   + 
                               "    author:" + host.get_author()  +
                              "    subject:" + host.get_subject() +
                                 "    ISBN:" + host.get_isbn()        );
  @)

  after Nonempty_Copy_List (@
    String stat;
    if (host.get_it().get_status().equals(new Boolean(false))) stat = new String("checked out");
    else stat = new String("available");
    System.out.println ( "Copy  #" + host.get_it().get_number() + "   --   Status:" + stat );
  @)   	 

  after CheckedOut (@
    System.out.println ("Copy #"+host.get_copy().get_number());
  @)
}

AddingVisitor {

  before Book (@
    if( host.get_entry().get_isbn().equals(get_isbn()) ) { 
      Nonempty_Copy_List newlist = new Nonempty_Copy_List ( 
       new Copy (new Integer(host.get_copies().get_first().get_it().get_number().intValue() + 1),
                 null, new Boolean(true)),
        host.get_copies().get_first() );
      host.get_copies().set_first( newlist );
    }
   
    
  @)
}


Main {
(@
  static public void main(String args[]) throws Exception {

    System.out.println(" *** START *** ");
    LibrarySystem lsys = new LibrarySystem (null, null, null);
    DataInputStream in = new DataInputStream( System.in );
    ActionVisitor av = new ActionVisitor(lsys, new Integer(2), null, lsys);
    System.out.println("Welcome to the Library System");
    System.out.print("library>"); System.out.flush();
    String line = in.readLine();
    while (line.equals("QUIT") == false) {
      try {
      ListOfCommands commands = ListOfCommands.parse(line);
      commands.Do_It(av);
      } catch (Exception e) { System.out.println("Syntax Error"); }
      System.out.print("library>");System.out.flush();
      line = in.readLine();
    }
    System.out.println(" *** DONE *** ");
  }
@)
}