History.java

package edu.kit.pse.ws2013.routekit.history;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Collections;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;

import edu.kit.pse.ws2013.routekit.util.Coordinates;

/**
 * A history of route calculation queries.
 */
public class History {

	/**
	 * The internal list of history entries.
	 */
	private final List<HistoryEntry> entries;

	/**
	 * Create a new, empty {link History}.
	 */
	public History() {
		this.entries = new LinkedList<>();
	}

	/**
	 * <p>
	 * Create a new {@link History} with the specified entries.
	 * </p>
	 * <p>
	 * For internal use only!
	 * </p>
	 * 
	 * @param entries
	 *            The entries of the new {@link History}.
	 * @see #load(File)
	 */
	private History(List<HistoryEntry> entries) {
		this.entries = entries;
	}

	/**
	 * Add a new {@link HistoryEntry entry} to the {@link History}. The
	 * {@link HistoryEntry#getDate() date} of the new entry will be the current
	 * date.
	 * 
	 * @param start
	 *            The start point.
	 * @param destination
	 *            The destination point.
	 */
	public void addEntry(Coordinates start, Coordinates destination) {
		entries.add(new HistoryEntry(start, destination, new Date()));
	}

	/**
	 * Saves the history to the specified file.
	 * 
	 * @param file
	 *            The file where the history should be saved.
	 * @throws IOException
	 */
	public void save(File file) throws IOException {
		try (BufferedWriter writer = new BufferedWriter(new FileWriter(file))) {
			for (HistoryEntry entry : entries.subList(
					Math.max(entries.size() - 100, 0), entries.size())) {
				writer.write(entry.toString());
				writer.newLine();
			}
		}
	}

	/**
	 * Loads a history from the specified file and returns it.
	 * 
	 * @param file
	 *            The file where the history should be loaded.
	 * @return A new {@link History} with the entries from the specified file.
	 * @throws IOException
	 */
	public static History load(File file) throws IOException {
		try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
			String line;
			List<HistoryEntry> entries = new LinkedList<>();
			while ((line = reader.readLine()) != null) {
				HistoryEntry entry = HistoryEntry.fromString(line);
				entries.add(entry);
			}
			return new History(entries);
		}
	}

	/**
	 * <p>
	 * Returns all entries from the history.
	 * </p>
	 * <p>
	 * The history may not be modified through the {@link List} returned by this
	 * method (or its iterator); attempts to do so will result in an
	 * {@link UnsupportedOperationException} (see
	 * {@link Collections#unmodifiableList(List)}).
	 * </p>
	 * <p>
	 * (Note that while the current implementation will return a list that will
	 * reflect future changes to the history, users should not rely on this
	 * behavior, and instead call this method again each time the history
	 * entries are needed.)
	 * </p>
	 * 
	 * @return An (unmodifiable) {@link List} containing all entries of the
	 *         history.
	 */
	public List<HistoryEntry> getEntries() {
		return Collections.unmodifiableList(entries);
	}
}