/* 
 * Program featuring an array to store and interactively manipulate a list of numbers. 
 */
package arrayplay;

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

public class NumberList {
    //Variable local to the class and hence global to the methods
    private static final int LIMIT = 1000;
    private static int [] numbers = new int[LIMIT];
    private static int numberOfNumbers = 0;
    private static Scanner commandReader = new Scanner(System.in);

    public static void main(String[] args){
        try {
            //Establish the array of numbers...
            readNumbers();
            //Check the data
            System.out.println("The Original List of Numbers...");
            displayNumbers();
            //Enter the interpreter
            interpreter();
        } catch (FileNotFoundException ex) {
            System.out.println("The file wasn't found. Please try again.");
            System.exit(-1);
        }
    }

    private static void displayNumbers() {
        for (int x=0; x< numberOfNumbers;x=x+1) {
            System.out.println(numbers[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 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 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");
        }
        numberOfNumbers=numberOfNumbers+1;
    }

    private static void addFirst() {
        for (int x=numberOfNumbers;x>0;x=x-1){
            numbers[x]=numbers[x-1];
        }
        numbers[0]=commandReader.nextInt();
    }

    private static void addLast() {
        numbers[numberOfNumbers]=commandReader.nextInt();
    }


    private static void interpretSwapCommand() {
        int position1=commandReader.nextInt();
        int position2=commandReader.nextInt();
        int temp=numbers[position1-1];
        numbers[position1-1]=numbers[position2-1];
        numbers[position2-1]=temp;
    }

    private static void interpretPrintCommand() {
        String operand=commandReader.next();
        if (operand.equalsIgnoreCase("FIRST")) {
            System.out.println(numbers[0]);
        } else if (operand.equalsIgnoreCase("LAST")){
            System.out.println(numbers[numberOfNumbers-1]);
        } else{
            int index=Integer.valueOf(operand);
            System.out.println(numbers[index-1]);
        }
    }

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

    private static void readNumbers() throws FileNotFoundException{
        Scanner scanner=establishScanner("NumberSet.txt");
        while (scanner.hasNext()) {
            numbers[numberOfNumbers] = scanner.nextInt();
            numberOfNumbers = numberOfNumbers + 1;
        }
    }

    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));
    }

}