using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using NSubstitute.ExceptionExtensions;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Templates;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.DeploymentManager.PendingUpdates;
using ZB.MOM.WW.ScadaBridge.TemplateEngine.Flattening;
using ZB.MOM.WW.Secrets.Abstractions;

namespace ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests;

/// <summary>
/// Gitea #62: <see cref="PendingUpdatesEvaluator"/> skips the fleet flatten while the
/// database-side config watermark and the secret-store stamp are unchanged, and never
/// otherwise. "Did a full evaluation happen" is observed as a call to the flatten seam
/// (<see cref="IFlatteningPipeline.ComputeRevisionHashAsync"/>) — the cost being avoided.
/// The watermark here is a substitute; the real reader's peer-node detection is proven
/// against SQL Server in <c>ConfigGraphWatermarkReaderTests</c>.
/// </summary>
public class PendingUpdatesShortCircuitTests
{
    private readonly ISiteRepository _siteRepo = Substitute.For<ISiteRepository>();
    private readonly IDeploymentManagerRepository _deploymentRepo = Substitute.For<IDeploymentManagerRepository>();
    private readonly IFlatteningPipeline _pipeline = Substitute.For<IFlatteningPipeline>();
    private readonly IConfigGraphWatermarkReader _watermark = Substitute.For<IConfigGraphWatermarkReader>();
    private readonly ISecretStore _secrets = Substitute.For<ISecretStore>();
    private readonly PendingUpdatesShortCircuitState _state = new();
    private string _token = "wm-1";
    private List<SecretMetadata> _secretRows = [Secret("db-pass", revision: 1)];

    /// <summary>Wires one site with one deployed, up-to-date instance.</summary>
    public PendingUpdatesShortCircuitTests()
    {
        _pipeline.CreateSession().Returns(_ => new FlattenSession(new TemplateGraphWatermark()));
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>()).Returns([new Site("Alpha", "site-a") { Id = 1 }]);
        _deploymentRepo.GetDeployedInstanceSummariesAsync(Arg.Any<CancellationToken>())
            .Returns([new Instance("Inst7") { Id = 7, SiteId = 1, State = InstanceState.Enabled }]);
        _deploymentRepo.GetDeployedRevisionHashesAsync(Arg.Any<CancellationToken>())
            .Returns(new Dictionary<int, string> { [7] = "h7" });
        _pipeline.ComputeRevisionHashAsync(7, Arg.Any<FlattenSession?>(), Arg.Any<CancellationToken>())
            .Returns(Result<string>.Success("h7"));
        _watermark.ReadAsync(Arg.Any<CancellationToken>()).Returns(_ => _token);
        _secrets.ListAsync(true, Arg.Any<CancellationToken>()).Returns(_ => (IReadOnlyList<SecretMetadata>)_secretRows);
    }

    private static SecretMetadata Secret(string name, long revision, string kek = "kek-1") => new()
    {
        Name = new SecretName(name),
        ContentType = SecretContentType.Text,
        KekId = kek,
        Revision = revision,
        CreatedUtc = new DateTimeOffset(2026, 11, 1, 0, 0, 0, TimeSpan.Zero),
        UpdatedUtc = new DateTimeOffset(2026, 11, 1, 0, 0, 0, TimeSpan.Zero).AddMinutes(revision),
    };

    private PendingUpdatesEvaluator Evaluator(int every = 10, bool wired = true)
    {
        var comms = new CommunicationService(Options.Create(new CommunicationOptions()), NullLogger<CommunicationService>.Instance);
        var options = Options.Create(new DeploymentManagerOptions { PendingUpdatesFullEvaluationEvery = every });
        var artifacts = new ArtifactDeploymentService(
            _siteRepo, _deploymentRepo, Substitute.For<ITemplateEngineRepository>(), Substitute.For<IExternalSystemRepository>(),
            comms, Substitute.For<IAuditService>(), options, NullLogger<ArtifactDeploymentService>.Instance,
            new ArtifactRevisionHashService(), new SiteSecretsCollector(_secrets));
        var deployments = new DeploymentService(
            _deploymentRepo, _siteRepo, Substitute.For<ITemplateEngineRepository>(), _pipeline, comms,
            new OperationLockManager(), Substitute.For<IAuditService>(), new DiffService(), new RevisionHashService(),
            new DeploymentStatusNotifier(NullLogger<DeploymentStatusNotifier>.Instance),
            options, Options.Create(new CommunicationOptions()), NullLogger<DeploymentService>.Instance);
        return wired
            ? new PendingUpdatesEvaluator(_siteRepo, _deploymentRepo, artifacts, deployments,
                NullLogger<PendingUpdatesEvaluator>.Instance, _watermark, _secrets, _state, options)
            : new PendingUpdatesEvaluator(_siteRepo, _deploymentRepo, artifacts, deployments,
                NullLogger<PendingUpdatesEvaluator>.Instance);
    }

    private int FlattenCalls() => _pipeline.ReceivedCalls()
        .Count(c => c.GetMethodInfo().Name == nameof(IFlatteningPipeline.ComputeRevisionHashAsync));

    /// <summary>Verifies that an unchanged watermark and secret stamp re-serve the snapshot without flattening.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task Unchanged_ReservesTheSnapshot_WithoutAFleetFlatten()
    {
        // A stale instance, so the re-served answer is visibly "something pending", not a blank one.
        _pipeline.ComputeRevisionHashAsync(7, Arg.Any<FlattenSession?>(), Arg.Any<CancellationToken>())
            .Returns(Result<string>.Success("h7-edited"));
        _deploymentRepo.GetDeployedSnapshotsByInstanceIdsAsync(Arg.Any<IReadOnlyCollection<int>>(), Arg.Any<CancellationToken>())
            .Returns(new Dictionary<int, Commons.Entities.Deployment.DeployedConfigSnapshot>
            {
                [7] = new("d", "h7", """{"InstanceUniqueName":"Inst7"}""") { InstanceId = 7 },
            });
        var evaluator = Evaluator();

        var first = await evaluator.EvaluateAsync();
        var second = await evaluator.EvaluateAsync();

        Assert.Equal(1, FlattenCalls());
        Assert.Equal(1, first.StaleInstanceCount);
        Assert.Equal(first.Sites, second.Sites);
        Assert.True(second.HasPendingUpdates);
        Assert.True(second.ComputedAt >= first.ComputedAt);
    }

    /// <summary>Verifies that a moved database watermark (e.g. a peer-node edit) forces a full evaluation.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task WatermarkMoved_ForcesAFullEvaluation()
    {
        var evaluator = Evaluator();
        await evaluator.EvaluateAsync();

        _token = "wm-2"; // the shared DB's rowversion/count moved — whichever node wrote it
        await evaluator.EvaluateAsync();

        Assert.Equal(2, FlattenCalls());
    }

    /// <summary>Verifies that a secret-store change (revision, tombstone, re-wrap under a new KEK) forces a full evaluation.</summary>
    /// <param name="change">Which secret change to apply.</param>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Theory]
    [InlineData("revision")]
    [InlineData("added")]
    [InlineData("deleted")]
    [InlineData("kek")]
    public async Task SecretStoreChanged_ForcesAFullEvaluation(string change)
    {
        var evaluator = Evaluator();
        await evaluator.EvaluateAsync();

        _secretRows = change switch
        {
            "revision" => [Secret("db-pass", revision: 2)],
            "added" => [Secret("db-pass", revision: 1), Secret("api-key", revision: 1)],
            "deleted" => [Secret("db-pass", revision: 1) with { IsDeleted = true }],
            _ => [Secret("db-pass", revision: 1, kek: "kek-2")],
        };
        await evaluator.EvaluateAsync();

        Assert.Equal(2, FlattenCalls());
    }

    /// <summary>Verifies that every Nth evaluation is full even when nothing changed (the safety net).</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task EveryNthEvaluation_IsFull_EvenWhenUnchanged()
    {
        var evaluator = Evaluator(every: 3);

        for (var i = 0; i < 7; i++)
            await evaluator.EvaluateAsync();

        // Evaluations 1, 4 and 7 are full; 2, 3, 5, 6 reuse.
        Assert.Equal(3, FlattenCalls());
    }

    /// <summary>Verifies that an unavailable watermark, a failing secret-store listing, or N=1 never short-circuit.</summary>
    /// <param name="mode">Which unavailability to simulate.</param>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Theory]
    [InlineData("no-watermark")]
    [InlineData("watermark-throws")]
    [InlineData("secret-list-throws")]
    [InlineData("every-1")]
    [InlineData("unwired")]
    public async Task NoTrustworthyToken_EveryEvaluationIsFull(string mode)
    {
        switch (mode)
        {
            case "no-watermark": _watermark.ReadAsync(Arg.Any<CancellationToken>()).Returns((string?)null); break;
            case "watermark-throws": _watermark.ReadAsync(Arg.Any<CancellationToken>()).ThrowsAsync(new TimeoutException()); break;
            case "secret-list-throws": _secrets.ListAsync(true, Arg.Any<CancellationToken>()).ThrowsAsync(new InvalidOperationException("store down")); break;
        }

        var evaluator = Evaluator(every: mode == "every-1" ? 1 : 10, wired: mode != "unwired");
        await evaluator.EvaluateAsync();
        await evaluator.EvaluateAsync();
        await evaluator.EvaluateAsync();

        Assert.Equal(3, FlattenCalls());
    }

    /// <summary>
    /// Verifies that an evaluation whose artifact hash could not be computed (a secret-store read
    /// failure while resolving a site's secret reference) is not reused, so the transient
    /// Out-of-date answer clears on the very next evaluation.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task UncleanEvaluation_IsNotReused()
    {
        _siteRepo.GetDataConnectionsBySiteIdAsync(1, Arg.Any<CancellationToken>())
            .Returns([new DataConnection("GW1", "MxGateway", 1) { PrimaryConfiguration = """{"ApiKey":"secret:db-pass"}""" }]);
        _secrets.GetAsync(Arg.Any<SecretName>(), Arg.Any<CancellationToken>()).ThrowsAsync(new TimeoutException("store down"));
        var evaluator = Evaluator();

        await evaluator.EvaluateAsync();
        await evaluator.EvaluateAsync();

        Assert.Equal(2, FlattenCalls());
    }

    /// <summary>Verifies that the cache's Re-check (forceRefresh) bypasses the short-circuit.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task CacheForceRefresh_BypassesTheShortCircuit()
    {
        var services = new ServiceCollection();
        services.AddSingleton(_state);
        services.AddScoped<IPendingUpdatesEvaluator>(_ => Evaluator());
        await using var provider = services.BuildServiceProvider();
        using var cache = new PendingUpdatesCache(
            provider.GetRequiredService<IServiceScopeFactory>(),
            Options.Create(new DeploymentManagerOptions()),
            new DeploymentStatusNotifier(NullLogger<DeploymentStatusNotifier>.Instance));

        await cache.GetAsync();
        await cache.GetAsync(forceRefresh: true); // unchanged token, but the operator asked: full
        Assert.Equal(2, FlattenCalls());

        await cache.GetAsync(forceRefresh: true);
        Assert.Equal(3, FlattenCalls());
    }

    /// <summary>Verifies that a deploy completion makes the next evaluation full.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task DeployCompletion_MakesTheNextEvaluationFull()
    {
        var notifier = new DeploymentStatusNotifier(NullLogger<DeploymentStatusNotifier>.Instance);
        var services = new ServiceCollection();
        services.AddSingleton(_state);
        services.AddScoped<IPendingUpdatesEvaluator>(_ => Evaluator());
        await using var provider = services.BuildServiceProvider();
        using var cache = new PendingUpdatesCache(
            provider.GetRequiredService<IServiceScopeFactory>(),
            Options.Create(new DeploymentManagerOptions()),
            notifier);

        await cache.GetAsync();
        notifier.NotifyStatusChanged(new DeploymentStatusChange("dep-7", 7, DeploymentStatus.Success));
        await cache.GetAsync();

        Assert.Equal(2, FlattenCalls());
    }
}