using NUnit.Framework;
using ProjectM.Simulation;
using Unity.Collections;
using Unity.Entities;

namespace ProjectM.Tests
{
    /// <summary>
    /// Pins the room-scoped teardown contract (<see cref="RoomTeardown.DestroyRoom"/>): destroying room i kills ONLY
    /// room-i entities — the other room survives (the DR-031/DR-040 cross-room-wipe regression, load-bearing for the
    /// ping-pong sub-slot handoff where two rooms transiently coexist), untagged entities are untouched, and each
    /// entity is destroyed at most once (single-visit ⇒ no double-destroy Playback throw).
    /// </summary>
    public class RoomTeardownTests
    {
        static Entity MakeRoomEntity(EntityManager em, byte room, bool asNode)
        {
            // Mimic real room content: some entities look like resource nodes, some like zone enemies — the
            // teardown must be type-agnostic (RoomTag is the only contract).
            var e = asNode
                ? em.CreateEntity(typeof(RoomTag), typeof(ResourceNode))
                : em.CreateEntity(typeof(RoomTag), typeof(ZoneEnemyTag));
            em.SetComponentData(e, new RoomTag { Room = room });
            return e;
        }

        [Test]
        public void DestroyRoom_KillsOnlyThatRoom_SparesOtherRoomAndUntagged()
        {
            using var world = new World("RoomTeardownTest");
            var em = world.EntityManager;

            for (int i = 0; i < 3; i++) MakeRoomEntity(em, 0, asNode: i % 2 == 0); // room 0: 3 entities
            for (int i = 0; i < 2; i++) MakeRoomEntity(em, 1, asNode: i % 2 == 0); // room 1: 2 entities
            var untagged = em.CreateEntity(typeof(ResourceNode));                   // e.g. a base-field node

            using var roomQuery = em.CreateEntityQuery(typeof(RoomTag));
            var ecb = new EntityCommandBuffer(Allocator.Temp);
            int destroyed = RoomTeardown.DestroyRoom(roomQuery, ecb, 0);
            ecb.Playback(em);
            ecb.Dispose();

            Assert.AreEqual(3, destroyed, "exactly room-0's entities were queued");
            using var remaining = em.CreateEntityQuery(typeof(RoomTag));
            var tags = remaining.ToComponentDataArray<RoomTag>(Allocator.Temp);
            Assert.AreEqual(2, tags.Length, "room 1 survives intact");
            for (int i = 0; i < tags.Length; i++)
                Assert.AreEqual(1, tags[i].Room, "every survivor belongs to room 1");
            tags.Dispose();
            Assert.IsTrue(em.Exists(untagged), "untagged (non-room) entities are never touched");
        }

        [Test]
        public void DestroyRoom_EmptyRoom_IsANoOp()
        {
            using var world = new World("RoomTeardownTest2");
            var em = world.EntityManager;
            MakeRoomEntity(em, 1, asNode: true);

            using var roomQuery = em.CreateEntityQuery(typeof(RoomTag));
            var ecb = new EntityCommandBuffer(Allocator.Temp);
            int destroyed = RoomTeardown.DestroyRoom(roomQuery, ecb, 0); // room 0 has nothing
            ecb.Playback(em);
            ecb.Dispose();

            Assert.AreEqual(0, destroyed);
            using var remaining = em.CreateEntityQuery(typeof(RoomTag));
            Assert.AreEqual(1, remaining.CalculateEntityCount(), "room 1 untouched");
        }
    }
}