using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.Windows.Threading;
using TechnologyAssembler.Core.Extensions;

namespace HashCalculator.GUI
{
    /// <summary>
    /// CopyableBox.xaml 的交互逻辑
    /// </summary>
    [SuppressMessage("Microsoft.Performance", "CA1812")]
    internal partial class CopyableBox : Window, IDisposable
    {
        private CopyableBoxViewModel ViewModel => (CopyableBoxViewModel)DataContext;

        public static void ShowDialog(Func<CancellationToken, Task<string>> action)
        {
            using var box = new CopyableBox();
            box.ViewModel.Initialize(action, box.Dispatcher);
            box.ShowDialog();
        }

        private CopyableBox()
        {
            InitializeComponent();
        }

        public void Dispose()
        {
            ViewModel.Dispose();
        }

        private void ClosingHandler(object sender, CancelEventArgs e)
        {
            if (ViewModel.ReadyToClose)
            {
                return;
            }

            e.Cancel = true;
            if (ViewModel.CloseCommand.CanExecuteValue)
            {
                ViewModel.CloseCommand.Execute(this);
            }

            return;
        }
    }

    [SuppressMessage("Microsoft.Performance", "CA1812")]
    internal class CopyableBoxViewModel : NotifyPropertyChanged, IDisposable
    {
        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
        private Task? _task;

        public const string InitialMessage = "正在加载…… 关闭窗口就可以取消加载（";

        private string _text = InitialMessage;
        public string Text
        {
            get => _text;
            private set => SetField(ref _text, value);
        }

        public string CloseButtonText => CloseCommand.CanExecuteValue ? "关闭窗口" : "正在关闭…";
        private bool _readyToClose = false;
        public bool ReadyToClose
        {
            get => _readyToClose;
            private set => SetField(ref _readyToClose, value);
        }

        public Command CopyCommand { get; }
        public Command<CopyableBox> CloseCommand { get; }

        public CopyableBoxViewModel()
        {
            CopyCommand = new Command(() =>
            {
                Clipboard.SetText(Text);
                return Task.CompletedTask;
            });

            CloseCommand = new Command<CopyableBox>(async window =>
            {
                CloseCommand.CanExecuteValue = false;
                Notify(nameof(CloseButtonText));

                if (_task != null)
                {
                    try
                    {
                        Cancel();
                        await _task.ConfigureAwait(true);
                    }
                    catch (OperationCanceledException) { }
                }

                ReadyToClose = true;
                window.Close();   
            });
        }

        public void Dispose()
        {
            Cancel();
            _cancellationTokenSource.Dispose();
        }

        public void Initialize(Func<CancellationToken, Task<string>> action, Dispatcher dispatcher)
        {
            _task = InitializationTask(action, dispatcher);
        }

        private async Task InitializationTask(Func<CancellationToken, Task<string>> action, Dispatcher dispatcher)
        {
            var utcBegin = DateTimeOffset.UtcNow;
            var timer = new DispatcherTimer(TimeSpan.FromMilliseconds(200), DispatcherPriority.Normal, (s, e) =>
            {
                var timeElapsed = DateTimeOffset.UtcNow - utcBegin;
                if (((DispatcherTimer)s).IsEnabled && timeElapsed.TotalSeconds > 1)
                {
                    Text = Text = $"{InitialMessage}\r\n目前耗时{timeElapsed}，稍微再等一下吧233";
                }
            }, dispatcher);
            timer.Start();

            var token = _cancellationTokenSource.Token;
            async Task<string> Action()
            {
                try
                {
                    return await action(token).ConfigureAwait(false);
                }
                catch (OperationCanceledException)
                {
                    return "操作已被取消";
                }
                finally
                {
                    timer.Stop();
                }
            }
            Text = await dispatcher.Invoke(Action).ConfigureAwait(true);
        }

        private void Cancel()
        {
            _cancellationTokenSource.Cancel();
        }
    }
}