using System;
using System.Threading;
using System.Threading.Tasks;
using Emby.Server.Implementations.MediaEncoding;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Moq;
using StackExchange.Redis;
using Xunit;

namespace Jellyfin.Server.Tests.HighAvailability;

/// <summary>
/// A transcode store that cannot be reached degrades silently: the client is configured not to abort
/// the connection and every call site swallows failures. Quick connect's startup read is what stops a
/// pod coming up against a dead store; this probe only reports it, so both of its outcomes are pinned
/// here - including that it never throws, which is what keeps the two policies from competing.
/// </summary>
public sealed class TranscodeStoreConnectivityProbeTests
{
    [Fact]
    public async Task StartAsync_Should_Log_Information_When_Reachable()
    {
        var database = new Mock<IDatabase>();
        database.Setup(db => db.PingAsync(It.IsAny<CommandFlags>())).ReturnsAsync(TimeSpan.FromMilliseconds(3));

        var (logger, probe) = CreateProbe(database.Object);

        await probe.StartAsync(CancellationToken.None);

        Assert.True(logger.HasEntry(LogLevel.Information, "reachable"));
        Assert.DoesNotContain(logger.Entries, entry => entry.Level >= LogLevel.Warning);
    }

    [Fact]
    public async Task StartAsync_Should_Log_Error_When_Unreachable()
    {
        var database = new Mock<IDatabase>();
        database.Setup(db => db.PingAsync(It.IsAny<CommandFlags>()))
            .ThrowsAsync(new RedisConnectionException(ConnectionFailureType.UnableToConnect, "no route to host"));

        var (logger, probe) = CreateProbe(database.Object);

        await probe.StartAsync(CancellationToken.None);

        Assert.True(logger.HasEntry(LogLevel.Error, "UNREACHABLE"));
    }

    [Fact]
    public async Task StartAsync_Should_Log_Error_Instead_Of_Aborting_Startup()
    {
        var services = new ServiceCollection();
        services.AddSingleton<IConnectionMultiplexer>(_ => throw new RedisConnectionException(ConnectionFailureType.UnableToConnect, "no route to host"));
        using var provider = services.BuildServiceProvider();

        var logger = new RecordingLogger<TranscodeStoreConnectivityProbe>();
        var probe = new TranscodeStoreConnectivityProbe(provider, logger);

        await probe.StartAsync(CancellationToken.None);

        Assert.True(logger.HasEntry(LogLevel.Error, "UNREACHABLE"));
    }

    private static (RecordingLogger<TranscodeStoreConnectivityProbe> Logger, TranscodeStoreConnectivityProbe Probe) CreateProbe(IDatabase database)
    {
        var multiplexer = new Mock<IConnectionMultiplexer>();
        multiplexer.Setup(redis => redis.GetDatabase(It.IsAny<int>(), It.IsAny<object>())).Returns(database);

        var services = new ServiceCollection();
        services.AddSingleton(multiplexer.Object);
        var provider = services.BuildServiceProvider();

        var logger = new RecordingLogger<TranscodeStoreConnectivityProbe>();
        return (logger, new TranscodeStoreConnectivityProbe(provider, logger));
    }
}