#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2011 Nuclex Development Labs

This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 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
IBM Common Public License for more details.

You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion

using System;
using System.Collections.Generic;

using Microsoft.Xna.Framework;

namespace Nuclex.Game.States {

  /// <summary>State the game can be in</summary>
  /// <remarks>
  ///   <para>
  ///     To obtain Draw() and Update() notifications, implement the IDrawable
  ///     and IUpdateable interfaces.
  ///   </para>
  ///   <para>
  ///     This class follows the usual game state concept: Instead of using
  ///     hard to maintain if/else trees for deciding whether to render the main menu,
  ///     game scene or credits scroller, each of the game's phases is put in its own
  ///     game state class. This improves modularity and helps keeping parts of code
  ///     separated that have nothing to with each other. The game state manager
  ///     allows multiple states to be active at the same time and manages these
  ///     active states in a stack, which is useful for realizing ingame menus
  ///     and nested scenes.
  ///   </para>
  ///   <para>
  ///     Game states can be either active or inactive and will be notified when this
  ///     state changes by the OnEntered() and OnLeaving() methods. Any game state
  ///     starts out as being inactive. Game states should only load and keep their
  ///     resources during their active period and free them again when they
  ///     become inactive.
  ///   </para>
  ///   <para>
  ///     In addition to being active and inactive, game states also have a pause mode.
  ///     This mode can only be entered by active game states and is used to put
  ///     the game state in the back when another game state is pushed on top of it
  ///     in the stack. Thus, if multiple game states are active, only the topmost
  ///     state can be in unpaused mode.
  ///   </para>
  /// </remarks>
  public interface IGameState {

    /// <summary>Called when the game state has been entered</summary>
    void Enter();

    /// <summary>Called when the game state is being left again</summary>
    void Leave();

    /// <summary>Called when the game state is being paused</summary>
    void Pause();

    /// <summary>Called when the game state is being resumed from pause mode</summary>
    void Resume();

  }

} // namespace Nuclex.Game.States