Astro Create Route for Client routing

create-route.ts

import type { z } from "astro/zod";

type ExtractParams<T extends string> =
  T extends `${string}[${infer Param}]${infer Rest}`
    ? { [K in Param | keyof ExtractParams<Rest>]: string }
    : {};

type IsEmptyObject<T> = keyof T extends never ? true : false;

type HrefArgs<T extends string, S extends z.ZodTypeAny | undefined> =
  IsEmptyObject<ExtractParams<T>> extends true
    ? S extends z.ZodTypeAny
      ? { searchParams: z.infer<S> }
      : void
    : S extends z.ZodTypeAny
      ? { params: ExtractParams<T>; searchParams: z.infer<S> }
      : { params: ExtractParams<T> };

type RouteConfig<T extends string, S extends z.ZodTypeAny | undefined> = {
  path: T;
  searchParams?: S;
};

export function createRoute<
  T extends string,
  S extends z.ZodTypeAny | undefined = undefined,
>(config: RouteConfig<T, S>) {
  return {
    getCachePath(): string {
      return config.path;
    },

    getParams(): ExtractParams<T> {
      const patternSegments = config.path.split("/");
      const pathSegments = window.location.pathname.split("/");
      const params: Record<string, string> = {};

      for (let i = 0; i < patternSegments.length; i++) {
        const seg = patternSegments[i];
        const match = seg.match(/^\[(.+)\]$/);
        if (match) {
          params[match[1]] = pathSegments[i] ?? "";
        }
      }

      return params as ExtractParams<T>;
    },

    href(
      ...args: HrefArgs<T, S> extends void ? [] : [args: HrefArgs<T, S>]
    ): string {
      const hrefArgs = args[0] as
        | {
            params?: Record<string, string>;
            searchParams?: Record<string, string>;
          }
        | undefined;

      let url = config.path.replace(
        /\[([^\]]+)\]/g,
        (_, key: string) => hrefArgs?.params?.[key] ?? "",
      );

      if (hrefArgs && "searchParams" in hrefArgs && hrefArgs.searchParams) {
        const qs = new URLSearchParams(
          hrefArgs.searchParams as Record<string, string>,
        );
        url += `?${qs.toString()}`;
      }

      return url;
    },
  };
}