using AngleSharp;
using AngleSharp.Dom;
using Ganss.Xss;
using Markdig;
using IConfiguration = Microsoft.Extensions.Configuration.IConfiguration;

namespace Dpz.Core.Web.Library;

/// <summary>
/// Mumble 视图帮助类，提供图片处理和 Markdown 转换等功能
/// </summary>
public class MumbleViewHelper(IConfiguration configuration)
{
    private readonly string _cdnHost = configuration["upyun:Host"] ?? string.Empty;
    private readonly IBrowsingContext _context = BrowsingContext.New(Configuration.Default);
    private readonly HtmlSanitizer _sanitizer = CreateSanitizer(configuration);

    /// <summary>
    /// 判断图片是否为自有 CDN 图片
    /// </summary>
    /// <param name="imageUrl">图片 URL</param>
    /// <returns>是否为自有 CDN 图片</returns>
    private bool IsOwnCdnImage(string? imageUrl)
    {
        if (string.IsNullOrWhiteSpace(_cdnHost) || string.IsNullOrWhiteSpace(imageUrl))
        {
            return false;
        }

        try
        {
            var imageUri = new Uri(imageUrl, UriKind.Absolute);
            var cdnUri = new Uri(_cdnHost, UriKind.Absolute);
            return string.Equals(imageUri.Host, cdnUri.Host, StringComparison.OrdinalIgnoreCase);
        }
        catch
        {
            return false;
        }
    }

    /// <summary>
    /// 获取缩略图 URL
    /// </summary>
    /// <param name="imageUrl">原图 URL</param>
    /// <returns>缩略图 URL</returns>
    public string GetThumbnailUrl(string imageUrl)
    {
        return IsOwnCdnImage(imageUrl) ? imageUrl + "!thumb" : imageUrl;
    }

    /// <summary>
    /// 处理 Markdown 并提取图片
    /// </summary>
    /// <param name="html">HTML 内容</param>
    /// <param name="sanitize">是否进行 XSS 清理，默认为 true</param>
    /// <returns>处理后的内容和图片列表</returns>
    public async Task<(string content, List<string> images)> ProcessHtmlAndExtractImages(
        string html,
        bool sanitize = true
    )
    {
        var document = await _context.OpenAsync(y => y.Content(html));
        var imageUrls = new List<string>();

        ProcessLinks(document);
        ExtractImages(document, imageUrls);

        var content = sanitize
            ? _sanitizer.Sanitize(document.Body?.InnerHtml ?? string.Empty)
            : document.Body?.InnerHtml ?? string.Empty;

        return (content, imageUrls);
    }

    /// <summary>
    /// 从 Markdown 提取图片（用于历史记录）
    /// </summary>
    /// <param name="markdown">Markdown 内容</param>
    /// <returns>处理后的 HTML 内容和图片列表</returns>
    public async Task<(string content, List<string> images)> ExtractImagesFromMarkdown(
        string markdown
    )
    {
        var pipeline = new MarkdownPipelineBuilder().DisableHtml().Build();
        var html = Markdown.ToHtml(markdown, pipeline);
        var document = await _context.OpenAsync(x => x.Content(html));
        var imageUrls = new List<string>();

        ExtractImages(document, imageUrls);

        return (document.Body?.InnerHtml ?? string.Empty, imageUrls);
    }

    /// <summary>
    /// 处理链接，添加 target 和 rel 属性
    /// </summary>
    private static void ProcessLinks(IDocument document)
    {
        var links = document.GetElementsByTagName("a");
        foreach (var link in links)
        {
            var href = link.GetAttribute("href");
            if (
                href != null
                && !href.StartsWith("javascript", StringComparison.CurrentCultureIgnoreCase)
            )
            {
                link.SetAttribute("target", "_blank");
                link.SetAttribute("rel", "noopener noreferrer");
            }
        }
    }

    /// <summary>
    /// 提取并移除图片元素
    /// </summary>
    private static void ExtractImages(IDocument document, List<string> imageUrls)
    {
        var images = document.GetElementsByTagName("img");
        var imagesToRemove = new List<IElement>();

        foreach (var img in images)
        {
            var src = img.GetAttribute("src");
            if (
                !string.IsNullOrWhiteSpace(src)
                && !src.Contains("notfound.png", StringComparison.OrdinalIgnoreCase)
            )
            {
                imageUrls.Add(src);
                imagesToRemove.Add(img);
            }
        }

        foreach (var img in imagesToRemove)
        {
            img.Remove();
        }
    }

    /// <summary>
    /// 创建 HtmlSanitizer 实例
    /// </summary>
    private static HtmlSanitizer CreateSanitizer(IConfiguration configuration)
    {
        var rule = configuration.GetSection("XSS").Get<CrossSiteRule>();
        return rule?.CustomHtmlSanitizer() as HtmlSanitizer ?? new HtmlSanitizer();
    }
}