using Chatbot.Api.Application.Services;
using Microsoft.AspNetCore.Authentication;
using System;
using System.Linq;
using System.Threading.Tasks;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Text.Encodings.Web;
using System.Text;
using Chatbot.Api.Domain.Entities;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Chatbot.Api.Authentication
{
    public class BasicAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>
    {
        private readonly IUserService _userService;

        public BasicAuthenticationHandler(IOptionsMonitor<AuthenticationSchemeOptions> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock, IUserService userService)
            : base(options, logger, encoder, clock)
        {
            _userService = userService;
        }

        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
        {
            if (!Request.Headers.ContainsKey("Authorization"))
                return AuthenticateResult.Fail("Missing Authorization Header");

            User user;
            try
            {
                var authHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
                var credentialBytes = Convert.FromBase64String(authHeader.Parameter);
                var credentials = Encoding.UTF8.GetString(credentialBytes).Split(':');
                var username = credentials.First();
                var password = credentials.Last();
                user = await _userService.Authenticate(username, password);
            }
            catch
            {
                return AuthenticateResult.Fail("Invalid Authorization Header");
            }

            if (user == null)
                return AuthenticateResult.Fail("Invalid Username or Password");

            var claims = new[] {
                new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
                new Claim(ClaimTypes.Name, user.UserName),
            };

            var identity = new ClaimsIdentity(claims, Scheme.Name);
            var principal = new ClaimsPrincipal(identity);
            var ticket = new AuthenticationTicket(principal, Scheme.Name);

            return AuthenticateResult.Success(ticket);
        }
    }
}