//
// $Id$
//
// Nenya library - tools for developing networked games
// Copyright (C) 2002-2010 Three Rings Design, Inc., All Rights Reserved
// http://www.threerings.net/code/nenya/
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

package com.threerings.media.util;

import java.awt.Graphics2D;

/**
 * A path is used to cause a {@link Pathable} to follow a particular path along the screen. The
 * {@link Pathable} is responsible for calling {@link #tick} on the path with reasonable frequency
 * (generally as a part of the frame tick. The path is responsible for updating the position of
 * the {@link Pathable} based on the time that has elapsed since the {@link Pathable} started down
 * the path.
 *
 * <p> The path should call the appropriate callbacks on the {@link Pathable} when appropriate
 * (e.g. {@link Pathable#pathBeginning}, {@link Pathable#pathCompleted}).
 */
public interface Path
{
    /**
     * Called once to let the path prepare itself for the process of animating the supplied
     * pathable. Path users should also call {@link #tick} after {@link #init} with the same
     * initialization timestamp.
     */
    public void init (Pathable pable, long tickStamp);

    /**
     * Called to request that this path update the position of the specified pathable based on the
     * supplied timestamp information. A path should record its initial timestamp and determine
     * the progress of the pathable along the path based on the time elapsed since the pathable
     * began down the path.
     *
     * @param pable the pathable whose position should be updated.
     * @param tickStamp the timestamp associated with this frame.
     *
     * @return true if the pathable's position was updated, false if the path determined that the
     * pathable should not move at this time.
     */
    public boolean tick (Pathable pable, long tickStamp);

    /**
     * This is called if the pathable is paused for some length of time and then unpaused. Paths
     * should adjust any time stamps they are maintaining internally by the delta so that time
     * maintains the illusion of flowing smoothly forward.
     */
    public void fastForward (long timeDelta);

    /**
     * Paint this path on the screen (used for debugging purposes only).
     */
    public void paint (Graphics2D gfx);

    /**
     * When a path is removed from a pathable, whether that is because the path was completed or
     * because it was replaced by another path, this method will be called to let the path know
     * that it is no longer associated with this pathable.
     */
    public void wasRemoved (Pathable pable);
}
