/
node-web-streams-helper.ts
292 lines (259 loc) · 7.67 KB
/
node-web-streams-helper.ts
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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 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 createBufferedTransformStream(): TransformStream<
Uint8Array,
Uint8Array
> {
let bufferedString = ''
let pendingFlush: Promise<void> | null = null
const flushBuffer = (controller: TransformStreamDefaultController) => {
if (!pendingFlush) {
pendingFlush = new Promise((resolve) => {
setTimeout(() => {
controller.enqueue(encodeText(bufferedString))
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: () => Promise<string>
): TransformStream<Uint8Array, Uint8Array> {
return new TransformStream({
async transform(chunk, controller) {
const flushedChunk = encodeText(await handleFlushEffect())
controller.enqueue(flushedChunk)
controller.enqueue(chunk)
},
})
}
export async function renderToInitialStream({
ReactDOMServer,
element,
}: {
ReactDOMServer: typeof import('react-dom/server')
element: React.ReactElement
}): Promise<
ReadableStream<Uint8Array> & {
allReady?: Promise<void>
}
> {
return await (ReactDOMServer as any).renderToReadableStream(element)
}
export async function continueFromInitialStream({
suffix,
dataStream,
generateStaticHTML,
flushEffectHandler,
renderStream,
}: {
suffix?: string
dataStream?: ReadableStream<Uint8Array>
generateStaticHTML: boolean
flushEffectHandler?: () => Promise<string>
renderStream: ReadableStream<Uint8Array> & {
allReady?: Promise<void>
}
}): 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 ? createFlushEffectStream(flushEffectHandler) : null,
suffixUnclosed != null ? createPrefixStream(suffixUnclosed) : null,
dataStream ? createInlineDataStream(dataStream) : null,
suffixUnclosed != null ? createSuffixStream(closeTag) : null,
].filter(Boolean) as any
return transforms.reduce(
(readable, transform) => readable.pipeThrough(transform),
renderStream
)
}
export async function renderToStream({
ReactDOMServer,
element,
suffix,
dataStream,
generateStaticHTML,
flushEffectHandler,
}: {
ReactDOMServer: typeof import('react-dom/server')
element: React.ReactElement
suffix?: string
dataStream?: ReadableStream<Uint8Array>
generateStaticHTML: boolean
flushEffectHandler?: () => Promise<string>
}): Promise<ReadableStream<Uint8Array>> {
const renderStream = await renderToInitialStream({ ReactDOMServer, element })
return continueFromInitialStream({
suffix,
dataStream,
generateStaticHTML,
flushEffectHandler,
renderStream,
})
}
export function createSuffixStream(
suffix: string
): TransformStream<Uint8Array, Uint8Array> {
return new TransformStream({
flush(controller) {
if (suffix) {
controller.enqueue(encodeText(suffix))
}
},
})
}
export function createPrefixStream(
prefix: string
): TransformStream<Uint8Array, Uint8Array> {
let prefixFlushed = false
let prefixPrefixFlushFinished: Promise<void> | null = null
return new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk)
if (!prefixFlushed && prefix) {
prefixFlushed = true
prefixPrefixFlushFinished = new Promise((res) => {
// NOTE: streaming flush
// Enqueue prefix part before the major chunks are enqueued so that
// prefix won't be flushed too early to interrupt the data stream
setTimeout(() => {
controller.enqueue(encodeText(prefix))
res()
})
})
}
},
flush(controller) {
if (prefixPrefixFlushFinished) return prefixPrefixFlushFinished
if (!prefixFlushed && prefix) {
prefixFlushed = true
controller.enqueue(encodeText(prefix))
}
},
})
}
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
}
},
})
}