using ProjectM.Simulation;
using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.NetCode;
using Unity.Transforms;

namespace ProjectM.Server
{
    /// <summary>
    /// Server-authoritative player spawn. On each received <see cref="GoInGameRequest"/>: mark the
    /// source connection in-game, instantiate the player ghost from the baked
    /// <see cref="PlayerSpawner"/>, stamp <see cref="GhostOwner"/> with the connection's
    /// <see cref="NetworkId"/>, place it at the spawn point, and link it to the connection's
    /// LinkedEntityGroup so it auto-despawns on disconnect. Mirrors the netcode "networked-cube"
    /// ModifiedGoInGameServer sample. All structural changes are batched through an
    /// <see cref="EntityCommandBuffer"/>.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    public partial struct GoInGameServerSystem : ISystem
    {
        bool _warnedMetaBlocked; // one-shot: a mis-authored subscene must not silently block spawns forever

        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<PlayerSpawner>();

            var builder = new EntityQueryBuilder(Allocator.Temp)
                .WithAll<GoInGameRequest, ReceiveRpcCommandRequest>();
            state.RequireForUpdate(state.GetEntityQuery(builder));
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            // Step 12a availability guard (review N2/L1-6): the born-correct meta seeding below needs the baked
            // catalog + the live director's tier record. Both are per-tick-uniform, so guard ONCE at the TOP,
            // BEFORE the ECB exists — a per-request continue would already have marked the connection in-game.
            // Nothing is consumed; RequireForUpdate re-passes and the request retries next tick (a ≤1-tick window
            // in practice — the director spawns at subscene-stream, before any GoInGame round-trip).
            if (!SystemAPI.TryGetSingleton<MetaUpgradeCatalog>(out var metaCatalog) || !metaCatalog.Value.IsCreated
                || !SystemAPI.TryGetSingletonBuffer<MetaTierState>(out var metaRecord, true))
            {
                if (!_warnedMetaBlocked)
                {
                    UnityEngine.Debug.LogWarning("GoInGameServerSystem: player spawn waiting on the meta catalog/director (a mis-authored subscene would block spawns forever).");
                    _warnedMetaBlocked = true;
                }
                return;
            }

            var spawner = SystemAPI.GetSingleton<PlayerSpawner>();

            // M5 home base: re-root the spawn ring on the baked BaseAnchor when present; fall back
            // to the spawner's SpawnPoint if the base subscene hasn't streamed in yet.
            var center = spawner.SpawnPoint;
            if (SystemAPI.TryGetSingleton<BaseAnchor>(out var baseAnchor))
                center = BaseGridMath.PlotCenter(baseAnchor);
            var ecb = new EntityCommandBuffer(Allocator.Temp);

            foreach (var (receive, goReq, requestEntity) in
                     SystemAPI.Query<RefRO<ReceiveRpcCommandRequest>, RefRO<GoInGameRequest>>().WithEntityAccess())
            {
                var connection = receive.ValueRO.SourceConnection;
                ecb.AddComponent<NetworkStreamInGame>(connection);

                var networkId = SystemAPI.GetComponent<NetworkId>(connection);

                var player = ecb.Instantiate(spawner.PlayerPrefab);
                ecb.SetComponent(player, LocalTransform.FromPosition(center + PlayerSpawnMath.SpawnOffset(networkId.Value, spawner.SpawnRingRadius, spawner.RingSlots)));
                ecb.SetComponent(player, new GhostOwner { NetworkId = networkId.Value });
                // Tag the player into the base region (M6 region/relevancy split).
                ecb.AddComponent(player, new RegionTag { Region = RegionId.Base });
                // Slice 2: seed the chosen class on the just-instantiated player. AbilityRef selects the Fire slot
                // (Warrior = cone / Ranger = projectile); the DRG-asymmetry traits ride permanent StatModifiers
                // (CharacterStatsRef stays Default -> deltas replicate via the OwnerSendType.All buffer). 0 -> Warrior.
                byte classId = ClassTraits.Normalize(goReq.ValueRO.ClassId);
                ecb.SetComponent(player, new AbilityRef { Id = ClassTraits.AbilityFor(classId) });
                ClassTraits.AppendSeeds(classId, player, ecb);
                // Expedition redesign: the server-only class anchor the meta systems key on (born-correct meta
                // seeding at Step 12a + per-class spend at Step 13 resolve the tier record through this).
                ecb.AddComponent(player, new PlayerClass { ClassId = classId });
                // Step 12a: born-correct PERMANENT meta seeding — replay this class's persisted tiers as
                // meta-band StatModifiers on the just-instantiated player (same ECB as Instantiate, the
                // ClassTraits idiom). Skip tier 0 / unknown ids (preserve-don't-crash); CLAMP a saved tier above a
                // rebalanced MaxTier (D-F5). Class gate via BoonMath.MaskFor (ClassId is the normalized
                // CharacterId 2/3 — a raw 1<<ClassId would compute bits 2/3 and silently skip everything).
                {
                    ref var metaPool = ref metaCatalog.Value.Value;
                    byte classBit = BoonMath.MaskFor(classId);
                    for (int m = 0; m < metaRecord.Length; m++)
                    {
                        if (metaRecord[m].ClassId != classId || metaRecord[m].Tier == 0) continue;
                        int defIdx = MetaMath.FindDef(ref metaPool, metaRecord[m].UpgradeId);
                        if (defIdx < 0) continue; // unknown id (catalog drift) — preserved on disk, skipped live
                        if ((metaPool.Defs[defIdx].ClassMask & classBit) == 0) continue;
                        byte tier = metaRecord[m].Tier < metaPool.Defs[defIdx].MaxTier
                            ? metaRecord[m].Tier : metaPool.Defs[defIdx].MaxTier;
                        ecb.AppendToBuffer(player, new StatModifier
                        {
                            Target = metaPool.Defs[defIdx].Target,
                            Op = metaPool.Defs[defIdx].Op,
                            Value = metaPool.Defs[defIdx].ValuePerTier * tier,
                            SourceId = Tuning.MetaSourceIdBase + metaRecord[m].UpgradeId,
                        });
                    }
                }

                // Auto-despawn the player when its owning connection is removed.
                ecb.AppendToBuffer(connection, new LinkedEntityGroup { Value = player });

                ecb.DestroyEntity(requestEntity);
            }

            ecb.Playback(state.EntityManager);
        }
    }
}