counterfact/dist/server/koa-middleware.js

a library for building a fake REST API for testing

import createDebug from "debug";
import koaProxy from "koa-proxies";
import { isProxyEnabledForPath } from "./is-proxy-enabled-for-path.js";
const debug = createDebug("counterfact:server:create-koa-app");
const HTTP_STATUS_CODE_OK = 200;
function addCors(ctx, headers) {
    // Always append CORS headers, reflecting back the headers requested if any
    ctx.set("Access-Control-Allow-Origin", headers?.origin ?? "*");
    ctx.set("Access-Control-Allow-Methods", "GET,HEAD,PUT,POST,DELETE,PATCH");
    ctx.set("Access-Control-Allow-Headers", headers?.["access-control-request-headers"] ?? []);
    ctx.set("Access-Control-Expose-Headers", headers?.["access-control-request-headers"] ?? []);
    ctx.set("Access-Control-Allow-Credentials", "true");
}
function getAuthObject(ctx) {
    const authHeader = ctx.request.headers.authorization;
    if (authHeader === undefined) {
        return undefined;
    }
    const [, base64Credentials] = authHeader.split(" ");
    if (base64Credentials === undefined) {
        return undefined;
    }
    const user = Buffer.from(base64Credentials, "base64").toString("utf8");
    const [username, password] = user.split(":");
    return { password, username };
}
export function koaMiddleware(dispatcher, config, proxy = koaProxy) {
    return async function middleware(ctx, next) {
        const { proxyUrl, routePrefix } = config;
        debug("middleware running for path: %s", ctx.request.path);
        debug("routePrefix: %s", routePrefix);
        if (!ctx.request.path.startsWith(routePrefix)) {
            return await next();
        }
        const auth = getAuthObject(ctx);
        const { body, headers, query } = ctx.request;
        const path = ctx.request.path.slice(routePrefix.length);
        const method = ctx.request.method;
        if (isProxyEnabledForPath(path, config) && proxyUrl) {
            return proxy("/", { changeOrigin: true, target: proxyUrl })(ctx, next);
        }
        addCors(ctx, headers);
        if (method === "OPTIONS") {
            ctx.status = HTTP_STATUS_CODE_OK;
            return undefined;
        }
        const response = await dispatcher.request({
            auth,
            body,
            /* @ts-expect-error the value of a header can be an array and we don't have a solution for that yet */
            headers,
            method,
            path,
            /* @ts-expect-error the value of a querystring item can be an array and we don't have a solution for that yet */
            query,
            req: { path: "", ...ctx.req },
        });
        ctx.body = response.body;
        if (response.headers) {
            for (const [key, value] of Object.entries(response.headers)) {
                ctx.set(key, value.toString());
            }
        }
        ctx.status = response.status ?? HTTP_STATUS_CODE_OK;
        return undefined;
    };
}