MultiTerm/MultiTerm.Wpf.CustomControl/MultiFormatTextBox/MultiFormatTextBox.cs

using MultiTerm.Core.Model;
using MultiTerm.Core.Types;
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace MultiTerm.Wpf.CustomControl;

public class MultiFormatTextBox : Control
{
    #region static content
    private static readonly Brush defaultBackgroundBrush = Brushes.White;
    private static readonly List<Format> formats = new()
    {
        // character input
        new Format("CHAR", "MultiFormatTextBox.CHAR.Background", FormatType.Character),
        // hex input
        new Format("HEX", "MultiFormatTextBox.HEX.Background", FormatType.Hexadecimal),
        // binary input
        new Format("BIN", "MultiFormatTextBox.BIN.Background", FormatType.Binary)
    };

    #endregion

    #region private content
    private const string comboBoxTemplateKey = "PART_ComboBox";
    private const string richTextBoxTemplateKey = "PART_RichTextBox";

    private ComboBox? comboBox;
    private RichTextBox? richTextBox;
    private Format? currentlySelectedFormat;
    private readonly object lockObj = new();

    #endregion


    #region Dependency Properties
    public static readonly DependencyProperty CurrentMultiFormatStringProperty =
        DependencyProperty.Register(
            name: "CurrentMultiFormatString",
            propertyType: typeof(MultiFormatString), 
            ownerType: typeof(MultiFormatTextBox),
            typeMetadata: new FrameworkPropertyMetadata(null, OnCurrentMultiFormatStringChanged));

    public static readonly RoutedEvent EnterPressedEvent;

    /// <summary>
    /// .NET Property for <see cref="EnterPressedEvent"/>
    /// </summary>
    public event RoutedEventHandler EnterPressed
    {
        add { this.AddHandler(EnterPressedEvent, value); }
        remove { this.RemoveHandler(EnterPressedEvent, value); }
    }

    /// <summary>
    /// .NET Property for CurrentMultiFormatString.
    /// </summary>
    [Bindable(true)]
    public MultiFormatString CurrentMultiFormatString
    {
        get { return (MultiFormatString)GetValue(CurrentMultiFormatStringProperty); }
        set { SetValue(CurrentMultiFormatStringProperty, value); }
    }
    #endregion

    static MultiFormatTextBox()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(MultiFormatTextBox), new FrameworkPropertyMetadata(typeof(MultiFormatTextBox)));

        EnterPressedEvent = EventManager.RegisterRoutedEvent("EnterPressed",
            RoutingStrategy.Bubble, typeof(RoutedEventArgs),
            typeof(MultiFormatTextBox));
    }

    ~MultiFormatTextBox()
    {
        // unregister events
        if (this.CurrentMultiFormatString != null && this.CurrentMultiFormatString is INotifyCollectionChanged incc)
        {
            incc.CollectionChanged -= this.MultiFormatString_CollectionChanged;
        }
    }

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        // initialize format background brushes
        Format.UpdateBackgroundBrushesFromResources(this, formats);
        // set initially selected format
        this.currentlySelectedFormat = formats.First();


        // get comboBox from template
        if (GetTemplateChild(comboBoxTemplateKey) is ComboBox comboBox)
        {
            this.comboBox = comboBox;
            this.comboBox.ItemsSource = Format.GetListOfNames(formats);
            this.comboBox.SelectedItem = currentlySelectedFormat.Name;
            this.comboBox.SelectionChanged += ComboBox_SelectionChanged;
        }
        else
        {
            throw new Exception($"Implementation fault, {comboBoxTemplateKey} not found in template.");
        }

        // get richTextBox from template
        if (GetTemplateChild(richTextBoxTemplateKey) is RichTextBox richTextBox)
        {
            this.richTextBox = richTextBox;
            this.richTextBox.AcceptsReturn = false;
            this.richTextBox.AcceptsTab = false;
            this.richTextBox.PreviewKeyDown += RichTextBox_KeyDown;
            this.richTextBox.PreviewTextInput += RichTextBox_PreviewTextInput;
            this.richTextBox.SelectionChanged += RichTextBox_SelectionChanged;
            DataObject.AddPastingHandler(this.richTextBox, OnRtbPaste);
        }
        else
        {
            throw new Exception($"Implementation fault, {richTextBoxTemplateKey} not found in template.");
        }
    }

    private static void OnCurrentMultiFormatStringChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        // extract instance and guard null
        if (d is not MultiFormatTextBox mftb) { return; }

        // register to collection changed event
        if (mftb.CurrentMultiFormatString is INotifyCollectionChanged incc)
        { 
            // remove handler
            incc.CollectionChanged -= mftb.MultiFormatString_CollectionChanged;
            // add new handler if not null
            if(e.NewValue != null)
            {
                incc.CollectionChanged += mftb.MultiFormatString_CollectionChanged;
            }
        }
    }

    /// <summary>
    /// Reacts on Collection Changed Events.
    /// </summary>
    private void MultiFormatString_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
    {
        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Add:
                // guard null
                if(e.NewItems == null) { return; }
                // add list to textbox
                this.AddItemsToTextBox(e.NewItems, e.NewStartingIndex);
                break;

            case NotifyCollectionChangedAction.Remove:
                // guard null
                if (e.OldItems == null) { return; }
                // remove list to textbox
                this.RemoveItemsFromTextBox(e.OldItems, e.OldStartingIndex);
                break;

            case NotifyCollectionChangedAction.Reset:
                // clear richtextbox add new paragraph
                this.richTextBox!.Document.Blocks.Clear();
                this.richTextBox!.Document.Blocks.Add(new Paragraph());
                break;

            case NotifyCollectionChangedAction.Replace:
            case NotifyCollectionChangedAction.Move:
            default:
                throw new NotImplementedException($"'{nameof(MultiFormatString_CollectionChanged)}()' does not support Action '{e.Action}'");
        }
    }

    private void RemoveItemsFromTextBox(System.Collections.IList items, int startingIndex)
    {
        // extract paragraph from richtextbox (last block is paragraph per default)
        if (this.richTextBox!.Document.Blocks.LastBlock is not Paragraph paragraph)
        {
            throw new Exception($"'{nameof(RemoveItemsFromTextBox)}()' found that {nameof(richTextBox)} has no paragraph as last block.");
        }

        if (items.Count > 1)
        {
            throw new Exception("Not supported");
        }

        string toRemoveString = string.Empty;
        if (items[0] is IFormattedCharacter character)
        {
            toRemoveString = character.Character;
        }
        else
        {
            throw new Exception("Not supported");
        }

        var inlineToRemove = paragraph.Inlines.ElementAt(new Index(startingIndex));  // paragraph.Inlines = zero based counting
        var textInline = new TextRange(inlineToRemove.ContentStart, inlineToRemove.ContentEnd);
        if(textInline.Text != toRemoveString)
        {
            throw new Exception("Tried to remove other element...");
        }
        paragraph.Inlines.Remove(inlineToRemove);
    }

    private void AddItemsToTextBox(System.Collections.IList items, int startingIndex)
    {
        int indexCounter = startingIndex;

        // extract paragraph from richtextbox (last block is paragraph per default)
        var paragraph = this.richTextBox!.Document.Blocks.LastBlock as Paragraph ?? throw new Exception($"'{nameof(AddItemsToTextBox)}()' found that {nameof(richTextBox)} has no paragraph as last block.");

        // iterate through formatted characters to add
        foreach (IFormattedCharacter item in items)
        {
            Run? run = null;

            if (item is FormattedCharacter formattedCharacter)
            {
                // text as run with correct background brush
                run = new Run(formattedCharacter.Character)
                {
                    Background = this.currentlySelectedFormat!.BackgroundBrush
                };
            }
            else if(item is SpacingCharacter spacingCharacter)
            {
                // text as run with default background brush
                run = new Run(spacingCharacter.Character)
                {
                    Background = defaultBackgroundBrush
                };
            }
            else
            {
                throw new Exception($"'{nameof(AddItemsToTextBox)}()' cannot handle items of type {item.GetType()}");
            }

            // if this is the first element to enter in the paragraph => simply add it
            if (paragraph!.Inlines.Count == 0)
            {
                paragraph.Inlines.Add(run);
            }
            // if the previous item is outside of the range => insert at first position
            else if(indexCounter - 1 < 0)
            {
                paragraph.Inlines.InsertBefore(paragraph.Inlines.FirstInline, run);
            }
            else // add to paragraph of richtextbox after previous inline
            {
                var previousInline = paragraph.Inlines.ElementAt(new Index(indexCounter - 1));  // paragraph.Inlines = zero based counting
                paragraph.Inlines.InsertAfter(previousInline, run);
            }

            // increment counter
            indexCounter++;
        }

        // update caret position to index position
        this.SetRtbCaretPosition(indexCounter);
    }

    private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        lock (lockObj) // lock so no richtextbox textchanged event can happen
        {
            // match all formats with the name selected in the combobox
            var matchingFormats = formats.Where(format => format.Name == (string)this.comboBox!.SelectedItem);

            // check if exactly one format was matched
            if (matchingFormats.Count() != 1)
            {
                throw new Exception($"{nameof(ComboBox_SelectionChanged)} could not match a correct amount of formats");
            }
            // set currently selected format, reset offset counter
            this.currentlySelectedFormat = matchingFormats.First();

            // focus textbox
            this.richTextBox!.Focus();
        }
    }

    private void RichTextBox_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            e.Handled = true;
            // raise event
            RoutedEventArgs args = new(EnterPressedEvent);
            RaiseEvent(args);
        }
        else if(e.Key == Key.Space)
        {
            e.Handled = true;

            // add space to MultiFormatString (will only work if currently character type is selected)
            InsertCharacterAtCaretPositionIntoCurrentMultiFormatString(" ");
        }
        // back one
        else if (e.Key == Key.Back)
        {
            var cursorPos = GetRtbCaretPosition();

            // remove previous element if it exists
            try
            {
                if (this.CurrentMultiFormatString.ElementAt(cursorPos - 1) != null)
                {
                    this.CurrentMultiFormatString.RemoveAt(cursorPos - 1);
                }
            }
            catch { }

            e.Handled = true;
        }
        // delete next (selection is not allowed)
        else if (e.Key == Key.Delete)
        {
            var cursorPos = GetRtbCaretPosition();

            // remove next element if it exists
            try
            {
                if (this.CurrentMultiFormatString.ElementAt(cursorPos) != null)
                {
                    this.CurrentMultiFormatString.RemoveAt(cursorPos);
                }
            }
            catch { }

            e.Handled = true;
        }
    }

    private int GetRtbCaretPosition()
    {
        // magic dividor of 3.... nobody knows why...
        return this.richTextBox!.Document.ContentStart.GetOffsetToPosition(this.richTextBox.CaretPosition) / 3;
    }

    private void SetRtbCaretPosition(int index)
    {
        // magic multiplicator of 3.... nobody knows why...
        this.richTextBox!.CaretPosition = this.richTextBox.Document.ContentStart.GetPositionAtOffset(index*3);
    }

    private void RichTextBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        // text is never directly inserted => therefore always handled
        e.Handled = true;

        // if more than one char inserted => illegal => cancel
        if(e.Text.Length > 1) { return; }

        this.InsertCharacterAtCaretPositionIntoCurrentMultiFormatString(e.Text);
    }

    private void OnRtbPaste(object sender, DataObjectPastingEventArgs e)
    {
        // get pasted data
        if (e.DataObject.GetDataPresent(typeof(string)))
        {
            // get data as string
            var text = (string)e.DataObject.GetData(typeof(string));
            // insert each character seperately
            foreach (var character in text)
            {
                this.InsertCharacterAtCaretPositionIntoCurrentMultiFormatString(character.ToString());
            }
        }

        // cancel pasting
        e.CancelCommand();
    }

    private void InsertCharacterAtCaretPositionIntoCurrentMultiFormatString(string text)
    {
        var caretPosition = this.GetRtbCaretPosition();

        // add char to MultiFormatString
        FormattedCharacter formattedCharacter = new(this.currentlySelectedFormat!.AssociatedFormatType, text);

        this.CurrentMultiFormatString.Insert(caretPosition, formattedCharacter);
        //this.CurrentMultiFormatString.Add(formattedCharacter);
    }

    private void RichTextBox_SelectionChanged(object sender, RoutedEventArgs e)
    {
        // do not allow selection
        if (this.richTextBox!.Selection.Text.Length > 0)
        {
            this.richTextBox!.Selection.Select(this.richTextBox.Selection.End, this.richTextBox.Selection.End);
        }
    }
}