using NUnit.Framework;
using ProjectM.Server;
using ProjectM.Simulation;
using Unity.Core;
using Unity.Entities;
using Unity.NetCode;
using System.Collections.Generic;

namespace ProjectM.Tests
{
    /// <summary>
    /// Validation matrix for <see cref="RouteSelectSystem"/> — the co-op route-pick receiver. Pins: a correctly
    /// stamped pick latches (the review's non-maskable acceptance criterion — a validation bug here silently
    /// degrades to the grace auto-pick and a linear game); the first-commit latch under two same-tick picks; the
    /// re-meaned run-identity stale-reject ((uint)ForRunEpoch == RunSeed); the layer stale-reject; index bounds;
    /// the N3 base-region sender reject; the closed-gate reject; and that requests are ALWAYS consumed.
    /// </summary>
    public class RouteSelectSystemTests
    {
        const uint Seed = 999u;
        const int GateLayer = 2;
        readonly List<World> _worlds = new();

        [TearDown]
        public void Cleanup()
        {
            foreach (var w in _worlds) if (w.IsCreated) w.Dispose();
            _worlds.Clear();
        }

        static (World world, SimulationSystemGroup group, Entity dir) MakeGateWorld(byte lifecycle = RunLifecycle.RouteSelect)
        {
            var world = new World("RouteSelectTest");
            var group = world.GetOrCreateSystemManaged<SimulationSystemGroup>();
            group.AddSystemToUpdateList(world.GetOrCreateSystem<RouteSelectSystem>());
            group.SortSystems();
            world.SetTime(new TimeData(elapsedTime: 0f, deltaTime: 1f / 60f));
            var em = world.EntityManager;

            var dir = em.CreateEntity(typeof(RunInfo), typeof(RunRuntime), typeof(RouteCommand));
            em.SetComponentData(dir, new RunInfo
            {
                Lifecycle = lifecycle,
                CurrentRoom = GateLayer,
                RunSeed = Seed,
                RouteOptionCount = 2,
                RouteOpt0Col = 0,
                RouteOpt1Col = 2,
            });
            em.SetComponentData(dir, new RunRuntime { RunSeed = Seed, RunEpoch = 3 });
            return (world, group, dir);
        }

        static Entity MakePlayer(EntityManager em, int networkId, byte region)
        {
            var e = em.CreateEntity(typeof(PlayerTag), typeof(GhostOwner), typeof(RegionTag));
            em.SetComponentData(e, new GhostOwner { NetworkId = networkId });
            em.SetComponentData(e, new RegionTag { Region = region });
            return e;
        }

        static void SendPick(EntityManager em, int networkId, byte optionIndex, int forSeed, int forLayer)
        {
            var conn = em.CreateEntity(typeof(NetworkId));
            em.SetComponentData(conn, new NetworkId { Value = networkId });
            var req = em.CreateEntity(typeof(RouteSelectRequest), typeof(ReceiveRpcCommandRequest));
            em.SetComponentData(req, new RouteSelectRequest { OptionIndex = optionIndex, ForRunEpoch = forSeed, ForLayer = forLayer });
            em.SetComponentData(req, new ReceiveRpcCommandRequest { SourceConnection = conn });
        }

        static int PendingRequests(EntityManager em)
        {
            using var q = em.CreateEntityQuery(typeof(RouteSelectRequest));
            return q.CalculateEntityCount();
        }

        [Test]
        public void ValidPick_Latches_WithTrueServerEpoch()
        {
            var (world, group, dir) = MakeGateWorld();
            using (world)
            {
            var em = world.EntityManager;
            MakePlayer(em, 1, RegionId.Expedition);
            SendPick(em, 1, optionIndex: 1, forSeed: (int)Seed, forLayer: GateLayer);

            group.Update();

            var cmd = em.GetComponentData<RouteCommand>(dir);
            Assert.AreEqual(1, cmd.HasPick, "a correctly-stamped pick MUST latch (non-maskable criterion)");
            Assert.AreEqual(1, cmd.OptionIndex, "the picked option");
            Assert.AreEqual(3, cmd.ForRunEpoch, "stamped from the TRUE server epoch, never the client echo");
            Assert.AreEqual(0, PendingRequests(em), "request consumed");
            }
        }

        [Test]
        public void TwoSameTickPicks_FirstWins()
        {
            var (world, group, dir) = MakeGateWorld();
            using (world)
            {
            var em = world.EntityManager;
            MakePlayer(em, 1, RegionId.Expedition);
            MakePlayer(em, 2, RegionId.Expedition);
            SendPick(em, 1, optionIndex: 0, forSeed: (int)Seed, forLayer: GateLayer); // created first -> wins
            SendPick(em, 2, optionIndex: 1, forSeed: (int)Seed, forLayer: GateLayer);

            group.Update();

            var cmd = em.GetComponentData<RouteCommand>(dir);
            Assert.AreEqual(1, cmd.HasPick, "exactly one commit");
            Assert.AreEqual(0, cmd.OptionIndex, "the FIRST accepted pick wins (in-place latch, DR-014)");
            Assert.AreEqual(0, PendingRequests(em), "both requests consumed");
            }
        }

        [Test]
        public void Rejects_WrongSeed_WrongLayer_OutOfRange_BaseSender_ClosedGate()
        {
            // Wrong run-identity token (a stale pick from the previous run).
            var (w1, g1, d1) = MakeGateWorld();
            _worlds.Add(w1);
            MakePlayer(w1.EntityManager, 1, RegionId.Expedition);
            SendPick(w1.EntityManager, 1, 0, forSeed: (int)Seed + 1, forLayer: GateLayer);
            g1.Update();
            Assert.AreEqual(0, w1.EntityManager.GetComponentData<RouteCommand>(d1).HasPick, "wrong seed rejected");
            Assert.AreEqual(0, PendingRequests(w1.EntityManager));

            // Wrong layer (a pick from the previous gate of the SAME run).
            var (w2, g2, d2) = MakeGateWorld();
            _worlds.Add(w2);
            MakePlayer(w2.EntityManager, 1, RegionId.Expedition);
            SendPick(w2.EntityManager, 1, 0, (int)Seed, forLayer: GateLayer - 1);
            g2.Update();
            Assert.AreEqual(0, w2.EntityManager.GetComponentData<RouteCommand>(d2).HasPick, "stale layer rejected");

            // Option index out of the published range.
            var (w3, g3, d3) = MakeGateWorld();
            _worlds.Add(w3);
            MakePlayer(w3.EntityManager, 1, RegionId.Expedition);
            SendPick(w3.EntityManager, 1, optionIndex: 2, (int)Seed, GateLayer); // count is 2 -> max index 1
            g3.Update();
            Assert.AreEqual(0, w3.EntityManager.GetComponentData<RouteCommand>(d3).HasPick, "out-of-range rejected");

            // Base-region sender (N3): a home-bound joiner cannot commit the party's route.
            var (w4, g4, d4) = MakeGateWorld();
            _worlds.Add(w4);
            MakePlayer(w4.EntityManager, 1, RegionId.Base);
            SendPick(w4.EntityManager, 1, 0, (int)Seed, GateLayer);
            g4.Update();
            Assert.AreEqual(0, w4.EntityManager.GetComponentData<RouteCommand>(d4).HasPick, "base sender rejected (N3)");

            // Gate closed (mid-room): the pick is dropped, never queued.
            var (w5, g5, d5) = MakeGateWorld(lifecycle: RunLifecycle.InRoom);
            _worlds.Add(w5);
            MakePlayer(w5.EntityManager, 1, RegionId.Expedition);
            SendPick(w5.EntityManager, 1, 0, (int)Seed, GateLayer);
            g5.Update();
            Assert.AreEqual(0, w5.EntityManager.GetComponentData<RouteCommand>(d5).HasPick, "closed gate rejected");
            Assert.AreEqual(0, PendingRequests(w5.EntityManager), "request still consumed");
        }

        [Test]
        public void AlreadyLatched_LaterPickIgnored()
        {
            var (world, group, dir) = MakeGateWorld();
            using (world)
            {
            var em = world.EntityManager;
            MakePlayer(em, 1, RegionId.Expedition);
            em.SetComponentData(dir, new RouteCommand { HasPick = 1, OptionIndex = 0, ForRunEpoch = 3, ForLayer = GateLayer });
            SendPick(em, 1, optionIndex: 1, (int)Seed, GateLayer);

            group.Update();

            var cmd = em.GetComponentData<RouteCommand>(dir);
            Assert.AreEqual(0, cmd.OptionIndex, "an already-latched gate ignores later picks");
            }
        }
    }
}