forked from vercel/next.js
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node-web-streams-helper.ts
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node-web-streams-helper.ts
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import { nonNullable } from '../lib/non-nullable'
export type ReactReadableStream = ReadableStream<Uint8Array> & {
allReady?: Promise<void> | undefined
}
export function encodeText(input: string) {
return new TextEncoder().encode(input)
}
export function decodeText(input?: Uint8Array, textDecoder?: TextDecoder) {
return textDecoder
? textDecoder.decode(input, { stream: true })
: new TextDecoder().decode(input)
}
export function readableStreamTee<T = any>(
readable: ReadableStream<T>
): [ReadableStream<T>, ReadableStream<T>] {
const transformStream = new TransformStream()
const transformStream2 = new TransformStream()
const writer = transformStream.writable.getWriter()
const writer2 = transformStream2.writable.getWriter()
const reader = readable.getReader()
function read() {
reader.read().then(({ done, value }) => {
if (done) {
writer.close()
writer2.close()
return
}
writer.write(value)
writer2.write(value)
read()
})
}
read()
return [transformStream.readable, transformStream2.readable]
}
export function chainStreams<T>(
streams: ReadableStream<T>[]
): ReadableStream<T> {
const { readable, writable } = new TransformStream()
let promise = Promise.resolve()
for (let i = 0; i < streams.length; ++i) {
promise = promise.then(() =>
streams[i].pipeTo(writable, { preventClose: i + 1 < streams.length })
)
}
return readable
}
export function streamFromArray(strings: string[]): ReadableStream<Uint8Array> {
// Note: we use a TransformStream here instead of instantiating a ReadableStream
// because the built-in ReadableStream polyfill runs strings through TextEncoder.
const { readable, writable } = new TransformStream()
const writer = writable.getWriter()
strings.forEach((str) => writer.write(encodeText(str)))
writer.close()
return readable
}
export async function streamToString(
stream: ReadableStream<Uint8Array>
): Promise<string> {
const reader = stream.getReader()
const textDecoder = new TextDecoder()
let bufferedString = ''
while (true) {
const { done, value } = await reader.read()
if (done) {
return bufferedString
}
bufferedString += decodeText(value, textDecoder)
}
}
export function createBufferedTransformStream(
transform: (v: string) => string | Promise<string> = (v) => v
): TransformStream<Uint8Array, Uint8Array> {
let bufferedString = ''
let pendingFlush: Promise<void> | null = null
const flushBuffer = (controller: TransformStreamDefaultController) => {
if (!pendingFlush) {
pendingFlush = new Promise((resolve) => {
setTimeout(async () => {
const buffered = await transform(bufferedString)
controller.enqueue(encodeText(buffered))
bufferedString = ''
pendingFlush = null
resolve()
}, 0)
})
}
return pendingFlush
}
const textDecoder = new TextDecoder()
return new TransformStream({
transform(chunk, controller) {
bufferedString += decodeText(chunk, textDecoder)
flushBuffer(controller)
},
flush() {
if (pendingFlush) {
return pendingFlush
}
},
})
}
export function createFlushEffectStream(
handleFlushEffect: () => string
): TransformStream<Uint8Array, Uint8Array> {
return new TransformStream({
transform(chunk, controller) {
const flushedChunk = encodeText(handleFlushEffect())
controller.enqueue(flushedChunk)
controller.enqueue(chunk)
},
})
}
export function renderToInitialStream({
ReactDOMServer,
element,
streamOptions,
}: {
ReactDOMServer: any
element: React.ReactElement
streamOptions?: any
}): Promise<ReactReadableStream> {
return ReactDOMServer.renderToReadableStream(element, streamOptions)
}
export function createHeadInjectionTransformStream(
inject: () => string
): TransformStream<Uint8Array, Uint8Array> {
let injected = false
return new TransformStream({
transform(chunk, controller) {
const content = decodeText(chunk)
let index
if (!injected && (index = content.indexOf('</head')) !== -1) {
injected = true
const injectedContent =
content.slice(0, index) + inject() + content.slice(index)
controller.enqueue(encodeText(injectedContent))
} else {
controller.enqueue(chunk)
}
},
})
}
// Suffix after main body content - scripts before </body>,
// but wait for the major chunks to be enqueued.
export function createDeferredSuffixStream(
suffix: string
): TransformStream<Uint8Array, Uint8Array> {
let suffixFlushed = false
let suffixFlushTask: Promise<void> | null = null
return new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk)
if (!suffixFlushed && suffix) {
suffixFlushed = true
suffixFlushTask = new Promise((res) => {
// NOTE: streaming flush
// Enqueue suffix part before the major chunks are enqueued so that
// suffix won't be flushed too early to interrupt the data stream
setTimeout(() => {
controller.enqueue(encodeText(suffix))
res()
})
})
}
},
flush(controller) {
if (suffixFlushTask) return suffixFlushTask
if (!suffixFlushed && suffix) {
suffixFlushed = true
controller.enqueue(encodeText(suffix))
}
},
})
}
export function createInlineDataStream(
dataStream: ReadableStream<Uint8Array>
): TransformStream<Uint8Array, Uint8Array> {
let dataStreamFinished: Promise<void> | null = null
return new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk)
if (!dataStreamFinished) {
const dataStreamReader = dataStream.getReader()
// NOTE: streaming flush
// We are buffering here for the inlined data stream because the
// "shell" stream might be chunkenized again by the underlying stream
// implementation, e.g. with a specific high-water mark. To ensure it's
// the safe timing to pipe the data stream, this extra tick is
// necessary.
dataStreamFinished = new Promise((res) =>
setTimeout(async () => {
try {
while (true) {
const { done, value } = await dataStreamReader.read()
if (done) {
return res()
}
controller.enqueue(value)
}
} catch (err) {
controller.error(err)
}
res()
}, 0)
)
}
},
flush() {
if (dataStreamFinished) {
return dataStreamFinished
}
},
})
}
export function createSuffixStream(
suffix: string
): TransformStream<Uint8Array, Uint8Array> {
return new TransformStream({
flush(controller) {
if (suffix) {
controller.enqueue(encodeText(suffix))
}
},
})
}
export async function continueFromInitialStream(
renderStream: ReactReadableStream,
{
suffix,
dataStream,
generateStaticHTML,
flushEffectHandler,
flushEffectsToHead,
}: {
suffix?: string
dataStream?: ReadableStream<Uint8Array>
generateStaticHTML: boolean
flushEffectHandler?: () => string
flushEffectsToHead: boolean
}
): Promise<ReadableStream<Uint8Array>> {
const closeTag = '</body></html>'
const suffixUnclosed = suffix ? suffix.split(closeTag)[0] : null
if (generateStaticHTML) {
await renderStream.allReady
}
const transforms: Array<TransformStream<Uint8Array, Uint8Array>> = [
createBufferedTransformStream(),
flushEffectHandler && !flushEffectsToHead
? createFlushEffectStream(flushEffectHandler)
: null,
suffixUnclosed != null ? createDeferredSuffixStream(suffixUnclosed) : null,
dataStream ? createInlineDataStream(dataStream) : null,
suffixUnclosed != null ? createSuffixStream(closeTag) : null,
createHeadInjectionTransformStream(() => {
// TODO-APP: Inject flush effects to end of head in app layout rendering, to avoid
// hydration errors. Remove this once it's ready to be handled by react itself.
const flushEffectsContent =
flushEffectHandler && flushEffectsToHead ? flushEffectHandler() : ''
return flushEffectsContent
}),
].filter(nonNullable)
return transforms.reduce(
(readable, transform) => readable.pipeThrough(transform),
renderStream
)
}