Request ID

import { Elysia } from "elysia";

export interface RequestIdOptions {
  /** Header name to read/write request ID (default: X-Request-ID) */
  headerName?: string;
  /** Custom ID generator (default: crypto.randomUUID) */
  generator?: () => string;
  /** Whether to set response header (default: true) */
  setResponseHeader?: boolean;
}

/**
 * Request ID middleware for Elysia
 * Generates or propagates request IDs for tracing and logging correlation
 */
export const requestId = (options: RequestIdOptions = {}) => {
  const config = {
    headerName: options.headerName ?? "X-Request-ID",
    generator: options.generator ?? (() => crypto.randomUUID()),
    setResponseHeader: options.setResponseHeader ?? true,
  };

  return new Elysia({ name: "request-id" })
    .derive({ as: "global" }, ({ request }) => {
      // Use existing request ID from header or generate new one
      const existingId = request.headers.get(config.headerName);
      const requestId = existingId || config.generator();

      return { requestId };
    })
    .onAfterHandle(({ requestId, set }) => {
      if (config.setResponseHeader) {
        set.headers[config.headerName] = requestId;
      }
    });
};

/**
 * Helper to create a logger that includes request ID
 */
export const createRequestLogger = (requestId: string) => ({
  info: (message: string, data?: Record<string, unknown>) => {
    console.log(JSON.stringify({ level: "info", requestId, message, ...data }));
  },
  warn: (message: string, data?: Record<string, unknown>) => {
    console.warn(JSON.stringify({ level: "warn", requestId, message, ...data }));
  },
  error: (message: string, data?: Record<string, unknown>) => {
    console.error(JSON.stringify({ level: "error", requestId, message, ...data }));
  },
  debug: (message: string, data?: Record<string, unknown>) => {
    if (process.env.NODE_ENV !== "production") {
      console.debug(JSON.stringify({ level: "debug", requestId, message, ...data }));
    }
  },
});

/* USAGE:

import { Elysia } from "elysia";
import { requestId, createRequestLogger } from "./middleware/request-id";

const app = new Elysia()
  .use(requestId())
  .get("/", ({ requestId }) => {
    const log = createRequestLogger(requestId);
    log.info("Processing request");
    
    return { message: "Hello", requestId };
  })
  .listen(3000);

// With custom options
const app = new Elysia()
  .use(requestId({
    headerName: "X-Correlation-ID",
    generator: () => `req_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`,
  }))
  .listen(3000);

*/