using System.Collections.Immutable;
using Microsoft.Data.Sqlite;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.LocalDb;
using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;
using ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
using ZB.MOM.WW.OtOpcUa.Runtime.ScriptedAlarms;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.ScriptedAlarms;

/// <summary>
///     The alarm comment audit trail lives in its own append-only table
///     (<see cref="AlarmConditionStateSchema.CommentsTable"/>) keyed by alarm id, so the condition
///     row stays a fixed size and a transition's write — and therefore its replication payload —
///     does not grow with the alarm's history.
/// </summary>
/// <remarks>
///     The payload is measured where it costs: the bytes the LocalDb capture triggers write into
///     <c>__localdb_oplog</c> for one save, which is exactly what ships to the pair peer. Both
///     tables are registered for capture here, as they are on a replicating node.
/// </remarks>
public sealed class LocalDbAlarmCommentAuditTests : IDisposable
{
    private static readonly DateTime T0 = new(2026, 06, 10, 12, 00, 00, DateTimeKind.Utc);

    private readonly string _dbPath =
        Path.Combine(Path.GetTempPath(), $"otopcua-alarm-comments-{Guid.NewGuid():N}.db");

    private readonly ServiceProvider _provider;
    private readonly ILocalDb _db;

    public LocalDbAlarmCommentAuditTests()
    {
        var configuration = new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?> { ["LocalDb:Path"] = _dbPath })
            .Build();

        _provider = new ServiceCollection()
            .AddZbLocalDb(configuration, db =>
            {
                using (var connection = db.CreateConnection())
                {
                    AlarmConditionStateSchema.Apply(connection);
                }

                db.RegisterReplicated(AlarmConditionStateSchema.StateTable);
                db.RegisterReplicated(AlarmConditionStateSchema.CommentsTable);
            })
            .BuildServiceProvider();

        _db = _provider.GetRequiredService<ILocalDb>();
    }

    public void Dispose()
    {
        _provider.Dispose();
        SqliteConnection.ClearAllPools();
        foreach (var path in new[] { _dbPath, $"{_dbPath}-wal", $"{_dbPath}-shm" })
        {
            try { if (File.Exists(path)) File.Delete(path); } catch { /* best effort */ }
        }
    }

    private LocalDbAlarmConditionStateStore NewStore()
        => new(_db, NullLogger<LocalDbAlarmConditionStateStore>.Instance);

    private static CancellationToken Ct => CancellationToken.None;

    private static ImmutableList<AlarmComment> Comments(int count, string prefix = "c")
    {
        var builder = ImmutableList.CreateBuilder<AlarmComment>();
        for (var i = 0; i < count; i++)
            builder.Add(new AlarmComment(T0.AddSeconds(i), "jane", "AddComment", $"{prefix}-{i:D6}"));
        return builder.ToImmutable();
    }

    /// <summary>An unacknowledged state carrying <paramref name="comments"/>, ready to be acked.</summary>
    private static AlarmConditionState Unacked(string alarmId, ImmutableList<AlarmComment> comments) =>
        AlarmConditionState.Fresh(alarmId, T0) with
        {
            Active = AlarmActiveState.Active,
            Acked = AlarmAckedState.Unacknowledged,
            Comments = comments,
        };

    private async Task<long> OplogHighWaterAsync() =>
        (await _db.QueryAsync("SELECT COALESCE(MAX(seq), 0) FROM __localdb_oplog", r => r.GetInt64(0), null, Ct))[0];

    /// <summary>Bytes captured into the oplog above <paramref name="afterSeq"/> — the replication payload.</summary>
    private async Task<long> OplogBytesAboveAsync(long afterSeq) =>
        (await _db.QueryAsync(
            "SELECT COALESCE(SUM(LENGTH(pk_json) + COALESCE(LENGTH(row_json), 0)), 0) FROM __localdb_oplog WHERE seq > @S",
            r => r.GetInt64(0),
            new { S = afterSeq },
            Ct))[0];

    private async Task<long> OplogEntriesAboveAsync(long afterSeq, string table) =>
        (await _db.QueryAsync(
            "SELECT COUNT(*) FROM __localdb_oplog WHERE seq > @S AND table_name = @T",
            r => r.GetInt64(0),
            new { S = afterSeq, T = table },
            Ct))[0];

    private async Task<long> ScalarAsync(string sql) =>
        (await _db.QueryAsync(sql, r => r.GetInt64(0), null, Ct))[0];

    /// <summary>
    ///     Seeds <paramref name="alarmId"/> with <paramref name="historyLength"/> comments, then
    ///     returns the oplog bytes one acknowledge transition (one new comment) costs.
    /// </summary>
    private async Task<long> AckTransitionBytesAsync(string alarmId, int historyLength, string ackComment)
    {
        var store = NewStore();
        var seeded = Unacked(alarmId, Comments(historyLength));
        await store.SaveAsync(seeded, Ct);

        var before = await OplogHighWaterAsync();
        var acked = Part9StateMachine.ApplyAcknowledge(seeded, "bob", ackComment, T0.AddDays(1)).State;
        await store.SaveAsync(acked, Ct);
        return await OplogBytesAboveAsync(before);
    }

    [Fact]
    public async Task TransitionPayload_IsConstant_WhetherTheAlarmCarries10OrTenThousandComments()
    {
        var small = await AckTransitionBytesAsync("alarm-small", 10, "ack");
        var large = await AckTransitionBytesAsync("alarm-large", 10_000, "ack");

        // Constant: the only difference allowed is the width of the new comment's ordinal ("10" vs
        // "10000", in pk_json and row_json) — a handful of bytes, not O(n). The alarm ids are the
        // same length on purpose.
        small.ShouldBeGreaterThan(0);
        Math.Abs(large - small).ShouldBeLessThanOrEqualTo(16,
            $"one ack transition cost {small} bytes at 10 comments but {large} at 10,000");
        large.ShouldBeLessThan(2_048);

        // Positive control on the instrument: the seeded history really is large and really was
        // captured — otherwise a "constant" result could just mean capture is off.
        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment WHERE scripted_alarm_id = 'alarm-large'"))
            .ShouldBe(10_001);
        var historyBytes = await ScalarAsync(
            "SELECT SUM(LENGTH(row_json)) FROM __localdb_oplog WHERE table_name = 'alarm_condition_comment'");
        historyBytes.ShouldBeGreaterThan(1_000_000);
    }

    [Fact]
    public async Task TransitionPayload_PositiveControl_TheMeasurementSeesTheNewCommentsBytes()
    {
        // Proves the measurement above is not vacuous: the oplog delta of a transition does carry
        // the appended comment, so a 4 KB comment costs at least 4 KB.
        var plain = await AckTransitionBytesAsync("alarm-plain", 10, "ack");
        var heavy = await AckTransitionBytesAsync("alarm-heavy", 10, new string('x', 4_096));

        (heavy - plain).ShouldBeGreaterThanOrEqualTo(4_096 * 2 - 16,
            "the comment text rides both the comment row and last_ack_comment on the condition row");
    }

    [Fact]
    public async Task Transition_WritesOneConditionRowAndOnlyTheAppendedCommentRow()
    {
        var store = NewStore();
        var seeded = Unacked("alarm-append", Comments(50));
        await store.SaveAsync(seeded, Ct);

        var before = await OplogHighWaterAsync();
        var acked = Part9StateMachine.ApplyAcknowledge(seeded, "bob", "ack", T0.AddDays(1)).State;
        await store.SaveAsync(acked, Ct);

        (await OplogEntriesAboveAsync(before, AlarmConditionStateSchema.StateTable)).ShouldBe(1);
        (await OplogEntriesAboveAsync(before, AlarmConditionStateSchema.CommentsTable)).ShouldBe(1);

        var loaded = await store.LoadAsync("alarm-append", Ct);
        loaded.ShouldNotBeNull();
        loaded.Comments.ShouldBe(acked.Comments);
    }

    [Fact]
    public async Task ConditionRow_StaysFixedSize_InlineColumnIsAlwaysEmpty()
    {
        var store = NewStore();
        await store.SaveAsync(Unacked("alarm-fixed", Comments(500)), Ct);

        (await _db.QueryAsync(
                "SELECT comments_json FROM alarm_condition_state WHERE scripted_alarm_id = 'alarm-fixed'",
                r => r.GetString(0), null, Ct))[0]
            .ShouldBe("[]");
        (await store.LoadAsync("alarm-fixed", Ct))!.Comments.Count.ShouldBe(500);
    }

    [Fact]
    public async Task UnchangedSave_WritesNoCommentRows()
    {
        var store = NewStore();
        var state = Unacked("alarm-idle", Comments(20));
        await store.SaveAsync(state, Ct);

        var before = await OplogHighWaterAsync();
        await store.SaveAsync(state with { LastTransitionUtc = T0.AddMinutes(1) }, Ct);

        (await OplogEntriesAboveAsync(before, AlarmConditionStateSchema.CommentsTable)).ShouldBe(0);
        (await OplogEntriesAboveAsync(before, AlarmConditionStateSchema.StateTable)).ShouldBe(1,
            "positive control: the save itself was captured");
    }

    [Fact]
    public async Task LoadAll_ReturnsEachAlarmsOwnTrailInOrder()
    {
        var store = NewStore();
        var a = Unacked("alarm-a", Comments(3, "a"));
        var b = Unacked("alarm-b", Comments(5, "b"));
        await store.SaveAsync(a, Ct);
        await store.SaveAsync(b, Ct);

        var all = (await store.LoadAllAsync(Ct)).ToDictionary(s => s.AlarmId);

        all["alarm-a"].Comments.ShouldBe(a.Comments);
        all["alarm-b"].Comments.ShouldBe(b.Comments);
    }

    [Fact]
    public async Task Remove_DeletesTheAlarmsTrail_AndAReCreatedAlarmStartsEmpty()
    {
        var store = NewStore();
        await store.SaveAsync(Unacked("alarm-gone", Comments(4)), Ct);
        await store.SaveAsync(Unacked("alarm-kept", Comments(2)), Ct);

        await store.RemoveAsync("alarm-gone", Ct);

        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment WHERE scripted_alarm_id = 'alarm-gone'"))
            .ShouldBe(0);
        (await store.LoadAsync("alarm-kept", Ct))!.Comments.Count.ShouldBe(2, "positive control");

        var recreated = AlarmConditionState.Fresh("alarm-gone", T0)
            with { Comments = ImmutableList.Create(new AlarmComment(T0, "amy", "AddComment", "new life")) };
        await store.SaveAsync(recreated, Ct);
        (await store.LoadAsync("alarm-gone", Ct))!.Comments.ShouldBe(recreated.Comments);
    }

    [Fact]
    public async Task CommentsAlreadyHeldAtAnOrdinal_AreNeverRewritten()
    {
        // Append-only: a save whose list disagrees with what is stored at an existing ordinal (the
        // peer's copy of the same logical entry already arrived) leaves the stored entry alone.
        var store = NewStore();
        var original = Unacked("alarm-ao", Comments(3));
        await store.SaveAsync(original, Ct);

        var rewritten = original with { Comments = original.Comments.SetItem(1, new AlarmComment(T0, "eve", "AddComment", "forged")) };
        await store.SaveAsync(rewritten, Ct);

        (await store.LoadAsync("alarm-ao", Ct))!.Comments.ShouldBe(original.Comments);
    }

    // ---- back-compat + migration -----------------------------------------------------------

    /// <summary>
    ///     The exact shape the pre-split store wrote into <c>comments_json</c>
    ///     (<c>JsonSerializerDefaults.Web</c>: camelCase, Utc timestamps with a trailing <c>Z</c>).
    /// </summary>
    private const string OldShapeCommentsJson =
        """[{"timestampUtc":"2026-06-10T10:00:00Z","user":"jane","kind":"Acknowledge","text":"checking pump"},{"timestampUtc":"2026-06-10T11:30:00.1234567Z","user":"bob","kind":"Confirm","text":"all clear"},{"timestampUtc":"2026-06-10T11:30:00.1234567Z","user":"system","kind":"AutoUnshelve","text":""}]""";

    private static readonly ImmutableList<AlarmComment> OldShapeComments = ImmutableList.Create(
        new AlarmComment(new DateTime(2026, 06, 10, 10, 00, 00, DateTimeKind.Utc), "jane", "Acknowledge", "checking pump"),
        new AlarmComment(new DateTime(2026, 06, 10, 11, 30, 00, DateTimeKind.Utc).AddTicks(1_234_567), "bob", "Confirm", "all clear"),
        new AlarmComment(new DateTime(2026, 06, 10, 11, 30, 00, DateTimeKind.Utc).AddTicks(1_234_567), "system", "AutoUnshelve", ""));

    private async Task InsertOldShapeRowAsync(string alarmId, string commentsJson = OldShapeCommentsJson) =>
        await _db.ExecuteAsync(
            """
            INSERT INTO alarm_condition_state
                (scripted_alarm_id, enabled_state, acked_state, confirmed_state, shelving_state,
                 shelving_expires_utc, last_ack_user, last_ack_comment, last_ack_utc,
                 last_confirm_user, last_confirm_comment, last_confirm_utc, comments_json, updated_at_utc)
            VALUES
                (@Id, 'Enabled', 'Acknowledged', 'Confirmed', 'Unshelved',
                 NULL, 'jane', 'checking pump', '2026-06-10T10:00:00.0000000Z',
                 'bob', 'all clear', '2026-06-10T11:30:00.1234567Z', @Json, '2026-06-10T11:30:00.1234567Z')
            """,
            new { Id = alarmId, Json = commentsJson },
            Ct);

    private static void ShouldBeTheOldShapeState(AlarmConditionState? loaded, string alarmId)
    {
        loaded.ShouldNotBeNull();
        loaded.AlarmId.ShouldBe(alarmId);
        loaded.Acked.ShouldBe(AlarmAckedState.Acknowledged);
        loaded.Confirmed.ShouldBe(AlarmConfirmedState.Confirmed);
        loaded.LastAckUser.ShouldBe("jane");
        loaded.LastConfirmComment.ShouldBe("all clear");
        loaded.Comments.ShouldBe(OldShapeComments);
        loaded.Comments.ShouldAllBe(c => c.TimestampUtc.Kind == DateTimeKind.Utc);
    }

    [Fact]
    public async Task OldShapeRow_WithInlineComments_LoadsExactlyAsBefore()
    {
        await InsertOldShapeRowAsync("alarm-legacy");

        ShouldBeTheOldShapeState(await NewStore().LoadAsync("alarm-legacy", Ct), "alarm-legacy");
        ShouldBeTheOldShapeState((await NewStore().LoadAllAsync(Ct)).Single(), "alarm-legacy");
    }

    [Fact]
    public async Task Migration_MovesInlineCommentsToTheAuditTable_AndClearsTheInlineColumn()
    {
        await InsertOldShapeRowAsync("alarm-m1");
        await InsertOldShapeRowAsync("alarm-m2");
        await InsertOldShapeRowAsync("alarm-empty", "[]");

        int migrated;
        using (var connection = _db.CreateConnection())
            migrated = AlarmConditionStateSchema.MigrateInlineComments(connection);

        migrated.ShouldBe(2);
        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment")).ShouldBe(6);
        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_state WHERE comments_json <> '[]'")).ShouldBe(0);

        ShouldBeTheOldShapeState(await NewStore().LoadAsync("alarm-m1", Ct), "alarm-m1");
        ShouldBeTheOldShapeState(await NewStore().LoadAsync("alarm-m2", Ct), "alarm-m2");
        (await NewStore().LoadAsync("alarm-empty", Ct))!.Comments.ShouldBeEmpty();
    }

    [Fact]
    public async Task Migration_IsIdempotent_ASecondRunChangesNothing()
    {
        await InsertOldShapeRowAsync("alarm-idem");
        using (var connection = _db.CreateConnection())
            AlarmConditionStateSchema.MigrateInlineComments(connection).ShouldBe(1, "positive control");

        var before = await OplogHighWaterAsync();
        using (var connection = _db.CreateConnection())
            AlarmConditionStateSchema.MigrateInlineComments(connection).ShouldBe(0);

        (await OplogHighWaterAsync()).ShouldBe(before, "a re-run must write nothing");
        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment")).ShouldBe(3);
        ShouldBeTheOldShapeState(await NewStore().LoadAsync("alarm-idem", Ct), "alarm-idem");
    }

    [Fact]
    public async Task Migration_OverAPartiallyMigratedRow_DoesNotDuplicateOrReorder()
    {
        // An inline row reappearing after its comments were already moved (e.g. a restored backup):
        // the ordinals already held are kept, nothing is duplicated.
        await InsertOldShapeRowAsync("alarm-partial");
        using (var connection = _db.CreateConnection())
            AlarmConditionStateSchema.MigrateInlineComments(connection);
        await _db.ExecuteAsync(
            "UPDATE alarm_condition_state SET comments_json = @Json WHERE scripted_alarm_id = 'alarm-partial'",
            new { Json = OldShapeCommentsJson }, Ct);

        using (var connection = _db.CreateConnection())
            AlarmConditionStateSchema.MigrateInlineComments(connection).ShouldBe(1);

        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment")).ShouldBe(3);
        ShouldBeTheOldShapeState(await NewStore().LoadAsync("alarm-partial", Ct), "alarm-partial");
    }

    [Fact]
    public async Task SavingALoadedOldShapeState_MovesItsCommentsAndAppendsTheNewOne()
    {
        // The lazy path: an old-shape row the boot migration never saw (it was written before the
        // first save on this build) still converges on the first save.
        await InsertOldShapeRowAsync("alarm-lazy");
        var store = NewStore();
        var loaded = await store.LoadAsync("alarm-lazy", Ct);

        var next = Part9StateMachine.ApplyAddComment(loaded!, "amy", "follow-up", T0.AddDays(2)).State;
        await store.SaveAsync(next, Ct);

        (await ScalarAsync("SELECT COUNT(*) FROM alarm_condition_comment WHERE scripted_alarm_id = 'alarm-lazy'"))
            .ShouldBe(4);
        (await _db.QueryAsync(
                "SELECT comments_json FROM alarm_condition_state WHERE scripted_alarm_id = 'alarm-lazy'",
                r => r.GetString(0), null, Ct))[0]
            .ShouldBe("[]");
        (await NewStore().LoadAsync("alarm-lazy", Ct))!.Comments.ShouldBe(next.Comments);
    }
}