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// Copyright 2022 Connor Logan. All rights reserved. MIT License.
/** * Metadata object for caching and tracking information about how a Request has * been routed so far in the handling process. */ export interface Context {  /** new URL(req.url) */  url: URL;  /** The current, unrouted portion of the requested path. */  path: string;  /** The raw query string parameters, as an object. */  query: Record<string, string | string[]>;  /** The path parameters captured during the routing process so far. */  param: Record<string, string>;  /**   * If this isn't null, this Response should be returned as soon as possible in   * the routing process. It means the path requested wasn't canonical, and this   * 302 Response will redirect the client to the canonical URL instead.   */  redirect: Response | null;}
const _context = Symbol("_context");
/** Record representing query string parameters. */export type QueryRecord = Record<string, string | string[]>;
/** Record representing path parameters captured during routing. */export type ParamRecord = Record<string, string>;
/** * Hook for getting routing metadata from a Request. If there isn't already a * Context associated with the Request, a new one will be generated. The same * Context object is returned on every subsequent call to `context()` with this * Request. * * Use this to get information about how the Request has been routed so far, if * at all. Routers read and modify this context internally and Endpoints read * from it when determining whether to respond to the Request or not (404). */export function context(request: Request): Context {  const req = request as Request & { [_context]?: Context };  if (req[_context]) {    return req[_context]!;  }
  const url = new URL(req.url);  const path = `/${url.pathname.split("/").filter((p) => !!p).join("/")}`;  let redirect: Response | null = null;  if (path !== url.pathname) {    url.pathname = path;    // NOTE: Don't use Response.redirect. It prevents modifying headers    // redirect = Response.redirect(url.href, 302);    redirect = new Response(null, {      status: 302,      headers: { "location": url.href },    });  }
  const query: Record<string, string | string[]> = {};  for (const [k, v] of url.searchParams.entries()) {    const old = query[k];    if (typeof old === "string") {      query[k] = [old, v];    } else if (Array.isArray(old)) {      query[k] = [...old, v];    } else {      query[k] = v;    }  }
  const ctx: Context = {    url,    path,    param: {},    query,    redirect,  };  Object.assign(req, { [_context]: ctx });  return ctx;}