import { createTRPCClient, httpBatchLink } from "@trpc/client";
import superjson from "superjson";
import type { AnyTRPCRouter } from "@trpc/server";

// Returns a tRPC client whose fetch is a stub honouring the provided mocks.
// Mocks are keyed by procedure path ("blog.articleBySlug") returning the
// raw response body.
export function createMockTrpcClient<TRouter extends AnyTRPCRouter>(
  mocks: Record<string, unknown> = {},
) {
  const fetchStub: typeof fetch = async (input) => {
    const url = typeof input === "string" ? input : (input as Request).url;
    const path = new URL(url, "http://mock").pathname.replace(/^\/api\/trpc\//, "");
    const result = mocks[path];
    if (result === undefined) {
      return new Response(JSON.stringify([{ error: { code: -32603, message: `No mock for ${path}` } }]), { status: 200 });
    }
    return new Response(JSON.stringify([{ result: { data: superjson.serialize(result) } }]), { status: 200 });
  };

  // httpBatchLink<TRouter> requires a conditional TransformerOptions<TRouter> that
  // depends on whether the router uses a transformer; making this generic-friendly
  // without parameterizing twice requires <any> here.
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  const link = httpBatchLink<any>({
    url: "http://mock/api/trpc",
    transformer: superjson,
    fetch: fetchStub,
  });

  return createTRPCClient<TRouter>({ links: [link] });
}