using Centron.BusinessLogic.Telemetry;
using Centron.Data.Entities.Telemetry;
using Centron.Host.AspNetCore.Telemetry;
using Centron.Interfaces.BL;
using JetBrains.Annotations;
using NSubstitute;

namespace Centron.Tests.BL.Telemetry;

[TestSubject(typeof(TelemetryAggregator))]
public class TelemetryAggregatorTest
{
    private static readonly DateTime _bucket = new(2026, 5, 2, 12, 15, 0, DateTimeKind.Utc);

    private static (TelemetryAggregator Aggregator, TelemetryBL BlMock) CreateAggregator()
    {
        var bl = Substitute.For<TelemetryBL>((Centron.DAO.DAOSession?)null);
        bl.UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>())
            .Returns(Result.AsSuccess());
        bl.UpsertApiCallBatch(Arg.Any<IReadOnlyCollection<ApiCallBucketIncrement>>())
            .Returns(Result.AsSuccess());

        // Lookup-resolution always returns one I3D per distinct name (auto-numbered, deterministic).
        var toolNameCounter = 0;
        bl.ResolveMcpToolNameI3Ds(Arg.Any<IReadOnlyCollection<string>>())
            .Returns(call =>
            {
                var names = call.Arg<IReadOnlyCollection<string>>();
                var dict = new Dictionary<string, int>(StringComparer.Ordinal);
                foreach (var n in names.Distinct(StringComparer.Ordinal))
                    dict[n] = ++toolNameCounter;
                return Result<Dictionary<string, int>>.AsSuccess(dict);
            });
        var methodNameCounter = 0;
        bl.ResolveApiMethodNameI3Ds(Arg.Any<IReadOnlyCollection<string>>())
            .Returns(call =>
            {
                var names = call.Arg<IReadOnlyCollection<string>>();
                var dict = new Dictionary<string, int>(StringComparer.Ordinal);
                foreach (var n in names.Distinct(StringComparer.Ordinal))
                    dict[n] = ++methodNameCounter;
                return Result<Dictionary<string, int>>.AsSuccess(dict);
            });
        var hardwareIdCounter = 0;
        bl.ResolveHardwareIDI3Ds(Arg.Any<IReadOnlyCollection<string>>())
            .Returns(call =>
            {
                var names = call.Arg<IReadOnlyCollection<string>>();
                var dict = new Dictionary<string, int>(StringComparer.Ordinal);
                foreach (var n in names.Distinct(StringComparer.Ordinal))
                    dict[n] = ++hardwareIdCounter;
                return Result<Dictionary<string, int>>.AsSuccess(dict);
            });
        bl.LoadAllHardwareIDs()
            .Returns(Result<List<HardwareIDLookup>>.AsSuccess(new List<HardwareIDLookup>()));

        var aggregator = new TelemetryAggregator(action => action(bl));
        return (aggregator, bl);
    }

    #region SnapToBucket

    [Theory]
    [InlineData(0, 0)]
    [InlineData(7, 0)]
    [InlineData(14, 0)]
    [InlineData(15, 15)]
    [InlineData(29, 15)]
    [InlineData(30, 30)]
    [InlineData(44, 30)]
    [InlineData(45, 45)]
    [InlineData(59, 45)]
    public void SnapToBucket_RoundsDownTo15MinuteBoundary(int inputMinute, int expectedMinute)
    {
        var input = new DateTime(2026, 5, 2, 12, inputMinute, 0, DateTimeKind.Utc);

        var snapped = TelemetryAggregator.SnapToBucket(input);

        Assert.Equal(expectedMinute, snapped.Minute);
        Assert.Equal(12, snapped.Hour);
    }

    [Fact]
    public void SnapToBucket_PreservesUtcKind()
    {
        var input = new DateTime(2026, 5, 2, 12, 17, 0, DateTimeKind.Utc);

        var snapped = TelemetryAggregator.SnapToBucket(input);

        Assert.Equal(DateTimeKind.Utc, snapped.Kind);
    }

    [Fact]
    public void SnapToBucket_StripsSecondsAndMilliseconds()
    {
        var input = new DateTime(2026, 5, 2, 12, 14, 59, 999, DateTimeKind.Utc);

        var snapped = TelemetryAggregator.SnapToBucket(input);

        Assert.Equal(0, snapped.Second);
        Assert.Equal(0, snapped.Millisecond);
        Assert.Equal(0, snapped.Minute);
    }

    #endregion

    #region IncrementToolUsage

    [Fact]
    public async Task IncrementToolUsage_MergesIdenticalKeysIntoSingleBucket()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<McpToolUsageBucketIncrement>? captured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());

        for (int i = 0; i < 5; i++)
            aggregator.IncrementToolUsage(42, "create_ticket", McpToolMode.User, _bucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        var item = Assert.Single(captured);
        Assert.Equal(42, item.UserID);
        Assert.True(item.ToolNameI3D > 0);
        Assert.Equal(McpToolMode.User, item.ToolMode);
        Assert.Equal(_bucket, item.BucketStartUtc);
        Assert.Equal(5, item.Increment);
    }

    [Fact]
    public async Task IncrementToolUsage_DistinctKeys_CreateSeparateBuckets()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<McpToolUsageBucketIncrement>? captured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());

        aggregator.IncrementToolUsage(1, "tool", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(2, "tool", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(3, "tool", McpToolMode.User, _bucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        Assert.Equal(3, captured.Count);
        Assert.All(captured, c => Assert.Equal(1, c.Increment));
        Assert.Equal(new[] { 1, 2, 3 }, captured.Select(c => c.UserID).OrderBy(x => x));
    }

    [Fact]
    public async Task IncrementToolUsage_DifferentBucketStarts_CreateSeparateBuckets()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<McpToolUsageBucketIncrement>? captured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());

        var laterBucket = _bucket.AddMinutes(15);
        aggregator.IncrementToolUsage(7, "tool", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(7, "tool", McpToolMode.User, laterBucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        Assert.Equal(2, captured.Count);
        Assert.All(captured, c => Assert.Equal(1, c.Increment));
    }

    [Theory]
    [InlineData(0, "tool")]
    [InlineData(-1, "tool")]
    [InlineData(1, "")]
    public async Task IncrementToolUsage_IgnoresInvalidInput(int userId, string toolName)
    {
        var (aggregator, bl) = CreateAggregator();

        aggregator.IncrementToolUsage(userId, toolName, McpToolMode.User, _bucket);
        await aggregator.FlushAsync(CancellationToken.None);

        bl.DidNotReceive().UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>());
    }

    [Fact]
    public async Task IncrementToolUsage_IgnoresNullToolName()
    {
        var (aggregator, bl) = CreateAggregator();

        aggregator.IncrementToolUsage(1, null!, McpToolMode.User, _bucket);
        await aggregator.FlushAsync(CancellationToken.None);

        bl.DidNotReceive().UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>());
    }

    [Fact]
    public async Task IncrementToolUsage_IsThreadSafe_UnderConcurrentLoad()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<McpToolUsageBucketIncrement>? captured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());

        Parallel.For(0, 10_000, _ =>
            aggregator.IncrementToolUsage(99, "tool", McpToolMode.User, _bucket));

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        var item = Assert.Single(captured);
        Assert.Equal(10_000, item.Increment);
    }

    #endregion

    #region IncrementApiCall

    [Theory]
    [InlineData(0, "method")]
    [InlineData(-1, "method")]
    [InlineData(1, "")]
    public async Task IncrementApiCall_IgnoresInvalidInput(int userId, string methodName)
    {
        var (aggregator, bl) = CreateAggregator();

        aggregator.IncrementApiCall(userId, TelemetryUserKind.User, TelemetryLicenseKind.Centron, methodName, _bucket);
        await aggregator.FlushAsync(CancellationToken.None);

        bl.DidNotReceive().UpsertApiCallBatch(Arg.Any<IReadOnlyCollection<ApiCallBucketIncrement>>());
    }

    [Fact]
    public async Task IncrementApiCall_IgnoresNullMethodName()
    {
        var (aggregator, bl) = CreateAggregator();

        aggregator.IncrementApiCall(1, TelemetryUserKind.User, TelemetryLicenseKind.Centron, null!, _bucket);
        await aggregator.FlushAsync(CancellationToken.None);

        bl.DidNotReceive().UpsertApiCallBatch(Arg.Any<IReadOnlyCollection<ApiCallBucketIncrement>>());
    }

    [Fact]
    public async Task IncrementApiCall_NullLicenseKind_AggregatedSeparatelyFromKnownLicense()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<ApiCallBucketIncrement>? captured = null;
        bl.UpsertApiCallBatch(Arg.Do<IReadOnlyCollection<ApiCallBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());

        // Both calls use the SAME UserKind so the test isolates the LicenseKind splitter
        // (would still pass even if UserKind were the discriminator if we varied it).
        aggregator.IncrementApiCall(1, TelemetryUserKind.User, null, "method", _bucket);
        aggregator.IncrementApiCall(1, TelemetryUserKind.User, TelemetryLicenseKind.Centron, "method", _bucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        Assert.Equal(2, captured.Count);
        Assert.Contains(captured, c => c.LicenseKind == null);
        Assert.Contains(captured, c => c.LicenseKind == TelemetryLicenseKind.Centron);
    }

    #endregion

    #region FlushAsync

    [Fact]
    public async Task FlushAsync_OnEmptyBuckets_DoesNotCallBl()
    {
        var (aggregator, bl) = CreateAggregator();

        await aggregator.FlushAsync(CancellationToken.None);

        bl.DidNotReceive().UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>());
        bl.DidNotReceive().UpsertApiCallBatch(Arg.Any<IReadOnlyCollection<ApiCallBucketIncrement>>());
    }

    [Fact]
    public async Task FlushAsync_PassesAggregatedIncrementsToBl()
    {
        var (aggregator, bl) = CreateAggregator();
        IReadOnlyCollection<McpToolUsageBucketIncrement>? tools = null;
        IReadOnlyCollection<ApiCallBucketIncrement>? apis = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => tools = b))
            .Returns(Result.AsSuccess());
        bl.UpsertApiCallBatch(Arg.Do<IReadOnlyCollection<ApiCallBucketIncrement>>(b => apis = b))
            .Returns(Result.AsSuccess());

        aggregator.IncrementToolUsage(1, "a", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(2, "b", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(3, "c", McpToolMode.User, _bucket);
        aggregator.IncrementApiCall(1, TelemetryUserKind.User, TelemetryLicenseKind.Centron, "m1", _bucket);
        aggregator.IncrementApiCall(2, TelemetryUserKind.WebAccount, TelemetryLicenseKind.Centron, "m2", _bucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(tools);
        Assert.NotNull(apis);
        Assert.Equal(3, tools.Count);
        Assert.Equal(2, apis.Count);
        Assert.Contains(tools, t => t.UserID == 2);
        Assert.Contains(apis, a => a.UserKind == TelemetryUserKind.WebAccount);
    }

    [Fact]
    public async Task FlushAsync_BatchesAt200ItemsPerCall()
    {
        var (aggregator, bl) = CreateAggregator();
        var batchSizes = new List<int>();
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => batchSizes.Add(b.Count)))
            .Returns(Result.AsSuccess());

        for (int i = 0; i < 450; i++)
            aggregator.IncrementToolUsage(i + 1, "tool", McpToolMode.User, _bucket);

        await aggregator.FlushAsync(CancellationToken.None);

        Assert.Equal(new[] { 200, 200, 50 }, batchSizes);
    }

    [Fact]
    public async Task FlushAsync_OnBlError_RestoresSnapshotIntoBuckets()
    {
        var (aggregator, bl) = CreateAggregator();
        var responses = new Queue<Result>();
        responses.Enqueue(Result.AsError("boom"));
        responses.Enqueue(Result.AsSuccess());

        IReadOnlyCollection<McpToolUsageBucketIncrement>? secondCallCaptured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>())
            .Returns(call =>
            {
                var arg = call.Arg<IReadOnlyCollection<McpToolUsageBucketIncrement>>();
                var result = responses.Dequeue();
                if (result.Status == ResultStatus.Success)
                    secondCallCaptured = arg;
                return result;
            });

        aggregator.IncrementToolUsage(1, "tool", McpToolMode.User, _bucket);
        aggregator.IncrementToolUsage(1, "tool", McpToolMode.User, _bucket);

        await aggregator.FlushAsync(CancellationToken.None);
        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(secondCallCaptured);
        var item = Assert.Single(secondCallCaptured);
        Assert.Equal(2, item.Increment);
    }

    [Fact]
    public async Task FlushAsync_OnBlError_RestoreCombinesWithIncrementsArrivedDuringFlush()
    {
        var (aggregator, bl) = CreateAggregator();
        var blocker = new ManualResetEventSlim(false);
        var midFlight = new ManualResetEventSlim(false);
        var firstCall = true;
        bl.UpsertMcpToolUsageBatch(Arg.Any<IReadOnlyCollection<McpToolUsageBucketIncrement>>())
            .Returns(_ =>
            {
                if (firstCall)
                {
                    firstCall = false;
                    midFlight.Set();
                    blocker.Wait();
                    return Result.AsError("boom");
                }
                return Result.AsSuccess();
            });

        aggregator.IncrementToolUsage(1, "tool", McpToolMode.User, _bucket);
        var flushTask = Task.Run(() => aggregator.FlushAsync(CancellationToken.None));
        midFlight.Wait();
        aggregator.IncrementToolUsage(1, "tool", McpToolMode.User, _bucket);
        blocker.Set();
        await flushTask;

        IReadOnlyCollection<McpToolUsageBucketIncrement>? captured = null;
        bl.UpsertMcpToolUsageBatch(Arg.Do<IReadOnlyCollection<McpToolUsageBucketIncrement>>(b => captured = b))
            .Returns(Result.AsSuccess());
        await aggregator.FlushAsync(CancellationToken.None);

        Assert.NotNull(captured);
        var item = Assert.Single(captured);
        Assert.Equal(2, item.Increment);
    }

    #endregion
}