using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace FlowScope.UI
{
    public sealed class UIScreenNavigator : IUIScreenNavigator
    {
        private readonly UIManager _uiManager;
        private readonly Stack<Action> _closeStack = new();

        public UIScreenNavigator(UIManager uiManager)
        {
            _uiManager = uiManager ?? throw new ArgumentNullException(nameof(uiManager));
        }

        public bool CanGoBack => _closeStack.Count > 1;

        public async Task<TPanel> PushAsync<TPanel, TViewModel>(
            TViewModel viewModel,
            CancellationToken cancellationToken)
            where TPanel : UIPanelBase<TViewModel>
        {
            var panel = await _uiManager.OpenAsync<TPanel, TViewModel>(viewModel, cancellationToken);
            _closeStack.Push(() => _uiManager.Close<TPanel>());
            return panel;
        }

        public void GoBack()
        {
            if (!CanGoBack)
            {
                return;
            }

            var close = _closeStack.Pop();
            close();
        }

        public void Clear()
        {
            while (_closeStack.Count > 0)
            {
                var close = _closeStack.Pop();
                close();
            }
        }
    }
}