MVVM BrainStorm

using System;

namespace Framework.Observables
{
    /// <summary>
    /// Microsoft Style MVVM
    /// </summary>
    /// <remarks>
    /// Pros :
    ///     - Standardized and tested
    ///     - No Unity Code (testable)
    ///  Cons :
    ///     - Inheritance
    ///     - Poor support for 'cs views' (string key comparison)
    ///     - get/set can be optional (if binding is oneway to source or one time)
    /// </remarks>
    public class ObservableObject : IPropertyChanged
    {
        public event PropertyChanged OnPropertyChanged = delegate { };

        public virtual void RaisePropertyChanged(string propertyName)
        {
            OnPropertyChanged(propertyName);
        }
    }

    /// <summary>
    /// Microsoft Style MVVM
    /// </summary>
    public class MicrosoftViewModel : ObservableObject
    {
        private string _userName;
        public string UserName
        {
            get { return _userName; }
            set
            {
                if (value == _userName)
                    return;
                _userName = value;
                RaisePropertyChange("UserName");
            }
        }

        private string _password;
        public string Password
        {
            get { return _password; }
            set
            {
                if (value == _password)
                    return;
                _password = value;
                RaisePropertyChange("Password");
            }
        }
        
        [Import]
        IAccountService accounts;

        public void SignIn()
        {
            //Call Service / Controller Here
            accounts.SignIn(UsernName, Password);
        }
    }

    /// <summary>
    /// Lorenzo Style MVVM
    /// </summary>
    /// <remarks>
    /// Pros :
    ///     - No Inheritance
    ///     - No PropertyName key comparison
    ///     - Support for databinding
    ///     - Support for 'cs views'
    ///     - No Unity Code (testable)
    ///  Cons :
    ///     - Unstandardized, will need to refactor binders
    ///  Notes :
    ///     - Observable<> can be optional (if binding is oneway to source or one time)
    /// </remarks>
    public class Observable<T>
    {
        public event Action<T> OnChange = delegate { };

        private T _value;
        public T Value
        {
            get { return _value; }
            set
            {
                if (Equals(value, Value))
                    return;
                _value = value;
                RaiseChanged();
            }
        }

        public virtual void RaiseChanged()
        {
            OnChange(Value);
        }

        //TODO Equals override, json support, Misc C# stuff
    }


    /// <summary>
    /// Lorenzo Style MVVM
    /// </summary>
    public class LorenzoViewModel
    {
        public Observable<string> UserName = new Observable<string>();
        public Observable<string> Password = new Observable<string>();
        public Observable<bool> IsBusy = new Observable<bool>();

        [Import]
        IAccountService accounts;

        public void SignIn()
        {
            //Call Service / Controller Here
            accounts.SignIn(UsernName, Password);
        }
    }

    
    /// <summary>
    /// Lorenzo Style MVVM for lazy people
    /// </summary>
    public class VentiViewModel
    {
        // AccountModel is a simple 'dto' with a username and password.
        // View has a single event it listens to and does a batch redraw of all fields
        public Observable<AccountModel> Model = new Observable<AccountModel>();

        [Import]
        IAccountService accounts;
        
        public void SignIn()
        {
          //Call Service / Controller Here
          accounts.SignIn(Model);
    }
    
    /// <summary>
    /// Raising View Navigation for discussion.
    /// Frankly, navigation is a little wierd with MVVM as we will want to navigate to/from a viewmodel
    /// </summary>
    public class VentiViewModel2
    {
        public Observable<AccountModel> Model = new Observable<AccountModel>();

        public Observable<bool> IsBusy = new Observable<bool>();
        
        [Import]
        IAccountService accounts;
        
        [Import]
        INavigationService navigation;

        public void SignIn()
        {
          IsBusy.Value = true;
          
          //Call Service / Controller Here
          ResponseModel response = await  accounts.SignIn(Model);
          
          IsBusy.Value = false;
          
          if(response.IsError)
          {
            //Show a view as a temporary popup
            await navigation.ShowPopupAsync(new ErrorViewModel(response.ErrorMessage));
          }
          else
          {
            //Present a new view
            navigation.PushView(new MainViewModel());
          }
        }
        
        public void Back()
        {
            // Back to previous page in the navigational stack
            navigation.PopAsync();
        }
    }
}