using System.Net;
using ErsatzTV.Core.Interfaces.Streaming;
using Microsoft.Extensions.Logging;

namespace ErsatzTV.Infrastructure.Streaming;

/// <summary>
///     Probes a media-server remote-stream URL over HTTP.
/// </summary>
/// <remarks>
///     Deliberately fail-open: only a definitive HTTP 404 reports the media as gone. A probe that
///     times out, errors, or returns any other status must never turn a tune that would have worked
///     into an error card, so every other outcome reports available. (ersatztv#473)
/// </remarks>
public class HttpRemoteStreamProber(
    IHttpClientFactory httpClientFactory,
    ILogger<HttpRemoteStreamProber> logger) : IRemoteStreamProber
{
    private static readonly TimeSpan ProbeTimeout = TimeSpan.FromSeconds(2);

    public async Task<bool> IsAvailable(string url, CancellationToken cancellationToken)
    {
        try
        {
            using var timeoutCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
            timeoutCts.CancelAfter(ProbeTimeout);

            using var request = new HttpRequestMessage(HttpMethod.Get, url);

            // ask for a single byte; media servers vary in their HEAD support, and this exercises the
            // same redirect chain ffmpeg will follow
            request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(0, 0);

            using HttpClient client = httpClientFactory.CreateClient();
            using HttpResponseMessage response = await client.SendAsync(
                request,
                HttpCompletionOption.ResponseHeadersRead,
                timeoutCts.Token);

            if (response.StatusCode is HttpStatusCode.NotFound)
            {
                logger.LogWarning("Media server reported 404 for remote stream {Url}", url);
                return false;
            }

            return true;
        }
        catch (Exception ex)
        {
            // fail open - a probe failure is not evidence that the media is gone
            logger.LogDebug(ex, "Unable to probe remote stream {Url}; assuming it is available", url);
            return true;
        }
    }
}