All files / lib/internal/http httpServer.ts

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import { Function1, pipe, returns } from "@reactive-js/core/lib/functions";
import { ObservableLike } from "@reactive-js/core/lib/observable";
import { isNone, isSome, none, Option } from "@reactive-js/core/lib/option";
import { fromObject, reduce } from "@reactive-js/core/lib/readonlyArray";
import { HttpResponse, HttpRequest } from "./interfaces";
 
export type HttpServer<
  THttpRequest extends HttpRequest<unknown>,
  THttpResponse extends HttpResponse<unknown>
> = (req: THttpRequest) => ObservableLike<THttpResponse>;
 
export type HttpRoutedRequest<T> = HttpRequest<T> & {
  readonly params: { readonly [param: string]: string };
};
 
// Prefix tree
type Router<TReq, TResp> = {
  readonly name: string;
  readonly handler?: HttpServer<HttpRoutedRequest<TReq>, HttpResponse<TResp>>;
  readonly children: { [segment: string]: Router<TReq, TResp> };
};
 
type Segment = {
  readonly name: string;
  child?: Segment;
};
 
const createSegments = (path: string): Segment => {
  const root: Segment = { name: "" };
 
  let acc = root;
  for (const name of path.split("/")) {
    const child: Segment = { name };
    acc.child = child;
    acc = child;
  }
 
  return root;
};
 
const serializeSegments = (segment: Segment): string => {
  let result = segment.name;
  while (isSome(segment.child)) {
    segment = segment.child;
    result += `/${segment.name}`;
  }
  return result;
};
 
const emptyRouter: Router<unknown, unknown> = {
  name: "",
  children: {},
};
 
const addHandler = <TReq, TResp>(
  router: Router<TReq, TResp>,
  { name, child }: Segment,
  handler: HttpServer<HttpRoutedRequest<TReq>, HttpResponse<TResp>>,
): Router<TReq, TResp> => {
  if (isNone(child)) {
    return {
      name,
      handler,
      children: router.children,
    };
  } else {
    const childName = child.name.startsWith(":") ? ":" : child.name;
    const childRouter =
      router.children[childName] ?? (emptyRouter as Router<TReq, TResp>);
    const newChildRouter = addHandler(childRouter, child, handler);
 
    return {
      name,
      handler: router.handler,
      children: {
        ...router.children,
        [childName]: newChildRouter,
      },
    };
  }
};
 
const findHandler = <TReq, TResp>(
  router: Router<TReq, TResp>,
  segment: Segment,
  params: { [param: string]: string },
): Option<[
  HttpServer<HttpRoutedRequest<TReq>, HttpResponse<TResp>>,
  { [param: string]: string },
]> => {
  const { child } = segment;
  const { handler } = router;
  if (isNone(child) && isSome(handler)) {
    return [handler, params];
  }
  if (isNone(child)) {
    return none;
  }
 
  const nameRouter = router.children[child.name];
  const nameRouterResult = isSome(nameRouter)
    ? findHandler(nameRouter, child, params)
    : none;
  if (isSome(nameRouterResult)) {
    return nameRouterResult;
  }
 
  const paramRouter = router.children[":"];
  const paramRouterResult = isSome(paramRouter)
    ? findHandler(paramRouter, child, {
        ...params,
        [paramRouter.name]: child.name,
      })
    : none;
  if (isSome(paramRouterResult)) {
    return paramRouterResult;
  }
 
  const globRouter = router.children["*"];
  const globRouterHandler = globRouter?.handler;
  if (isSome(globRouterHandler)) {
    const newParams = {
      ...params,
      ["*"]: serializeSegments(child),
    };
 
    return [globRouterHandler, newParams];
  }
 
  return none;
};
 
export const createRoutingHttpServer = <TReq, TResp>(
  routes: {
    [path: string]: HttpServer<HttpRoutedRequest<TReq>, HttpResponse<TResp>>;
  },
  notFoundHandler: Function1<
    HttpRequest<TReq>,
    ObservableLike<HttpResponse<TResp>>
  >,
): HttpServer<HttpRequest<TReq>, HttpResponse<TResp>> => {
  const router = pipe(
    routes,
    fromObject(),
    reduce(
      (acc: Router<TReq, TResp>, [path, handler]) =>
        addHandler(acc, createSegments(path), handler),
      returns(emptyRouter),
    ),
  );
 
  return (request: HttpRequest<TReq>) => {
    const segments = createSegments(request.uri.pathname);
    const result = findHandler(router, segments, {});
 
    if (isSome(result)) {
      const [handler, params] = result;
      const requestWithParams: HttpRoutedRequest<TReq> = {
        ...request,
        params,
      };
      return handler(requestWithParams);
    } else {
      return notFoundHandler(request);
    }
  };
};