using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Sozsoft.Mcp.Dtos;

namespace Sozsoft.Mcp;

/// <summary>
/// Talep aciklamasina yapistirilan gorseller HtmlEditor'da base64 <c>data:</c> URI olarak
/// saklanir. Model bu metni resim olarak goremez; gorseller ayiklanip MCP gorsel icerigi olarak
/// iletilir, metinde yerlerine bir isaret kalir. Yalnizca modelin okuyabildigi bicimler ayiklanir;
/// digerleri (svg gibi) metinde oldugu gibi birakilir.
/// </summary>
internal static partial class McpDevRequestImages
{
    private static readonly HashSet<string> SupportedMimeTypes = new(StringComparer.OrdinalIgnoreCase)
    {
        "image/png", "image/jpeg", "image/gif", "image/webp"
    };

    [GeneratedRegex("""<img\b[^>]*?\bsrc\s*=\s*["']data:(?<mime>image/[\w.+-]+);base64,(?<data>[^"']+)["'][^>]*>""", RegexOptions.IgnoreCase)]
    private static partial Regex EmbeddedImage();

    public static (string? Html, List<McpDevRequestImageDto> Images) Extract(string? html)
    {
        var images = new List<McpDevRequestImageDto>();
        if (string.IsNullOrEmpty(html))
        {
            return (html, images);
        }

        var text = EmbeddedImage().Replace(html, match =>
        {
            var mimeType = match.Groups["mime"].Value.ToLowerInvariant();
            var data = Regex.Replace(match.Groups["data"].Value, @"\s+", string.Empty);

            if (!SupportedMimeTypes.Contains(mimeType) || !IsBase64(data))
            {
                return match.Value;
            }

            var placeholder = $"[image-{images.Count + 1}]";
            images.Add(new McpDevRequestImageDto { Placeholder = placeholder, MimeType = mimeType, Data = data });

            return placeholder;
        });

        return (text, images);
    }

    private static bool IsBase64(string data)
        => Convert.TryFromBase64String(data, new byte[data.Length * 3 / 4], out _);
}