using System.Text.Json;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Deployment;
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.Interfaces.Transport;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
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.ScadaBridge.TemplateEngine.Validation;

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

/// <summary>
/// Coverage for <see cref="PendingUpdatesEvaluator"/> — the single fleet-wide read
/// behind the Central UI rail indicator and the Sites page badges.
///
/// <para>
/// The evaluator is built over the REAL <see cref="ArtifactDeploymentService"/> and
/// <see cref="DeploymentService"/> (substituting only their repository and flattening
/// seams, as the sibling suites do), because the two properties worth pinning are
/// exactly the ones a mocked collaborator would paper over: that the artifact state
/// is decided by comparing the site's STORED hash against a hash recomputed from the
/// current definitions, and that only instances the operator has actually deployed
/// are ever handed to the staleness batch.
/// </para>
/// </summary>
public class PendingUpdatesEvaluatorTests
{
    private readonly ISiteRepository _siteRepo = Substitute.For<ISiteRepository>();
    private readonly ITemplateEngineRepository _templateRepo = Substitute.For<ITemplateEngineRepository>();
    private readonly IExternalSystemRepository _externalSystemRepo = Substitute.For<IExternalSystemRepository>();
    private readonly INotificationRepository _notificationRepo = Substitute.For<INotificationRepository>();
    private readonly IDeploymentManagerRepository _deploymentRepo = Substitute.For<IDeploymentManagerRepository>();
    private readonly IFlatteningPipeline _pipeline = Substitute.For<IFlatteningPipeline>();
    private readonly IAuditService _audit = Substitute.For<IAuditService>();
    private readonly RevisionHashService _hasher = new();
    private readonly ArtifactRevisionHashService _artifactHasher = new();

    private readonly ArtifactDeploymentService _artifactService;
    private readonly DeploymentService _deploymentService;
    private readonly PendingUpdatesEvaluator _evaluator;

    /// <summary>
    /// Builds the evaluator over the real services; every repository and the
    /// flattening pipeline are substituted.
    /// </summary>
    public PendingUpdatesEvaluatorTests()
    {
        _pipeline.CreateSession().Returns(new FlattenSession(new TemplateGraphWatermark()));

        var comms = new CommunicationService(
            Options.Create(new CommunicationOptions()),
            NullLogger<CommunicationService>.Instance);

        _artifactService = new ArtifactDeploymentService(
            _siteRepo, _deploymentRepo, _templateRepo, _externalSystemRepo, _notificationRepo,
            comms, _audit,
            Options.Create(new DeploymentManagerOptions()),
            NullLogger<ArtifactDeploymentService>.Instance,
            _artifactHasher);

        _deploymentService = new DeploymentService(
            _deploymentRepo,
            _siteRepo,
            _pipeline,
            comms,
            new OperationLockManager(),
            _audit,
            new DiffService(),
            _hasher,
            new DeploymentStatusNotifier(NullLogger<DeploymentStatusNotifier>.Instance),
            Substitute.For<IStaleInstanceProbe>(),
            Options.Create(new DeploymentManagerOptions()),
            Options.Create(new CommunicationOptions()),
            NullLogger<DeploymentService>.Instance);

        _evaluator = new PendingUpdatesEvaluator(
            _siteRepo, _templateRepo, _artifactService, _deploymentService,
            NullLogger<PendingUpdatesEvaluator>.Instance);
    }

    // ── arrange helpers ──────────────────────────────────────────────────────

    /// <summary>Stubs the site list read.</summary>
    private void ArrangeSites(params Site[] sites) =>
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>()).Returns(sites);

    /// <summary>Stubs the instance list read.</summary>
    private void ArrangeInstances(params Instance[] instances) =>
        _templateRepo.GetAllInstancesAsync(Arg.Any<CancellationToken>()).Returns(instances);

    /// <summary>Builds an instance in the given lifecycle state at the given site.</summary>
    private static Instance MakeInstance(int id, int siteId, InstanceState state) =>
        new($"Inst{id}") { Id = id, SiteId = siteId, State = state };

    /// <summary>Builds a one-attribute flattened config with the given scalar value.</summary>
    private static FlattenedConfiguration ScalarConfig(string value) => new()
    {
        InstanceUniqueName = "TestInst",
        Attributes = [new ResolvedAttribute { CanonicalName = "Setpoint", Value = value, DataType = "Int32" }]
    };

    /// <summary>Stubs a successful flatten of <paramref name="instanceId"/> at the given hash.</summary>
    private void ArrangeFlatten(int instanceId, FlattenedConfiguration config, string hash) =>
        _pipeline.FlattenAndValidateAsync(
                instanceId, Arg.Any<CancellationToken>(), Arg.Any<bool>(), Arg.Any<FlattenSession?>())
            .Returns(Result<FlatteningPipelineResult>.Success(
                new FlatteningPipelineResult(config, hash, ValidationResult.Success())));

    /// <summary>Stubs a FAILED flatten of <paramref name="instanceId"/> — the "unknown" leg.</summary>
    private void ArrangeFlattenFailure(int instanceId) =>
        _pipeline.FlattenAndValidateAsync(
                instanceId, Arg.Any<CancellationToken>(), Arg.Any<bool>(), Arg.Any<FlattenSession?>())
            .Returns(Result<FlatteningPipelineResult>.Failure("template missing"));

    /// <summary>Stubs the (InstanceId, RevisionHash) projection read.</summary>
    private void ArrangeDeployedHashes(params (int InstanceId, string Hash)[] rows) =>
        _deploymentRepo.GetDeployedRevisionHashesAsync(Arg.Any<CancellationToken>())
            .Returns(rows.ToDictionary(r => r.InstanceId, r => r.Hash));

    /// <summary>Stubs the fat snapshot read for <paramref name="instanceId"/>.</summary>
    private void ArrangeSnapshot(int instanceId, FlattenedConfiguration config, string frozenHash) =>
        _deploymentRepo.GetDeployedSnapshotByInstanceIdAsync(instanceId, Arg.Any<CancellationToken>())
            .Returns(new DeployedConfigSnapshot("dep1", frozenHash, JsonSerializer.Serialize(config))
            {
                InstanceId = instanceId,
                DeployedAt = DateTimeOffset.UtcNow
            });

    /// <summary>
    /// Asks the artifact service what the site's hash WOULD be right now — the value a
    /// successful deploy would have stamped, i.e. what makes a site read Current.
    /// </summary>
    private async Task<string> CurrentArtifactHashAsync(Site site) =>
        (await _artifactService.ComputeCurrentArtifactHashesAsync([site]))[site.Id];

    // ── artifact state ───────────────────────────────────────────────────────

    [Fact]
    public async Task EvaluateAsync_NullStoredHash_IsNeverDeployedAndNotAPendingUpdate()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        ArrangeSites(site);
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        var row = Assert.Single(snapshot.Sites);
        Assert.Equal(ArtifactDeploymentState.NeverDeployed, row.ArtifactState);
        Assert.Null(row.ArtifactsDeployedAt);
        // NeverDeployed is the operator not having deployed yet, not a pending
        // update: it is surfaced on the Sites page but never counted or nagged about.
        Assert.Equal(0, snapshot.StaleArtifactSiteCount);
        Assert.False(snapshot.HasPendingUpdates);
    }

    [Fact]
    public async Task EvaluateAsync_StoredHashMatchesCurrentDefinitions_IsCurrent()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        var deployedAt = DateTimeOffset.UtcNow.AddHours(-2);
        site.ArtifactRevisionHash = await CurrentArtifactHashAsync(site);
        site.ArtifactsDeployedAt = deployedAt;
        ArrangeSites(site);
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        var row = Assert.Single(snapshot.Sites);
        Assert.Equal(ArtifactDeploymentState.Current, row.ArtifactState);
        Assert.Equal(deployedAt, row.ArtifactsDeployedAt);
        Assert.Equal(0, snapshot.StaleArtifactSiteCount);
        Assert.False(snapshot.HasPendingUpdates);
    }

    [Fact]
    public async Task EvaluateAsync_StoredHashDiffersFromCurrentDefinitions_IsOutOfDateAndCounted()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        site.ArtifactRevisionHash = "a-hash-from-an-older-artifact-set";
        site.ArtifactsDeployedAt = DateTimeOffset.UtcNow.AddDays(-3);
        ArrangeSites(site);
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        var row = Assert.Single(snapshot.Sites);
        Assert.Equal(ArtifactDeploymentState.OutOfDate, row.ArtifactState);
        Assert.Equal(1, snapshot.StaleArtifactSiteCount);
        Assert.True(snapshot.HasPendingUpdates);
    }

    [Fact]
    public async Task EvaluateAsync_CarriesSiteIdentityOntoTheRow()
    {
        var site = new Site("Alpha Plant", "site-a") { Id = 7 };
        ArrangeSites(site);
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        var row = Assert.Single(snapshot.Sites);
        Assert.Equal(7, row.SiteId);
        Assert.Equal("site-a", row.SiteIdentifier);
        Assert.Equal("Alpha Plant", row.SiteName);
    }

    // ── instance counts ──────────────────────────────────────────────────────

    [Fact]
    public async Task EvaluateAsync_CountsDeployedStaleAndUnknownInstancesPerSite()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        ArrangeSites(site);
        // 1 = deployed + stale, 2 = deployed but un-evaluatable, 3 = never deployed.
        ArrangeInstances(
            MakeInstance(1, 1, InstanceState.Enabled),
            MakeInstance(2, 1, InstanceState.Disabled),
            MakeInstance(3, 1, InstanceState.NotDeployed));

        var deployedConfig = ScalarConfig("5");
        var deployedHash = _hasher.ComputeHash(deployedConfig);
        ArrangeDeployedHashes((1, deployedHash), (2, deployedHash));
        ArrangeFlatten(1, ScalarConfig("9"), _hasher.ComputeHash(ScalarConfig("9")));
        ArrangeSnapshot(1, deployedConfig, deployedHash);
        ArrangeFlattenFailure(2);

        var snapshot = await _evaluator.EvaluateAsync();

        var row = Assert.Single(snapshot.Sites);
        Assert.Equal(2, row.DeployedInstanceCount);
        Assert.Equal(1, row.StaleInstanceCount);
        Assert.Equal(1, row.UnknownInstanceCount);
        Assert.Equal(1, snapshot.StaleInstanceCount);
        Assert.True(snapshot.HasPendingUpdates);
    }

    [Fact]
    public async Task EvaluateAsync_NotDeployedInstancesAreNeverHandedToTheStalenessBatch()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        ArrangeSites(site);
        ArrangeInstances(
            MakeInstance(1, 1, InstanceState.Enabled),
            MakeInstance(2, 1, InstanceState.NotDeployed));

        var config = ScalarConfig("5");
        var hash = _hasher.ComputeHash(config);
        // Instance 2 deliberately HAS a leftover deployed-hash row (an undeploy that
        // left the snapshot behind), so the staleness batch would happily evaluate it
        // if its id were passed — the filter under test is the State gate, not the
        // batch's own omission of instances with no snapshot.
        ArrangeDeployedHashes((1, hash), (2, hash));
        ArrangeFlatten(1, config, hash);
        ArrangeFlatten(2, config, hash);

        var snapshot = await _evaluator.EvaluateAsync();

        // A NotDeployed instance has nothing to be stale against; flattening it would
        // be pure cost on every TTL expiry, so it must never reach the batch.
        await _pipeline.Received(1).FlattenAndValidateAsync(
            1, Arg.Any<CancellationToken>(), Arg.Any<bool>(), Arg.Any<FlattenSession?>());
        await _pipeline.DidNotReceive().FlattenAndValidateAsync(
            2, Arg.Any<CancellationToken>(), Arg.Any<bool>(), Arg.Any<FlattenSession?>());
        Assert.Equal(1, snapshot.Sites.Single().DeployedInstanceCount);
    }

    [Fact]
    public async Task EvaluateAsync_AttributesInstanceCountsToTheirOwnSite()
    {
        var alpha = new Site("Alpha", "site-a") { Id = 1 };
        var bravo = new Site("Bravo", "site-b") { Id = 2 };
        ArrangeSites(alpha, bravo);
        ArrangeInstances(
            MakeInstance(1, 1, InstanceState.Enabled),
            MakeInstance(2, 2, InstanceState.Enabled));

        var deployedConfig = ScalarConfig("5");
        var deployedHash = _hasher.ComputeHash(deployedConfig);
        ArrangeDeployedHashes((1, deployedHash), (2, deployedHash));
        ArrangeFlatten(1, deployedConfig, deployedHash);
        ArrangeFlatten(2, ScalarConfig("9"), _hasher.ComputeHash(ScalarConfig("9")));
        ArrangeSnapshot(2, deployedConfig, deployedHash);

        var snapshot = await _evaluator.EvaluateAsync();

        Assert.Equal(0, snapshot.Sites.Single(s => s.SiteId == 1).StaleInstanceCount);
        Assert.Equal(1, snapshot.Sites.Single(s => s.SiteId == 2).StaleInstanceCount);
        Assert.Equal(1, snapshot.StaleInstanceCount);
    }

    [Fact]
    public async Task EvaluateAsync_NothingStale_HasNoPendingUpdates()
    {
        var site = new Site("Alpha", "site-a") { Id = 1 };
        site.ArtifactRevisionHash = await CurrentArtifactHashAsync(site);
        ArrangeSites(site);
        ArrangeInstances(MakeInstance(1, 1, InstanceState.Enabled));

        var config = ScalarConfig("5");
        var hash = _hasher.ComputeHash(config);
        ArrangeDeployedHashes((1, hash));
        ArrangeFlatten(1, config, hash);

        var snapshot = await _evaluator.EvaluateAsync();

        Assert.Equal(1, snapshot.Sites.Single().DeployedInstanceCount);
        Assert.Equal(0, snapshot.StaleInstanceCount);
        Assert.Equal(0, snapshot.StaleArtifactSiteCount);
        Assert.False(snapshot.HasPendingUpdates);
    }

    // ── ordering, ComputedAt, ForSites ───────────────────────────────────────

    [Fact]
    public async Task EvaluateAsync_OrdersSitesByNameIgnoringCase()
    {
        ArrangeSites(
            new Site("charlie", "site-c") { Id = 3 },
            new Site("Alpha", "site-a") { Id = 1 },
            new Site("bravo", "site-b") { Id = 2 });
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        Assert.Equal(["Alpha", "bravo", "charlie"], snapshot.Sites.Select(s => s.SiteName));
    }

    [Fact]
    public async Task EvaluateAsync_StampsComputedAt()
    {
        var before = DateTimeOffset.UtcNow;
        ArrangeSites(new Site("Alpha", "site-a") { Id = 1 });
        ArrangeInstances();

        var snapshot = await _evaluator.EvaluateAsync();

        Assert.InRange(snapshot.ComputedAt, before, DateTimeOffset.UtcNow);
    }

    [Fact]
    public async Task EvaluateAsync_ExceptionsPropagate()
    {
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
            .Returns<IReadOnlyList<Site>>(_ => throw new InvalidOperationException("db down"));

        // The caller's single-flight cache discards a faulted flight and the UI
        // renders "unavailable"; swallowing here would make a broken fleet read
        // "up to date", which is the one answer that must never be invented.
        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => _evaluator.EvaluateAsync());
        Assert.Equal("db down", ex.Message);
    }

    [Fact]
    public void ForSites_KeepsOnlyTheNamedSitesAndTheSameComputedAt()
    {
        var computedAt = DateTimeOffset.UtcNow.AddMinutes(-1);
        var snapshot = new PendingUpdatesSnapshot(computedAt,
        [
            new SitePendingUpdates(1, "site-a", "Alpha", ArtifactDeploymentState.OutOfDate, null, 2, 2, 0),
            new SitePendingUpdates(2, "site-b", "Bravo", ArtifactDeploymentState.Current, null, 1, 1, 0),
            new SitePendingUpdates(3, "site-c", "Charlie", ArtifactDeploymentState.OutOfDate, null, 0, 0, 0)
        ]);

        var scoped = snapshot.ForSites(new HashSet<int> { 2 });

        Assert.Equal(computedAt, scoped.ComputedAt);
        var row = Assert.Single(scoped.Sites);
        Assert.Equal(2, row.SiteId);
        // The totals are recomputed over the kept sites, so a site-scoped user is
        // never shown a count that includes a site they cannot see.
        Assert.Equal(1, scoped.StaleInstanceCount);
        Assert.Equal(0, scoped.StaleArtifactSiteCount);
        Assert.True(scoped.HasPendingUpdates);
    }

    [Fact]
    public void ForSites_EmptyScope_YieldsNoPendingUpdates()
    {
        var snapshot = new PendingUpdatesSnapshot(DateTimeOffset.UtcNow,
        [
            new SitePendingUpdates(1, "site-a", "Alpha", ArtifactDeploymentState.OutOfDate, null, 2, 2, 0)
        ]);

        var scoped = snapshot.ForSites(new HashSet<int>());

        Assert.Empty(scoped.Sites);
        Assert.False(scoped.HasPendingUpdates);
    }

    [Fact]
    public void Snapshot_Totals_SumAcrossSites()
    {
        var snapshot = new PendingUpdatesSnapshot(DateTimeOffset.UtcNow,
        [
            new SitePendingUpdates(1, "site-a", "Alpha", ArtifactDeploymentState.OutOfDate, null, 4, 2, 1),
            new SitePendingUpdates(2, "site-b", "Bravo", ArtifactDeploymentState.NeverDeployed, null, 0, 0, 0),
            new SitePendingUpdates(3, "site-c", "Charlie", ArtifactDeploymentState.Current, null, 3, 3, 0)
        ]);

        Assert.Equal(5, snapshot.StaleInstanceCount);
        // NeverDeployed is deliberately not counted alongside OutOfDate.
        Assert.Equal(1, snapshot.StaleArtifactSiteCount);
        Assert.True(snapshot.HasPendingUpdates);
    }
}