/**
 * Copyright (c) Microsoft Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
export class PortTransport {
    _lastId = 0;
    _port;
    _callbacks = new Map();
    constructor(port, handler) {
        this._port = port;
        port.addEventListener('message', async (event) => {
            const message = event.data;
            const { id, ackId, method, params, result } = message;
            if (ackId) {
                const callback = this._callbacks.get(ackId);
                this._callbacks.delete(ackId);
                this._resetRef();
                callback?.(result);
                return;
            }
            const handlerResult = await handler(method, params);
            if (id)
                this._port.postMessage({ ackId: id, result: handlerResult });
        });
        // Make sure to unref **after** adding a 'message' event listener.
        // https://nodejs.org/api/worker_threads.html#portref
        this._resetRef();
    }
    post(method, params) {
        this._port.postMessage({ method, params });
    }
    async send(method, params) {
        return await new Promise(f => {
            const id = ++this._lastId;
            this._callbacks.set(id, f);
            this._resetRef();
            this._port.postMessage({ id, method, params });
        });
    }
    _resetRef() {
        if (this._callbacks.size) {
            // When we are waiting for a response, ref the port to prevent this process from exiting.
            this._port.ref();
        }
        else {
            // When we are not waiting for a response, unref the port to prevent this process
            // from hanging forever.
            this._port.unref();
        }
    }
}
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