using IdentityServer.PublishedLanguage.Dto;
using IdentityServer.Wrapper.Services;
using Microsoft.AspNetCore.Authentication;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using NDB.Security.Authentication.Identity.Abstractions;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Text.Encodings.Web;
using System.Threading.Tasks;

namespace NDB.Security.Authentication.Identity
{
    public class IdentityAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>
    {
        private readonly IIdentityService _identityService;
        private readonly IAuthenticationOptions _authenticationOptions;

        public IdentityAuthenticationHandler(IOptionsMonitor<AuthenticationSchemeOptions> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock, IIdentityService identityService, IAuthenticationOptions authenticationOptions)
            : base(options, logger, encoder, clock)
        {
            _identityService = identityService;
            _authenticationOptions = authenticationOptions;
        }

        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
        {
            if (!Request.Headers.ContainsKey("Authorization"))
            {
                var authenticateAsGuest = _authenticationOptions.AuthenticateAsGuest?.Invoke(Request) ?? false;
                if (authenticateAsGuest)
                {
                    var guestTicket = GetAuthenticationTicket(new User() { UserId = _authenticationOptions.GuestUserId, UserName = _authenticationOptions.GuestUserName });
                    return AuthenticateResult.Success(guestTicket);
                }

                return AuthenticateResult.Fail("Missing Authorization Header");
            }

            User user;
            try
            {
                var authorizationHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
                var token = authorizationHeader.Parameter;
                user = await _identityService.Authorize(token);
            }
            catch
            {
                return AuthenticateResult.Fail("Invalid Authorization Header");
            }

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

            var ticket = GetAuthenticationTicket(user);
            return AuthenticateResult.Success(ticket);
        }

        private AuthenticationTicket GetAuthenticationTicket(User user)
        {
            var claims = new[] {
                new Claim(ClaimTypes.NameIdentifier, user.UserId.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 ticket;
        }
    }
}