StarSim

CreateSystemsViewModel.cs (4900B)

---

 using ReactiveUI;
 
 using StarSimLib.Contexts;
 using StarSimLib.Models;
 
 using System;
 using System.Linq;
 using System.Windows.Input;
 
 namespace StarSimGui.ViewModels.Database_ViewModels
 {
     /// <summary>
     /// Represents the create systems view.
     /// </summary>
     public class CreateSystemsViewModel : ViewModelBase
     {
         /// <summary>
         /// The program database.
         /// </summary>
         private readonly SimulatorContext dbContext;
 
         /// <summary>
         /// Backing field for the <see cref="BodyMass"/> property.
         /// </summary>
         private double bodyMass;
 
         /// <summary>
         /// Backing field for the <see cref="BodyName"/> property.
         /// </summary>
         private string bodyName;
 
         /// <summary>
         /// Initialises a new instance of the <see cref="CreateSystemsViewModel"/> class.
         /// </summary>
         public CreateSystemsViewModel()
         {
             IObservable<bool> canCreate = this.WhenAnyValue(x => x.BodyName, x => x.BodyMass,
                 (name, mass) => !string.IsNullOrEmpty(name) && !string.IsNullOrWhiteSpace(name) && mass > 0);
 
             CreateBodyCommand = ReactiveCommand.Create(CreateBodyCommandImpl, canCreate);
 
             ResetBodyCommand = ReactiveCommand.Create(ResetBodyCommandImpl);
         }
 
         /// <summary>
         /// Initialises a new instance of the <see cref="CreateSystemsViewModel"/> class.
         /// </summary>
         /// <param name="context">The <see cref="SimulatorContext"/> instance in which program data is stored.</param>
         public CreateSystemsViewModel(in SimulatorContext context) : this()
         {
             dbContext = context;
         }
 
         /// <summary>
         /// Signifies that the database should be updated.
         /// </summary>
         public event Action DatabaseEdited;
 
         /// <summary>
         /// The mass of the body to create.
         /// </summary>
         public double BodyMass
         {
             get
             {
                 return bodyMass;
             }
             set
             {
                 bodyMass = value;
                 this.RaisePropertyChanged();
             }
         }
 
         /// <summary>
         /// The name of the body to create.
         /// </summary>
         public string BodyName
         {
             get
             {
                 return bodyName;
             }
             set
             {
                 bodyName = value;
                 this.RaisePropertyChanged();
             }
         }
 
         /// <summary>
         /// Command invoked whenever the user wants to add the currently edited body to the database.
         /// </summary>
         public ICommand CreateBodyCommand { get; }
 
         /// <summary>
         /// Provides feedback about the changes made to the database.
         /// </summary>
         public string Feedback { get; private set; }
 
         /// <summary>
         /// Command invoked whenever the user wants to reset the currently edited body.
         /// </summary>
         public ICommand ResetBodyCommand { get; }
 
         /// <summary>
         /// Invoked whenever the user wants to add the currently edited body to the database.
         /// </summary>
         private void CreateBodyCommandImpl()
         {
             if (dbContext.Bodies.Any(body => body.Name.Equals(BodyName)))
             {
                 Feedback = "Body with the same name already exists in the database.";
                 this.RaisePropertyChanged(nameof(Feedback));
             }
 
             try
             {
                 Body lastBody = dbContext.Bodies.OrderBy(body => body.Id).Last();
 
                 Body newBody = new Body(lastBody.Id + 1, BodyName, BodyMass);
 
                 dbContext.Bodies.Add(newBody);
 
                 Feedback = "Body was successfully added to the database.";
                 this.RaisePropertyChanged(nameof(Feedback));
 
                 OnDatabaseEdited();
             }
             catch (Exception)
             {
                 Feedback = "Body could not be added to the database.";
                 this.RaisePropertyChanged(nameof(Feedback));
             }
         }
 
         /// <summary>
         /// Invokes the <see cref="DatabaseEdited"/> event.
         /// </summary>
         private void OnDatabaseEdited()
         {
             DatabaseEdited?.Invoke();
         }
 
         /// <summary>
         /// Invoked whenever the user wants to reset the currently edited body.
         /// </summary>
         private void ResetBodyCommandImpl()
         {
             BodyName = string.Empty;
             BodyMass = 0;
             Feedback = string.Empty;
             this.RaisePropertyChanged(nameof(Feedback));
         }
 
         /// <summary>
         /// Refreshed the database sources for this view model.
         /// </summary>
         internal void HandleDatabaseRefresh()
         {
         }
     }
 }