using System;
using System.Threading.Tasks;
using gehGassi.Core.Interfaces;
using gehGassi.Web.Helper;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace gehGassi.Web.Auth
{
    /// <summary>
    /// Verteilter Ticketstore für AuthenticationTickets
    /// </summary>
    public class DistributedCacheTicketStore : ITicketStore
    {
        private readonly IOptions<SessionSettings> _sessionSettings;
        private const string KeyPrefix = "AuthSessionStore-";
        private readonly IDistributedCache _cache;

        public DistributedCacheTicketStore(IOptions<SessionSettings> sessionSettings, IDistributedCache cache)
        {
            _sessionSettings = sessionSettings;
            _cache = cache;
        }

        public async Task<string> StoreAsync(AuthenticationTicket ticket)
        {
            var key = KeyPrefix + ticket.Principal.Identity.Name;
            await RenewAsync(key, ticket);
            return key;
        }

        public Task RenewAsync(string key, AuthenticationTicket ticket)
        {
            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            var options = new DistributedCacheEntryOptions();
            var expiresUtc = ticket.Properties.ExpiresUtc;
            if (expiresUtc.HasValue)
            {
                options.SetAbsoluteExpiration(expiresUtc.Value);
            }
            options.SetSlidingExpiration(TimeSpan.FromMinutes(_sessionSettings.Value.TimeOut));

            var serializedTicket = TicketSerializer.Default.Serialize(ticket);
            _cache.Set(key, serializedTicket, options);

            return Task.FromResult(0);
        }

        public Task<AuthenticationTicket> RetrieveAsync(string key)
        {
            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            AuthenticationTicket ticket = null;

            var storedTicket = _cache.Get(key);

            if (storedTicket != null)
            {
                ticket = TicketSerializer.Default.Deserialize(storedTicket);
            }
            return Task.FromResult(ticket);
        }

        public Task RemoveAsync(string key)
        {
            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            _cache.Remove(key);
            return Task.FromResult(0);
        }
    }

    /// <summary>
    /// Verteilter Ticketstore für AuthenticationTickets der diese initial von einer DB lädt und wieder speichern kann.
    /// Übersteht "Server-Resets"
    /// </summary>
    public class DistributedCachePersistedTicketStore : ITicketStore
    {
        private bool _initialized;
        private IServiceProvider _serivceProvider;
        private readonly IOptions<SessionSettings> _sessionSettings;
        private const string KeyPrefix = "AuthSessionStore-";
        private readonly IDistributedCache _cache;

        public DistributedCachePersistedTicketStore(IOptions<SessionSettings> sessionSettings, IDistributedCache cache, IServiceProvider serviceProvider)
        {
            _sessionSettings = sessionSettings;
            _cache = cache;
            _initialized = false;
            _serivceProvider = serviceProvider;
        }

        private async Task InitializeAsync()
        {
            using var scope = _serivceProvider.CreateScope();
            var persistedTicketService = scope.ServiceProvider.GetRequiredService<IPersistedTicketService>();
            var items = await persistedTicketService.GetAllAsync();
            foreach (var item in items)
            {
                var options = new DistributedCacheEntryOptions();
                var expiresUtc = item.Expires;
                if (expiresUtc.HasValue)
                {
                    options.SetAbsoluteExpiration(expiresUtc.Value);
                }
                options.SetSlidingExpiration(TimeSpan.FromMinutes(_sessionSettings.Value.TimeOut));

                if (await _cache.GetAsync(item.Key) == null)
                    _cache.Set(item.Key, item.Ticket, options);
            }
            _initialized = true;
        }

        public async Task<string> StoreAsync(AuthenticationTicket ticket)
        {
            if (!_initialized)
                await InitializeAsync();

            var key = KeyPrefix + ticket.Principal.Identity.Name;
            await RenewAsync(key, ticket);
            return key;
        }

        public async Task RenewAsync(string key, AuthenticationTicket ticket)
        {
            if (!_initialized)
                await InitializeAsync();

            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            var options = new DistributedCacheEntryOptions();
            var expiresUtc = ticket.Properties.ExpiresUtc;
            if (expiresUtc.HasValue)
            {
                options.SetAbsoluteExpiration(expiresUtc.Value);
            }
            options.SetSlidingExpiration(TimeSpan.FromMinutes(_sessionSettings.Value.TimeOut));

            var serializedTicket = TicketSerializer.Default.Serialize(ticket);
            _cache.Set(key, serializedTicket, options);

            using var scope = _serivceProvider.CreateScope();
            var persistedTicketService = scope.ServiceProvider.GetRequiredService<IPersistedTicketService>();

            var userId = key.Replace(KeyPrefix, "");
            var expires = ticket.Properties.ExpiresUtc;
            var byteTicket = SerializeToBytes(ticket);

            await persistedTicketService.SaveAsync(key, userId, byteTicket, expires);
            await persistedTicketService.CommitAsync("System");
        }

        public async Task<AuthenticationTicket> RetrieveAsync(string key)
        {
            if (!_initialized)
                await InitializeAsync();

            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            AuthenticationTicket ticket = null;

            var storedTicket = _cache.Get(key);

            if (storedTicket != null)
            {
                ticket = TicketSerializer.Default.Deserialize(storedTicket);
            }
            return ticket;
        }

        public async Task RemoveAsync(string key)
        {
            if (!_initialized)
                await InitializeAsync();

            if (!key.StartsWith(KeyPrefix))
                key = KeyPrefix + key;

            using var scope = _serivceProvider.CreateScope();
            var persistedTicketService = scope.ServiceProvider.GetRequiredService<IPersistedTicketService>();
            var ticket = await RetrieveAsync(key);

            _cache.Remove(key);

            await persistedTicketService.RemoveAsync(key);
            await persistedTicketService.CommitAsync("System");
        }

        private byte[] SerializeToBytes(AuthenticationTicket source)
        => TicketSerializer.Default.Serialize(source);

        private AuthenticationTicket DeserializeFromBytes(byte[] source)
            => source == null ? null : TicketSerializer.Default.Deserialize(source);
    }
}