#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2019 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 Nuclex.Support;

namespace Nuclex.Windows.Forms.ViewModels {

  /// <summary>Base class for view models that have multiple child view models</summary>
  /// <typeparam name="TPageEnumeration">Enum type by which pages can be indicated</typeparam>
  public abstract class MultiPageViewModel<TPageEnumeration> : Observable
    where TPageEnumeration : IEquatable<TPageEnumeration> {

    /// <summary>Initializes a new multi-page view model</summary>
    /// <param name="windowManager">
    ///   Window manager the view model uses to create child views
    /// </param>
    /// <param name="cachePageViewModels">
    ///   Whether child view models will be kept alive and reused
    /// </param>
    public MultiPageViewModel(IWindowManager windowManager, bool cachePageViewModels = false) {
      this.windowManager = windowManager;
    }

    /// <summary>Child page that is currently being displayed by the view model</summary>
    public TPageEnumeration ActivePage {
      get { return this.activePage; }
      set {
        if(!this.activePage.Equals(value)) {
          this.activePage = value;
          OnPropertyChanged(nameof(ActivePage));
        }
      }
    }

    /// <summary>Windowmanager that can create view models and display other views</summary>
    protected IWindowManager WindowManager {
      get { return this.windowManager; }
    }

    /// <summary>Creates a view model for the specified page</summary>
    /// <param name="page">Page for which a view model will be created</param>
    /// <returns>The view model for the specified page</returns>
    protected abstract object createViewModelForPage(TPageEnumeration page);

    /// <summary>Page that is currently active in the multi-page view model</summary>
    private TPageEnumeration activePage;
    /// <summary>Window manager that can be used to display other views</summary>
    private IWindowManager windowManager;

  }

} // namespace Nuclex.Windows.Forms.ViewModels