using Akka.Cluster;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Interfaces;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Admin;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;

namespace ZB.MOM.WW.OtOpcUa.Host.IntegrationTests;

/// <summary>
/// Failover scenarios layered on <see cref="TwoNodeClusterHarness"/> Stop/Restart primitives.
/// Covers graceful node loss, rejoin on the same Akka port, and deployment under reduced membership.
/// </summary>
public sealed class FailoverDuringDeployTests
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    /// <summary>Verifies that stopping node B shrinks the cluster to one up member.</summary>
    [Fact]
    public async Task Stopping_node_b_shrinks_cluster_to_one_up_member()
    {
        await using var harness = await TwoNodeClusterHarness.StartAsync();
        Akka.Cluster.Cluster.Get(harness.NodeASystem).State.Members
            .Count(m => m.Status == MemberStatus.Up).ShouldBe(2);

        await harness.StopNodeBAsync();
        await harness.WaitForClusterSizeAsync(1, TimeSpan.FromSeconds(20));

        Akka.Cluster.Cluster.Get(harness.NodeASystem).State.Members
            .Count(m => m.Status == MemberStatus.Up).ShouldBe(1);
    }

    /// <summary>Verifies that a restarted node B rejoins the cluster on the same port.</summary>
    [Fact]
    public async Task Restarted_node_b_rejoins_cluster_on_same_port()
    {
        await using var harness = await TwoNodeClusterHarness.StartAsync();

        await harness.StopNodeBAsync();
        await harness.WaitForClusterSizeAsync(1, TimeSpan.FromSeconds(20));

        await harness.RestartNodeBAsync();

        Akka.Cluster.Cluster.Get(harness.NodeASystem).State.Members
            .Count(m => m.Status == MemberStatus.Up).ShouldBe(2);
        Akka.Cluster.Cluster.Get(harness.NodeBSystem).State.Members
            .Count(m => m.Status == MemberStatus.Up).ShouldBe(2);
    }

    /// <summary>Verifies that a deployment started with node B down seals with one-node state.</summary>
    [Fact]
    public async Task Deployment_started_with_node_b_down_seals_with_one_node_state()
    {
        // Establishes that ConfigPublishCoordinator.DiscoverDriverNodes snapshots membership at
        // dispatch time — when only node A is Up, only one ApplyAck is expected and the
        // deployment seals without B ever participating.
        await using var harness = await TwoNodeClusterHarness.StartAsync();
        await harness.SeedDefaultClusterAsync();

        await harness.StopNodeBAsync();
        await harness.WaitForClusterSizeAsync(1, TimeSpan.FromSeconds(20));

        await using var scope = harness.NodeA.Services.CreateAsyncScope();
        var client = scope.ServiceProvider.GetRequiredService<IAdminOperationsClient>();

        var result = await client.StartDeploymentAsync(createdBy: "alice@test", Ct);
        result.Outcome.ShouldBe(StartDeploymentOutcome.Accepted);
        var deploymentId = result.DeploymentId!.Value.Value;

        await WaitForAsync(async () =>
        {
            await using var db = await CreateDbAsync(harness);
            var d = await db.Deployments.AsNoTracking()
                .FirstOrDefaultAsync(d => d.DeploymentId == deploymentId, Ct);
            return d?.Status == DeploymentStatus.Sealed;
        }, TimeSpan.FromSeconds(15));

        await using var db = await CreateDbAsync(harness);
        var nodeStates = await db.NodeDeploymentStates.AsNoTracking()
            .Where(s => s.DeploymentId == deploymentId)
            .ToListAsync(Ct);
        nodeStates.Count.ShouldBe(1);
        nodeStates[0].Status.ShouldBe(NodeDeploymentStatus.Applied);
    }

    private static async Task<OtOpcUaConfigDbContext> CreateDbAsync(TwoNodeClusterHarness harness)
    {
        var factory = harness.NodeA.Services.GetRequiredService<IDbContextFactory<OtOpcUaConfigDbContext>>();
        return await factory.CreateDbContextAsync();
    }

    private static async Task WaitForAsync(Func<Task<bool>> condition, TimeSpan timeout)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (DateTime.UtcNow < deadline)
        {
            if (await condition()) return;
            await Task.Delay(200);
        }
        throw new TimeoutException($"Condition not met within {timeout}");
    }
}
