using System;
using System.Threading;

namespace game.PlayerDataStorage
{
    internal enum PlayerKVGuardPoint { Compare, ReadLocal, Update, Immediate, Sync, Lifecycle, PrefsSave }
    internal sealed class PlayerKVLoadSideEffectException : InvalidOperationException
    { internal PlayerKVLoadSideEffectException() : base("KV controlled load rejected a legacy side effect.") { } }
    internal sealed class PlayerKVGameLoadGuard : IDisposable
    {
        static readonly object gate=new object();
        static PlayerKVGameLoadGuard owner;
        readonly int[] counts=new int[7];
        int violations;
        bool disposed;
        private PlayerKVGameLoadGuard() { }
        internal static bool TryEnter(out PlayerKVGameLoadGuard lease)
        {
            lock(gate)
            {
                lease=null; if(owner!=null) return false;
                owner=lease=new PlayerKVGameLoadGuard(); return true;
            }
        }
        internal bool IsCurrent { get { lock(gate) return !disposed && ReferenceEquals(owner,this); } }
        internal int Violations => Volatile.Read(ref violations);
        internal int Count(PlayerKVGuardPoint point) => Volatile.Read(ref counts[(int)point]);
        internal static bool Reject(PlayerKVGuardPoint point)
        {
            lock(gate)
            {
                if(owner==null) return false;
                Interlocked.Increment(ref owner.counts[(int)point]); Interlocked.Increment(ref owner.violations); return true;
            }
        }
        internal static void RequireLegacyAllowed(PlayerKVGuardPoint point)
        { if(Reject(point)) throw new PlayerKVLoadSideEffectException(); }
        public void Dispose()
        {
            lock(gate) { if(disposed) return; disposed=true; if(ReferenceEquals(owner,this)) owner=null; }
        }
    }
}