using Microsoft.Data.Sqlite;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;

namespace ZB.MOM.WW.ScadaBridge.StoreAndForward.Tests;

/// <summary>
/// WP-11: Tests for async replication to standby.
/// </summary>
public class ReplicationServiceTests : IAsyncLifetime, IDisposable
{
    private readonly SqliteConnection _keepAlive;
    private readonly StoreAndForwardStorage _storage;
    private readonly ReplicationService _replicationService;

    public ReplicationServiceTests()
    {
        var dbName = $"RepTests_{Guid.NewGuid():N}";
        var connStr = $"Data Source={dbName};Mode=Memory;Cache=Shared";
        _keepAlive = new SqliteConnection(connStr);
        _keepAlive.Open();

        _storage = new StoreAndForwardStorage(connStr, NullLogger<StoreAndForwardStorage>.Instance);

        var options = new StoreAndForwardOptions { ReplicationEnabled = true };
        _replicationService = new ReplicationService(
            options, NullLogger<ReplicationService>.Instance);
    }

    public async Task InitializeAsync() => await _storage.InitializeAsync();

    public Task DisposeAsync() => Task.CompletedTask;

    public void Dispose() => _keepAlive.Dispose();

    [Fact]
    public void ReplicateEnqueue_NoHandler_DoesNotThrow()
    {
        var msg = CreateMessage("rep1");
        _replicationService.ReplicateEnqueue(msg);
    }

    [Fact]
    public async Task ReplicateEnqueue_WithHandler_ForwardsOperation()
    {
        ReplicationOperation? captured = null;
        _replicationService.SetReplicationHandler(op =>
        {
            captured = op;
            return Task.CompletedTask;
        });

        var msg = CreateMessage("rep2");
        _replicationService.ReplicateEnqueue(msg);

        await Task.Delay(200);

        Assert.NotNull(captured);
        Assert.Equal(ReplicationOperationType.Add, captured!.OperationType);
        Assert.Equal("rep2", captured.MessageId);
    }

    [Fact]
    public async Task ReplicateRemove_WithHandler_ForwardsRemoveOperation()
    {
        ReplicationOperation? captured = null;
        _replicationService.SetReplicationHandler(op =>
        {
            captured = op;
            return Task.CompletedTask;
        });

        _replicationService.ReplicateRemove("rep3");

        await Task.Delay(200);

        Assert.NotNull(captured);
        Assert.Equal(ReplicationOperationType.Remove, captured!.OperationType);
        Assert.Equal("rep3", captured.MessageId);
    }

    [Fact]
    public async Task ReplicatePark_WithHandler_ForwardsParkOperation()
    {
        ReplicationOperation? captured = null;
        _replicationService.SetReplicationHandler(op =>
        {
            captured = op;
            return Task.CompletedTask;
        });

        var msg = CreateMessage("rep4");
        _replicationService.ReplicatePark(msg);

        await Task.Delay(200);

        Assert.NotNull(captured);
        Assert.Equal(ReplicationOperationType.Park, captured!.OperationType);
    }

    [Fact]
    public async Task ApplyReplicatedOperationAsync_Add_EnqueuesMessage()
    {
        var msg = CreateMessage("apply1");
        var operation = new ReplicationOperation(ReplicationOperationType.Add, "apply1", msg);

        await _replicationService.ApplyReplicatedOperationAsync(operation, _storage);

        var retrieved = await _storage.GetMessageByIdAsync("apply1");
        Assert.NotNull(retrieved);
    }

    [Fact]
    public async Task ApplyReplicatedOperationAsync_Remove_DeletesMessage()
    {
        var msg = CreateMessage("apply2");
        await _storage.EnqueueAsync(msg);

        var operation = new ReplicationOperation(ReplicationOperationType.Remove, "apply2", null);
        await _replicationService.ApplyReplicatedOperationAsync(operation, _storage);

        var retrieved = await _storage.GetMessageByIdAsync("apply2");
        Assert.Null(retrieved);
    }

    [Fact]
    public async Task ApplyReplicatedOperationAsync_Park_UpdatesStatus()
    {
        var msg = CreateMessage("apply3");
        await _storage.EnqueueAsync(msg);

        var operation = new ReplicationOperation(ReplicationOperationType.Park, "apply3", msg);
        await _replicationService.ApplyReplicatedOperationAsync(operation, _storage);

        var retrieved = await _storage.GetMessageByIdAsync("apply3");
        Assert.NotNull(retrieved);
        Assert.Equal(StoreAndForwardMessageStatus.Parked, retrieved!.Status);
    }

    [Fact]
    public void ReplicateEnqueue_WhenReplicationDisabled_DoesNothing()
    {
        var options = new StoreAndForwardOptions { ReplicationEnabled = false };
        var service = new ReplicationService(options, NullLogger<ReplicationService>.Instance);

        bool handlerCalled = false;
        service.SetReplicationHandler(_ => { handlerCalled = true; return Task.CompletedTask; });

        service.ReplicateEnqueue(CreateMessage("disabled1"));

        Assert.False(handlerCalled);
    }

    [Fact]
    public async Task ReplicateEnqueue_HandlerThrows_DoesNotPropagateException()
    {
        _replicationService.SetReplicationHandler(_ =>
            throw new InvalidOperationException("standby down"));

        _replicationService.ReplicateEnqueue(CreateMessage("err1"));

        await Task.Delay(200);
        // No exception -- fire-and-forget, best-effort
    }

    // ── Task 10 (arch review 02): ordered, observable replication dispatch ──

    [Fact]
    public void ReplicationOperations_AreDispatchedInIssueOrder()
    {
        var seen = new List<(ReplicationOperationType, string)>();
        _replicationService.SetReplicationHandler(op =>
        {
            seen.Add((op.OperationType, op.MessageId));
            return Task.CompletedTask;
        });

        for (var i = 0; i < 200; i++)
        {
            _replicationService.ReplicateEnqueue(CreateMessage($"m{i}"));
            _replicationService.ReplicateRemove($"m{i}");
        }

        // Inline dispatch: by the time the calls return, every op was handed to the
        // handler, Add strictly before Remove per id. Pre-fix (Task.Run) this was
        // racy in both count and order.
        Assert.Equal(400, seen.Count);
        for (var i = 0; i < 200; i++)
        {
            Assert.Equal((ReplicationOperationType.Add, $"m{i}"), seen[2 * i]);
            Assert.Equal((ReplicationOperationType.Remove, $"m{i}"), seen[2 * i + 1]);
        }
    }

    [Fact]
    public void ReplicationHandlerThrow_IsSwallowed_AndLoggedAtWarning()
    {
        var logger = new CapturingLogger<ReplicationService>();
        var service = new ReplicationService(new StoreAndForwardOptions(), logger);
        service.SetReplicationHandler(_ => throw new InvalidOperationException("peer gone"));

        service.ReplicateRemove("m1"); // must not throw

        Assert.Contains(logger.Entries, e => e.Level == LogLevel.Warning);
    }

    private static StoreAndForwardMessage CreateMessage(string id)
    {
        return new StoreAndForwardMessage
        {
            Id = id,
            Category = StoreAndForwardCategory.ExternalSystem,
            Target = "target",
            PayloadJson = "{}",
            RetryCount = 0,
            MaxRetries = 50,
            RetryIntervalMs = 30000,
            CreatedAt = DateTimeOffset.UtcNow,
            Status = StoreAndForwardMessageStatus.Pending
        };
    }

    /// <summary>Minimal in-memory logger that records level + rendered message.</summary>
    private sealed class CapturingLogger<T> : ILogger<T>
    {
        public List<(LogLevel Level, string Message)> Entries { get; } = new();
        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;
        public bool IsEnabled(LogLevel logLevel) => true;
        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
            Func<TState, Exception?, string> formatter)
            => Entries.Add((logLevel, formatter(state, exception)));
    }
}