/* 
  * Program featuring an arraylist to store and interactively manipulate a list of numbers. 
  */
 package arraylistplay;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.util.ArrayList;
 import java.util.Scanner;

 public class WordList {
     // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
     private static final int LIMIT = 1000;
     private static ArrayList<String> words = new ArrayList<>(LIMIT);
     private static int numberOfWords = 0;
     private static Scanner commandReader = new Scanner(System.in);


     public static void main(String[] args) {
         try {
             // ESTABLISH THE ARRAY OF WORDS
             readWords();
             // CHECK THE DATA
             // System.out.println("nThe original list of numbers ...");
             // displayNumbers();
             // ENTER THE INTERPRETER
             interpreter();
         } catch (FileNotFoundException ex) {
             System.out.println("The file was not found. Please think again.");
             System.exit(-1);
         }
     }
     // Assuming that the data file will be found in the public_html/data
     // subdirectory of the user’s home directory.
     private static Scanner establishScanner(String fn) throws FileNotFoundException {
         String separator = File.separator;
         String homeDirectory = System.getProperty("user.home");
         String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
         String fullFileName = path + fn;
         return new Scanner(new File(fullFileName));
     }

     private static void readWords() throws FileNotFoundException {
         Scanner scanner = establishScanner("WordSet.txt");
         while (scanner.hasNext()) {
             words.add(numberOfWords, scanner.next());
             numberOfWords = numberOfWords + 1;
         }
     }

     private static void displayWords() {
         for (int x = 0; x < numberOfWords; x = x + 1) {
             System.out.println(words.get(x));
         }
     }

     private static void interpreter() {
         System.out.print(">>> ");
         String command = commandReader.next();
         if (command.equalsIgnoreCase("DISPLAY")) {
             interpreterDisplayCommand();
         } else if (command.equalsIgnoreCase("PRINT")) {
             interpretPrintCommand();
         } else if (command.equalsIgnoreCase("SWAP")) {
             interpretSwapCommand();
         } else if (command.equalsIgnoreCase("ADD")) {
             interpretAddCommand();
         } else if (command.equalsIgnoreCase("HELP")) {
             interpretHelpCommand();
         } else if (command.equalsIgnoreCase("EXIT")) {
             System.exit(0);
         } else {
             System.out.println("### Unrecognizable command: " + command);
         }
         interpreter();
     }

     private static void interpreterDisplayCommand() {
         displayWords();
     }

     private static void interpretPrintCommand() {
         String operand = commandReader.next();
         if (operand.equalsIgnoreCase("FIRST")) {
             System.out.println(words.get(0));
         } else if (operand.equalsIgnoreCase("LAST")) {
             System.out.println(words.get(numberOfWords - 1));
         } else {
             int index = Integer.valueOf(operand);
             System.out.println(words.get(index - 1));
         }
     }
     private static void interpretHelpCommand() {
     System.out.println("HELP - display a menu of commands");
     System.out.println("DISPLAY - display the list of words");
     System.out.println("PRINT - print a word (FIRST;LAST;nth)");
     System.out.println("SWAP - exchange two elements (nth;mth)");
     System.out.println("ADD - add a word to the list (FIRST;LAST)");
     System.out.println("EXIT - terminate execution of the program");
     }

     private static void interpretSwapCommand() {
         int position1 = commandReader.nextInt();
         int position2 = commandReader.nextInt();
         String temp = words.get(position1 - 1);
         words.set(position1 - 1, words.get(position2 - 1));
         words.set(position2 - 1, temp);
     }
     private static void interpretAddCommand() {
         String position = commandReader.next();
         if (position.equalsIgnoreCase("LAST")) {
             addLast();
         } else if (position.equalsIgnoreCase("FIRST")) {
             addFirst();
         } else {
             System.out.println("### invalid operand for add command");
         }
         numberOfWords = numberOfWords + 1;
     }
     private static void addLast() {
         words.set(numberOfWords, commandReader.next());
     }
     private static void addFirst() {
         for (int x = numberOfWords; x > 0; x = x - 1) {
             words.set(x, words.get(x - 1));
         }
         words.set(0, commandReader.next());
     }
 }