MultiTerm/MultiTerm.Wpf/View/ConsoleView.xaml.cs

using MultiTerm.Core.ViewModel;
using System;
using System.Linq;
using System.Windows.Controls;
using System.Windows.Input;

namespace MultiTerm.Wpf.View;

public partial class ConsoleView : UserControl
{
    private ConsoleViewModel? viewModel;

    public ConsoleView()
    {
        InitializeComponent();
    }

    /// <summary>
    /// After user control finished loading, the data context is casted and stored locally.
    /// </summary>
    private void UserControl_Loaded(object sender, System.Windows.RoutedEventArgs e)
    {
        // cast to correct type
        if (this.DataContext is not ConsoleViewModel dataContextVm)
        {
            throw new InvalidOperationException($"{nameof(ConsoleView)} got wrong type of DataContext.");
        }
        // store locally
        this.viewModel = dataContextVm;
    }

    private void SendableMessageTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
    {
        // send if the key was enter
        if (e.Key == Key.Enter)
        {
            // do not forward key => is handled
            e.Handled = true;
            this.viewModel!.Send();
        }
        // key up => recall previous history element
        else if (e.Key == Key.Up)
        { 
            // do not forward key => is handled
            e.Handled = true;
            this.viewModel!.RecallElementFromHistory(previous: true);
            this.sendableMessageTextBox.CaretIndex = this.sendableMessageTextBox.Text.Length;  // set cursor to end
        }
        // key down => recall next history element
        else if (e.Key == Key.Down)
        {
            // do not forward key => is handled
            e.Handled = true;
            this.viewModel!.RecallElementFromHistory(previous: false);
            this.sendableMessageTextBox.CaretIndex = this.sendableMessageTextBox.Text.Length;  // set cursor to end
        }
    }

    private void DataTextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        // scroll to end
        if (sender is not TextBox textBox) { return; }
        textBox.ScrollToEnd();
    }

    private void SendableMessageTextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        // more than one change and added length is more than 1 letter
        // => suspect change results from inserting an element from the send history or pasted from the clipboard
        if (e.Changes.Count >= 1 && e.Changes.First().AddedLength > 1)
        {   
            // focus the textbox
            this.sendableMessageTextBox.Focus();
            // set cursor to end
            this.sendableMessageTextBox.CaretIndex = this.sendableMessageTextBox.Text.Length; 
        }
    }
}