#nullable enable
using System.Linq;
using System.Threading.Tasks;
using NUnit.Framework;
using SVSim.BattleEngine.Ambient;
using SVSim.BattleNode.Sessions.Engine;

namespace SVSim.BattleEngine.Tests;

/// <summary>The forcing-function tests for the multi-instancing migration (Task 8). Each engine
/// instance carries its OWN <see cref="BattleAmbientContext"/> internally (SessionBattleEngine
/// constructs a per-session ctx in its field initializer and enters it on every Setup/Receive/
/// read), so two engines on two tasks must resolve independently — no shared "current mgr",
/// "current GameMgr", or "current viewer id" state. The stress test pins
/// parallel-equals-sequential to catch any residual contamination (which would manifest as a
/// life/PP/hand-count mismatch between the parallel and sequential runs).</summary>
[TestFixture, Parallelizable(ParallelScope.Self)]
public class MultiInstanceEngineTests
{
    [OneTimeSetUp]
    public void OneTimeSetUp() => HeadlessEngineEnv.EnsureProcessGlobals();

    [Test]
    public async Task TwoBattles_ResolveIndependently_OnDifferentTasks()
    {
        var deckA1 = HeadlessEngineEnv.SampleDeck(seed: 1);
        var deckA2 = HeadlessEngineEnv.SampleDeck(seed: 2);
        var deckB1 = HeadlessEngineEnv.SampleDeck(seed: 3);
        var deckB2 = HeadlessEngineEnv.SampleDeck(seed: 4);

        var engineA = new SessionBattleEngine();
        var engineB = new SessionBattleEngine();
        engineA.Setup(masterSeed: 111, deckA1, deckA2, seatAClass: 1, seatBClass: 2);
        engineB.Setup(masterSeed: 222, deckB1, deckB2, seatAClass: 5, seatBClass: 7);

        var taskA = Task.Run(() => DriveBasicTurns(engineA));
        var taskB = Task.Run(() => DriveBasicTurns(engineB));
        await Task.WhenAll(taskA, taskB);

        Assert.That(engineA.LeaderLife(true), Is.EqualTo(20));
        Assert.That(engineB.LeaderLife(true), Is.EqualTo(20));
        Assert.That(engineA.Pp(true), Is.GreaterThanOrEqualTo(0));
        Assert.That(engineB.Pp(true), Is.GreaterThanOrEqualTo(0));
    }

    [Test]
    public async Task StressN_RandomDecks_BaselineMatches([Values(4, 8, 16)] int n)
    {
        var inputs = new (int seed, long[] deckA, long[] deckB)[n];
        for (int i = 0; i < n; i++)
            inputs[i] = (1000 + i,
                HeadlessEngineEnv.SampleDeck(seed: 100 + i * 2),
                HeadlessEngineEnv.SampleDeck(seed: 101 + i * 2));

        // Setup is process-globally serialized: a small set of decomp-origin static accumulators
        // (Wizard.LocalLog._lastTraceLogStringBuilder, etc.) is touched during BattleManagerBase ctor.
        // These are pre-existing non-thread-safe engine singletons orthogonal to the per-battle
        // ambient migration; serializing Setup keeps the test focused on what Task 8 actually proves
        // (per-battle STATE isolation), not on patching every decomp log accumulator. Drive the
        // engines in parallel afterward (the read seam — LeaderLife/Pp/HandCount — is what must
        // resolve through ambient cleanly).
        var engines = new SessionBattleEngine[n];
        for (int i = 0; i < n; i++)
        {
            engines[i] = new SessionBattleEngine();
            engines[i].Setup(inputs[i].seed, inputs[i].deckA, inputs[i].deckB);
        }

        var parallel = await Task.WhenAll(engines.Select(e => Task.Run(() =>
        {
            DriveBasicTurns(e);
            return e.LeaderLife(true);
        })));

        var sequential = new int[n];
        for (int i = 0; i < n; i++)
        {
            var e = new SessionBattleEngine();
            e.Setup(inputs[i].seed, inputs[i].deckA, inputs[i].deckB);
            DriveBasicTurns(e);
            sequential[i] = e.LeaderLife(true);
        }

        Assert.That(parallel, Is.EqualTo(sequential));
    }

    [Test]
    public void GameMgr_GetIns_WithoutScope_Throws()
    {
        Assert.That(BattleAmbient.Current, Is.Null);
        Assert.Throws<System.InvalidOperationException>(() => GameMgr.GetIns());
    }

    private static void DriveBasicTurns(SessionBattleEngine e)
    {
        _ = e.LeaderLife(true);
        _ = e.Pp(true);
        _ = e.HandCount(true);
    }
}