GiveGoldViewModel.cs

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using System.Threading.Tasks;
using PhotoSharingApp.Universal.Commands;
using PhotoSharingApp.Universal.Models;
using PhotoSharingApp.Universal.Services;
using PhotoSharingApp.Universal.Views;

namespace PhotoSharingApp.Universal.ViewModels
{
    /// <summary>
    /// The ViewModel for the give gold view.
    /// </summary>
    public class GiveGoldViewModel : ViewModelBase
    {
        private string _annotationText;
        private readonly IDialogService _dialogService;
        private bool _isBusy;
        private readonly IPhotoService _photoService;

        /// <summary>
        /// Creates a new instance.
        /// </summary>
        /// <param name="photoService">The photo service.</param>
        /// <param name="dialogService">The dialog service.</param>
        public GiveGoldViewModel(IPhotoService photoService, IDialogService dialogService)
        {
            _photoService = photoService;
            _dialogService = dialogService;

            // Initialize commands
            CancelCommand = new RelayCommand(OnCancel);
        }

        /// <summary>
        /// Gets or sets the annotation.
        /// </summary>
        public Annotation Annotation { get; private set; }

        /// <summary>
        /// Gets or sets the annotation text.
        /// </summary>
        public string AnnotationText
        {
            get { return _annotationText; }
            set
            {
                if (value != _annotationText)
                {
                    _annotationText = value;
                    NotifyPropertyChanged(nameof(AnnotationText));
                }
            }
        }

        /// <summary>
        /// Gets the cancel command.
        /// </summary>
        public RelayCommand CancelCommand { get; }

        /// <summary>
        /// Gets the amount of gold to give.
        /// </summary>
        public int GoldToGive { get; } = 1;

        /// <summary>
        /// Gets or sets the busy state.
        /// </summary>
        public bool IsBusy
        {
            get { return _isBusy; }
            set
            {
                if (value != _isBusy)
                {
                    _isBusy = value;
                    NotifyPropertyChanged(nameof(IsBusy));
                }
            }
        }

        /// <summary>
        /// Gets or sets the photo.
        /// </summary>
        public Photo Photo { get; set; }

        /// <summary>
        /// Loads the state.
        /// </summary>
        public override async Task LoadState()
        {
            await base.LoadState();
        }

        private void OnCancel()
        {
            Annotation = null;
        }

        public async Task<bool> PostAnnotationToService()
        {
            try
            {
                IsBusy = true;

                var serviceResult = await _photoService.PostAnnotation(Photo, _annotationText, GoldToGive);

                // If annotation was succesfully posted, update HasUserGivenGold, and store annotation
                if (serviceResult != null)
                {
                    Photo.HasUserGivenGold = true;
                    Annotation = serviceResult;

                    return true;
                }

                return false;
            }
            catch (InsufficientBalanceException)
            {
                await _dialogService.ShowNotification("InsufficientBalance_Message", "InsufficientBalance_Title");

                return false;
            }
            catch (ServiceException)
            {
                await _dialogService.ShowGenericServiceErrorNotification();

                return false;
            }
            finally
            {
                IsBusy = false;
            }
        }
    }
}