TelegramPWA/src/util/createPostMessageInterface.ts

import type {
  ApiUpdate,
  CancellableCallback,
  OriginMessageData,
  OriginMessageEvent,
  WorkerPayload,
} from './PostMessageConnector';

import { DEBUG } from '../config';
import { createCallbackManager } from './callbacks';
import { throttleWithTickEnd } from './schedulers';

declare const self: WorkerGlobalScope;

const callbackState = new Map<string, CancellableCallback>();

type ApiConfig =
  // eslint-disable-next-line @typescript-eslint/no-redundant-type-constituents
  ((name: string, ...args: any[]) => any | [any, ArrayBuffer[]])
  | Record<string, AnyFunction>;
type SendToOrigin = (data: WorkerPayload, transferables?: Transferable[]) => void;

const messageHandlers = createCallbackManager();
onmessage = messageHandlers.runCallbacks;

export function createWorkerInterface(api: ApiConfig, channel?: string) {
  let pendingPayloads: WorkerPayload[] = [];
  let pendingTransferables: Transferable[] = [];

  const sendToOriginOnTickEnd = throttleWithTickEnd(() => {
    const data = { channel, payloads: pendingPayloads };
    const transferables = pendingTransferables;

    pendingPayloads = [];
    pendingTransferables = [];

    if (transferables.length) {
      postMessage(data, transferables);
    } else {
      postMessage(data);
    }
  });

  function sendToOrigin(payload: WorkerPayload, transferables?: Transferable[]) {
    pendingPayloads.push(payload);

    if (transferables) {
      pendingTransferables.push(...transferables);
    }

    sendToOriginOnTickEnd();
  }

  handleErrors(sendToOrigin);

  messageHandlers.addCallback((message: OriginMessageEvent) => {
    if (message.data?.channel === channel) {
      onMessage(api, message.data, sendToOrigin);
    }
  });
}

function onMessage(
  api: ApiConfig,
  data: OriginMessageData,
  sendToOrigin: SendToOrigin,
  onUpdate?: (update: ApiUpdate) => void,
) {
  if (!onUpdate) {
    onUpdate = (update: ApiUpdate) => {
      sendToOrigin({
        type: 'update',
        update,
      });
    };
  }

  data.payloads.forEach(async (payload) => {
    switch (payload.type) {
      case 'init': {
        const { args } = payload;
        if (typeof api === 'function') {
          await api('init', onUpdate, ...args);
        } else {
          await api.init?.(onUpdate, ...args);
        }

        break;
      }

      case 'callMethod': {
        const {
          messageId, name, args, withCallback,
        } = payload;

        try {
          if (typeof api !== 'function' && !api[name]) return;

          if (messageId && withCallback) {
            const callback = (...callbackArgs: any[]) => {
              const lastArg = callbackArgs[callbackArgs.length - 1];

              sendToOrigin({
                type: 'methodCallback',
                messageId,
                callbackArgs,
              }, isTransferable(lastArg) ? [lastArg] : undefined);
            };

            callbackState.set(messageId, callback);

            args.push(callback as never);
          }

          const response = typeof api === 'function'
            ? await api(name, ...args)
            : await api[name](...args);
          const { arrayBuffer } = (typeof response === 'object' && 'arrayBuffer' in response && response) || {};
          if (messageId) {
            sendToOrigin(
              {
                type: 'methodResponse',
                messageId,
                response,
              },
              arrayBuffer ? [arrayBuffer] : undefined,
            );
          }
        } catch (error: any) {
          if (DEBUG) {
            // eslint-disable-next-line no-console
            console.error(error);
          }

          if (messageId) {
            sendToOrigin({
              type: 'methodResponse',
              messageId,
              error: { message: error.message },
            });
          }
        }

        if (messageId) {
          callbackState.delete(messageId);
        }

        break;
      }

      case 'cancelProgress': {
        const callback = callbackState.get(payload.messageId);
        if (callback) {
          callback.isCanceled = true;
        }

        break;
      }
    }
  });
}

function isTransferable(obj: any) {
  return obj instanceof ArrayBuffer || obj instanceof ImageBitmap;
}

function handleErrors(sendToOrigin: SendToOrigin) {
  self.onerror = (e) => {
    // eslint-disable-next-line no-console
    console.error(e);
    sendToOrigin({ type: 'unhandledError', error: { message: e.error.message || 'Uncaught exception in worker' } });
  };

  self.addEventListener('unhandledrejection', (e) => {
    // eslint-disable-next-line no-console
    console.error(e);
    sendToOrigin({ type: 'unhandledError', error: { message: e.reason.message || 'Uncaught rejection in worker' } });
  });
}