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fallbackServiceStub.ts
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fallbackServiceStub.ts
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/**
* Copyright 2021 Google LLC
*
* 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.
*/
/* global window */
/* global AbortController */
import nodeFetch from 'node-fetch';
import {Response as NodeFetchResponse} from 'node-fetch';
import {AbortController as NodeAbortController} from 'abort-controller';
import {hasWindowFetch, hasAbortController} from './featureDetection';
import {AuthClient} from './fallback';
import {StreamArrayParser} from './streamArrayParser';
import {pipeline, PipelineSource} from 'stream';
interface NodeFetchType {
(url: RequestInfo, init?: RequestInit): Promise<Response>;
}
export interface FallbackServiceStub {
// Compatible with gRPC service stub
[method: string]: (
request: {},
options?: {},
metadata?: {},
callback?: (err?: Error, response?: {} | undefined) => void
) => StreamArrayParser | {cancel: () => void};
}
export type FetchParametersMethod = 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE';
export interface FetchParameters {
headers: {[key: string]: string};
body: Buffer | Uint8Array | string;
method: FetchParametersMethod;
url: string;
}
export function generateServiceStub(
rpcs: {[name: string]: protobuf.Method},
protocol: string,
servicePath: string,
servicePort: number,
authClient: AuthClient,
requestEncoder: (
rpc: protobuf.Method,
protocol: string,
servicePath: string,
servicePort: number,
request: {},
numericEnums: boolean
) => FetchParameters,
responseDecoder: (
rpc: protobuf.Method,
ok: boolean,
response: Buffer | ArrayBuffer
) => {},
numericEnums: boolean
) {
const fetch = hasWindowFetch()
? window.fetch
: (nodeFetch as unknown as NodeFetchType);
const serviceStub: FallbackServiceStub = {
// close method should close all cancel controllers. If this feature request in the future, we can have a cancelControllerFactory that tracks created cancel controllers, and abort them all in close method.
close: () => {
return {cancel: () => {}};
},
};
for (const [rpcName, rpc] of Object.entries(rpcs)) {
serviceStub[rpcName] = (
request: {},
options?: {[name: string]: string},
_metadata?: {} | Function,
callback?: Function
) => {
options ??= {};
// We cannot use async-await in this function because we need to return the canceller object as soon as possible.
// Using plain old promises instead.
let fetchParameters: FetchParameters;
try {
fetchParameters = requestEncoder(
rpc,
protocol,
servicePath,
servicePort,
request,
numericEnums
);
} catch (err) {
// we could not encode parameters; pass error to the callback
// and return a no-op canceler object.
if (callback) {
callback(err);
}
return {
cancel() {},
};
}
const cancelController = hasAbortController()
? new AbortController()
: new NodeAbortController();
const cancelSignal = cancelController.signal as AbortSignal;
let cancelRequested = false;
const url = fetchParameters.url;
const headers = fetchParameters.headers;
for (const key of Object.keys(options)) {
headers[key] = options[key][0];
}
const streamArrayParser = new StreamArrayParser(rpc);
authClient
.getRequestHeaders()
.then(authHeader => {
const fetchRequest: RequestInit = {
headers: {
...authHeader,
...headers,
},
body: fetchParameters.body as
| string
| Buffer
| Uint8Array
| undefined,
method: fetchParameters.method,
signal: cancelSignal,
};
if (
fetchParameters.method === 'GET' ||
fetchParameters.method === 'DELETE'
) {
delete fetchRequest['body'];
}
return fetch(url, fetchRequest);
})
.then((response: Response | NodeFetchResponse) => {
if (response.ok && rpc.responseStream) {
pipeline(
response.body as PipelineSource<unknown>,
streamArrayParser,
(err: unknown) => {
if (
err &&
(!cancelRequested ||
(err instanceof Error && err.name !== 'AbortError'))
) {
if (callback) {
callback(err);
}
streamArrayParser.emit('error', err);
}
}
);
return;
} else {
return Promise.all([
Promise.resolve(response.ok),
response.arrayBuffer(),
])
.then(([ok, buffer]: [boolean, Buffer | ArrayBuffer]) => {
const response = responseDecoder(rpc, ok, buffer);
callback!(null, response);
})
.catch((err: Error) => {
if (!cancelRequested || err.name !== 'AbortError') {
if (rpc.responseStream) {
if (callback) {
callback(err);
}
streamArrayParser.emit('error', err);
} else if (callback) {
callback(err);
} else {
throw err;
}
}
});
}
})
.catch((err: unknown) => {
if (rpc.responseStream) {
if (callback) {
callback(err);
}
streamArrayParser.emit('error', err);
} else if (callback) {
callback(err);
} else {
throw err;
}
});
if (rpc.responseStream) {
return streamArrayParser;
}
return {
cancel: () => {
cancelRequested = true;
cancelController.abort();
},
};
};
}
return serviceStub;
}