using System.Diagnostics;
using System.Reflection;
using Grpc.Net.Client;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.Secrets.Abstractions;
using ZB.MOM.WW.Secrets.Replicator.Grpc.DependencyInjection;
using ZB.MOM.WW.Secrets.Replicator.Grpc.V1;
using ZB.MOM.WW.Secrets.Sqlite;

namespace ZB.MOM.WW.Secrets.Replicator.Grpc.Tests;

/// <summary>
/// Convergence behaviour of the follower's pull-only sweep, exercised against real SQLite stores on
/// both sides so the assertions are about actual persisted state rather than mock interactions.
/// </summary>
public sealed class GrpcSecretSyncServiceTests : IDisposable
{
    private readonly List<string> _dbPaths = [];
    private readonly SqliteSecretStore _local;
    private readonly SqliteSecretStore _hubStore;
    private readonly FakeHubReader _hub;
    private readonly RecordingLogger<GrpcSecretSyncService> _logger = new();
    private readonly RecordingLogger<GrpcSecretsHubClient> _clientLogger = new();
    private readonly RecordingCacheInvalidator _cache = new();

    public GrpcSecretSyncServiceTests()
    {
        _local = CreateStore();
        _hubStore = CreateStore();
        _hub = new FakeHubReader(_hubStore);
    }

    private SqliteSecretStore CreateStore()
    {
        string path = Path.Combine(Path.GetTempPath(), $"zb-grpc-sync-{Guid.NewGuid():N}.db");
        _dbPaths.Add(path);
        var factory = new SecretsSqliteConnectionFactory(path);
        new SqliteSecretsStoreMigrator(factory).MigrateAsync(CancellationToken.None).GetAwaiter().GetResult();
        return new SqliteSecretStore(factory);
    }

    private GrpcSecretSyncService CreateService(TimeSpan? interval = null) => new(
        _local,
        _hub,
        _cache,
        Options.Create(new SecretsGrpcHubClientOptions
        {
            Endpoint = "https://central:5001",
            BearerToken = "unused-by-the-fake",
            SyncInterval = interval ?? TimeSpan.FromHours(1),
        }),
        _logger);

    private static StoredSecret Row(string name, byte marker) => new()
    {
        Name = new SecretName(name),
        ContentType = SecretContentType.Text,
        Ciphertext = [marker],
        Nonce = [1],
        Tag = [2],
        WrappedDek = [3],
        WrapNonce = [4],
        WrapTag = [5],
        KekId = "sha256:test",
        Revision = 0,
        CreatedUtc = DateTimeOffset.UtcNow,
        UpdatedUtc = DateTimeOffset.UtcNow,
    };

    [Fact]
    public async Task Sweep_pulls_a_secret_the_node_has_never_seen()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);

        int pulled = await CreateService().SweepAsync(CancellationToken.None);

        Assert.Equal(1, pulled);

        StoredSecret? local = await _local.GetAsync(new SecretName("db/password"), CancellationToken.None);
        Assert.NotNull(local);
        Assert.Equal(0xAA, local!.Ciphertext[0]);
    }

    [Fact]
    public async Task Sweep_pulls_the_row_byte_identically()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);
        await _hubStore.UpsertAsync(Row("db/password", 0xBB), CancellationToken.None);

        StoredSecret hubRow = (await _hubStore.GetAsync(new SecretName("db/password"), CancellationToken.None))!;

        await CreateService().SweepAsync(CancellationToken.None);

        StoredSecret localRow = (await _local.GetAsync(new SecretName("db/password"), CancellationToken.None))!;

        Assert.Equal(hubRow.Ciphertext, localRow.Ciphertext);
        Assert.Equal(hubRow.WrappedDek, localRow.WrappedDek);
        Assert.Equal(hubRow.KekId, localRow.KekId);
        Assert.Equal(hubRow.Revision, localRow.Revision);
        Assert.Equal(hubRow.UpdatedUtc, localRow.UpdatedUtc);
    }

    [Fact]
    public async Task Sweep_applies_a_hub_tombstone_over_a_live_local_row()
    {
        await _hubStore.UpsertAsync(Row("api/key", 0xBB), CancellationToken.None);
        await CreateService().SweepAsync(CancellationToken.None);

        await _hubStore.DeleteAsync(new SecretName("api/key"), "admin", CancellationToken.None);
        int pulled = await CreateService().SweepAsync(CancellationToken.None);

        Assert.Equal(1, pulled);

        StoredSecret localRow = (await _local.GetAsync(new SecretName("api/key"), CancellationToken.None))!;
        Assert.True(localRow.IsDeleted);
    }

    [Fact]
    public async Task Sweep_is_idempotent_so_a_converged_follower_stays_quiet()
    {
        await _hubStore.UpsertAsync(Row("api/key", 0xBB), CancellationToken.None);

        GrpcSecretSyncService service = CreateService();
        await service.SweepAsync(CancellationToken.None);

        int pulled = await service.SweepAsync(CancellationToken.None);

        Assert.Equal(0, pulled);
    }

    [Fact]
    public async Task Sweep_skips_the_fetch_when_the_hub_has_nothing_newer()
    {
        await CreateService().SweepAsync(CancellationToken.None);

        Assert.Equal(0, _hub.GetManyCallCount);
    }

    [Fact]
    public async Task Sweep_never_sends_a_local_only_secret_hub_ward()
    {
        // Pull-only: a row this node holds and the hub does not stays put. In the SQL-Server
        // topology this would be pushed; here central is the sole origin of every update, and the
        // contract has no write RPC to push it with.
        await _local.UpsertAsync(Row("only/local", 0x11), CancellationToken.None);

        int pulled = await CreateService().SweepAsync(CancellationToken.None);

        Assert.Equal(0, pulled);
        Assert.Empty(await _hubStore.GetManifestAsync(CancellationToken.None));
    }

    [Fact]
    public void The_hub_reader_seam_exposes_no_write_operation()
    {
        // The structural half of pull-only. The proto has no write RPC; this pins that the client's
        // own seam cannot grow one either, so a future edit has to break this test on purpose.
        string[] members = typeof(ISecretsHubReader)
            .GetMethods(BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly)
            .Select(m => m.Name)
            .Order(StringComparer.Ordinal)
            .ToArray();

        Assert.Equal(["GetManifestAsync", "GetManyAsync"], members);
    }

    [Theory]
    [InlineData("ComputePushSet")]
    [InlineData("ReadLocalAsync")]
    [InlineData("ApplyReplicatedAsync")]
    public void The_client_package_never_names_a_hub_ward_write_path(string forbidden)
    {
        // ComputePushSet and ReadLocalAsync are the two reconciler entry points that assemble rows
        // to move toward a peer; ApplyReplicatedAsync on a hub-side store is how they would land.
        // Pull-only is an owner-confirmed invariant, so the guard is a source scan rather than a
        // behavioural test: a future edit has to delete this test on purpose to reintroduce a push.
        foreach (string file in ClientSourceFiles())
        {
            string source = File.ReadAllText(file);

            Assert.DoesNotContain(
                forbidden,
                StripComments(source),
                StringComparison.Ordinal);
        }
    }

    // The client half of the package — deliberately excludes the server-side files, which legitimately
    // read a local store to serve the hub.
    private static IEnumerable<string> ClientSourceFiles()
    {
        string root = PackageSourceRoot();

        string[] files =
        [
            Path.Combine(root, "GrpcSecretSyncService.cs"),
            Path.Combine(root, "GrpcSecretsHubClient.cs"),
            Path.Combine(root, "Wire", "WireToDomain.cs"),
            Path.Combine(root, "DependencyInjection", "SecretsGrpcHubClientExtensions.cs"),
        ];

        foreach (string file in files)
        {
            Assert.True(File.Exists(file), $"expected client source file is missing: {file}");
        }

        return files;
    }

    private static string PackageSourceRoot()
    {
        DirectoryInfo? dir = new(AppContext.BaseDirectory);

        while (dir is not null && !File.Exists(Path.Combine(dir.FullName, "ZB.MOM.WW.Secrets.slnx")))
        {
            dir = dir.Parent;
        }

        Assert.NotNull(dir);

        return Path.Combine(dir!.FullName, "src", "ZB.MOM.WW.Secrets.Replicator.Grpc");
    }

    // Comments explain what the code deliberately does NOT do, and naming the forbidden member is
    // exactly how that is explained — so the scan looks at code only.
    private static string StripComments(string source)
    {
        IEnumerable<string> lines = source
            .Split('\n')
            .Select(line => line.TrimStart())
            .Where(line => !line.StartsWith("//", StringComparison.Ordinal)
                && !line.StartsWith("///", StringComparison.Ordinal)
                && !line.StartsWith('*'));

        return string.Join('\n', lines);
    }

    [Fact]
    public async Task Sweep_evicts_the_resolver_cache_for_applied_names_only()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);
        await _local.UpsertAsync(Row("only/local", 0x11), CancellationToken.None);

        await CreateService().SweepAsync(CancellationToken.None);

        Assert.Equal(["db/password"], _cache.Invalidated.Select(n => n.Value));
    }

    [Fact]
    public async Task A_hub_outage_on_the_manifest_call_propagates_out_of_the_raw_sweep()
    {
        // Establishes that the fake really fails, so the next two tests prove containment rather
        // than an accidentally-healthy hub.
        _hub.FailManifestWith = () => new InvalidOperationException("hub unreachable");

        await Assert.ThrowsAsync<InvalidOperationException>(
            () => CreateService().SweepAsync(CancellationToken.None));
    }

    [Fact]
    public async Task A_hub_outage_on_the_manifest_call_never_escapes_the_background_loop()
    {
        await _local.UpsertAsync(Row("api/key", 0xBB), CancellationToken.None);
        StoredSecret before = (await _local.GetAsync(new SecretName("api/key"), CancellationToken.None))!;

        _hub.FailManifestWith = () => new InvalidOperationException("hub unreachable");

        await RunOneStartupSweepAsync(() => _hub.ManifestCallCount > 0);

        StoredSecret after = (await _local.GetAsync(new SecretName("api/key"), CancellationToken.None))!;
        Assert.Equal(before.Ciphertext, after.Ciphertext);
        Assert.Equal(before.Revision, after.Revision);
        Assert.Equal(before.UpdatedUtc, after.UpdatedUtc);
        Assert.False(after.IsDeleted);
        Assert.Equal(1, _logger.WarningCount);
    }

    [Fact]
    public async Task A_hub_outage_on_the_fetch_call_never_escapes_the_background_loop()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);
        _hub.FailFetchWith = () => new InvalidOperationException("hub unreachable mid-fetch");

        await RunOneStartupSweepAsync(() => _hub.GetManyCallCount > 0);

        Assert.Null(await _local.GetAsync(new SecretName("db/password"), CancellationToken.None));
        Assert.Equal(1, _logger.WarningCount);
    }

    [Fact]
    public async Task A_quiet_sweep_logs_nothing_at_information()
    {
        await RunOneStartupSweepAsync(() => _hub.ManifestCallCount > 0);

        Assert.Equal(0, _logger.InformationCount);
        Assert.Equal(0, _logger.WarningCount);
    }

    [Fact]
    public async Task A_sweep_that_moved_rows_reports_how_many_it_pulled()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);

        await RunOneStartupSweepAsync(() => _hub.GetManyCallCount > 0);

        Assert.Equal(1, _logger.InformationCount);
    }

    [Fact]
    public async Task Startup_sync_can_be_switched_off()
    {
        await _hubStore.UpsertAsync(Row("db/password", 0xAA), CancellationToken.None);

        var service = new GrpcSecretSyncService(
            _local,
            _hub,
            _cache,
            Options.Create(new SecretsGrpcHubClientOptions
            {
                Endpoint = "https://central:5001",
                BearerToken = "unused-by-the-fake",
                SyncInterval = TimeSpan.FromHours(1),
                SyncOnStartup = false,
            }),
            _logger);

        await service.StartAsync(CancellationToken.None);
        await service.StopAsync(CancellationToken.None);

        Assert.Equal(0, _hub.ManifestCallCount);
    }

    [Fact]
    public async Task A_malformed_row_never_poisons_the_batch_it_arrived_in()
    {
        // The failure this guards against is not "one row is lost" — it is that the pull set never
        // changes, so the identical malformed row re-fails the identical sweep every interval and
        // the node never converges on anything, indistinguishable in the log from a hub outage.
        SecretRow bad = TestWire.Row("api/key", 0xBB);
        bad.ContentType = "Kerberos";

        var invoker = new FakeSecretsHubCallInvoker
        {
            ManifestResponse = new GetManifestResponse
            {
                Entries =
                {
                    TestWire.Entry("db/password"), TestWire.Entry("api/key"), TestWire.Entry("svc/token"),
                },
            },
            SecretsResponse = new GetSecretsResponse
            {
                Secrets = { TestWire.Row("db/password", 0xAA), bad, TestWire.Row("svc/token", 0xCC) },
            },
        };

        int pulled = await CreateServiceOverTheWire(invoker).SweepAsync(CancellationToken.None);

        Assert.Equal(2, pulled);
        Assert.NotNull(await _local.GetAsync(new SecretName("db/password"), CancellationToken.None));
        Assert.NotNull(await _local.GetAsync(new SecretName("svc/token"), CancellationToken.None));
        Assert.Null(await _local.GetAsync(new SecretName("api/key"), CancellationToken.None));
        Assert.Single(_clientLogger.Warnings);
    }

    [Fact]
    public async Task A_malformed_manifest_entry_never_poisons_the_manifest_it_arrived_in()
    {
        ManifestEntry bad = TestWire.Entry("api/key");
        bad.UpdatedUtc = "not-a-timestamp";

        var invoker = new FakeSecretsHubCallInvoker
        {
            ManifestResponse = new GetManifestResponse
            {
                Entries = { TestWire.Entry("db/password"), bad, TestWire.Entry("svc/token") },
            },
            SecretsResponse = new GetSecretsResponse
            {
                Secrets = { TestWire.Row("db/password", 0xAA), TestWire.Row("svc/token", 0xCC) },
            },
        };

        int pulled = await CreateServiceOverTheWire(invoker).SweepAsync(CancellationToken.None);

        Assert.Equal(2, pulled);
        Assert.Equal(["db/password", "svc/token"], invoker.LastSecretsRequest!.Names);
        Assert.Single(_clientLogger.Warnings);
    }

    // A sweep wired to the REAL hub client over a fake CallInvoker, so the parse boundary the other
    // tests bypass (the FakeHubReader hands over domain types already) is actually exercised.
    private GrpcSecretSyncService CreateServiceOverTheWire(FakeSecretsHubCallInvoker invoker)
    {
        IOptions<SecretsGrpcHubClientOptions> options = Options.Create(new SecretsGrpcHubClientOptions
        {
            Endpoint = "https://central:5001",
            BearerToken = "hub-token",
            SyncInterval = TimeSpan.FromHours(1),
        });

        var client = new GrpcSecretsHubClient(
            new SecretsHub.SecretsHubClient(invoker), options, _clientLogger);

        return new GrpcSecretSyncService(_local, client, _cache, options, _logger);
    }

    [Fact]
    public void Registration_refuses_a_configuration_with_no_bearer_token()
    {
        IConfiguration config = new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?>
            {
                ["Secrets:GrpcHub:Endpoint"] = "https://central:5001",
            })
            .Build();

        InvalidOperationException ex = Assert.Throws<InvalidOperationException>(
            () => new ServiceCollection().AddZbSecretsGrpcHubClient(config));

        Assert.Contains("Secrets:GrpcHub:BearerToken", ex.Message, StringComparison.Ordinal);
    }

    [Fact]
    public void Registration_does_not_hijack_an_application_s_own_grpc_channel()
    {
        // GrpcChannel is a framework type, so an application that already has one registered for its
        // own dependency must keep it — and this package must still dial the hub, not that endpoint.
        IConfiguration config = new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?>
            {
                ["Secrets:GrpcHub:Endpoint"] = "https://central:5001",
                ["Secrets:GrpcHub:BearerToken"] = "token",
            })
            .Build();

        using GrpcChannel applicationChannel = GrpcChannel.ForAddress("https://somewhere-else:9999");

        ServiceCollection services = new();
        services.AddSingleton(applicationChannel);
        services.AddZbSecretsGrpcHubClient(config);

        using ServiceProvider provider = services.BuildServiceProvider();

        Assert.Same(applicationChannel, provider.GetRequiredService<GrpcChannel>());
        Assert.NotSame(
            applicationChannel,
            provider.GetRequiredKeyedService<GrpcChannel>(
                SecretsGrpcHubClientExtensions.ChannelServiceKey));
    }

    [Fact]
    public void Registration_with_no_fallbacks_resolves_the_plain_single_endpoint_client()
    {
        // The zero-fallback registration graph is the pre-0.5.0 one, unchanged: one keyed channel,
        // one GrpcSecretsHubClient as the reader. Consumers wired before FallbackEndpoints existed
        // must see an identical container shape.
        ServiceCollection services = new();
        services.AddLogging();
        services.AddZbSecretsGrpcHubClient(HubConfig());

        using ServiceProvider provider = services.BuildServiceProvider();

        Assert.IsType<GrpcSecretsHubClient>(provider.GetRequiredService<ISecretsHubReader>());
        Assert.NotNull(provider.GetRequiredKeyedService<GrpcChannel>(
            SecretsGrpcHubClientExtensions.ChannelServiceKey));
        Assert.Null(provider.GetKeyedService<GrpcChannel>(
            $"{SecretsGrpcHubClientExtensions.ChannelServiceKey}:fallback:0"));
    }

    [Fact]
    public void Registration_with_fallbacks_resolves_the_failover_reader_over_one_channel_per_endpoint()
    {
        ServiceCollection services = new();
        services.AddLogging();
        services.AddZbSecretsGrpcHubClient(HubConfig(new Dictionary<string, string?>
        {
            ["Secrets:GrpcHub:FallbackEndpoints:0"] = "https://central-b:5001",
            ["Secrets:GrpcHub:FallbackEndpoints:1"] = "https://central-c:5001",
        }));

        using ServiceProvider provider = services.BuildServiceProvider();

        Assert.IsType<FailoverSecretsHubReader>(provider.GetRequiredService<ISecretsHubReader>());

        GrpcChannel primary = provider.GetRequiredKeyedService<GrpcChannel>(
            SecretsGrpcHubClientExtensions.ChannelServiceKey);
        GrpcChannel fallback0 = provider.GetRequiredKeyedService<GrpcChannel>(
            $"{SecretsGrpcHubClientExtensions.ChannelServiceKey}:fallback:0");
        GrpcChannel fallback1 = provider.GetRequiredKeyedService<GrpcChannel>(
            $"{SecretsGrpcHubClientExtensions.ChannelServiceKey}:fallback:1");

        // Each channel dials its own endpoint — three distinct singletons, container-owned.
        Assert.Equal("central-a:5001", primary.Target);
        Assert.Equal("central-b:5001", fallback0.Target);
        Assert.Equal("central-c:5001", fallback1.Target);
    }

    [Fact]
    public void Registration_refuses_a_malformed_fallback_endpoint_at_startup()
    {
        InvalidOperationException ex = Assert.Throws<InvalidOperationException>(() =>
            new ServiceCollection().AddZbSecretsGrpcHubClient(HubConfig(new Dictionary<string, string?>
            {
                ["Secrets:GrpcHub:FallbackEndpoints:0"] = "not a uri",
            })));

        Assert.Contains("Secrets:GrpcHub:FallbackEndpoints", ex.Message, StringComparison.Ordinal);
    }

    // A minimal valid hub-client configuration, extendable per test.
    private static IConfiguration HubConfig(Dictionary<string, string?>? extra = null)
    {
        var values = new Dictionary<string, string?>
        {
            ["Secrets:GrpcHub:Endpoint"] = "https://central-a:5001",
            ["Secrets:GrpcHub:BearerToken"] = "token",
        };

        foreach ((string key, string? value) in extra ?? [])
        {
            values[key] = value;
        }

        return new ConfigurationBuilder().AddInMemoryCollection(values).Build();
    }

    // Runs the hosted service through one startup sweep and shuts it down, asserting that nothing
    // escaped ExecuteAsync. The long sync interval means exactly one sweep happens.
    private async Task RunOneStartupSweepAsync(Func<bool> sweepObserved)
    {
        GrpcSecretSyncService service = CreateService();

        await service.StartAsync(CancellationToken.None);

        var deadline = Stopwatch.StartNew();

        while (!sweepObserved() && deadline.Elapsed < TimeSpan.FromSeconds(10))
        {
            await Task.Delay(10);
        }

        await service.StopAsync(CancellationToken.None);

        Assert.True(sweepObserved(), "the startup sweep never ran");
        Assert.NotNull(service.ExecuteTask);
        Assert.False(service.ExecuteTask!.IsFaulted);
    }

    public void Dispose()
    {
        Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();

        foreach (string db in _dbPaths)
        {
            foreach (string path in new[] { db, db + "-wal", db + "-shm" })
            {
                if (File.Exists(path))
                {
                    File.Delete(path);
                }
            }
        }
    }

    /// <summary>
    /// An <see cref="ISecretsHubReader"/> backed by a real SQLite store, standing in for the
    /// central-hosted hub. Backed by a real store rather than a dictionary for the same reason the
    /// SQL-Server suite is: the behaviour under test is last-writer-wins convergence, and a
    /// hand-rolled fake would re-implement the very logic the tests exist to check.
    /// </summary>
    private sealed class FakeHubReader(SqliteSecretStore store) : ISecretsHubReader
    {
        public int ManifestCallCount { get; private set; }

        public int GetManyCallCount { get; private set; }

        public Func<Exception>? FailManifestWith { get; set; }

        public Func<Exception>? FailFetchWith { get; set; }

        public Task<IReadOnlyList<SecretManifestEntry>> GetManifestAsync(CancellationToken ct)
        {
            ManifestCallCount++;

            return FailManifestWith is null
                ? store.GetManifestAsync(ct)
                : Task.FromException<IReadOnlyList<SecretManifestEntry>>(FailManifestWith());
        }

        public async Task<IReadOnlyList<StoredSecret>> GetManyAsync(
            IReadOnlyList<SecretName> names, CancellationToken ct)
        {
            GetManyCallCount++;

            if (FailFetchWith is not null)
            {
                throw FailFetchWith();
            }

            var rows = new List<StoredSecret>(names.Count);

            foreach (SecretName name in names)
            {
                StoredSecret? row = await store.GetAsync(name, ct);

                if (row is not null)
                {
                    rows.Add(row);
                }
            }

            return rows;
        }
    }

    private sealed class RecordingCacheInvalidator : ISecretCacheInvalidator
    {
        public List<SecretName> Invalidated { get; } = [];

        public void Invalidate(SecretName name) => Invalidated.Add(name);
    }

}