AvaloniaCoreRTDemo/src/Windows/ViewModels/ApplicationModelBase.cs

using System;
using System.Reactive;
using Avalonia.Controls;

using AvaloniaCoreRTDemo.Interfaces;

using ReactiveUI;

namespace AvaloniaCoreRTDemo.Windows.ViewModels
{
    internal abstract class ApplicationModelBase : ReactiveObject
    {
        private readonly IThemeSwitch _themeSwitch;
        private Boolean _aboutEnable = true;
        private Boolean _defaultLightEnable = false;
        private Boolean _defaultDarkEnable = false;
        private Boolean _fluentLightEnable = false;
        private Boolean _fluentDarkEnable = false;

        public Boolean AboutEnabled
        {
            get => this._aboutEnable;
            set => this.RaiseAndSetIfChanged(ref this._aboutEnable, value);
        }

        public Boolean DefaultLightEnabled
        {
            get => this._defaultLightEnable;
            set => this.RaiseAndSetIfChanged(ref this._defaultLightEnable, value);
        }

        public Boolean DefaultDarkEnabled
        {
            get => this._defaultDarkEnable;
            set => this.RaiseAndSetIfChanged(ref this._defaultDarkEnable, value);
        }

        public Boolean FluentLightEnabled
        {
            get => this._fluentLightEnable;
            set => this.RaiseAndSetIfChanged(ref this._fluentLightEnable, value);
        }

        public Boolean FluentDarkEnabled
        {
            get => this._fluentDarkEnable;
            set => this.RaiseAndSetIfChanged(ref this._fluentDarkEnable, value);
        }
        
        public ReactiveCommand<Unit, Unit> FileExitCommand { get; }

        public ApplicationModelBase(IThemeSwitch themeSwitch)
        {
            this._themeSwitch = themeSwitch;
            this.IntializeTheme(themeSwitch.Current);
            this.FileExitCommand = ReactiveCommand.Create(RunFileExit);
        }

        public abstract void HelpAboutMethod();
        public abstract void DefaultLightMethod();
        public abstract void DefaultDarkMethod();
        public abstract void FluentLightMethod();
        public abstract void FluentDarkMethod();

        protected async void RunHelpAbout(Window currentWindow)
        {
            if (this.AboutEnabled)
                try
                {
                    this.AboutEnabled = false;
                    await new AboutWindow(IsDarkTheme(this._themeSwitch.Current)).ShowDialog(currentWindow);
                }
                finally
                {
                    this.AboutEnabled = true;
                }
        }

        protected void SetTheme(ApplicationTheme theme)
        {
            this.IntializeTheme(theme);
            this._themeSwitch.ChangeTheme(theme);
        }

        private void RunFileExit() => Environment.Exit(0);

        private void IntializeTheme(ApplicationTheme theme)
        {
            this.DefaultLightEnabled = theme != ApplicationTheme.SimpleLight;
            this.DefaultDarkEnabled = theme != ApplicationTheme.SimpleDark;
            this.FluentLightEnabled = theme != ApplicationTheme.FluentLight;
            this.FluentDarkEnabled = theme != ApplicationTheme.FluentDark;
        }

        private static Boolean IsDarkTheme(ApplicationTheme? theme)
            => theme switch
            {
                ApplicationTheme.SimpleDark => true,
                ApplicationTheme.FluentDark => true,
                _ => false,
            };
    }
}