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

/**
 * This class contains methods that read input from the keyboard, and
 * from a text file.
 */

public class Input
{

    /**
     * Some sample code that reads two integers from the keyboard and 
     * prints them out.  It will crash if the user doesn't behave.
     */
    public static void readTwoInts() 
    {
        System.out.println("Please enter two integers:");
        Scanner input = new Scanner(System.in); // Create scanner reading from keyboard
        int a = input.nextInt();    // Read an integer
        System.out.println("Got it -- I read the "+a+" you entered");
        int b = input.nextInt();    // Read another one
        System.out.println("Thanks.  Got the "+b+" as well.");
    }
    
    /**
     * Asks the user some questions, then suggests a user name for them.
     */
    public void suggestUsername() 
    {
        System.out.println("Please enter your first and last names:");
        Scanner input = new Scanner(System.in); // Create a Scanner, reading from keyboard
        String firstName = input.next();        // Read two "words" from the input,
        String lastName = input.next();         // and store them in variables.
        
        System.out.println("Thanks, "+firstName+". What's your favorite number?");
        int fav = input.nextInt();
        
        // Now that we've got the user's inputs, we'll do some operations
        // to create a user name for them
        
        String name = firstName.substring(0,1) + lastName;
        System.out.println("Your user name is "+name+(2*fav));
        
    }

    /**
     * We wrote a version of this in class.  I'm putting it here so you have another
     * example of some working code to look at as you implement the other methods.
     * 
     * @param filename  The name of the file to read from.
     */
    public static void printAllLines(String filename) throws FileNotFoundException
    {
        File theFile = new File(filename);  // Create File object corresponding to the file
        if (theFile.exists()) {
            Scanner scan = new Scanner(theFile);    // Scanner reads from file!
            while(scan.hasNext()) {
                String line = scan.nextLine();
                System.out.println(line);
            }
        }
        else {
            System.out.println("The file doesn't exist!");
        }
    }

    /**
     * This method asks the user for a filename, then calls the
     * printAllLines method above. Doing it this way means we don't need
     * to have BlueJ pop up a dialog box for us to get the filename.
     */
    public static void printContents() throws FileNotFoundException
    {
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter a filename:");
        String filename = scan.next();
        printAllLines(filename);
    }
    
    /**
     * Prints only the values greater than zero.  This is basically the method above
     * but now with an if statement in the body of the loop, and reading integers
     * rather than strings.
     */
    public void printPositiveValues(String fileName) throws FileNotFoundException 
    {
        int data;
        Scanner input;
        input = new Scanner(new File(fileName));
        while(input.hasNextInt()) {
            data = input.nextInt();
            if (data > 0) {
                System.out.println(data);
            }
        }
    }  

    /**
     * Sums values until we encounter a negative number.  This assumes that
     * there's at least one number in the file, though it still works even if
     * the first (and maybe only) value is negative.
     */
    public int sumUntilNegative(String fileName) throws FileNotFoundException 
    {
        int total;
        int data;
        total = 0;
        Scanner input = new Scanner(new File(fileName));
        data = 0;   // "Trick" it to get the loop started
        while(data >= 0 && input.hasNextInt()) {
            data = input.nextInt();     // Might be negative...
            if (data > 0) {             // If it's not, add to total
                total = total + data;
            }
        }
        return total;
    }  

    /**
     * Prints information each time it finds two identical neighboring values.  This
     * requires keeping TWO values from the sequence -- current and previous.
     */
    public void findIdenticalNeighbors(String fileName) throws FileNotFoundException 
    {
        int current;    // The most recently read value
        int previous;   // The one before that
        Scanner input = new Scanner(new File(fileName));
        previous = input.nextInt();
        while(input.hasNext()) {
            current = input.nextInt();
            if (current == previous) {
                System.out.println("Two in a row: "+current);
            }
            previous = current;
        }
    }  
}