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
    {
        [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)
        {
            var spawner = SystemAPI.GetSingleton<PlayerSpawner>();
            var ecb = new EntityCommandBuffer(Allocator.Temp);

            foreach (var (receive, requestEntity) in
                     SystemAPI.Query<RefRO<ReceiveRpcCommandRequest>>().WithAll<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(spawner.SpawnPoint + PlayerSpawnMath.SpawnOffset(networkId.Value, spawner.SpawnRingRadius, spawner.RingSlots)));
                ecb.SetComponent(player, new GhostOwner { NetworkId = networkId.Value });

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

                ecb.DestroyEntity(requestEntity);
            }

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