using System.IO.Pipelines;
using System.IO.Pipes;
using AyCode.Core.Serializers.Binaries;
using AyCode.Core.Tests.TestModels;
using static AyCode.Core.Tests.TestModels.AcSerializerModels;

namespace AyCode.Core.Tests.Serialization;

/// <summary>
/// Cross-platform NamedPipe IPC roundtrip tests proving AcBinarySerializer's streaming framework
/// works on arbitrary <c>PipeWriter</c>/<c>PipeReader</c> sources without per-transport adapters.
///
/// <para>The serializer/deserializer surface intentionally has NO NamedPipe-specific helpers —
/// the tests own the <see cref="NamedPipeServerStream"/> / <see cref="NamedPipeClientStream"/>
/// lifecycle directly and call the generic
/// <see cref="AcBinarySerializer.SerializeChunked{T}(T, PipeWriter, AcBinarySerializerOptions)"/> +
/// <see cref="AcBinaryDeserializer.Deserialize{T}(AsyncPipeReaderInput, AcBinarySerializerOptions)"/>
/// primitives, with the receive-side drain implemented via the test-only
/// <see cref="AsyncPipeReaderInputExtensions.DrainFromAsync"/> extension. The same generic
/// primitives apply to FileStream / NetworkStream / custom transports — consumers own the
/// transport lifecycle, framework stays transport-agnostic.</para>
///
/// <para>With <c>BufferWriterChunkSize = 256</c>, even small test payloads cross multiple chunk
/// boundaries on the wire — exercises the real chunking + sliding-window cycling behavior.</para>
/// </summary>
[TestClass]
public class AcBinarySerializerNamedPipeTests
{
    [TestMethod]
    public async Task RoundTrip_SmallChunkSize_PayloadEquals()
    {
        var pipeName = $"AcBinaryTest-{Guid.NewGuid():N}";

        // 256-byte chunk size = Kestrel slab default; small enough to force multi-chunk framing
        // for our 50-item payload, exercises the AsyncSegment chunked wire format end-to-end.
        var opts = new AcBinarySerializerOptions { BufferWriterChunkSize = 256 };
        var original = CreatePayload(50);

        var result = await RunNamedPipeRoundTripAsync(pipeName, original, opts);

        Assert.IsNotNull(result);
        AssertPayloadEquals(original, result);
    }

    [TestMethod]
    public async Task RoundTrip_LargeScalePayload_ChunkSize256_StructuralEquality()
    {
        // Production-scale payload via TestDataFactory: 100 root items × 3 pallets × 3 measurements × 4 points
        // = ~3700 deeply-nested objects with shared references (50 tags, 20 users, metadata, 10 categories).
        // Serialized size ~few hundred KB → many chunks at chunkSize=256 → real backpressure-driven streaming
        // (sequential per-chunk flush on StreamPipeWriter, bytes flow incrementally as consumer drains).

#if DEBUG
        // Capture BOTH receiver and sender state to diagnose StreamPipeWriter interaction if needed.
        var diagLogs = new List<string>();

        AsyncPipeReaderInput.DiagnosticLog = msg => diagLogs.Add($"[R] {msg}");
        AsyncPipeWriterOutput.DiagnosticLog = msg => diagLogs.Add($"[S] {msg}");
#endif
        try
        {
            var pipeName = $"AcBinaryTest-{Guid.NewGuid():N}";
            var opts = new AcBinarySerializerOptions { BufferWriterChunkSize = 256 };
            var original = TestDataFactory.CreateLargeScaleBenchmarkOrder(rootItemCount: 100);

            var result = await RunNamedPipeRoundTripAsync(pipeName, original, opts);

            Assert.IsNotNull(result);
            Assert.AreEqual(original.Id, result.Id);
            Assert.AreEqual(original.OrderNumber, result.OrderNumber);
            Assert.AreEqual(original.Status, result.Status);
            Assert.AreEqual(original.TotalAmount, result.TotalAmount);

            // Deep structure: count items + pallets + measurements + points must match exactly
            var origCounts = CountTestOrderHierarchy(original);
            var resultCounts = CountTestOrderHierarchy(result);

            Assert.AreEqual(origCounts.items, resultCounts.items, "Items count mismatch");
            Assert.AreEqual(origCounts.pallets, resultCounts.pallets, "Pallets count mismatch");
            Assert.AreEqual(origCounts.measurements, resultCounts.measurements, "Measurements count mismatch");
            Assert.AreEqual(origCounts.points, resultCounts.points, "Points count mismatch");
        }
        finally
        {
#if DEBUG
            AsyncPipeReaderInput.DiagnosticLog = null;
            AsyncPipeWriterOutput.DiagnosticLog = null;

            if (diagLogs.Count > 0)
            {
                Console.WriteLine($"=== Sender [S] + Receiver [R] DiagnosticLog trail ({diagLogs.Count} entries) ===");

                // Print last 60 entries (most relevant to failure point)
                var startIdx = Math.Max(0, diagLogs.Count - 60);
                if (startIdx > 0) Console.WriteLine($"  ... ({startIdx} earlier entries elided)");

                for (var i = startIdx; i < diagLogs.Count; i++) Console.WriteLine($"  [{i}] {diagLogs[i]}");

                Console.WriteLine($"=== End DiagnosticLog ===");
            }
#endif
        }
    }

    /// <summary>
    /// Owns the full NamedPipe lifecycle: binds server, accepts connect, drives the generic
    /// <see cref="AcBinarySerializer.SerializeChunked{T}(T, PipeWriter, AcBinarySerializerOptions)"/> on
    /// the client side, and on the server side runs the canonical drain+deserialize pair
    /// (test-only <see cref="AsyncPipeReaderInputExtensions.DrainFromAsync"/> on the calling thread,
    /// <see cref="AcBinaryDeserializer.Deserialize{T}(AsyncPipeReaderInput, AcBinarySerializerOptions)"/>
    /// on a Task.Run BG thread). The framework helpers know nothing about NamedPipe — only PipeWriter /
    /// PipeReader.
    /// </summary>
    private static async Task<T?> RunNamedPipeRoundTripAsync<T>(string pipeName, T original, AcBinarySerializerOptions opts)
    {
        // Server-side bind is synchronous (NamedPipeServerStream ctor registers the pipe with
        // the OS), so the client can immediately attempt connect once we hand off to async.
        await using var pipeServer = new NamedPipeServerStream(pipeName, PipeDirection.In, 1, PipeTransmissionMode.Message, System.IO.Pipes.PipeOptions.Asynchronous);

        var receiveTask = Task.Run(async () =>
        {
            await pipeServer.WaitForConnectionAsync().ConfigureAwait(false);
            var pipeReader = PipeReader.Create(pipeServer);

            // Inlined version of what the removed DeserializeFromPipeReaderAsync used to do:
            // single-message mode + drain on calling thread + deserialize on Task.Run BG.
            using var input = new AsyncPipeReaderInput(initialCapacity: opts.BufferWriterChunkSize * 2, multiMessage: false);
            var deserTask = Task.Run(() => AcBinaryDeserializer.Deserialize<T>(input, opts));
            await input.DrainFromAsync(pipeReader).ConfigureAwait(false);
            return await deserTask.ConfigureAwait(false);
        });

        await using var pipeClient = new NamedPipeClientStream(".", pipeName, PipeDirection.Out, System.IO.Pipes.PipeOptions.Asynchronous);
        await pipeClient.ConnectAsync().ConfigureAwait(false);

        var pipeWriter = PipeWriter.Create(pipeClient);
        try
        {
            // Public PipeWriter overload (raw chunked stream — no per-chunk frame headers,
            // bit-compatible with Serialize(v, opts) byte[] output). Auto-selects sequential
            // flush strategy because PipeWriter.Create(stream) returns StreamPipeWriter
            // (race-incompatible with parallel send).
            AcBinarySerializer.SerializeChunked(original, pipeWriter, opts);
        }
        finally
        {
            await pipeWriter.CompleteAsync().ConfigureAwait(false);
        }

        return await receiveTask.ConfigureAwait(false);
    }

    private static (int items, int pallets, int measurements, int points) CountTestOrderHierarchy(TestOrder order)
    {
        var items = order.Items.Count;
        int pallets = 0, measurements = 0, points = 0;

        foreach (var item in order.Items)
        {
            pallets += item.Pallets.Count;
            foreach (var p in item.Pallets)
            {
                measurements += p.Measurements.Count;
                points += p.Measurements.Sum(m => m.Points.Count);
            }
        }

        return (items, pallets, measurements, points);
    }

    // Note: a "default chunk size" test was deliberately omitted. The default
    // AcBinarySerializerOptions.BufferWriterChunkSize used to be 65536, which exceeded the
    // UINT16 max (256). Fixed in this work to 256. Tests above explicitly set chunk size
    // for reproducibility regardless of default.

    private static TestParentWithDateTimeItemCollection CreatePayload(int itemCount)
    {
        var now = DateTime.UtcNow;
        var items = new List<TestEntityWithDateTimeAndInt>(itemCount);

        for (var i = 0; i < itemCount; i++)
        {
            items.Add(new TestEntityWithDateTimeAndInt
            {
                Id = i + 1,
                IntValue = i * 3,
                Created = now.AddMinutes(-i),
                Modified = now.AddMinutes(i),
                StatusCode = i % 4,
                Name = $"item-{i}"
            });
        }

        return new TestParentWithDateTimeItemCollection
        {
            Id = 11,
            Name = "named-pipe-roundtrip",
            Created = now,
            Items = items
        };
    }

    private static void AssertPayloadEquals(TestParentWithDateTimeItemCollection expected, TestParentWithDateTimeItemCollection actual)
    {
        Assert.AreEqual(expected.Id, actual.Id);
        Assert.AreEqual(expected.Name, actual.Name);
        Assert.AreEqual(expected.Created, actual.Created);

        Assert.IsNotNull(expected.Items);
        Assert.IsNotNull(actual.Items);
        Assert.AreEqual(expected.Items.Count, actual.Items.Count);

        for (var i = 0; i < expected.Items.Count; i++)
        {
            var e = expected.Items[i];
            var a = actual.Items[i];

            Assert.AreEqual(e.Id, a.Id);
            Assert.AreEqual(e.IntValue, a.IntValue);
            Assert.AreEqual(e.Created, a.Created);
            Assert.AreEqual(e.Modified, a.Modified);
            Assert.AreEqual(e.StatusCode, a.StatusCode);
            Assert.AreEqual(e.Name, a.Name);
        }
    }
}