import type { MiddlewareHandler } from "hono";

const REQUEST_ID_HEADER = "x-request-id";
const MAX_REQUEST_ID_LENGTH = 128;
const PRINTABLE_ASCII = /^[\x20-\x7E]+$/;

export type ApiRequestIdVariables = {
  requestId: string;
};

export type RequestIdLogger = {
  error?: (fields: Record<string, unknown>, message: string) => void;
  info?: (fields: Record<string, unknown>, message: string) => void;
};

export type RequestIdMiddlewareOptions = {
  logger?: RequestIdLogger;
};

export function createRequestIdMiddleware(
  options: RequestIdMiddlewareOptions = {}
): MiddlewareHandler<{ Variables: ApiRequestIdVariables }> {
  return async (c, next) => {
    const requestId = normalizeRequestId(c.req.header(REQUEST_ID_HEADER));
    const startedAt = performance.now();

    c.set("requestId", requestId);

    await next();
    c.header(REQUEST_ID_HEADER, requestId);

    if (c.error) {
      options.logger?.error?.({ ...createLogFields(c, requestId, startedAt), error: c.error }, "API request failed");
      return;
    }

    options.logger?.info?.(createLogFields(c, requestId, startedAt), "API request completed");
  };
}

function normalizeRequestId(value: string | undefined): string {
  const requestId = value?.trim();

  if (!requestId || requestId.length > MAX_REQUEST_ID_LENGTH || !PRINTABLE_ASCII.test(requestId)) {
    return crypto.randomUUID();
  }

  return requestId;
}

function createLogFields(c: Parameters<MiddlewareHandler>[0], requestId: string, startedAt: number) {
  return {
    requestId,
    method: c.req.method,
    path: c.req.path,
    status: c.res.status,
    durationMs: Math.max(0, Math.round(performance.now() - startedAt)),
  };
}