using Unity.Collections;
using Unity.Entities;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Phase 1.7 per-projectile mechanic-changer state — SERVER-ONLY, NOT a <c>[GhostField]</c> (mirrors
    /// <see cref="KnockbackState"/>): it adds no replicated surface, so the <see cref="Projectile"/> ghost hash
    /// stays FROZEN (adding fields to the ghost <see cref="Projectile"/> component itself would change its
    /// StableTypeHash → serializer hash → ghost re-bake; a separate server-only component does not). Baked inert
    /// on the projectile prefab; seeded server-side at spawn (<c>AbilityFireSystem</c>) from the owner's
    /// <see cref="BoonEffects"/>, and read only by <c>ProjectileDamageSystem</c> (also server-only) — the owner's
    /// predicted projectile needs no local copy (pierce = server delays despawn → client reconciles via ghost
    /// persistence; chain = server rewrites the replicated <see cref="Projectile.Direction"/>; pull just flips the
    /// server-stamped <see cref="KnockbackState.Dir"/>).
    /// </summary>
    public struct ProjectileEffectState : IComponentData
    {
        /// <summary>Enemy hits remaining before the projectile despawns (0 = destroy on next hit).</summary>
        public byte PierceRemaining;
        /// <summary>Chain-to-next-target hops remaining after a hit.</summary>
        public byte ChainRemaining;
        /// <summary>bit0 = Pull (stamp knockback TOWARD the shooter instead of away).</summary>
        public byte Flags;
        /// <summary>Targets already hit by this projectile — excluded DURING target selection so a surviving
        /// (pierced/chained) projectile never re-hits the same enemy across ticks. Overflow ⇒ destroy (natural cap).</summary>
        public FixedList64Bytes<Entity> Hit;
    }

    /// <summary>Bit masks for <see cref="ProjectileEffectState.Flags"/>.</summary>
    public static class ProjectileEffectFlag
    {
        public const byte Pull = 1;
    }
}