using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Core.Hosting;
using ZB.MOM.WW.OtOpcUa.Server.Phase7;

namespace ZB.MOM.WW.OtOpcUa.Server.Tests.Phase7;

/// <summary>
///     PR B.4 — pins the precedence order Phase7Composer uses to pick an
///     <see cref="IAlarmHistorianWriter"/>:
///     driver-provided > DI-registered > none. Driver wins so a future
///     GalaxyDriver-as-IAlarmHistorianWriter takes the write path directly,
///     preserving the v1 invariant where a driver that natively owns the
///     historian client doesn't bounce through the sidecar IPC.
/// </summary>
[Trait("Category", "Unit")]
public sealed class Phase7ComposerWriterSelectionTests
{
    [Fact]
    public async Task No_driver_no_injected_writer_returns_null()
    {
        await using var host = new DriverHost();

        var writer = Phase7Composer.SelectAlarmHistorianWriter(host, injectedWriter: null, out var source);

        writer.ShouldBeNull();
        source.ShouldBeNull();
    }

    [Fact]
    public async Task Injected_writer_only_is_selected()
    {
        await using var host = new DriverHost();
        var injected = new RecordingWriter("from-di");

        var writer = Phase7Composer.SelectAlarmHistorianWriter(host, injected, out var source);

        writer.ShouldBeSameAs(injected);
        source.ShouldStartWith("di:");
    }

    [Fact]
    public async Task Driver_writer_wins_over_injected()
    {
        await using var host = new DriverHost();
        var driver = new FakeDriverWithWriter("drv-1", "drv-out");
        await host.RegisterAsync(driver, driverConfigJson: "{}", CancellationToken.None);

        var injected = new RecordingWriter("from-di");
        var writer = Phase7Composer.SelectAlarmHistorianWriter(host, injected, out var source);

        writer.ShouldBeSameAs(driver);
        source.ShouldBe("driver:drv-1");
    }

    [Fact]
    public async Task First_driver_implementing_writer_wins()
    {
        await using var host = new DriverHost();
        var driverNoWriter = new FakeDriverWithoutWriter("drv-1");
        var driverWithWriter = new FakeDriverWithWriter("drv-2", "drv-out");

        await host.RegisterAsync(driverNoWriter, "{}", CancellationToken.None);
        await host.RegisterAsync(driverWithWriter, "{}", CancellationToken.None);

        var writer = Phase7Composer.SelectAlarmHistorianWriter(host, injectedWriter: null, out var source);

        writer.ShouldBeSameAs(driverWithWriter);
        source.ShouldBe("driver:drv-2");
    }

    private sealed class RecordingWriter : IAlarmHistorianWriter
    {
        public string Tag { get; }
        public RecordingWriter(string tag) { Tag = tag; }

        public Task<IReadOnlyList<HistorianWriteOutcome>> WriteBatchAsync(
            IReadOnlyList<AlarmHistorianEvent> batch, CancellationToken cancellationToken)
        {
            var outcomes = new HistorianWriteOutcome[batch.Count];
            for (var i = 0; i < outcomes.Length; i++) outcomes[i] = HistorianWriteOutcome.Ack;
            return Task.FromResult<IReadOnlyList<HistorianWriteOutcome>>(outcomes);
        }
    }

    private sealed class FakeDriverWithoutWriter : IDriver
    {
        public FakeDriverWithoutWriter(string id) { DriverInstanceId = id; }
        public string DriverInstanceId { get; }
        public string DriverType => "FakeNoWriter";
        public Task InitializeAsync(string c, CancellationToken ct) => Task.CompletedTask;
        public Task ReinitializeAsync(string c, CancellationToken ct) => Task.CompletedTask;
        public Task ShutdownAsync(CancellationToken ct) => Task.CompletedTask;
        public DriverHealth GetHealth() => new(DriverState.Healthy, DateTime.UtcNow, null);
        public long GetMemoryFootprint() => 0;
        public Task FlushOptionalCachesAsync(CancellationToken ct) => Task.CompletedTask;
    }

    private sealed class FakeDriverWithWriter : IDriver, IAlarmHistorianWriter
    {
        private readonly RecordingWriter _writer;
        public FakeDriverWithWriter(string id, string tag)
        {
            DriverInstanceId = id;
            _writer = new RecordingWriter(tag);
        }
        public string DriverInstanceId { get; }
        public string DriverType => "FakeWithWriter";
        public Task InitializeAsync(string c, CancellationToken ct) => Task.CompletedTask;
        public Task ReinitializeAsync(string c, CancellationToken ct) => Task.CompletedTask;
        public Task ShutdownAsync(CancellationToken ct) => Task.CompletedTask;
        public DriverHealth GetHealth() => new(DriverState.Healthy, DateTime.UtcNow, null);
        public long GetMemoryFootprint() => 0;
        public Task FlushOptionalCachesAsync(CancellationToken ct) => Task.CompletedTask;

        public Task<IReadOnlyList<HistorianWriteOutcome>> WriteBatchAsync(
            IReadOnlyList<AlarmHistorianEvent> batch, CancellationToken cancellationToken)
            => _writer.WriteBatchAsync(batch, cancellationToken);
    }
}