/* 
  * program featuring an ArrayList to store and interactively manipulate a list of words. 
  */

 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 thus global to the method
       private static String inputFileName = "WordSet.txt";
       private static ArrayList<String> words = new ArrayList<>();
       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
               readWordsFromFile();

               // check the data
               System.out.println("The original list of words ...");
               displayWords();

               // 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 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 readWordsFromFile() throws FileNotFoundException {
           // equate a scanner with the input file
           Scanner scanner = establishScanner("WordSet.text");
           // read the words from the file into the ArrayList
           while (scanner.hasNext()) {
               words.add(scanner.next());
               // numberOfWords = numberOfWords + 1;
           }
       }

       private static void displayWords() {
           for (int x = 0; x < words.size(); 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(words.size()-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 numbers");
           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
           System.out.println("SWAP - exchange two elements (nth;mth)");
           System.out.println("ADD - add a number 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(position2-1);
           words.set(position2 - 1, words.get(position1 - 1));
           //System.out.println(temp);
           words.set(position1 - 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");
           }
       }

       private static void addLast() {
           words.set(words.size()-1,commandReader.next());
       }

       private static void addFirst() {
           words.add(0,commandReader.next());
       }
  }