using System;
using System.Reactive.Linq;
using ReactiveUI;
using XmlAuthority.Common;
using XmlAuthority.Common.Extensions;
using XmlAuthority.DocumentManagement.Contracts.Commands.Presentation;
using XmlAuthority.DocumentManagement.Desktop.Properties;
using XmlAuthority.DocumentManagement.Desktop.Services;
using XmlAuthority.Services.Application.Contracts;

namespace XmlAuthority.DocumentManagement.Desktop.Commands
{
    internal sealed class SaveDocumentCommand : PresentationCommandBase, ISaveDocumentCommand
    {
        private readonly ICurrentDocumentIdMonitor _currentDocumentIdMonitor;

        public SaveDocumentCommand(
            ISaveFileService saveFileService,
            IMessageService messageService,
            ICurrentDocumentIdMonitor currentDocumentIdMonitor)
        {
            _currentDocumentIdMonitor = currentDocumentIdMonitor;

            var command = ReactiveCommand.Create(() => { }, CanExecuteWhenDocumentOpen);

            Instance = command;
            Instance.ThrownExceptions.Subscribe(ex => messageService.ShowWarning(string.Format(Resources.DocumentSavingErrorMessage, ex.Message)));

            command.WithLatestFrom(_currentDocumentIdMonitor.CurrentDocumentIdStream, (_, tgt) => tgt)
                .Subscribe(async tgt => await saveFileService.SaveAsync(tgt.Value));
        }

        private IObservable<bool> CanExecuteWhenDocumentOpen => _currentDocumentIdMonitor.CurrentDocumentIdStream.Select(x => x.HasValue);
    }
}


        public static IObservable<TResult> WithLatestFrom<TLeft, TRight, TResult>(
            this IObservable<TLeft> source,
            IObservable<TRight> other,
            Func<TLeft, TRight, TResult> resultSelector)
        {
            return source.Publish(os =>
                other.Select(a => os
                    .Select(b => resultSelector(b, a)))
                    .Switch());
        }