using System;
using System.Threading;
using System.Threading.Tasks;

namespace game.PlayerDataStorage
{
    // A store belongs to one login. Callers retain this instance across awaits.
    public interface IPlayerSaveStore
    {
        bool IsCurrent { get; }
        PlayerSaveReadResult Read(string key);
        PlayerSaveWriteResult Write(string key, string value, bool remoteStore = true);
        Task<PlayerSaveConfirmation> WriteAndConfirmAsync(string key, string value, CancellationToken token = default);
        Task<PlayerSaveConfirmation> ConfirmAsync(PlayerSaveReceipt receipt, CancellationToken token = default);
        Task<PlayerSaveConfirmation> FlushAsync(CancellationToken token = default);
    }

    public sealed class PlayerSaveReadResult
    {
        public bool Success => Error == null;
        public bool? Found { get; }
        public string Value { get; }
        public string Error { get; }
        internal PlayerSaveReadResult(bool found, string value) { Found = found; Value = value; }
        internal PlayerSaveReadResult(string error) { Error = error ?? "ReadFailed"; }
        public string ValueOrThrow()
        {
            if (!Success) throw new InvalidOperationException("Player save read failed: " + Error);
            return Value;
        }
    }

    public sealed class PlayerSaveReceipt
    {
        internal readonly IPlayerSaveStore Store;
        internal readonly object Ticket;
        internal PlayerSaveReceipt(IPlayerSaveStore store, object ticket) { Store = store; Ticket = ticket; }
    }

    public sealed class PlayerSaveWriteResult
    {
        public bool Accepted => Error == null;
        public string Error { get; }
        public PlayerSaveReceipt Receipt { get; }
        internal PlayerSaveWriteResult(PlayerSaveReceipt receipt) { Receipt = receipt; }
        internal PlayerSaveWriteResult(string error) { Error = error ?? "WriteRejected"; }
        public void RequireAccepted()
        {
            if (!Accepted) throw new InvalidOperationException("Player save write rejected: " + Error);
        }
    }

    // Buffered and LocalOnly are deliberately different from cloud confirmation.
    public enum PlayerSaveStatus { Confirmed, Buffered, LocalOnly, Rejected, Superseded, Unknown, Cancelled }
    public sealed class PlayerSaveConfirmation
    {
        public PlayerSaveStatus Status { get; }
        public bool Confirmed => Status == PlayerSaveStatus.Confirmed;
        public string Error { get; }
        internal PlayerSaveConfirmation(PlayerSaveStatus status, string error = null) { Status = status; Error = error; }
    }
}