using System;

namespace game.PlayerDataStorage
{
    internal enum PlayerKVKeyReadError { None, InvalidInput, LoadGuardActive, StaleOrClosing, NotReady }

    /// <summary>
    /// A detached key observation, not authority for a later gameplay mutation.
    /// Found=null means failure; Found=false means a valid snapshot lacked the key;
    /// Found=true means a value exists, including the empty string.
    /// </summary>
    internal sealed class PlayerKVKeyReadResult
    {
        internal PlayerKVKeyReadError Error { get; }
        internal bool Success => Error == PlayerKVKeyReadError.None;
        internal bool? Found { get; }
        internal string Value { get; }
        internal string OwnerInstanceId { get; }
        internal string PlayerId { get; }
        internal long? Epoch { get; }

        internal PlayerKVKeyReadResult(PlayerKVKeyReadError error, PlayerKVGameSessionHandle handle,
            bool? found = null, string value = null)
        {
            if (error == PlayerKVKeyReadError.None && (!found.HasValue || (found.Value && value == null)))
                throw new ArgumentException("A successful key observation requires an existence verdict.");
            Error = error;
            OwnerInstanceId = handle?.OwnerInstanceId;
            PlayerId = handle?.PlayerId;
            Epoch = handle?.Epoch;
            Found = Success ? found : null;
            Value = Success && found == true ? value : null;
        }
    }
}