using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Backend;
using ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Ipc;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests
{
    /// <summary>
    ///     PR C.1 — pins the trinary outcome → IPC bool[] mapping that the sidecar uses
    ///     on the WriteAlarmEvents reply. Per-event outcomes:
    ///       Ack → true,  RetryPlease → false,  PermanentFail → false.
    ///     The sender's B.4 widens the IPC bool back into the trinary outcome at the
    ///     IPC boundary using structured diagnostics; the wire intentionally collapses
    ///     to "ok / not-ok".
    /// </summary>
    [Trait("Category", "Unit")]
    public sealed class AahClientManagedAlarmEventWriterTests
    {
        [Fact]
        public async Task Empty_batch_returns_empty_array_without_invoking_backend()
        {
            var backend = new RecordingBackend(_ => throw new InvalidOperationException("must not invoke for empty input"));
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var result = await writer.WriteAsync(Array.Empty<AlarmHistorianEventDto>(), CancellationToken.None);

            result.ShouldBeEmpty();
            backend.Calls.ShouldBe(0);
        }

        [Fact]
        public async Task Single_ack_outcome_maps_to_true()
        {
            var backend = new RecordingBackend(events => events.Select(_ => AlarmHistorianWriteOutcome.Ack).ToArray());
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var result = await writer.WriteAsync(new[] { Event("E1") }, CancellationToken.None);

            result.ShouldBe(new[] { true });
        }

        [Fact]
        public async Task Mixed_batch_preserves_per_slot_ordering()
        {
            // Ack / Retry / Permanent / Ack — the sender uses positional matching against
            // its queue, so every slot must hit the exact bool corresponding to its input.
            var backend = new RecordingBackend(_ => new[]
            {
                AlarmHistorianWriteOutcome.Ack,
                AlarmHistorianWriteOutcome.RetryPlease,
                AlarmHistorianWriteOutcome.PermanentFail,
                AlarmHistorianWriteOutcome.Ack,
            });
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var result = await writer.WriteAsync(
                new[] { Event("E1"), Event("E2"), Event("E3"), Event("E4") },
                CancellationToken.None);

            result.ShouldBe(new[] { true, false, false, true });
        }

        [Fact]
        public async Task Backend_exception_marks_whole_batch_RetryPlease()
        {
            var backend = new RecordingBackend(_ => throw new InvalidOperationException("cluster unreachable"));
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var result = await writer.WriteAsync(
                new[] { Event("E1"), Event("E2"), Event("E3") },
                CancellationToken.None);

            // Whole batch must end up as "not ok" (RetryPlease at the trinary layer) —
            // dropping a transiently-failed batch corrupts the sender's queue.
            result.ShouldBe(new[] { false, false, false });
        }

        [Fact]
        public async Task Cancellation_propagates_from_backend()
        {
            var backend = new RecordingBackend(_ => throw new OperationCanceledException());
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var ex = await Should.ThrowAsync<OperationCanceledException>(() =>
                writer.WriteAsync(new[] { Event("E1") }, CancellationToken.None));
            ex.ShouldNotBeNull();
        }

        [Fact]
        public async Task Backend_returning_wrong_count_degrades_to_RetryPlease()
        {
            // Backend returns more outcomes than inputs — defensive degrade rather than
            // letting a backend bug desync the sender's queue accounting.
            var backend = new RecordingBackend(_ => new[]
            {
                AlarmHistorianWriteOutcome.Ack,
                AlarmHistorianWriteOutcome.Ack,
            });
            var writer = new AahClientManagedAlarmEventWriter(backend);

            var result = await writer.WriteAsync(new[] { Event("E1") }, CancellationToken.None);

            result.ShouldBe(new[] { false });
        }

        [Theory]
        // hresult 0 + clean → Ack
        [InlineData(0, false, false, AlarmHistorianWriteOutcome.Ack)]
        // hresult 0 but malformed → PermanentFail (malformed wins)
        [InlineData(0, false, true, AlarmHistorianWriteOutcome.PermanentFail)]
        // non-zero hresult + comm error → RetryPlease
        [InlineData(unchecked((int)0x80131500), true, false, AlarmHistorianWriteOutcome.RetryPlease)]
        // non-zero hresult, no comm flag, no malformed → conservative RetryPlease
        [InlineData(unchecked((int)0x80131500), false, false, AlarmHistorianWriteOutcome.RetryPlease)]
        // any malformed input → PermanentFail regardless of hresult
        [InlineData(unchecked((int)0x80131500), true, true, AlarmHistorianWriteOutcome.PermanentFail)]
        public void MapOutcome_table(int hresult, bool isCommunicationError, bool isMalformedInput, AlarmHistorianWriteOutcome expected)
        {
            AahClientManagedAlarmEventWriter
                .MapOutcome(hresult, isCommunicationError, isMalformedInput)
                .ShouldBe(expected);
        }

        private static AlarmHistorianEventDto Event(string id) => new AlarmHistorianEventDto
        {
            EventId = id,
            SourceName = "Tank01",
            ConditionId = "Tank01.Level.HiHi",
            AlarmType = "AnalogLimitAlarm.HiHi",
            Message = "Tank 01 high-high level",
            Severity = 750,
            EventTimeUtcTicks = DateTime.UtcNow.Ticks,
            AckComment = null,
        };

        private sealed class RecordingBackend : IAlarmHistorianWriteBackend
        {
            private readonly Func<AlarmHistorianEventDto[], AlarmHistorianWriteOutcome[]> _produce;
            public int Calls { get; private set; }

            public RecordingBackend(Func<AlarmHistorianEventDto[], AlarmHistorianWriteOutcome[]> produce)
            {
                _produce = produce;
            }

            public Task<AlarmHistorianWriteOutcome[]> WriteBatchAsync(
                AlarmHistorianEventDto[] events, CancellationToken cancellationToken)
            {
                Calls++;
                return Task.FromResult(_produce(events));
            }
        }
    }
}