CustomAuthenticationHandler.cs

using JWT;
using Microsoft.AspNetCore.Authorization;
using Repositories;

namespace demo {
    public class CustomAuthenticationHandler : AuthorizationHandler<CustomAuthenticationRequirement>
    {
        protected readonly UserRepository UserRepository;

        public CustomAuthenticationHandler(UserRepository userRepository)
        {
            this.UserRepository = userRepository;
        }

        protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context, CustomAuthenticationRequirement requirement)
        {
            if(context.Resource is not HttpContext){
                context.Fail();
                await Task.CompletedTask;
                return;
            }

            var ctx = (HttpContext)context.Resource;
            var result = await JWTService.isSignedIn(ctx, UserRepository);

            if(!result.IsSuccess){
                if(result.Exception is JWT.JWTInvalidUserOrToken){
                    context.Fail(new AuthorizationFailureReason(this, 
                        "User or token invalid!"));
                    await Task.CompletedTask;
                    return;
                }

                if(result.Exception is JWT.JWTInvalidOrMissingToken){
                    context.Fail(new AuthorizationFailureReason(this, 
                        "Invalid or missing token!"));
                    await Task.CompletedTask;
                    return;
                }

                if(result.Exception is JWT.JWTLoginExpired){
                    context.Fail(new AuthorizationFailureReason(this, 
                        "User login expired! Log in again!"));
                    await Task.CompletedTask;
                    return;
                }

                context.Fail();
                await Task.CompletedTask;
                return;
            }

            context.Succeed(requirement);
            await Task.CompletedTask;
        }
    }

}