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

/* Java application for the purpose of testing the behavior of
** instances of the ReversibleCounter class.
** Author: R. McCloskey, Sept. 2025
*/

public class RevCounterTester {

   // User commands
   private static final char QUIT = 'Q';
   private static final char HELP = 'H';
   private static final char INCREMENT = 'I';
   private static final char DECREMENT = 'D';
   private static final char TOGGLE = 'T';

   private static Scanner input;
   private static boolean echo;
   private static boolean keepGoing;
   private static ReversibleCounter revCounter;

   public static void main(String[] args) throws FileNotFoundException { 

      System.out.println("Welcome to the RevCounterTester program.\n");
   
      // Establish the source of input to which the Scanner is attached.
      // If a command line argument is provided, it is taken to be the
      // name of a file from which to read input.  Otherwise input will
      // be read from the standard input (i.e., the keyboard).
      establishInputSource(args);

      // Make a new instance of ReversibleCounter
      revCounter = makeNewRevCounter();
      System.out.printf("After initialization, %s\n\n", revCounter);
   
      printHelp();

      keepGoing = true;
      while (keepGoing) {
         try {
            performCommand();
            System.out.println(revCounter);
         }
         catch (Exception e) {
            e.printStackTrace(System.out);
         }
      }
      System.out.println("Goodbye.");
   }

   private static void performCommand() {
      // prompt for and get input
      String response = getInput("\n> ").trim().toUpperCase();  
      char command = response.charAt(0);

      if (command == QUIT) { keepGoing = false; }
      else if (command == HELP) { printHelp(); }
      else if (command == INCREMENT) { revCounter.increment(); }
      else if (command == DECREMENT) { revCounter.decrement(); }
      else if (command == TOGGLE) { revCounter.toggleMode(); }
      else { System.out.println("Unknown command; ignoring;"); }
   }

   private static void printHelp() {
      System.out.println("Available commands:");
      System.out.println("-------------------");
      System.out.println(QUIT + " (Quit)");
      System.out.println(HELP + " (Help)");
      System.out.println(INCREMENT + " (Increment)");
      System.out.println(DECREMENT + " (Decrement)");
      System.out.println(TOGGLE + " (Toggle the mode)");
   }   

   /* Prompts for an initial count value to be entered and then returns
   ** a new ReversibleCounter object with that initial value.
   */
   private static ReversibleCounter makeNewRevCounter() {
      ReversibleCounter result = null;
      String response = getInput("Enter initial count value: ").trim();
      try {
         if (response.length() == 0) { 
            result = new ReversibleCounter();
         }
         else {
            int val = Integer.parseInt(response);
            result = new ReversibleCounter(val);
         }
      }
      catch (Exception e) {
         e.printStackTrace(System.out);
         System.out.println("\nInvalid input: Program aborting.");
         System.exit(0);
      }
      return result;
   }


   /* Prints a prompt and returns a line of input read from the input Scanner.
   */
   private static String getInput(String prompt) {
      System.out.print(prompt);
      String result = input.nextLine();
      if (echo) { System.out.println(result); }
      return result;
   }

   /* Establishes the source of input from which the Scanner ('input') 
   ** will read.  If args[] is not empty, the file whose name is args[0]
   ** will be the input source.  Otherwise it will be the keyboard.
   */
   private static void establishInputSource(String[] args) {
      if (args.length != 0) {
         try {
            input = new Scanner(new File(args[0]));
            echo = true;
         }
         catch (FileNotFoundException e) {
            e.printStackTrace();
            System.out.println("File named " + args[0] + " not found");
            System.exit(0);
         }
      }
      else {
         input = new Scanner(System.in);
         echo = false;
      }
   }

}