using AngleSharp;
using AngleSharp.Dom;

namespace Nuuru.Server.Services;

public enum HtmlEnrichmentTarget
{
    ForumPost = 1
}

public enum HtmlEnrichmentPhase
{
    Immediate = 1,
    Deferred = 2
}

public sealed record HtmlEnrichmentContext(HtmlEnrichmentTarget Target, int? ForumPostId = null)
{
    public static HtmlEnrichmentContext ForForumPost(int? forumPostId = null) => new(HtmlEnrichmentTarget.ForumPost, forumPostId);
}

public sealed record HtmlEnrichmentResult(string Html, int Version);

public interface IHtmlEnrichmentService
{
    int ImmediateVersion { get; }
    int CurrentVersion { get; }
    bool NeedsEnrichment(string html, int contentHtmlVersion, HtmlEnrichmentContext context);
    Task<HtmlEnrichmentResult> EnrichImmediateAsync(string html, HtmlEnrichmentContext context, CancellationToken cancellationToken = default);
    Task<HtmlEnrichmentResult> EnrichAsync(string html, HtmlEnrichmentContext context, CancellationToken cancellationToken = default);
}

public interface IHtmlEnricher
{
    HtmlEnrichmentPhase Phase { get; }
    Task<bool> EnrichAsync(IDocument document, HtmlEnrichmentContext context, CancellationToken cancellationToken = default);
}

public sealed class HtmlEnrichmentService : IHtmlEnrichmentService
{
    private static readonly IBrowsingContext BrowsingContext = AngleSharp.BrowsingContext.New(Configuration.Default);
    public const int ForumPostImmediateContentHtmlVersion = 1;
    public const int ForumPostContentHtmlVersion = 3;

    private readonly IReadOnlyList<IHtmlEnricher> _enrichers;

    public HtmlEnrichmentService(IEnumerable<IHtmlEnricher> enrichers)
    {
        _enrichers = enrichers.ToList();
    }

    public int ImmediateVersion => ForumPostImmediateContentHtmlVersion;
    public int CurrentVersion => ForumPostContentHtmlVersion;

    public bool NeedsEnrichment(string html, int contentHtmlVersion, HtmlEnrichmentContext context)
    {
        return !string.IsNullOrWhiteSpace(html) && contentHtmlVersion < GetTargetVersion(context, HtmlEnrichmentPhase.Deferred);
    }

    public Task<HtmlEnrichmentResult> EnrichImmediateAsync(string html, HtmlEnrichmentContext context, CancellationToken cancellationToken = default)
    {
        return EnrichInternalAsync(html, context, HtmlEnrichmentPhase.Immediate, cancellationToken);
    }

    public Task<HtmlEnrichmentResult> EnrichAsync(string html, HtmlEnrichmentContext context, CancellationToken cancellationToken = default)
    {
        return EnrichInternalAsync(html, context, HtmlEnrichmentPhase.Deferred, cancellationToken);
    }

    private async Task<HtmlEnrichmentResult> EnrichInternalAsync(
        string html,
        HtmlEnrichmentContext context,
        HtmlEnrichmentPhase maxPhase,
        CancellationToken cancellationToken)
    {
        var targetVersion = GetTargetVersion(context, maxPhase);
        if (string.IsNullOrWhiteSpace(html))
            return new HtmlEnrichmentResult(html, targetVersion);

        var document = await BrowsingContext.OpenAsync(req => req.Content(html), cancellationToken);

        foreach (var enricher in _enrichers)
        {
            if (enricher.Phase > maxPhase)
                continue;

            await enricher.EnrichAsync(document, context, cancellationToken);
        }

        return new HtmlEnrichmentResult(document.Body?.InnerHtml ?? html, targetVersion);
    }

    private static int GetTargetVersion(HtmlEnrichmentContext context, HtmlEnrichmentPhase maxPhase)
    {
        return context.Target switch
        {
            HtmlEnrichmentTarget.ForumPost => maxPhase == HtmlEnrichmentPhase.Immediate
                ? ForumPostImmediateContentHtmlVersion
                : ForumPostContentHtmlVersion,
            _ => ForumPostContentHtmlVersion
        };
    }
}