using Microsoft.Data.SqlClient;
using Microsoft.EntityFrameworkCore;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Types.Audit;
using ScadaLink.Commons.Types.Enums;
using ScadaLink.ConfigurationDatabase;
using ScadaLink.ConfigurationDatabase.Repositories;
using ScadaLink.ConfigurationDatabase.Tests.Migrations;
using Xunit;

namespace ScadaLink.ConfigurationDatabase.Tests.Repositories;

/// <summary>
/// Bundle D (#23 M1) integration tests for <see cref="AuditLogRepository"/>. Uses
/// the same <see cref="MsSqlMigrationFixture"/> as the Bundle C migration tests so
/// raw-SQL paths (the IF NOT EXISTS insert, partition switch) execute against a
/// real partitioned schema. Tests scope all queries by a per-test
/// <c>SourceSiteId</c> guid suffix so they neither collide with one another nor
/// require cleanup.
/// </summary>
public class AuditLogRepositoryTests : IClassFixture<MsSqlMigrationFixture>
{
    private readonly MsSqlMigrationFixture _fixture;

    public AuditLogRepositoryTests(MsSqlMigrationFixture fixture)
    {
        _fixture = fixture;
    }

    [SkippableFact]
    public async Task InsertIfNotExistsAsync_FreshEvent_WritesOneRow()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var evt = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc));
        await repo.InsertIfNotExistsAsync(evt);

        // Re-read in a fresh context so we exercise the persisted row, not the
        // (already-bypassed) change tracker.
        await using var readContext = CreateContext();
        var loaded = await readContext.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .ToListAsync();

        Assert.Single(loaded);
        Assert.Equal(evt.EventId, loaded[0].EventId);
    }

    [SkippableFact]
    public async Task InsertIfNotExistsAsync_DuplicateEventId_IsNoOp_NoExceptionNoDuplicate()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var occurredAt = new DateTime(2026, 5, 20, 11, 0, 0, DateTimeKind.Utc);
        var first = NewEvent(siteId, occurredAtUtc: occurredAt, errorMessage: "first");
        await repo.InsertIfNotExistsAsync(first);

        // Same EventId, different payload — first-write-wins, the second call is silently a no-op.
        var second = first with { ErrorMessage = "second-should-be-ignored" };
        await repo.InsertIfNotExistsAsync(second);

        await using var readContext = CreateContext();
        var loaded = await readContext.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .ToListAsync();

        Assert.Single(loaded);
        Assert.Equal("first", loaded[0].ErrorMessage);
    }

    [SkippableFact]
    public async Task QueryAsync_ReturnsRowsInOccurredDescOrder()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 1, 9, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(10)));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(20)));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(3, rows.Count);
        Assert.True(rows[0].OccurredAtUtc > rows[1].OccurredAtUtc);
        Assert.True(rows[1].OccurredAtUtc > rows[2].OccurredAtUtc);
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByChannel()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 2, 9, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, channel: AuditChannel.ApiOutbound));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), channel: AuditChannel.Notification));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), channel: AuditChannel.Notification));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                Channels: new[] { AuditChannel.Notification },
                SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Equal(AuditChannel.Notification, r.Channel));
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByMultipleChannels_ReturnsUnion()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 2, 14, 0, 0, DateTimeKind.Utc);
        // One row per channel; the multi-value filter must return the union of
        // ApiOutbound + Notification and exclude DbOutbound.
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, channel: AuditChannel.ApiOutbound));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), channel: AuditChannel.Notification));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), channel: AuditChannel.DbOutbound));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                Channels: new[] { AuditChannel.ApiOutbound, AuditChannel.Notification },
                SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Contains(r.Channel, new[] { AuditChannel.ApiOutbound, AuditChannel.Notification }));
        Assert.DoesNotContain(rows, r => r.Channel == AuditChannel.DbOutbound);
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByMultipleStatuses_ReturnsUnion()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 2, 15, 0, 0, DateTimeKind.Utc);
        // Failed + Parked are requested; Delivered must be excluded.
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, status: AuditStatus.Failed));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), status: AuditStatus.Parked));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), status: AuditStatus.Delivered));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                Statuses: new[] { AuditStatus.Failed, AuditStatus.Parked },
                SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Contains(r.Status, new[] { AuditStatus.Failed, AuditStatus.Parked }));
        Assert.DoesNotContain(rows, r => r.Status == AuditStatus.Delivered);
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByMultipleSourceSiteIds_ReturnsUnion()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteA = NewSiteId();
        var siteB = NewSiteId();
        var siteC = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 2, 16, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteA, occurredAtUtc: t0));
        await repo.InsertIfNotExistsAsync(NewEvent(siteB, occurredAtUtc: t0.AddMinutes(1)));
        await repo.InsertIfNotExistsAsync(NewEvent(siteC, occurredAtUtc: t0.AddMinutes(2)));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteA, siteB }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Contains(r.SourceSiteId, new[] { siteA, siteB }));
        Assert.DoesNotContain(rows, r => r.SourceSiteId == siteC);
    }

    [SkippableFact]
    public async Task QueryAsync_EmptyChannelList_DoesNotConstrain()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 2, 17, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, channel: AuditChannel.ApiOutbound));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), channel: AuditChannel.Notification));

        // An empty Channels list must mean "no filter" — NOT WHERE 1=0.
        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                Channels: Array.Empty<AuditChannel>(),
                SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
    }

    [SkippableFact]
    public async Task QueryAsync_FilterBySourceSiteId()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        var otherSiteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 3, 9, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1)));
        await repo.InsertIfNotExistsAsync(NewEvent(otherSiteId, occurredAtUtc: t0.AddMinutes(2)));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Equal(siteId, r.SourceSiteId));
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByExecutionId_ReturnsMatchingRows()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var executionId = Guid.NewGuid();
        var t0 = new DateTime(2026, 5, 3, 12, 0, 0, DateTimeKind.Utc);
        // Two rows share the ExecutionId; one carries a different ExecutionId and
        // one leaves it null — both must be excluded by the single-value filter.
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0, executionId: executionId));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(1), executionId: executionId));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(2), executionId: Guid.NewGuid()));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(3), executionId: null));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                SourceSiteIds: new[] { siteId },
                ExecutionId: executionId),
            new AuditLogPaging(PageSize: 10));

        Assert.Equal(2, rows.Count);
        Assert.All(rows, r => Assert.Equal(executionId, r.ExecutionId));
    }

    [SkippableFact]
    public async Task QueryAsync_FilterByTimeRange()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 4, 9, 0, 0, DateTimeKind.Utc);
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(30)));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddHours(2)));

        var rows = await repo.QueryAsync(
            new AuditLogQueryFilter(
                SourceSiteIds: new[] { siteId },
                FromUtc: t0.AddMinutes(10),
                ToUtc: t0.AddHours(1)),
            new AuditLogPaging(PageSize: 10));

        Assert.Single(rows);
        Assert.Equal(t0.AddMinutes(30), rows[0].OccurredAtUtc);
    }

    [SkippableFact]
    public async Task QueryAsync_Keyset_NextPageStartsAfterCursor()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        var t0 = new DateTime(2026, 5, 5, 9, 0, 0, DateTimeKind.Utc);
        // Five rows at one-minute intervals. Page-size 2 → page 1 returns minutes 4,3.
        // Cursor (minutes 3) → page 2 returns minutes 2,1. Cursor (minutes 1) → page 3 returns minute 0.
        for (var i = 0; i < 5; i++)
        {
            await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: t0.AddMinutes(i)));
        }

        var page1 = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(PageSize: 2));

        Assert.Equal(2, page1.Count);
        Assert.Equal(t0.AddMinutes(4), page1[0].OccurredAtUtc);
        Assert.Equal(t0.AddMinutes(3), page1[1].OccurredAtUtc);

        var cursor = page1[^1];
        var page2 = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(
                PageSize: 2,
                AfterOccurredAtUtc: cursor.OccurredAtUtc,
                AfterEventId: cursor.EventId));

        Assert.Equal(2, page2.Count);
        Assert.Equal(t0.AddMinutes(2), page2[0].OccurredAtUtc);
        Assert.Equal(t0.AddMinutes(1), page2[1].OccurredAtUtc);

        var cursor2 = page2[^1];
        var page3 = await repo.QueryAsync(
            new AuditLogQueryFilter(SourceSiteIds: new[] { siteId }),
            new AuditLogPaging(
                PageSize: 2,
                AfterOccurredAtUtc: cursor2.OccurredAtUtc,
                AfterEventId: cursor2.EventId));

        Assert.Single(page3);
        Assert.Equal(t0.AddMinutes(0), page3[0].OccurredAtUtc);
    }

    [SkippableFact]
    public async Task InsertIfNotExistsAsync_ConcurrentDuplicateInserts_ProduceExactlyOneRow()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();

        // Single event used by every parallel call — same EventId, same payload.
        // The repository's IF NOT EXISTS … INSERT pattern has a check-then-act
        // race window between sessions; under concurrent load SQL Server can
        // raise a unique-index violation (error 2601) on UX_AuditLog_EventId.
        // Bundle A's hardening swallows 2601/2627 so duplicates collapse silently.
        var evt = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 5, 20, 12, 0, 0, DateTimeKind.Utc));

        // 50 parallel inserters, each with its own DbContext (DbContext is not
        // thread-safe). Parallel.ForEachAsync aggregates exceptions, so a single
        // unhandled 2601 from the repository would fail this test loudly.
        await Parallel.ForEachAsync(
            Enumerable.Range(0, 50),
            new ParallelOptions { MaxDegreeOfParallelism = 50 },
            async (_, ct) =>
            {
                await using var context = CreateContext();
                var repo = new AuditLogRepository(context);
                await repo.InsertIfNotExistsAsync(evt, ct);
            });

        await using var readContext = CreateContext();
        var count = await readContext.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .CountAsync();

        Assert.Equal(1, count);
    }

    [SkippableFact]
    public async Task QueryAsync_Keyset_SameOccurredAtUtc_TiebreaksOnEventId()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Four events all sharing the exact same OccurredAtUtc — the keyset
        // cursor must lean on the EventId tiebreaker (descending) to page
        // deterministically. Bundle D's reviewer flagged this as a deferred
        // verification because it depends on EF Core 10 translating
        // Guid.CompareTo against SQL Server's uniqueidentifier sort order.
        var occurredAt = new DateTime(2026, 5, 20, 13, 0, 0, DateTimeKind.Utc);

        // Build four distinct Guids; we don't care about the literal ordering
        // produced by Guid.CompareTo — only that paging is deterministic and
        // covers every row exactly once.
        var events = Enumerable.Range(0, 4)
            .Select(_ => NewEvent(siteId, occurredAtUtc: occurredAt))
            .ToList();

        foreach (var e in events)
        {
            await repo.InsertIfNotExistsAsync(e);
        }

        var filter = new AuditLogQueryFilter(SourceSiteIds: new[] { siteId });

        var page1 = await repo.QueryAsync(filter, new AuditLogPaging(PageSize: 2));
        Assert.Equal(2, page1.Count);
        Assert.All(page1, r => Assert.Equal(occurredAt, r.OccurredAtUtc));

        var cursor = page1[^1];
        var page2 = await repo.QueryAsync(
            filter,
            new AuditLogPaging(
                PageSize: 2,
                AfterOccurredAtUtc: cursor.OccurredAtUtc,
                AfterEventId: cursor.EventId));

        Assert.Equal(2, page2.Count);
        Assert.All(page2, r => Assert.Equal(occurredAt, r.OccurredAtUtc));

        var page1Ids = page1.Select(r => r.EventId).ToHashSet();
        var page2Ids = page2.Select(r => r.EventId).ToHashSet();

        // No overlap between pages.
        Assert.Empty(page1Ids.Intersect(page2Ids));

        // Every inserted EventId appears in exactly one of the two pages.
        var allIds = page1Ids.Union(page2Ids).ToHashSet();
        Assert.Equal(4, allIds.Count);
        Assert.True(events.Select(e => e.EventId).ToHashSet().SetEquals(allIds));
    }

    // ------------------------------------------------------------------------
    // M6-T4 Bundle C: SwitchOutPartitionAsync drop-and-rebuild integration tests
    // ------------------------------------------------------------------------
    //
    // The partition-switch path replaces M1's NotSupportedException stub with
    // the production drop-DROP-INDEX → CREATE-staging → SWITCH PARTITION →
    // DROP-staging → CREATE-INDEX dance documented in alog.md §4. These tests
    // verify the side effects an outsider can observe:
    //   * rows in the targeted month are removed
    //   * rows in OTHER months are NOT touched
    //   * UX_AuditLog_EventId still exists after a successful switch
    //   * InsertIfNotExistsAsync's first-write-wins idempotency still holds
    //     after a switch (the rebuilt index is real)
    //   * a thrown SqlException leaves UX_AuditLog_EventId rebuilt (the CATCH
    //     branch's recovery path runs)

    [SkippableFact]
    public async Task SwitchOutPartitionAsync_OldPartition_RemovesRows_NewPartitionsKept()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Three distinct months — Jan, Feb, Mar 2026 — so the switch on Jan's
        // boundary purges exactly one month's worth of rows. Boundary values
        // come from the partition function's pre-seeded list (alog.md §4).
        var janEvt = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 1, 15, 10, 0, 0, DateTimeKind.Utc));
        var febEvt = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 2, 15, 10, 0, 0, DateTimeKind.Utc));
        var marEvt = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 3, 15, 10, 0, 0, DateTimeKind.Utc));
        await repo.InsertIfNotExistsAsync(janEvt);
        await repo.InsertIfNotExistsAsync(febEvt);
        await repo.InsertIfNotExistsAsync(marEvt);

        // Boundary value '2026-01-01' identifies the January 2026 partition under
        // RANGE RIGHT semantics ($PARTITION returns the partition into which the
        // boundary value itself falls — the partition whose lower bound is the
        // boundary).
        await repo.SwitchOutPartitionAsync(new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc));

        await using var readContext = CreateContext();
        var remaining = await readContext.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .ToListAsync();

        Assert.DoesNotContain(remaining, e => e.EventId == janEvt.EventId);
        Assert.Contains(remaining, e => e.EventId == febEvt.EventId);
        Assert.Contains(remaining, e => e.EventId == marEvt.EventId);
    }

    [SkippableFact]
    public async Task SwitchOutPartitionAsync_RebuildsUxIndex_AfterSwitch()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Pick a different month per test so successive test runs (which share
        // the fixture's MSSQL database) don't tread on each other.
        await repo.SwitchOutPartitionAsync(new DateTime(2026, 4, 1, 0, 0, 0, DateTimeKind.Utc));

        await using var verifyContext = CreateContext();
        var indexExists = await ScalarAsync<int>(
            verifyContext,
            "SELECT COUNT(*) FROM sys.indexes " +
            "WHERE name = 'UX_AuditLog_EventId' AND object_id = OBJECT_ID('dbo.AuditLog');");
        Assert.Equal(1, indexExists);
    }

    [SkippableFact]
    public async Task SwitchOutPartitionAsync_InsertIfNotExistsAsync_StillEnforcesFirstWriteWins_AfterSwitch()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Pre-existing row in May 2026 — must survive a switch on a different
        // (older) partition.
        var preExisting = NewEvent(siteId, occurredAtUtc: new DateTime(2026, 5, 20, 9, 0, 0, DateTimeKind.Utc));
        await repo.InsertIfNotExistsAsync(preExisting);

        // Switch out the June 2026 partition (different month, empty).
        await repo.SwitchOutPartitionAsync(new DateTime(2026, 6, 1, 0, 0, 0, DateTimeKind.Utc));

        // Re-attempting the same EventId after the switch must STILL be a no-op
        // (UX_AuditLog_EventId is the index that enables idempotency; if the
        // rebuild left it broken, this insert would silently produce a duplicate
        // row and the count assertion below would catch it).
        var dup = preExisting with { ErrorMessage = "second-should-be-ignored-after-switch" };
        await repo.InsertIfNotExistsAsync(dup);

        await using var readContext = CreateContext();
        var rows = await readContext.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .ToListAsync();

        Assert.Single(rows);
        Assert.Equal(preExisting.EventId, rows[0].EventId);
        // First-write-wins: the original ErrorMessage (null) survives.
        Assert.Null(rows[0].ErrorMessage);
    }

    [SkippableFact]
    public async Task SwitchOutPartitionAsync_PartialFailure_RebuildsUxIndex_RaisesException()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Force a deterministic switch failure with an inbound FOREIGN KEY:
        // ALTER TABLE … SWITCH refuses to move rows out of a partition that's
        // referenced by an FK from another table, raising msg 4928
        // ("ALTER TABLE SWITCH statement failed because target table … has a
        // foreign key …"). The CATCH branch then rolls back and rebuilds the
        // unique index — which the assertion below verifies.
        //
        // The probe table is uniquely named with a guid suffix so reruns of
        // this test inside the same fixture DB never collide. We clean it up
        // in the finally so the constraint never leaks into other tests.
        var probeTable = $"AuditFkProbe_{Guid.NewGuid():N}".Substring(0, 32);
        await using (var setup = new SqlConnection(_fixture.ConnectionString))
        {
            await setup.OpenAsync();
            await using var cmd = setup.CreateCommand();
            // Composite FK references AuditLog's composite PK (EventId, OccurredAtUtc).
            cmd.CommandText =
                $"CREATE TABLE dbo.[{probeTable}] ( " +
                $"  EventId uniqueidentifier NOT NULL, " +
                $"  OccurredAtUtc datetime2(7) NOT NULL, " +
                $"  CONSTRAINT FK_{probeTable}_AuditLog FOREIGN KEY (EventId, OccurredAtUtc) " +
                $"    REFERENCES dbo.AuditLog(EventId, OccurredAtUtc));";
            await cmd.ExecuteNonQueryAsync();
        }

        try
        {
            var ex = await Assert.ThrowsAnyAsync<SqlException>(
                () => repo.SwitchOutPartitionAsync(new DateTime(2026, 9, 1, 0, 0, 0, DateTimeKind.Utc)));
            // Smoke-check the message references the SWITCH statement so we
            // know we hit the engineered failure, not some unrelated error.
            Assert.Contains("SWITCH", ex.Message, StringComparison.OrdinalIgnoreCase);
        }
        finally
        {
            // Always drop the probe table so the FK is gone before the next
            // test runs against the shared fixture.
            await using var cleanup = new SqlConnection(_fixture.ConnectionString);
            await cleanup.OpenAsync();
            await using var cmd = cleanup.CreateCommand();
            cmd.CommandText =
                $"IF OBJECT_ID('dbo.[{probeTable}]', 'U') IS NOT NULL DROP TABLE dbo.[{probeTable}];";
            await cmd.ExecuteNonQueryAsync();
        }

        // The CATCH block in the production SQL guarantees UX_AuditLog_EventId
        // is rebuilt regardless of which step failed inside the TRY.
        await using var verifyContext = CreateContext();
        var indexExists = await ScalarAsync<int>(
            verifyContext,
            "SELECT COUNT(*) FROM sys.indexes " +
            "WHERE name = 'UX_AuditLog_EventId' AND object_id = OBJECT_ID('dbo.AuditLog');");
        Assert.Equal(1, indexExists);
    }

    // ------------------------------------------------------------------------
    // M6-T4 Bundle C: GetPartitionBoundariesOlderThanAsync
    // ------------------------------------------------------------------------

    [SkippableFact]
    public async Task GetPartitionBoundariesOlderThanAsync_ReturnsBoundaries_WithMaxOccurredOlderThanThreshold()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Seed events in two months: July 2026 (old) and August 2026 (new).
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: new DateTime(2026, 7, 10, 0, 0, 0, DateTimeKind.Utc)));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: new DateTime(2026, 8, 10, 0, 0, 0, DateTimeKind.Utc)));

        // Threshold = Aug 1 2026 — July partition's MAX (July 10) is older;
        // August partition's MAX (August 10) is newer. We expect only the July
        // boundary back.
        var threshold = new DateTime(2026, 8, 1, 0, 0, 0, DateTimeKind.Utc);
        var boundaries = await repo.GetPartitionBoundariesOlderThanAsync(threshold);

        // The repo may also return EARLIER boundaries that have no data (their
        // MAX is NULL → treated as "no data, nothing to purge" by the contract).
        // We only assert the inclusion/exclusion that matters for our seeded
        // rows.
        Assert.Contains(new DateTime(2026, 7, 1, 0, 0, 0, DateTimeKind.Utc), boundaries);
        Assert.DoesNotContain(new DateTime(2026, 8, 1, 0, 0, 0, DateTimeKind.Utc), boundaries);
    }

    // ------------------------------------------------------------------------
    // M7-T13 Bundle E: GetKpiSnapshotAsync — Health-dashboard Audit KPI tiles
    // ------------------------------------------------------------------------
    //
    // The dashboard's "Audit volume" tile reads TotalEventsLastHour and the
    // "Audit error rate" tile reads ErrorEventsLastHour / TotalEventsLastHour.
    // The repository must (a) count rows whose OccurredAtUtc falls in
    // [nowUtc - window, nowUtc] and (b) within that scope count rows whose
    // Status ∈ {Failed, Parked, Discarded} as "error". BacklogTotal is left at
    // zero here — the service layer composes it in from the health aggregator.
    //
    // To keep the test deterministic against the shared fixture DB, each test
    // pins an obscure-distant nowUtc and seeds rows with OccurredAtUtc inside a
    // narrow band centred on that anchor — no other test in this class seeds
    // there, so the global count equals the seeded count for that band.

    [SkippableFact]
    public async Task GetKpiSnapshotAsync_WithMixedStatusRows_ReturnsCorrectTotalsAndErrors()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = NewSiteId();
        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Anchor in November 2026 — no other test in this class seeds there.
        var nowUtc = new DateTime(2026, 11, 20, 10, 0, 0, DateTimeKind.Utc);
        // Seed 3 success + 1 Failed + 1 Parked + 1 Discarded inside the trailing
        // 1h window; plus 1 row outside the window that must be excluded.
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-5), status: AuditStatus.Delivered));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-10), status: AuditStatus.Delivered));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-15), status: AuditStatus.Delivered));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-20), status: AuditStatus.Failed));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-25), status: AuditStatus.Parked));
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-30), status: AuditStatus.Discarded));
        // Outside-window row (2h before nowUtc).
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddHours(-2), status: AuditStatus.Failed));
        // Submitted is in-flight, not an "error" — must NOT count toward errors.
        await repo.InsertIfNotExistsAsync(NewEvent(siteId, occurredAtUtc: nowUtc.AddMinutes(-2), status: AuditStatus.Submitted));

        var snapshot = await repo.GetKpiSnapshotAsync(
            window: TimeSpan.FromHours(1),
            nowUtc: nowUtc);

        // 7 rows fall in the trailing 1h window (3 Delivered + 1 Failed + 1 Parked + 1 Discarded + 1 Submitted).
        // The 2h-before-nowUtc Failed row is excluded by the window.
        Assert.Equal(7, snapshot.TotalEventsLastHour);
        // Only Failed/Parked/Discarded count as errors → 3.
        Assert.Equal(3, snapshot.ErrorEventsLastHour);
        // The service layer fills BacklogTotal; the repo leaves it at 0.
        Assert.Equal(0, snapshot.BacklogTotal);
        // AsOfUtc echoes the anchor.
        Assert.Equal(nowUtc, snapshot.AsOfUtc);
    }

    [SkippableFact]
    public async Task GetKpiSnapshotAsync_EmptyWindow_ReturnsZeroTotals()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        // Anchor in December 2026 — no test seeds there, so the window is empty.
        var nowUtc = new DateTime(2026, 12, 20, 10, 0, 0, DateTimeKind.Utc);

        var snapshot = await repo.GetKpiSnapshotAsync(
            window: TimeSpan.FromMinutes(1),
            nowUtc: nowUtc);

        Assert.Equal(0, snapshot.TotalEventsLastHour);
        Assert.Equal(0, snapshot.ErrorEventsLastHour);
        Assert.Equal(0, snapshot.BacklogTotal);
        Assert.Equal(nowUtc, snapshot.AsOfUtc);
    }

    private async Task<T> ScalarAsync<T>(ScadaLinkDbContext context, string sql)
    {
        var conn = context.Database.GetDbConnection();
        if (conn.State != System.Data.ConnectionState.Open)
        {
            await conn.OpenAsync();
        }
        await using var cmd = conn.CreateCommand();
        cmd.CommandText = sql;
        var result = await cmd.ExecuteScalarAsync();
        if (result is null || result is DBNull)
        {
            return default!;
        }
        return (T)Convert.ChangeType(result, typeof(T) == typeof(string) ? typeof(string) : Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T))!;
    }

    // --- helpers ------------------------------------------------------------

    private ScadaLinkDbContext CreateContext()
    {
        var options = new DbContextOptionsBuilder<ScadaLinkDbContext>()
            .UseSqlServer(_fixture.ConnectionString)
            .Options;
        return new ScadaLinkDbContext(options);
    }

    private static string NewSiteId() =>
        "test-bundle-d-" + Guid.NewGuid().ToString("N").Substring(0, 8);

    private static AuditEvent NewEvent(
        string siteId,
        DateTime occurredAtUtc,
        AuditChannel channel = AuditChannel.ApiOutbound,
        AuditKind kind = AuditKind.ApiCall,
        AuditStatus status = AuditStatus.Delivered,
        string? errorMessage = null,
        Guid? executionId = null) =>
        new()
        {
            EventId = Guid.NewGuid(),
            OccurredAtUtc = occurredAtUtc,
            Channel = channel,
            Kind = kind,
            Status = status,
            SourceSiteId = siteId,
            ErrorMessage = errorMessage,
            ExecutionId = executionId,
        };
}