using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Paca.Core.Config;
using Paca.Core.Hls;
using Xunit;

namespace Paca.Tests.Core;

public class DirectDownloaderIntegrityGateTests : IDisposable
{
    private readonly string _testDir;

    public DirectDownloaderIntegrityGateTests()
    {
        _testDir = Path.Combine(Path.GetTempPath(), "paca_direct_test_" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(_testDir);
    }

    public void Dispose()
    {
        try { if (Directory.Exists(_testDir)) Directory.Delete(_testDir, recursive: true); }
        catch { }
    }

    [Fact]
    public void Gate471_DirectDownloader_GuessExt_DetectsExtensions_FromUrlAndMediaType()
    {
        // Direct extension in URL
        Assert.Equal(".mp4", DirectDownloader.GuessExt("", new Uri("https://paca.stream/video.mp4")));
        Assert.Equal(".webm", DirectDownloader.GuessExt("", new Uri("https://paca.stream/clip.webm")));
        Assert.Equal(".mkv", DirectDownloader.GuessExt("", new Uri("https://paca.stream/movie.mkv")));
        Assert.Equal(".mp3", DirectDownloader.GuessExt("", new Uri("https://paca.stream/audio.mp3")));
        Assert.Equal(".flac", DirectDownloader.GuessExt("", new Uri("https://paca.stream/track.flac")));

        // Fallback from MIME ContentType
        Assert.Equal(".mp4", DirectDownloader.GuessExt("video/mp4", new Uri("https://paca.stream/stream?id=123")));
        Assert.Equal(".webm", DirectDownloader.GuessExt("video/webm", new Uri("https://paca.stream/stream?id=123")));
        Assert.Equal(".m4a", DirectDownloader.GuessExt("audio/mp4", new Uri("https://paca.stream/stream?id=123")));
    }

    [Fact]
    public async Task Gate472_DirectDownloader_VerifiesChecksum_WhenProvided_AndMatches()
    {
        var content = "PACA-DIRECT-DOWNLOAD-VERIFIED-DATA";
        var bytes = Encoding.UTF8.GetBytes(content);
        var sha256 = Convert.ToHexString(SHA256.HashData(bytes)).ToLowerInvariant();

        var handler = new SimpleMockHttp(bytes);
        using var client = new HttpClient(handler);
        var config = new AppConfig();
        var downloader = new DirectDownloader(client, config);

        var outputBase = Path.Combine(_testDir, "test_success");
        var resultPath = await downloader.DownloadAsync(
            new Uri("https://paca.test/file.mp4"),
            outputBase,
            progress: null,
            ct: CancellationToken.None,
            expectedSha256: sha256
        );

        Assert.True(File.Exists(resultPath));
        Assert.Equal(bytes.Length, new FileInfo(resultPath).Length);
        Assert.False(File.Exists(outputBase + ".part"));
    }

    [Fact]
    public async Task Gate473_DirectDownloader_ThrowsInvalidDataException_WhenChecksumMismatches()
    {
        var content = "TAMPERED-DATA-PAYLOAD";
        var bytes = Encoding.UTF8.GetBytes(content);

        var handler = new SimpleMockHttp(bytes);
        using var client = new HttpClient(handler);
        var config = new AppConfig();
        var downloader = new DirectDownloader(client, config);

        var outputBase = Path.Combine(_testDir, "test_corrupt");

        await Assert.ThrowsAsync<InvalidDataException>(async () =>
        {
            await downloader.DownloadAsync(
                new Uri("https://paca.test/file.mp4"),
                outputBase,
                progress: null,
                ct: CancellationToken.None,
                expectedSha256: "0000000000000000000000000000000000000000000000000000000000000000"
            );
        });
    }

    [Fact]
    public async Task Gate474_DirectDownloader_AtomicPartCommit_CleansPartFile_UponCompletion()
    {
        var content = "PACA-ATOMIC-COMMIT-STREAM";
        var bytes = Encoding.UTF8.GetBytes(content);

        var handler = new SimpleMockHttp(bytes);
        using var client = new HttpClient(handler);
        var config = new AppConfig();
        var downloader = new DirectDownloader(client, config);

        var outputBase = Path.Combine(_testDir, "atomic_output");
        var final = await downloader.DownloadAsync(
            new Uri("https://paca.test/video.mp4"),
            outputBase
        );

        Assert.True(File.Exists(final));
        Assert.False(File.Exists(outputBase + ".part"));
    }

    private sealed class SimpleMockHttp : HttpMessageHandler
    {
        private readonly byte[] _data;

        public SimpleMockHttp(byte[] data)
        {
            _data = data;
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            var response = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new ByteArrayContent(_data)
            };
            response.Content.Headers.ContentType = new MediaTypeHeaderValue("video/mp4");
            response.Content.Headers.ContentLength = _data.Length;
            return Task.FromResult(response);
        }
    }
}