using System.Text.Json;
using Microsoft.Extensions.Logging.Abstractions;
using NSubstitute;
using ZB.MOM.WW.CBDDC.Core;
using ZB.MOM.WW.CBDDC.Core.Storage;
using ZB.MOM.WW.CBDDC.Core.Sync;
using ZB.MOM.WW.CBDDC.Persistence;
using ZB.MOM.WW.CBDDC.Persistence.Lmdb;
using ZB.MOM.WW.CBDDC.Persistence.Surreal;

namespace ZB.MOM.WW.CBDDC.Sample.Console.Tests;

public class LmdbOplogMigrationTests
{
    [Fact]
    public async Task FeatureFlags_DualWrite_WritesToBothStores()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();

        var flags = new LmdbOplogFeatureFlags
        {
            UseLmdbOplog = true,
            DualWriteOplog = true,
            PreferLmdbReads = false
        };

        var store = new FeatureFlagOplogStore(
            surrealStore,
            lmdbStore,
            flags,
            logger: NullLogger<FeatureFlagOplogStore>.Instance);

        var entry = CreateEntry("Users", "dual-write", "node-a", 100, 0, "");
        await store.AppendOplogEntryAsync(entry);

        (await surrealStore.GetEntryByHashAsync(entry.Hash)).ShouldNotBeNull();
        (await lmdbStore.GetEntryByHashAsync(entry.Hash)).ShouldNotBeNull();
    }

    [Fact]
    public async Task FeatureFlags_PreferLmdbReads_ReconcilesFromSurrealWhenLmdbMissingEntries()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();

        var flags = new LmdbOplogFeatureFlags
        {
            UseLmdbOplog = true,
            DualWriteOplog = false,
            PreferLmdbReads = true,
            ReconciliationInterval = TimeSpan.Zero
        };

        var entry = CreateEntry("Users", "reconcile-1", "node-a", 200, 0, "");

        // Simulate crash window where only Surreal persisted before LMDB migration store starts.
        await surrealStore.AppendOplogEntryAsync(entry);
        (await lmdbStore.GetEntryByHashAsync(entry.Hash)).ShouldBeNull();

        var store = new FeatureFlagOplogStore(
            surrealStore,
            lmdbStore,
            flags,
            logger: NullLogger<FeatureFlagOplogStore>.Instance);

        OplogEntry? resolved = await store.GetEntryByHashAsync(entry.Hash);
        resolved.ShouldNotBeNull();
        resolved.Hash.ShouldBe(entry.Hash);

        // Reconciliation should have backfilled LMDB.
        (await lmdbStore.GetEntryByHashAsync(entry.Hash)).ShouldNotBeNull();

        OplogMigrationTelemetrySnapshot telemetry = store.GetTelemetrySnapshot();
        telemetry.ReconciliationRuns.ShouldBeGreaterThanOrEqualTo(1);
        telemetry.ReconciledEntries.ShouldBeGreaterThanOrEqualTo(1);
    }

    [Fact]
    public async Task FeatureFlags_ShadowValidation_RecordsMismatchTelemetry()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();
        var telemetry = new OplogMigrationTelemetry();

        var flags = new LmdbOplogFeatureFlags
        {
            UseLmdbOplog = true,
            DualWriteOplog = true,
            PreferLmdbReads = false,
            EnableReadShadowValidation = true
        };

        var store = new FeatureFlagOplogStore(
            surrealStore,
            lmdbStore,
            flags,
            telemetry,
            NullLogger<FeatureFlagOplogStore>.Instance);

        var entry = CreateEntry("Users", "shadow-mismatch-1", "node-a", 210, 0, "");
        await surrealStore.AppendOplogEntryAsync(entry);

        OplogEntry? resolved = await store.GetEntryByHashAsync(entry.Hash);
        resolved.ShouldNotBeNull();

        OplogMigrationTelemetrySnapshot snapshot = store.GetTelemetrySnapshot();
        snapshot.ShadowComparisons.ShouldBe(1);
        snapshot.ShadowMismatches.ShouldBe(1);
    }

    [Fact]
    public async Task FeatureFlags_RollbackToSurreal_UsesSurrealForWritesAndReads()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();

        var flags = new LmdbOplogFeatureFlags
        {
            UseLmdbOplog = true,
            DualWriteOplog = false,
            PreferLmdbReads = false
        };

        var store = new FeatureFlagOplogStore(
            surrealStore,
            lmdbStore,
            flags,
            logger: NullLogger<FeatureFlagOplogStore>.Instance);

        var entry = CreateEntry("Users", "rollback-1", "node-a", 220, 0, "");
        await store.AppendOplogEntryAsync(entry);

        (await surrealStore.GetEntryByHashAsync(entry.Hash)).ShouldNotBeNull();
        (await lmdbStore.GetEntryByHashAsync(entry.Hash)).ShouldBeNull();

        OplogEntry? routedRead = await store.GetEntryByHashAsync(entry.Hash);
        routedRead.ShouldNotBeNull();
        routedRead.Hash.ShouldBe(entry.Hash);
    }

    [Fact]
    public async Task BackfillTool_BackfillAndValidate_ReportsSuccess()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();
        var tool = new LmdbOplogBackfillTool(surrealStore, lmdbStore, NullLogger<LmdbOplogBackfillTool>.Instance);

        var first = CreateEntry("Users", "backfill-1", "node-a", 300, 0, "");
        var second = CreateEntry("Users", "backfill-2", "node-a", 301, 0, first.Hash);
        var third = CreateEntry("Users", "backfill-3", "node-b", 302, 0, "");
        var fourth = CreateEntry("Users", "backfill-4", "node-b", 303, 0, third.Hash);

        await surrealStore.AppendOplogEntryAsync(first);
        await surrealStore.AppendOplogEntryAsync(second);
        await surrealStore.AppendOplogEntryAsync(third);
        await surrealStore.AppendOplogEntryAsync(fourth);

        LmdbOplogBackfillReport report = await tool.BackfillAsync(DatasetId.Primary);

        report.IsSuccess.ShouldBeTrue();
        report.CountsMatch.ShouldBeTrue();
        report.CountsPerNodeMatch.ShouldBeTrue();
        report.LatestHashPerNodeMatch.ShouldBeTrue();
        report.HashSpotChecksPassed.ShouldBeTrue();
        report.ChainSpotChecksPassed.ShouldBeTrue();
        report.SourceCount.ShouldBe(4);
        report.DestinationCount.ShouldBe(4);
    }

    [Fact]
    public async Task BackfillTool_BackfillAndValidate_WorksPerDataset()
    {
        await using var surrealHarness = new SurrealTestHarness();
        var surrealStore = surrealHarness.CreateOplogStore();
        using var lmdbStore = CreateLmdbStore();
        var tool = new LmdbOplogBackfillTool(surrealStore, lmdbStore, NullLogger<LmdbOplogBackfillTool>.Instance);

        var logsEntryA = CreateEntry("Logs", "log-1", "node-a", 400, 0, "");
        var logsEntryB = CreateEntry("Logs", "log-2", "node-a", 401, 0, logsEntryA.Hash);
        var primaryEntry = CreateEntry("Users", "primary-1", "node-a", 500, 0, "");

        await surrealStore.AppendOplogEntryAsync(logsEntryA, DatasetId.Logs);
        await surrealStore.AppendOplogEntryAsync(logsEntryB, DatasetId.Logs);
        await surrealStore.AppendOplogEntryAsync(primaryEntry, DatasetId.Primary);

        LmdbOplogBackfillReport logsReport = await tool.BackfillAsync(DatasetId.Logs);
        logsReport.IsSuccess.ShouldBeTrue();
        logsReport.SourceCount.ShouldBe(2);
        logsReport.DestinationCount.ShouldBe(2);

        (await lmdbStore.GetEntryByHashAsync(logsEntryA.Hash, DatasetId.Logs)).ShouldNotBeNull();
        (await lmdbStore.GetEntryByHashAsync(logsEntryB.Hash, DatasetId.Logs)).ShouldNotBeNull();
        (await lmdbStore.GetEntryByHashAsync(primaryEntry.Hash, DatasetId.Primary)).ShouldBeNull();
    }

    private static LmdbOplogStore CreateLmdbStore()
    {
        string rootPath = Path.Combine(Path.GetTempPath(), "cbddc-lmdb-migration", Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(rootPath);

        return new LmdbOplogStore(
            Substitute.For<IDocumentStore>(),
            new LastWriteWinsConflictResolver(),
            new VectorClockService(),
            new LmdbOplogOptions
            {
                EnvironmentPath = rootPath,
                MapSizeBytes = 64L * 1024 * 1024,
                MaxDatabases = 16
            },
            null,
            NullLogger<LmdbOplogStore>.Instance);
    }

    private static OplogEntry CreateEntry(
        string collection,
        string key,
        string nodeId,
        long wall,
        int logic,
        string previousHash)
    {
        return new OplogEntry(
            collection,
            key,
            OperationType.Put,
            JsonSerializer.SerializeToElement(new { key }),
            new HlcTimestamp(wall, logic, nodeId),
            previousHash);
    }
}