using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Ghost component on the projectile prefab. Drives predicted+server movement and carries the
    /// classification key used to reconcile a client's predicted-spawned projectile with the server's
    /// authoritative ghost. <see cref="Direction"/> is replicated so the server's auto-targeted aim
    /// reconciles the client's raw-aim prediction; <see cref="SpawnId"/> is replicated so it lives in
    /// snapshot history for the predicted-spawn classifier. Speed/Damage/Range are baked on the prefab
    /// (identical both worlds → deterministic) and not replicated; DistanceTravelled is integrated
    /// locally each tick and not replicated.
    /// </summary>
    public struct Projectile : IComponentData
    {
        /// <summary>Planar XZ travel direction (world XZ mapped to float2 x,y), normalized.</summary>
        [GhostField(Quantization = 1000)] public float2 Direction;

        /// <summary>
        /// Classification key: (ownerNetId << 16) | absoluteFireCount. Replicated so it is present
        /// in snapshot history; the client classifier matches this against its predicted spawn.
        /// </summary>
        [GhostField] public uint SpawnId;

        /// <summary>Travel speed in units/second. Baked on the prefab; not replicated.</summary>
        public float Speed;

        /// <summary>Damage applied on hit. Baked on the prefab; not replicated.</summary>
        public float Damage;

        /// <summary>Max travel distance before the server expires the projectile. Baked on the prefab; not replicated.</summary>
        public float Range;

        /// <summary>Integrated distance travelled (predicted on client + authoritative on server). Not replicated.</summary>
        public float DistanceTravelled;

        /// <summary>This tick's travel step (Speed*dt), written by ProjectileMoveSystem so a plain-group harvest
        /// sweep is tunnelling-safe without depending on its own variable-frame clock. Server-local; not replicated.</summary>
        public float LastStep;
    }
}