using System;
namespace ProjectI.Combat.Statuses
{
    // Host-only state. An exhausted mask remains an exposure until its source-owned expiry.
    public sealed class ScanWeakPointState
    {
        public ScanWeakPointSnapshot Snapshot { get; private set; }
        private uint generation;
        public bool CanBeginGeneration=>generation<uint.MaxValue;
        public void Reset(uint lifetime)
        { Snapshot=new ScanWeakPointSnapshot { Lifetime=lifetime }; }
        public bool Begin(uint lifetime,double now,double until,byte[] anchors)
        {
            if(lifetime==0||Snapshot.Lifetime!=lifetime||!Finite(now)||!Finite(until)||until<=now||anchors==null||anchors.Length!=3
                ||anchors[0]==anchors[1]||anchors[0]==anchors[2]||anchors[1]==anchors[2]||generation==uint.MaxValue)return false;
            if(Snapshot.Active(lifetime,now))return false;
            Snapshot=new ScanWeakPointSnapshot { Lifetime=lifetime,Generation=++generation,StartedAt=now,ExpiresAt=until,
                Anchor0=anchors[0],Anchor1=anchors[1],Anchor2=anchors[2],RemainingMask=7 };return true;
        }
        public void RefreshExpiry(double until)
        {
            var value=Snapshot;value.ExpiresAt=Finite(until)?until:0;Snapshot=value;
        }
        public bool TryConsume(byte slot,uint expectedGeneration,uint lifetime,double now)
        {
            if(expectedGeneration!=Snapshot.Generation||!Snapshot.SlotActive(slot,lifetime,now))return false;
            var value=Snapshot;value.RemainingMask=(byte)(value.RemainingMask&~(1<<slot));Snapshot=value;return true;
        }
        private static bool Finite(double value)=>!double.IsNaN(value)&&!double.IsInfinity(value)&&value>=0;
    }
}