using Microsoft.Extensions.Logging;

namespace Nuuru.Server.Services;

public interface IPostCacheInvalidationService
{
    Task PurgePostMutationAsync(
        int postId,
        CancellationToken cancellationToken = default);

    Task PurgePostMutationsAsync(
        IEnumerable<int> postIds,
        CancellationToken cancellationToken = default);
}

public sealed class PostCacheInvalidationService : IPostCacheInvalidationService
{
    private readonly ICloudflareCachePurgeService _cloudflareCachePurgeService;
    private readonly ILogger<PostCacheInvalidationService> _logger;

    public PostCacheInvalidationService(
        ICloudflareCachePurgeService cloudflareCachePurgeService,
        ILogger<PostCacheInvalidationService> logger)
    {
        _cloudflareCachePurgeService = cloudflareCachePurgeService;
        _logger = logger;
    }

    public Task PurgePostMutationAsync(
        int postId,
        CancellationToken cancellationToken = default)
    {
        return PurgePostMutationsAsync([postId], cancellationToken);
    }

    public async Task PurgePostMutationsAsync(
        IEnumerable<int> postIds,
        CancellationToken cancellationToken = default)
    {
        var paths = BuildPaths(postIds);
        if (paths.Count == 0)
        {
            return;
        }

        var purged = await _cloudflareCachePurgeService.PurgeUrisAsync(paths, cancellationToken);
        if (!purged)
        {
            _logger.LogDebug("Cloudflare post cache purge skipped or failed for {Paths}", paths);
        }
    }

    private static List<string> BuildPaths(IEnumerable<int> postIds)
    {
        return postIds
            .Distinct()
            .SelectMany(static postId => new[]
            {
                $"/api/booru/posts/{postId}/file",
                $"/api/booru/posts/{postId}/file-watermark",
                $"/api/booru/posts/{postId}/thumbnail"
            })
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToList();
    }
}