using System.Text.Json;
using Akka.Actor;
using Akka.TestKit.Xunit2;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.DebugView;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Actors;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.TestSupport;
using ZB.MOM.WW.ScadaBridge.TestSupport;

namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Actors;

/// <summary>
/// Review 2026-10-21 01/SR-P1: the instance reconcile sweep compared only name / enabled /
/// revision, yet materialised every row's <c>config_json</c> on every tick — tens of MB of LOH
/// strings per minute on a healthy large site. It now reads a metadata-only projection and
/// fetches a full row only for an instance it actually starts or restarts.
/// </summary>
public class InstanceSweepMetadataReadTests : TestKit, IDisposable
{
    private readonly SiteStorageService _storage;
    private readonly ScriptCompilationService _compilationService;
    private readonly SharedScriptLibrary _sharedScriptLibrary;
    private readonly TestLocalDb _localDb;

    private int _fullTableReads;
    private int _singleRowReads;

    /// <summary>Creates a temporary LocalDb-backed site store per test.</summary>
    public InstanceSweepMetadataReadTests()
    {
        _localDb = TestLocalDb.CreateTemp("sweep-metadata-read");
        _storage = new SiteStorageService(_localDb.Db, NullLogger<SiteStorageService>.Instance);
        _storage.InitializeAsync().GetAwaiter().GetResult();
        _compilationService = new ScriptCompilationService(NullLogger<ScriptCompilationService>.Instance);
        _sharedScriptLibrary = new SharedScriptLibrary(
            _compilationService, NullLogger<SharedScriptLibrary>.Instance);
    }

    /// <inheritdoc />
    void IDisposable.Dispose()
    {
        Shutdown();
        var path = _localDb.Path;
        _localDb.Dispose();
        TestLocalDb.DeleteFiles(path);
    }

    private static string ConfigJson(string name) => JsonSerializer.Serialize(new FlattenedConfiguration
    {
        InstanceUniqueName = name,
        Attributes = [new ResolvedAttribute { CanonicalName = "A", Value = "1", DataType = "Int32" }]
    });

    private async Task<List<DeployedInstance>> CountingFullLoad()
    {
        Interlocked.Increment(ref _fullTableReads);
        return await _storage.GetAllDeployedConfigsAsync();
    }

    private async Task<DeployedInstance?> CountingSingleRowLoad(string name)
    {
        Interlocked.Increment(ref _singleRowReads);
        return await _storage.GetDeployedConfigAsync(name);
    }

    private IActorRef CreateBootedDeploymentManager()
    {
        var health = new DeploymentManagerStartupProbe();
        Func<Task<List<DeployedInstance>>> fullLoad = CountingFullLoad;
        Func<string, Task<DeployedInstance?>> rowLoad = CountingSingleRowLoad;
        var dm = ActorOf(Props.Create(() => new DeploymentManagerActor(
            _storage,
            _compilationService,
            _sharedScriptLibrary,
            null,
            new SiteRuntimeOptions { InstanceSweepIntervalSeconds = 1, StartupBatchDelayMs = 10 },
            NullLogger<DeploymentManagerActor>.Instance,
            null,
            health,
            null,
            null,
            null,
            null,
            fullLoad,
            null,
            null,
            null,
            rowLoad,
            null)));
        AwaitCondition(() => health.ReportCount > 0, TimeSpan.FromSeconds(20), TimeSpan.FromMilliseconds(25));
        return dm;
    }

    private async Task<bool> IsRunningAsync(IActorRef dm, string name)
    {
        var snapshot = await dm.Ask<DebugViewSnapshot>(
            new DebugSnapshotRequest(name, Guid.NewGuid().ToString("N")), TimeSpan.FromSeconds(5));
        return !snapshot.InstanceNotFound;
    }

    /// <summary>A healthy site's sweep never reads a config blob: one full read (boot), zero row reads.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task HealthySweep_ReadsNoConfigJson()
    {
        await _storage.StoreDeployedConfigAsync("P1", ConfigJson("P1"), "d1", "r1", true);
        await _storage.StoreDeployedConfigAsync("P2", ConfigJson("P2"), "d2", "r2", true);
        var dm = CreateBootedDeploymentManager();
        await AwaitAssertAsync(async () => Assert.True(await IsRunningAsync(dm, "P2")), TimeSpan.FromSeconds(10));

        await Task.Delay(TimeSpan.FromSeconds(4)); // several sweep ticks

        Assert.Equal(1, Volatile.Read(ref _fullTableReads));
        Assert.Equal(0, Volatile.Read(ref _singleRowReads));
    }

    /// <summary>
    /// A repair still works: a row that appears after boot (as CDC replication would deliver it)
    /// is started, its config fetched by a single-row read.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task SweepStart_FetchesOnlyTheRowItStarts()
    {
        var dm = CreateBootedDeploymentManager();
        await _storage.StoreDeployedConfigAsync("Late1", ConfigJson("Late1"), "d1", "r1", true);

        await AwaitAssertAsync(async () => Assert.True(await IsRunningAsync(dm, "Late1")), TimeSpan.FromSeconds(15));

        Assert.Equal(1, Volatile.Read(ref _fullTableReads));
        Assert.Equal(1, Volatile.Read(ref _singleRowReads));
    }
}