using System.Globalization;
using System.Text.RegularExpressions;
using System.Windows.Data;
using System.Windows.Documents;

namespace Melskin.Converters.Internal;

/// <summary>
/// StringToCodeConverter 类实现了 IValueConverter 接口，用于将字符串转换为具有代码样式的 RichTextBox 控件。该类提供了一个静态实例 Instance，用于在 XAML 中方便地引用。
/// 通过 Convert 方法，可以将输入的字符串转换为富文本格式，并且会对字符串中的特殊字符（如引号、尖括号等）进行高亮显示。ConvertBack 方法返回 DependencyProperty.UnsetValue，表示不支持反向转换。
/// </summary>
internal class StringToCodeConverter : IValueConverter
{
    //显式静态构造函数告诉c#编译器
    //不将type标记为beforefieldinit
    static StringToCodeConverter()
    {
    }

    private StringToCodeConverter()
    {
    }

    /// <summary>
    /// 
    /// </summary>
    public static StringToCodeConverter Instance { get; } = new();

    /// <inheritdoc />
    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
    {
        var str = value as string;
        var textBox = new RichTextBox()
        {
            IsReadOnly = true,
            FontSize = 12,
            Foreground = Brushes.Red,
            BorderThickness = new Thickness(0),
        };

        if (string.IsNullOrEmpty(str)) return textBox;
        const string pattern = "=\".*?\"|[</>]";
        var index = 0;

        var document = new FlowDocument();
        var paragraph = new Paragraph();
        var inlines = paragraph.Inlines;
        str = str?.Replace(@"\n", Environment.NewLine).Replace(@"\t", "\t");

        if (str != null)
        {
            foreach (Match match in Regex.Matches(str, pattern))
            {
                inlines.Add(str.Substring(index, match.Index - index));
                inlines.Add(new Run(match.Value) { Foreground = Brushes.Blue });
                index = match.Index + match.Length;
            }

            inlines.Add(str.Substring(index));
        }

        document.Blocks.Add(paragraph);
        textBox.Document = document;

        return textBox;
    }

    /// <inheritdoc />
    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
    {
        return DependencyProperty.UnsetValue;
    }
}