using AngleSharp.Dom;
using Microsoft.EntityFrameworkCore;
using Nuuru.Server.Data;

namespace Nuuru.Server.Services;

public sealed class EmbeddedImageDimensionsHtmlEnricher : IHtmlEnricher
{
    public HtmlEnrichmentPhase Phase => HtmlEnrichmentPhase.Immediate;

    private readonly ApplicationDbContext _context;
    private readonly int _thumbnailMaxWidth;
    private readonly int _thumbnailMaxHeight;

    public EmbeddedImageDimensionsHtmlEnricher(
        ApplicationDbContext context,
        IConfiguration configuration)
    {
        _context = context;
        _thumbnailMaxWidth = configuration.GetValue<int>("Thumbnails:MaxWidth", 300);
        _thumbnailMaxHeight = configuration.GetValue<int>("Thumbnails:MaxHeight", 300);
    }

    public async Task<bool> EnrichAsync(IDocument document, HtmlEnrichmentContext context, CancellationToken cancellationToken = default)
    {
        if (context.Target != HtmlEnrichmentTarget.ForumPost)
            return false;

        var images = document.QuerySelectorAll("img").OfType<IElement>().ToList();
        if (images.Count == 0)
            return false;

        var attachmentIds = images
            .Select(GetAttachmentId)
            .Where(id => id.HasValue)
            .Select(id => id!.Value)
            .Distinct()
            .ToList();

        Dictionary<Guid, (int Width, int Height)> attachmentDimensions;
        if (attachmentIds.Count == 0)
        {
            attachmentDimensions = [];
        }
        else
        {
            attachmentDimensions = await _context.ForumPostAttachments
                .AsNoTracking()
                .Where(attachment => attachmentIds.Contains(attachment.Id) && attachment.Width.HasValue && attachment.Height.HasValue)
                .ToDictionaryAsync(
                    attachment => attachment.Id,
                    attachment => (attachment.Width!.Value, attachment.Height!.Value),
                    cancellationToken);
        }

        var changed = false;

        foreach (var image in images)
        {
            var attachmentId = GetAttachmentId(image);
            if (!attachmentId.HasValue)
                continue;

            if (!attachmentDimensions.TryGetValue(attachmentId.Value, out var dimensions))
                continue;

            var src = image.GetAttribute("src");
            var targetDimensions = src?.Contains("/thumb", StringComparison.OrdinalIgnoreCase) == true
                ? ScaleToFit(dimensions.Width, dimensions.Height, _thumbnailMaxWidth, _thumbnailMaxHeight)
                : dimensions;

            if (HasDimensions(image)
                && image.GetAttribute("width") == targetDimensions.Width.ToString()
                && image.GetAttribute("height") == targetDimensions.Height.ToString())
            {
                continue;
            }

            image.SetAttribute("width", targetDimensions.Width.ToString());
            image.SetAttribute("height", targetDimensions.Height.ToString());
            changed = true;
        }

        return changed;
    }

    private static Guid? GetAttachmentId(IElement image)
    {
        var rawAttachmentId = image.GetAttribute("data-attachment-id");
        return Guid.TryParse(rawAttachmentId, out var attachmentId) ? attachmentId : null;
    }

    private static bool HasDimensions(IElement image)
    {
        return int.TryParse(image.GetAttribute("width"), out var width) && width > 0
            && int.TryParse(image.GetAttribute("height"), out var height) && height > 0;
    }

    private static (int Width, int Height) ScaleToFit(int width, int height, int maxWidth, int maxHeight)
    {
        if (width <= 0 || height <= 0 || maxWidth <= 0 || maxHeight <= 0)
            return (width, height);

        var scale = Math.Min(1d, Math.Min((double)maxWidth / width, (double)maxHeight / height));
        return ((int)Math.Max(1, Math.Round(width * scale)), (int)Math.Max(1, Math.Round(height * scale)));
    }
}