using Chtn.CSharp.SDK.Core;
using Chtn.CSharp.SDK.Models.Session;
using Chtn.CSharpSDK.Interfaces;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Chtn.CSharp.SDK.Services
{
    public interface ISessionManager
    {
        void AddSession(Session session);
        List<Session> LoadSessions();
        Task<bool> ValidateSessions(IAuthService authService);
        Session GetPreferredUser();
        void SetPreferredUser(string userId);
    }

    public class SessionManagerProvider : ISessionManager
    {
        private readonly IDatabaseAPI _database;
        private readonly IKeyringAPI _keyring;
        private const string SESSION_KEY = "active_sessions";
        private const string PREFERRED_USER_KEY = "preferred_user_id";

        public SessionManagerProvider(IDatabaseAPI database, IKeyringAPI keyring)
        {
            _database = database ?? throw new ArgumentNullException(nameof(database));
            _keyring = keyring ?? throw new ArgumentNullException(nameof(keyring));
        }

        public void AddSession(Session session)
        {
            var sessions = LoadSessions();
            if (!sessions.Any(s => s.UserData.UserId == session.UserData.UserId))
            {
                sessions.Add(session);
                SaveSessions(sessions);
            }
        }

        public List<Session> LoadSessions()
        {
            var data = _database.Get("system", SESSION_KEY);
            if (string.IsNullOrEmpty(data)) return new List<Session>();

            try
            {
                return JsonConvert.DeserializeObject<List<Session>>(data);
            }
            catch
            {
                return new List<Session>();
            }
        }

        public async Task<bool> ValidateSessions(IAuthService authService)
        {
            var current = GetPreferredUser();
            if (current == null || string.IsNullOrEmpty(current.Token)) return false;

            var req = new ValidateSessionReq { Token = current.Token };

            var resp = await authService.ValidateSession(req);

            return resp != null && resp.ValidationOk;
        }

        public Session GetPreferredUser()
        {
            var userId = _keyring.Get(PREFERRED_USER_KEY);
            if (string.IsNullOrEmpty(userId)) return null;

            return LoadSessions().FirstOrDefault(s => s.UserData.UserId == userId);
        }

        public void SetPreferredUser(string userId)
        {
            _keyring.Set(PREFERRED_USER_KEY, userId);
        }

        private void SaveSessions(List<Session> sessions)
        {
            var json = JsonConvert.SerializeObject(sessions);
            _database.Set("system", SESSION_KEY, json);
            _database.Flush();
        }
    }
}