#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.All)]
public class MultiInstanceEngineTests
{
    [OneTimeSetUp]
    public void OneTimeSetUp() => HeadlessEngineEnv.EnsureProcessGlobals();

    [Test]
    public async Task TwoBattles_ResolveIndependently_OnDifferentTasks()
    {
        var engineA = new SessionBattleEngine();
        var engineB = new SessionBattleEngine();
        engineA.Setup(masterSeed: 111, HeadlessEngineEnv.SampleDeck(), HeadlessEngineEnv.SampleDeck(),
            seatAClass: 1, seatBClass: 2);
        engineB.Setup(masterSeed: 222, HeadlessEngineEnv.SampleDeck(), HeadlessEngineEnv.SampleDeck(),
            seatAClass: 5, seatBClass: 7);

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

        // Pin the engines' post-Setup state to concrete starting values: LeaderLife=20 (InitLeaderLife's
        // DefaultLeaderLife, applied by SessionBattleEngine.Setup), Pp=0 (pre-first-turn, no PP refill
        // has run), HandCount=0 (Setup builds the deck/leader graph but doesn't deal an opening hand —
        // mulligan/draw happens once a turn-start phase runs, which DriveBasicTurns doesn't trigger).
        // Both engines must report the SAME starting state regardless of distinct masterSeeds, which is
        // the cross-contamination property under test: ambient isolation means neither engine's reads
        // can leak into the other's seat lookups.
        Assert.That(engineA.LeaderLife(true), Is.EqualTo(20));
        Assert.That(engineB.LeaderLife(true), Is.EqualTo(20));
        Assert.That(engineA.Pp(true), Is.EqualTo(0));
        Assert.That(engineB.Pp(true), Is.EqualTo(0));
        Assert.That(engineA.HandCount(true), Is.EqualTo(0));
        Assert.That(engineB.HandCount(true), Is.EqualTo(0));
    }

    [Test]
    public async Task StressN_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(), HeadlessEngineEnv.SampleDeck());

        // Setup AND Drive both parallelize: the residual decomp-origin static accumulators
        // (Wizard.LocalLog._lastTraceLogStringBuilder etc.) and the Unity Resources shim
        // cache are now thread-safe (static lock / ConcurrentDictionary), so two engines
        // constructing in parallel no longer corrupts shared scratch state. The full
        // construct-then-read pipeline runs concurrently per task and the result still
        // pins to the sequential baseline — that is the cross-contamination property
        // under test (ambient isolation + safe shared statics).
        var parallel = await Task.WhenAll(inputs.Select(input => Task.Run(() =>
        {
            var e = new SessionBattleEngine();
            e.Setup(input.seed, input.deckA, input.deckB);
            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);
    }
}
