import java.util.ArrayList;
import java.util.Random;

/**
 * This class stores a list of books
 * @author cs161
 * @version spring2019
 */
public class BookCase{
    // Instance variables
    private int numBooks;
    private ArrayList<Book> books;
    private Random rng;
    
    /**
     * Creates a new empty bookcase
     */
    public BookCase(){
        numBooks = 0;
        books = new ArrayList<Book>();
        rng = new Random();
    }

    /**
     * Adds a book to the book case
     * @param title The title of the book
     * @param author The author of the book
     */
    public void addBook(String title, String author){
        Book b = new Book(title, author);
        books.add(b);
        numBooks++;
    }

    /**
     * Checks if a book is contained in the book case
     * @param findBook The title of the book
     * @return True if the book occurs in the book case, false otherwise
     */    
    public boolean containsBook(String findBook){
        int bookCount = books.size()-1;
        // NOTE: THIS SHOULD BE A FOR LOOP. WHY?
        while(bookCount >= 0){
            Book curr = books.get(bookCount);
            String currTitle = curr.getTitle();
            if(findBook.equals(currTitle)){
                return true;
            }
            bookCount--;
        }
        return false;
    }

    private boolean isValid(int position){
        return position < books.size() && position >= 0;
    }
    
    /**
     * Removes a book from the list
     * @param currPosition The index of the book to be moved
     */
    public void removeBook(int currPosition){
        if(isValid(currPosition)){
            books.remove(currPosition);
        }
    }

    /**
     * Moves the book at the specified index to the first spot
     * in the book case
     * @param currPosition The index of the book to be moved
     */
    public void promoteBook(int currPosition){
        if(isValid(currPosition)){            
            Book selected = books.remove(currPosition);
            books.add(0, selected);
        }        
    }

    /**
     * Returns the title of a random book in the book case
     * @return The title of a randomly chosen book
     */
    public String getRandomBook(){
        int index = rng.nextInt(numBooks);
        Book chosen = books.get(index);
        String title = chosen.getTitle();
        return title;
    }

    /**
     * Returns a string representation of the state of the bookcase
     * @return A string representing the bookcase
     */
    public String toString(){
        // NOTE: THIS SHOULD BE A FOR-LOOP. WHY?
        int place = 0;
        String s = "";
        while(place < books.size()){
            Book selected = books.get(place);
            String info = selected.toString();
            s = s + info + "\n";
            place++;
        }        
        return s;
    }
}