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;
        }

        /// <summary>Remove every <see cref="StatModifier"/> row whose SourceId lies in [lo, hiExclusive) — the
        /// run-scoped BOON strip (per-pick distinct ids share the band; one call clears the whole run's boons while
        /// class/meta/equip bands survive untouched). Idempotent; RemoveAtSwapBack. Returns the count removed.</summary>
        public static int RemoveBySourceIdRange(DynamicBuffer<StatModifier> mods, uint lo, uint hiExclusive)
        {
            int removed = 0;
            for (int j = mods.Length - 1; j >= 0; j--)
                if (mods[j].SourceId >= lo && mods[j].SourceId < hiExclusive) { mods.RemoveAtSwapBack(j); removed++; }
            return removed;
        }

        /// <summary>Phase 1.7: guarantee EXACTLY ONE row per <paramref name="sourceId"/> in BOTH the replicated
        /// <see cref="StatModifier"/> buffer and this server-only <see cref="TimedModifier"/> buffer (remove-then-add) so a
        /// timed buff REFRESHES (re-stamps <paramref name="untilTick"/>) rather than stacking on a repeat grant. Used by
        /// <c>KillRewardSystem</c> for Frenzy so successive kills extend the surge instead of compounding the modifier.</summary>
        public static void Upsert(DynamicBuffer<StatModifier> mods, DynamicBuffer<TimedModifier> timed,
            uint sourceId, byte target, byte op, float value, uint untilTick)
        {
            RemoveBySourceId(mods, sourceId);
            for (int j = timed.Length - 1; j >= 0; j--)
                if (timed[j].SourceId == sourceId) timed.RemoveAtSwapBack(j);
            mods.Add(new StatModifier { Target = target, Op = op, Value = value, SourceId = sourceId });
            timed.Add(new TimedModifier { SourceId = sourceId, UntilTick = untilTick });
        }

        /// <summary>Phase 1.7: remove every server-only <see cref="TimedModifier"/> row matching <paramref name="sourceId"/>
        /// (the paired <see cref="StatModifier"/> is cleared separately — e.g. the Returning boon-band range-strip). This
        /// closes the cross-run gap where a stale Frenzy timed row could outlive its StatModifier. Returns the count removed.</summary>
        public static int RemoveBySourceId(DynamicBuffer<TimedModifier> timed, uint sourceId)
        {
            int removed = 0;
            for (int j = timed.Length - 1; j >= 0; j--)
                if (timed[j].SourceId == sourceId) { timed.RemoveAtSwapBack(j); removed++; }
            return removed;
        }


    }
}