counterfact/dist/server/web-server/openapi-middleware.js

Generate a TypeScript-based mock server from an OpenAPI spec in seconds — with stateful routes, hot reload, and REPL support.

import { bundle } from "@apidevtools/json-schema-ref-parser";
import { dump } from "js-yaml";
import { applyOverlays } from "../../util/apply-overlay.js";
/**
 * Returns a Koa middleware that serves a bundled OpenAPI document as YAML at
 * the given `pathPrefix`.
 *
 * The served document is augmented with a `servers` entry (OpenAPI 3.x) and a
 * `host` field (OpenAPI 2.x / Swagger) so that the Swagger UI can send
 * requests to the running Counterfact instance.
 *
 * @param pathPrefix - The URL path at which to serve the document, e.g.
 *   `"/counterfact/openapi"`. Requests to any other path fall through to the
 *   next middleware.
 * @param document - Descriptor providing `path` (file path or URL to the
 *   source OpenAPI document) and `baseUrl` (the base URL to inject, e.g.
 *   `"//localhost:3100/api"`).
 * @returns A Koa middleware function.
 */
export function openapiMiddleware(pathPrefix, document) {
    return async (ctx, next) => {
        if (ctx.URL.pathname !== pathPrefix) {
            return await next();
        }
        const openApiDocument = (await bundle(document.path));
        if (document.overlays && document.overlays.length > 0) {
            await applyOverlays(openApiDocument, document.overlays);
        }
        openApiDocument.servers ??= [];
        openApiDocument.servers.unshift({
            name: "Counterfact",
            description: "Counterfact",
            url: document.baseUrl,
        });
        // OpenApi 2 support:
        openApiDocument.host = document.baseUrl;
        ctx.body = dump(openApiDocument);
    };
}