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Create request handler using the fetch API Request/Response types from a @bufbuild/connect universal handler (early and barely tested)
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// Copyright 2021-2023 Buf Technologies, Inc. | |
// | |
// 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. | |
import {UniversalHandler, UniversalServerRequest, UniversalServerResponse} from "@bufbuild/connect/protocol"; | |
/** | |
* FetchHandler is equivalent to a UniversalHandler. It takes a fetch Request | |
* and returns a promise of a fetch Response. It has the same metadata | |
* properties "requestPath" etc. that UniversalHandler has. | |
*/ | |
type FetchHandler = ((req: Request) => Promise<Response>) & Omit<UniversalHandler, "">; | |
/** | |
* Convert a universal handler to a fetch handler - a function that takes a | |
* fetch Request and returns a promise of a fetch Response. | |
*/ | |
export function createFetchHandler(uHandler: UniversalHandler): FetchHandler { | |
async function handleFetch(req: Request) { | |
const uReq = universalServerRequestToFetch(req); | |
const uRes = await uHandler(uReq); | |
return universalServerResponseToFetch(uRes); | |
} | |
return Object.assign(handleFetch, uHandler); | |
} | |
function universalServerRequestToFetch(req: Request): UniversalServerRequest { | |
const url = new URL(req.url) | |
return { | |
httpVersion: "1.1", | |
method: req.method, | |
url, | |
header: req.headers, | |
body: fetchBodyToByteStream(req.body), | |
}; | |
} | |
function universalServerResponseToFetch(res: UniversalServerResponse): Response { | |
let body: ReadableStream<Uint8Array> | Uint8Array | null = null; | |
if (res.body instanceof Uint8Array) { | |
body = res.body; | |
} else if (res.body !== undefined) { | |
const it = res.body[Symbol.asyncIterator](); | |
body = new ReadableStream<Uint8Array>(<UnderlyingSource<Uint8Array>>{ | |
async pull(controller: ReadableByteStreamController) { | |
const r = await it.next() | |
if (r.done) { | |
controller.close(); | |
return; | |
} | |
await controller.enqueue(r.value); | |
} | |
}); | |
} | |
return new Response( | |
body, | |
{ | |
status: res.status, | |
headers: res.header | |
} | |
); | |
} | |
async function* fetchBodyToByteStream(body: Request["body"]): AsyncIterable<Uint8Array> { | |
if (body === null) { | |
return; | |
} | |
const reader = body.getReader(); | |
for (;;) { | |
const r = await reader.read(); | |
if (r.done) { | |
break; | |
} | |
yield r.value; | |
} | |
} |
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