using System;
using System.Collections.Generic;
using System.IdentityModel.Tokens.Jwt;
using System.Linq;
using System.Security.Claims;
using System.Text;
using Flexitime.Objects;
using FlexitimeAPI.Models;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using RandomNameGeneratorLibrary;

namespace FlexitimeAPI.Services
{
    public interface IUserService
    {
        LoginResponse Authenticate(LoginRequest model);
        IEnumerable<User> GetAll();
        User GetById(int id);
    }

    public class UserService : IUserService
    {
        private PersonNameGenerator _personGenerator;
        // users hardcoded for simplicity, store in a db with hashed passwords in production applications
        private List<User> _users;

        private readonly AppSettings _appSettings;

        public UserService(IOptions<AppSettings> appSettings)
        {
            _appSettings = appSettings.Value;
            _personGenerator = new PersonNameGenerator();
            var random = new Random();
            var vals = Enum.GetValues(typeof(UserState));

            _users = Enumerable.Range(2, 6).Select(index =>
            {
                var first = _personGenerator.GenerateRandomFirstName();
                var last = _personGenerator.GenerateRandomLastName();

                return new User
                {
                    UserId = index,
                    LoginId = $"{first}{last}",
                    Password = "12345",
                    FirstName = first,
                    LastName = last,
                    HoursPerWeek = 37,
                    IsContractor = false,
                    State = (UserState)vals.GetValue(random.Next(2, vals.Length))
                };
            }).ToList();

            //create default known admin user..
            _users.Add(new User
            {
                UserId = 1,
                LoginId = "admin",
                Password = "P@ssw0rd!",
                FirstName = "Admin",
                LastName = "User",
                HoursPerWeek = 37,
                IsContractor = false,
                State = UserState.In
            });
        }

        public LoginResponse Authenticate(LoginRequest model)
        {
            var user = _users.SingleOrDefault(x => x.LoginId == model.Username && x.Password == model.Password);

            // return null if user not found
            if (user == null) return null;

            // authentication successful so generate jwt token
            var token = GenerateJwtToken(user);

            return new LoginResponse(user, token);
        }

        public IEnumerable<User> GetAll()
        {
            return _users;
        }

        public User GetById(int id)
        {
            return _users.FirstOrDefault(x => x.UserId == id);
        }

        // helper methods

        private string GenerateJwtToken(User user)
        {
            // generate token that is valid for 7 days
            var tokenHandler = new JwtSecurityTokenHandler();
            var key = Encoding.ASCII.GetBytes(_appSettings.Secret);

            List<Claim> claims = new List<Claim>()
            {

            };

            //var jwt = new JwtSecurityToken(issuer:"FlexitimeUI",claims:claims);

            var tokenDescriptor = new SecurityTokenDescriptor
            {
                
                Subject = new ClaimsIdentity(new[] { new Claim("id", user.UserId.ToString()) }),
                Expires = DateTime.UtcNow.AddHours(2),
                Issuer = "FlexitimeUI",
                NotBefore = DateTime.UtcNow.AddSeconds(-5),
                IssuedAt = DateTime.UtcNow,
                //Claims = claims,
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(key), SecurityAlgorithms.HmacSha256Signature)
            };
            var token = tokenHandler.CreateToken(tokenDescriptor);
            //tokenHandler.
            return tokenHandler.WriteToken(token);
        }
    }
}