BrowserModel.java

import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ResourceBundle;

/**
 * This represents the heart of the browser: the collections that organize all
 * the URLs into useful structures.
 * 
 * @author Robert C. Duvall
 */
public class BrowserModel {
	// constants
	public static final String PROTOCOL_PREFIX = "http://";
	// state
	private URL myHome;
	private URL myCurrentURL;
	private int myCurrentIndex;
	private List<URL> myHistory;
	private Map<String, URL> myFavorites;
    private ResourceBundle myErrorResources;

	/**
	 * Creates an empty model.
	 */
	public BrowserModel() {
		myHome = null;
		myCurrentURL = null;
		myCurrentIndex = -1;
		myHistory = new ArrayList<>();
		myFavorites = new HashMap<>();
	}

	/**
     * Returns the first page in next history, null if next history is empty.
	 * @throws BrowserException 
     */
    public URL next () throws BrowserException {
        if (hasNext()) {
            myCurrentIndex++;
            return myHistory.get(myCurrentIndex);
        }
        throw new BrowserException(myErrorResources.getString("HistoryException"));
    }

	/**
	 * Returns the first page in back history, null if back history is empty.
	 * @throws BrowserException 
	 */
	public URL back() throws BrowserException {
		if (hasPrevious()) {
			myCurrentIndex--;
			return myHistory.get(myCurrentIndex);
		}
        throw new BrowserException(myErrorResources.getString("BackException"));
	}



	/**
	 * Changes current page to given URL, removing next history.
	 * @throws BrowserException 
	 */
	public URL go(String url) throws BrowserException {
		myCurrentURL = completeURL(url);
		if (myCurrentURL != null) {
			if (hasNext()) {
				myHistory = myHistory.subList(0, myCurrentIndex + 1);
			}
			myHistory.add(myCurrentURL);
			myCurrentIndex++;
		}
		return myCurrentURL;
	}

	/**
	 * Returns true if there is a next URL available
	 */
	public boolean hasNext() {
		return myCurrentIndex < (myHistory.size() - 1);
	}

	/**
	 * Returns true if there is a previous URL available
	 */
	public boolean hasPrevious() {
		return myCurrentIndex > 0;
	}

	/**
	 * Returns URL of the current home page or null if none is set.
	 */
	public URL getHome() {
		return myHome;
	}

	/**
	 * Sets current home page to the current URL being viewed.
	 */
	public void setHome() {
		// just in case, might be called before a page is visited
		if (myCurrentURL != null) {
			myHome = myCurrentURL;
		}
	}

	/**
	 * Adds current URL being viewed to favorites collection with given name.
	 */
	public void addFavorite(String name) {
		// just in case, might be called before a page is visited
		if (name != null && !name.equals("") && myCurrentURL != null) {
			myFavorites.put(name, myCurrentURL);
		}
	}

	/**
	 * Returns URL from favorites associated with given name, null if none set.
	 * @throws BrowserException 
	 */
	public URL getFavorite(String name) throws BrowserException {
		if (name != null && !name.equals("") && myFavorites.containsKey(name)) {
			return myFavorites.get(name);
		}
        throw new BrowserException(myErrorResources.getString("FavoriteException"));
	}

	// deal with a potentially incomplete URL
	private URL completeURL(String possible) throws BrowserException {
		try {
			// try it as is
			return new URL(possible);
		} catch (MalformedURLException e) {
			try {
				// try it as a relative link
				// BUGBUG: need to generalize this :(
				return new URL(myCurrentURL.toString() + "/" + possible);
			} catch (MalformedURLException ee) {
				try {
					// e.g., let user leave off initial protocol
					return new URL(PROTOCOL_PREFIX + possible);
				} catch (MalformedURLException eee) {
			        throw new BrowserException(myErrorResources.getString("HistoryException"));
				}
			}
		}
	}
}