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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.Controls.Primitives;

namespace Tango.SharedUI.Components
{
    /// <summary>
    /// Represents an MVVM TextBox controller
    /// </summary>
    /// <seealso cref="System.Windows.DependencyObject" />
    public class TextController : DependencyObject
    {
        private TextBox _textBox;
        private bool _isMouseDown;

        /// <summary>
        /// Determines whether an element is Controller.
        /// </summary>
        public static readonly DependencyProperty ControllerProperty =
            DependencyProperty.RegisterAttached("Controller",
            typeof(TextController), typeof(TextController),
            new FrameworkPropertyMetadata(null,ControllerChanged));

        /// <summary>
        /// On controller changed.
        /// </summary>
        /// <param name="d">The d.</param>
        /// <param name="e">The <see cref="DependencyPropertyChangedEventArgs"/> instance containing the event data.</param>
        /// <exception cref="System.ArgumentException">The text controller component can only handle elements of type TextBox.</exception>
        private static void ControllerChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (d != null && e.NewValue != null)
            {
                if (!(d is TextBox))
                {
                    throw new ArgumentException("The text controller component can only handle elements of type TextBox.");
                }

                (e.NewValue as TextController).SetTextBox(d as TextBox);
            }
        }

        /// <summary>
        /// Sets the Controller attached property.
        /// </summary>
        /// <param name="element">The element.</param>
        /// <param name="value">if set to <c>true</c> [value].</param>
        public static void SetController(FrameworkElement element, TextController value)
        {
            element.SetValue(ControllerProperty, value);
        }

        /// <summary>
        /// Gets the Controller attached property.
        /// </summary>
        /// <param name="element">The element.</param>
        /// <returns></returns>
        public static TextController GetController(FrameworkElement element)
        {
            return (TextController)element.GetValue(ControllerProperty);
        }

        /// <summary>
        /// Gets or sets a value indicating whether to automatically scroll to end of text.
        /// </summary>
        public bool AutoScrollToEnd { get; set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="TextController"/> class.
        /// </summary>
        public TextController()
        {
            AutoScrollToEnd = true;
        }

        /// <summary>
        /// Sets the text box.
        /// </summary>
        /// <param name="textBox">The text box.</param>
        private void SetTextBox(TextBox textBox)
        {
            _textBox = textBox;
            _textBox.PreviewMouseDown += (_, __) => _isMouseDown = true;
            _textBox.PreviewMouseUp += (_, __) => _isMouseDown = false;
        }

        /// <summary>
        /// Appends the specified text.
        /// </summary>
        /// <param name="text">The text.</param>
        public void WriteLine(String text)
        {
            Write(text + Environment.NewLine);
        }

        /// <summary>
        /// Appends the specified text.
        /// </summary>
        /// <param name="text">The text.</param>
        public void Write(String text)
        {
            Invoke(() =>
            {
                _textBox.AppendText(text);

                if (AutoScrollToEnd && !_isMouseDown)
                {
                    ScrollToEnd();
                }
            });
        }

        /// <summary>
        /// Sets the specified text.
        /// </summary>
        /// <param name="text">The text.</param>
        public void Set(String text)
        {
            Invoke(() =>
            {
                _textBox.Text = text;

                if (AutoScrollToEnd && !_isMouseDown)
                {
                    ScrollToEnd();
                }
            });
        }

        /// <summary>
        /// Clears the text.
        /// </summary>
        public void Clear()
        {
            Invoke(() =>
            {
                _textBox.Clear();
            });
        }

        /// <summary>
        /// Scrolls to the end of the text.
        /// </summary>
        public void ScrollToEnd()
        {
            _textBox.ScrollToEnd();
        }

        /// <summary>
        /// Invokes the specified action.
        /// </summary>
        /// <param name="action">The action.</param>
        private void Invoke(Action action)
        {
            Dispatcher.BeginInvoke(action);
        }
    }
}