Fabric.Backend.Guild/src/common/request-context.middleware.ts

import { randomUUID } from 'crypto';
import { NextFunction, Request, Response } from 'express';
import { MetricsService } from './metrics.service.js';

type ReqWithId = Request & { requestId?: string };

export function createRequestContextMiddleware(service: 'center' | 'guild', metrics: MetricsService) {
  return (req: ReqWithId, res: Response, next: NextFunction): void => {
    const headerId = req.headers['x-request-id'];
    const requestId =
      (Array.isArray(headerId) ? headerId[0] : headerId) || randomUUID();

    req.requestId = requestId;
    res.setHeader('x-request-id', requestId);

    const startedAt = Date.now();
    res.on('finish', () => {
      const durationMs = Date.now() - startedAt;
      metrics.record(res.statusCode, durationMs);

      const log = {
        level: 'info',
        service,
        requestId,
        method: req.method,
        path: req.originalUrl,
        statusCode: res.statusCode,
        durationMs,
        timestamp: new Date().toISOString(),
      };
      console.log(JSON.stringify(log));
    });

    next();
  };
}