using System.Security.Cryptography;
using System.Text;
using Fitness_core_BE.Models.IOs;
using Microsoft.AspNetCore.Mvc.Filters;

namespace Fitness_core_BE.Helpers
{
    // Gates the subscription-billing worker endpoint behind a single shared secret in the
    // X-Worker-Key header. Distinct from JwtMiddleware/CustomMiddleware (human/agent session
    // auth) and from PaymentService:InternalApiKey (Core's own outbound key to Payment-Service) —
    // this authenticates the trusted scheduler calling back into Core. Writes the 401/503
    // response directly (like RequiresPermissionAttribute) rather than throwing, because Core
    // has no global exception handler to turn a thrown exception into the right status code on
    // this unauthenticated route.
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public sealed class RequireWorkerKeyAttribute : Attribute, IAsyncActionFilter
    {
        public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
        {
            var configuration = context.HttpContext.RequestServices.GetService(typeof(IConfiguration)) as IConfiguration;
            var configuredKey = configuration?["Worker:InternalApiKey"];

            if (string.IsNullOrWhiteSpace(configuredKey))
            {
                await WriteErrorAsync(context, 503, "Worker:InternalApiKey is not configured.");
                return;
            }

            var providedKey = context.HttpContext.Request.Headers["X-Worker-Key"].FirstOrDefault();
            if (string.IsNullOrWhiteSpace(providedKey) || !FixedTimeEquals(providedKey, configuredKey))
            {
                await WriteErrorAsync(context, 401, "Invalid worker key.");
                return;
            }

            await next();
        }

        private static async Task WriteErrorAsync(ActionExecutingContext context, int statusCode, string message)
        {
            context.HttpContext.Response.StatusCode = statusCode;
            await context.HttpContext.Response.WriteAsJsonAsync(new ApiResponse<object>
            {
                StatusCode = statusCode,
                Message = message,
                Data = null
            });
        }

        private static bool FixedTimeEquals(string a, string b)
        {
            return CryptographicOperations.FixedTimeEquals(Encoding.UTF8.GetBytes(a), Encoding.UTF8.GetBytes(b));
        }
    }
}