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


 package arrayplay;

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

 public class WordList {

     // variables local to the class and thus global to the method
     private static final int LIMIT = 1000;
     private static String inputFileName = "WordSet.txt";
     private static String[] words = new String [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
             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 an over-sized array
         String[] temp = new String[LIMIT];
         int index = 0;
         while (scanner.hasNext()) {
             String word = scanner.next();
             temp[index] = word;
             index = index + 1;
         }
         numberOfWords = index;
         // transfer the words into a perfectly sized array
         for (int x = 0; x < numberOfWords; x = x+1) {
             words[x] = temp[x];
         }
     }

     private static void displayWords() {
         for (int x = 0; x < numberOfWords; x = x + 1) {
             System.out.println(words[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[0]);
         } else if (operand.equalsIgnoreCase("LAST")) {
             System.out.println(words[numberOfWords-1]);
         } else {
             int index = Integer.valueOf(operand);
             System.out.println(words[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[position1 - 1];
         words[position1 - 1] = words[position2 - 1];
         words[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[numberOfWords] = commandReader.next();
     }

     private static void addFirst() {
         for (int x = numberOfWords; x > 0; x = x-1) {
             words[x] = words[x -1];
         }
         words[0] = commandReader.next();
     }
  }