window.ts

import { AnyProcedure, AnyRouter, TRPCError } from '@trpc/server';
import { Unsubscribable, isObservable } from '@trpc/server/observable';

import { TRPC_BROWSER_LOADED_EVENT } from '../shared/constants';
import { isTRPCRequestWithId } from '../shared/trpcMessage';
import type { MinimalWindow, TRPCChromeResponse } from '../types';
import { CreateHandlerOptions } from './base';
import { getErrorFromUnknown } from './errors';

type WindowOptions = {
  window: MinimalWindow;
  postWindow?: MinimalWindow;
  postOrigin?: string;
};
type WindowContextOptions = { req: { origin: string }; res: undefined };

export const createWindowHandler = <TRouter extends AnyRouter>(
  opts: CreateHandlerOptions<TRouter, WindowContextOptions, WindowOptions>,
) => {
  const { router, createContext, onError, window, postOrigin } = opts;
  if (!window) {
    console.warn("Skipping window handler creation: 'opts.window' not defined");
    return;
  }

  const loadListener = opts.postWindow ?? window.opener ?? window;
  loadListener.postMessage(TRPC_BROWSER_LOADED_EVENT, { targetOrigin: postOrigin });

  // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
  const { transformer } = router._def._config;
  const subscriptions = new Map<number | string, Unsubscribable>();
  const listeners: (() => void)[] = [];

  const cleanup = () => listeners.forEach((unsub) => unsub());
  window.addEventListener('beforeunload', cleanup);
  listeners.push(() => window.removeEventListener('beforeunload', cleanup));

  const onMessage = async (event: MessageEvent<unknown>) => {
    const { data: message, source } = event;
    const postWindow = opts.postWindow ?? source ?? window;
    if (!postWindow || !isTRPCRequestWithId(message)) return;

    const { trpc } = message;
    const sendResponse = (response: TRPCChromeResponse['trpc']) => {
      postWindow.postMessage(
        {
          trpc: { id: trpc.id, jsonrpc: trpc.jsonrpc, ...response },
        } as TRPCChromeResponse,
        { targetOrigin: postOrigin },
      );
    };

    if (trpc.method === 'subscription.stop') {
      subscriptions.get(trpc.id)?.unsubscribe();
      subscriptions.delete(trpc.id);
      return sendResponse({ result: { type: 'stopped' } });
    }
    const { method, params, id } = trpc;

    const ctx = await createContext?.({ req: { origin: event.origin }, res: undefined });
    const handleError = (cause: unknown) => {
      const error = getErrorFromUnknown(cause);

      onError?.({
        error,
        type: method,
        path: params.path,
        input: params.input,
        ctx,
        req: { origin: event.origin },
      });

      sendResponse({
        // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
        error: router.getErrorShape({
          error,
          type: method,
          path: params.path,
          input: params.input,
          ctx,
        }),
      });
    };

    try {
      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
      const input = transformer.input.deserialize(trpc.params.input);
      const caller = router.createCaller(ctx);

      const procedureFn = trpc.params.path
        .split('.')
        // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-return, @typescript-eslint/no-explicit-any
        .reduce((acc, segment) => acc[segment], caller as any) as AnyProcedure;

      // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
      const result = await procedureFn(input);
      if (trpc.method !== 'subscription') {
        return sendResponse({
          // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call
          result: { type: 'data', data: transformer.output.serialize(result) },
        });
      }

      if (!isObservable(result)) {
        throw new TRPCError({
          message: `Subscription ${params.path} did not return an observable`,
          code: 'INTERNAL_SERVER_ERROR',
        });
      }

      const subscription = result.subscribe({
        next: (data) => sendResponse({ result: { type: 'data', data } }),
        error: handleError,
        complete: () => sendResponse({ result: { type: 'stopped' } }),
      });

      if (subscriptions.has(id)) {
        subscription.unsubscribe();
        sendResponse({ result: { type: 'stopped' } });
        throw new TRPCError({ message: `Duplicate id ${id}`, code: 'BAD_REQUEST' });
      }

      listeners.push(() => subscription.unsubscribe());
      subscriptions.set(id, subscription);
      sendResponse({ result: { type: 'started' } });
    } catch (cause) {
      handleError(cause);
    }
  };

  window.addEventListener('message', onMessage);
  listeners.push(() => window.removeEventListener('message', onMessage));
};