using Unity.Burst;
using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;
using Unity.Transforms;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Canonical predicted system: advances each player's planar (XZ) position from twin-stick Move
    /// input. Runs inside the prediction loop on the owning client (re-simulated on rollback) and
    /// once per tick on the server; filtered to <see cref="Simulate"/> so only predicted ghosts move.
    /// Deterministic by construction: uses <c>SystemAPI.Time.DeltaTime</c> (the fixed tick step)
    /// only — no wall-clock, no <c>System.Random</c>. Move is clamped to unit length so diagonal
    /// keyboard movement is not faster than cardinal. Move speed is the data-driven
    /// <see cref="EffectiveCharacterStats.MoveSpeed"/> (authored base + active modifiers), recomputed
    /// each tick by <see cref="StatRecomputeSystem"/> which runs before this system.
    /// </summary>
    [UpdateInGroup(typeof(PredictedSimulationSystemGroup))]
    [BurstCompile]
    public partial struct PlayerMoveSystem : ISystem
    {
        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            float dt = SystemAPI.Time.DeltaTime;

            foreach (var (transform, input, stats) in
                     SystemAPI.Query<RefRW<LocalTransform>, RefRO<PlayerInput>, RefRO<EffectiveCharacterStats>>()
                         .WithAll<Simulate>())
            {
                float2 move = input.ValueRO.Move;
                if (math.lengthsq(move) > 1f)
                    move = math.normalize(move);

                float3 delta = new float3(move.x, 0f, move.y) * stats.ValueRO.MoveSpeed * dt;
                transform.ValueRW.Position += delta;
            }
        }
    }
}