using Unity.Entities;

namespace ProjectM.Simulation
{
    /// <summary>
    /// SERVER-ONLY expiry tracker paired with a <see cref="StatModifier"/> by <see cref="SourceId"/>. It is NOT a
    /// [GhostField] and lives in a SEPARATE buffer so the replicated <see cref="StatModifier"/> layout stays
    /// byte-identical — adding ANY member (even non-ghost) to a [GhostField] buffer element regenerates its
    /// serializer/stride/hash = an effective ghost re-bake. To grant a TIMED buff, append both a StatModifier and a
    /// TimedModifier sharing one unique SourceId; <c>TimedModifierExpirySystem</c> removes the matching StatModifier
    /// when <see cref="UntilTick"/> elapses, and that removal replicates for free via the StatModifier [GhostField]
    /// buffer (OwnerSendType.All), so StatRecomputeSystem reverts the effective stat on both worlds with no change.
    /// </summary>
    public struct TimedModifier : IBufferElementData
    {
        /// <summary>Matches the <see cref="StatModifier.SourceId"/> this row governs.</summary>
        public uint SourceId;

        /// <summary>Server tick at which the paired StatModifier expires (0 = no expiry / inert; schedule via TickUtil.NonZero).</summary>
        public uint UntilTick;
    }

    /// <summary>Pure helpers for removing modifiers by provenance (clear-by-type / timed expiry). Deterministic, no RNG/wall-clock.</summary>
    public static class TimedModifierUtil
    {
        /// <summary>Remove every <see cref="StatModifier"/> row whose SourceId matches (RemoveAtSwapBack). Returns the count removed.</summary>
        public static int RemoveBySourceId(DynamicBuffer<StatModifier> mods, uint sourceId)
        {
            int removed = 0;
            for (int j = mods.Length - 1; j >= 0; j--)
                if (mods[j].SourceId == sourceId) { mods.RemoveAtSwapBack(j); removed++; }
            return removed;
        }
    }
}