using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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.Navigation;
using System.Windows.Shapes;

namespace HashCalculator.GUI
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        internal ViewModel ViewModel => (ViewModel)DataContext;
        private bool _autoscroll = true;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void OnButtomScrollViewerScrollChanged(object sender, ScrollChangedEventArgs e)
        {
            var scrollViewer = (ScrollViewer)e.Source;
            // User scroll event : set or unset auto-scroll mode
            if (e.ExtentHeightChange == 0)
            {   // Content unchanged : user scroll event
                if (scrollViewer.VerticalOffset == scrollViewer.ScrollableHeight)
                {   // Scroll bar is in bottom
                    // Set auto-scroll mode
                    _autoscroll = true;
                }
                else
                {   // Scroll bar isn't in bottom
                    // Unset auto-scroll mode
                    _autoscroll = false;
                }
            }

            // Content scroll event : auto-scroll eventually
            if (_autoscroll && e.ExtentHeightChange != 0)
            {   // Content changed and auto-scroll mode set
                // Autoscroll
                scrollViewer.ScrollToVerticalOffset(scrollViewer.ExtentHeight);
            }
        }
    }
}