using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Fido2NetLib;
using gehGassi.Core.Interfaces;
using gehGassi.Domain.Users;

namespace gehGassi.Core.Services
{
    /// <summary>
    /// Service der die Verwaltung von Fido-Credentials realisiert
    /// </summary>
    [ExcludeFromCodeCoverage]
    public class FidoService : ServiceBase<FidoStoredCredential>, IFidoService
    {
        private readonly IUserService _userService;

        /// <summary>
        /// Erstellt eine Instanz
        /// </summary>
        /// <param name="unitOfWork">Instanz eines IUnitOfWork</param>
        /// <param name="userService">Instanz eines IUserService</param>
        public FidoService(IUnitOfWork unitOfWork, IUserService userService) : base(unitOfWork)
        {
            _userService = userService;
        }

        /// <summary>
        /// Gibt eine gefilterte Liste von Fido-Credentials zurück
        /// </summary>
        /// <param name="filter">Filterbegriff der in bestimmten Feldern gesucht wird</param>
        /// <returns>List betroffener Fido-Credentials</returns>
        public IQueryable<FidoStoredCredential> Filter(string filter)
        {
            return Repository.Query(c => c.Name.Contains(filter));
        }

        /// <summary>
        /// Gibt eine gefilterte Liste von Fido-Credentials für einen Benutzer zurück
        /// </summary>
        /// <param name="filter">Filterbegriff der in bestimmten Feldern gesucht wird</param>
        /// <param name="username">Benutzername</param>
        /// <returns>List betroffener Fido-Credentials</returns>
        public IQueryable<FidoStoredCredential> Filter(string filter, string username)
        {
            return Repository.Query(c => c.Name.Contains(filter) && c.Username == username);
        }

        /// <summary>
        /// Erstellen eines Fido-Credentials
        /// </summary>
        /// <returns>Fido-Credential</returns>
        public FidoStoredCredential Create()
        {
            var item = new FidoStoredCredential
            {
                RegDate = DateTimeOffset.UtcNow
            };
            return item;
        }

        /// <summary>
        /// Gibt alle Credentials für einen Benutzer zurück
        /// </summary>
        /// <param name="username">Benutzername</param>
        /// <returns>Liste Credentials</returns>
        public async Task<List<FidoStoredCredential>> GetCredentialsAsync(string username)
        {
            return (await Repository.FindAsync(c => c.Username == username).ConfigureAwait(false)).ToList();
        }

        /// <summary>
        /// Gibt eine Liste aller Benutzer zurück die über eine CredentialId verfügen
        /// </summary>
        /// <param name="credentialId">CredentialId</param>
        /// <returns>Liste Fido2 User</returns>
        public async Task<List<Fido2User>> GetUsersByCredentialIdAsync(byte[] credentialId)
        {
            var credentialIdString = Base64Url.Encode(credentialId);
            var credential = await Repository.SingleOrDefaultAsync(c => c.DescriptorJson.Contains(credentialIdString));
            if (credential == null)
                return new List<Fido2User>();

            var users = await _userService.FindAsync(c => Encoding.UTF8.GetBytes(c.UserName).SequenceEqual(credential.UserId));
            return users.Select(c => new Fido2User()
            {
                Name = c.UserName,
                Id = Encoding.UTF8.GetBytes(c.UserName)
            }).ToList();
        }

        /// <summary>
        /// Gibt zurück ob ein Benutzer über Fido credentials verfügt
        /// </summary>
        /// <param name="username">Benutzername</param>
        /// <returns>true wenn ja, false sonst</returns>
        public async Task<bool> HasFidoCredentialsAsync(string username)
        {
            return (await Repository.CountAsync(c => c.Username == username).ConfigureAwait(false)) > 0;
        }

        /// <summary>
        /// Gibt ein Credential zurück
        /// </summary>
        /// <param name="id">CredentialId</param>
        /// <returns>FidoStoredCredential</returns>
        public async Task<FidoStoredCredential> GetByIdAsync(byte[] id)
        {
            var credentialIdString = Base64Url.Encode(id);
            return await Repository.FirstOrDefaultAsync(c => c.DescriptorJson.Contains(credentialIdString)).ConfigureAwait(false);
        }

        /// <summary>
        /// Gibt eine Liste von Credentials anhand des userHandles zurück
        /// </summary>
        /// <param name="userHandle">Userhandle</param>
        /// <returns>Liste Credentials</returns>
        public async Task<List<FidoStoredCredential>> GetCredentialsByUserHandleAsync(byte[] userHandle)
        {
            return (await Repository.FindAsync(c => c.UserHandle.SequenceEqual(userHandle)).ConfigureAwait(false)).ToList();
        }

        /// <summary>
        /// Aktualisieren des Counters
        /// </summary>
        /// <param name="credentialId"></param>
        /// <param name="counter"></param>
        /// <returns>Task</returns>
        public async Task UpdateCounterAsync(byte[] credentialId, uint counter)
        {
            var credentialIdString = Base64Url.Encode(credentialId);
            var item = await Repository.FirstOrDefaultAsync(c => c.DescriptorJson.Contains(credentialIdString)).ConfigureAwait(false);
            item.SignatureCounter = counter;
            await CommitAsync("System");
        }
    }
}