ttui/src/TinyTUI/Text/ITextMeasurer.cs

namespace TinyTUI.Text;

/// <summary>
/// 按终端字符单元宽度规则测量和裁剪字符串
/// </summary>
public interface ITextMeasurer
{
    /// <summary>
    /// 获取字符串占用的终端字符单元数量
    /// </summary>
    int GetWidth(string value);

    /// <summary>
    /// 裁剪字符串使其渲染宽度不超过给定字符单元宽度
    /// </summary>
    string Truncate(string value, int maxWidth);

    /// <summary>
    /// 裁剪字符串并在确实发生裁剪时追加省略符
    /// </summary>
    string Truncate(string value, int maxWidth, string ellipsis, bool pad = false)
    {
        if (maxWidth <= 0)
            return string.Empty;

        var width = GetWidth(value);
        if (width <= maxWidth)
            return pad ? value + new string(' ', maxWidth - width) : value;

        var ellipsisWidth = GetWidth(ellipsis);
        if (ellipsisWidth >= maxWidth)
        {
            var ellipsisSlice = Slice(ellipsis, 0, maxWidth, strict: true);
            var clipped = ellipsisSlice.Text.Length == 0 ? string.Empty : $"\e[0m{ellipsisSlice.Text}\e[0m";
            return pad ? clipped + new string(' ', Math.Max(0, maxWidth - ellipsisSlice.Width)) : clipped;
        }

        var prefix = Slice(value, 0, maxWidth - ellipsisWidth, strict: true);
        var result = ellipsis.Length == 0
            ? $"{prefix.Text}\e[0m"
            : $"{prefix.Text}\e[0m{ellipsis}\e[0m";

        return pad ? result + new string(' ', Math.Max(0, maxWidth - prefix.Width - ellipsisWidth)) : result;
    }

    /// <summary>
    /// 按可见列切出字符串片段并返回片段实际宽度
    /// </summary>
    TextSlice Slice(string value, int startColumn, int maxWidth, bool strict = true)
    {
        if (startColumn <= 0)
        {
            var text = Truncate(value, maxWidth);
            return new TextSlice(text, GetWidth(text));
        }

        var prefix = Truncate(value, startColumn);
        var remainder = value[prefix.Length..];
        var sliced = Truncate(remainder, maxWidth);
        return new TextSlice(sliced, GetWidth(sliced));
    }

    /// <summary>
    /// 按可见宽度换行并尽量保留终端样式状态
    /// </summary>
    IReadOnlyList<string> Wrap(string value, int width)
    {
        if (value.Length == 0)
            return [string.Empty];

        if (width <= 0)
            return value.Split('\n').Select(_ => string.Empty).ToArray();

        var lines = new List<string>();
        foreach (var line in value.Split('\n'))
        {
            if (GetWidth(line) <= width)
            {
                lines.Add(line);
                continue;
            }

            for (var column = 0; column < GetWidth(line); column += width)
                lines.Add(Slice(line, column, width, strict: true).Text);
        }

        return lines.Count == 0 ? [string.Empty] : lines;
    }
}