using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace LightlessSyncStaticFilesServer.Services;

public class CDNDownloadsService
{
    public enum ResultStatus
    {
        Disabled,
        Unauthorized,
        NotFound,
        Success
    }

    public readonly record struct Result(ResultStatus Status, FileInfo? File, Stream? Stream, long? ContentLength);

    private readonly CDNDownloadUrlService _cdnDownloadUrlService;
    private readonly CachedFileProvider _cachedFileProvider;

    public CDNDownloadsService(CDNDownloadUrlService cdnDownloadUrlService, CachedFileProvider cachedFileProvider)
    {
        _cdnDownloadUrlService = cdnDownloadUrlService;
        _cachedFileProvider = cachedFileProvider;
    }

    public bool DownloadsEnabled => _cdnDownloadUrlService.DirectDownloadsEnabled;

    public async Task<Result> GetDownloadAsync(string hash, long expiresUnixSeconds, string signature, CancellationToken ct)
    {
        if (!_cdnDownloadUrlService.DirectDownloadsEnabled)
        {
            return new Result(ResultStatus.Disabled, null, null, null);
        }

        if (string.IsNullOrEmpty(signature) || string.IsNullOrEmpty(hash))
        {
            return new Result(ResultStatus.Unauthorized, null, null, null);
        }

        hash = hash.ToUpperInvariant();

        if (!_cdnDownloadUrlService.TryValidateSignature(hash, expiresUnixSeconds, signature))
        {
            return new Result(ResultStatus.Unauthorized, null, null, null);
        }

        var fileResult = await _cachedFileProvider.GetFileStreamForDirectDownloadAsync(hash, ct).ConfigureAwait(false);
        if (fileResult == null)
        {
            return new Result(ResultStatus.NotFound, null, null, null);
        }

        return new Result(ResultStatus.Success, fileResult.Value.File, fileResult.Value.Stream, fileResult.Value.ContentLength);
    }
}