using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Deployments;
using ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Uns;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Deployments;

/// <summary>
///     Pins the <see cref="DeploymentDriftProbe"/> watermark contract: the expensive
///     <c>ConfigComposer</c> recomposition runs only when the <c>ConfigEdit</c> audit watermark (or the
///     sealed revision hash) has moved, and it definitely still runs when it has.
/// </summary>
public sealed class DeploymentDriftProbeTests
{
    private const string SealedHash = "sealed-hash-aaaa";

    [Fact]
    public async Task An_unchanged_watermark_reuses_the_cached_verdict()
    {
        var name = $"drift-{Guid.NewGuid():N}";
        var factory = UnsTreeTestDb.Factory(name);
        var compose = new CountingCompose(SealedHash);
        var probe = new DeploymentDriftProbe(factory, compose.ComposeAsync);

        var first = await probe.GetDriftAsync(SealedHash, CancellationToken.None);
        var second = await probe.GetDriftAsync(SealedHash, CancellationToken.None);

        // Nothing mutated between the calls, so the second call must be served from the cache.
        compose.Count.ShouldBe(1);
        first.ShouldBe(false);
        second.ShouldBe(false);
    }

    [Fact]
    public async Task A_new_config_edit_recomposes()
    {
        var name = $"drift-{Guid.NewGuid():N}";
        var factory = UnsTreeTestDb.Factory(name);
        var compose = new CountingCompose(SealedHash);
        var probe = new DeploymentDriftProbe(factory, compose.ComposeAsync);

        var before = await probe.GetDriftAsync(SealedHash, CancellationToken.None);
        before.ShouldBe(false);

        // An edit lands: the audit row moves the watermark, and the (faked) composer now reports a
        // different revision — the probe must recompose and flip the verdict.
        await using (var db = UnsTreeTestDb.CreateNamed(name))
        {
            db.ConfigEdits.Add(new ConfigEdit
            {
                EntityType = "Equipment",
                EntityId = Guid.NewGuid(),
                FieldsJson = "{}",
                EditedBy = "test",
                SourceNode = "node-1",
                EditedAtUtc = DateTime.UtcNow,
            });
            await db.SaveChangesAsync();
        }

        compose.Result = "a-different-hash";
        var after = await probe.GetDriftAsync(SealedHash, CancellationToken.None);

        compose.Count.ShouldBe(2);
        after.ShouldBe(true);
    }

    /// <summary>Stand-in for the <c>ConfigComposer</c> seam that counts how often it was invoked.</summary>
    private sealed class CountingCompose(string result)
    {
        public string Result { get; set; } = result;

        public int Count { get; private set; }

        public Task<string> ComposeAsync(OtOpcUaConfigDbContext db)
        {
            Count++;
            return Task.FromResult(Result);
        }
    }
}