import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

/* Java application whose purpose is to test the methods of the 
** IndexedSequence class (the generic version of the solution to
** CMPS 144, Spring 2019, Prog. Assg. #1).
**
** Author: R. McCloskey
** Date: February 2019
*/
public class IndSeqTester {

   private static char NEW_CODE = 'N';
   private static char GET_CODE = 'G';
   private static char PUT_CODE = 'P';
   private static char DISPLAY_CODE = 'D';
   private static char HELP_CODE = 'H';
   private static char QUIT_CODE = 'Q';

   private static Scanner input;
   private static boolean echo;

   private static IndexedSequence<String> seqOfStr;

   public static void main(String[] args) throws FileNotFoundException {
      // Establish the Scanner so that it reads from either the file whose name
      // was provided as a command-line argument or, absent any such argument,
      // from the keyboard.
      if (args.length != 0) {
         input = new Scanner(new File(args[0]));
         echo = true;
      }   
      else {  // no command line arg to specify input file name
         input = new Scanner(System.in);
         echo = false;
      }   

      performCommands();
      System.out.println("\nGoodbye.");
   }

   /* Processes commands provided as input, applying them to the sequence
   ** referred to by the global variable seqOfStr.
   ** Aside from the Quit ('Q') and Help ('H') commands, there is 'N' 
   ** (to make a new sequence via the constructor), 'G' (to call get()), 
   ** 'P' (to call put()), and 'D' (to display the sequence).
   ** Examples:
   **   "N 15 -4" : creates a sequence of length 14 with starting index -4
   **   "G 5" : retrieves (and prints) the item at position 5
   **   "P 4 17" : places 17 at position 4
   **   "D" : displays the sequence
   */
   private static void performCommands() {

      boolean keepGoing = true;
      while (keepGoing) {
         try {
            System.out.print("\nEnter command (H for help): ");
            String command = input.next();
            if (echo) { System.out.println(command); }

            char operation = command.charAt(0);
            //String rest = command.substring(1).trim();

            if (operation == NEW_CODE) { performNew(); }
            else if (operation == GET_CODE) { performGet(); }
            else if (operation == PUT_CODE) { performPut(); }
            else if (operation == DISPLAY_CODE) { performDisplay(); }
            else if (operation == HELP_CODE) { printHelp(); }
            else if (operation == QUIT_CODE) { keepGoing = false; }
            else {
               System.out.println(operation + " is not a known operation code");
               input.nextLine();
            }
         }
         catch (NullPointerException e) {
            e.printStackTrace(System.out);
            if (seqOfStr == null) {
               System.out.println("First use the " + NEW_CODE + 
                                  " command to create a new sequence.");
            }
         }
         catch (Exception e) {
            e.printStackTrace(System.out);
         }
      }
   }

   private static void performNew() {
       int len = input.nextInt();
       int startIndex = input.nextInt();
       input.nextLine();
       System.out.printf("Creating new sequence of length %d " +
                         "with index range starting at %d\n",
                         len, startIndex);
       seqOfStr = new IndexedSequence<String>(len, startIndex);
   }

   private static void performGet() {
      int pos = input.nextInt();
      input.nextLine();
      System.out.printf("String at position %d is %s\n",
                        pos, seqOfStr.get(pos));
   }

   private static void performPut() {
      int pos = input.nextInt();
      String str = input.next();  // a String
      input.nextLine();
      System.out.printf("Putting %s at position %d\n", str, pos);
      seqOfStr.put(pos, str);
   }

   private static void performDisplay() {
      System.out.println(seqOfStr.toString());
      input.nextLine();
   }

   private static void printHelp() {
      System.out.println("Examples of commands:");
      System.out.println("  N 8 5  (to create a new sequence with range 5..12");
      System.out.println("  G 10   (to retrieve element at position 10)");
      System.out.println("  P 7 Glork (to put \"Glork\" into position 7)");
      System.out.println("  D      (to display the sequence)");
      System.out.println("  Q      (to quit)");
   }

}