68 lines
2.7 KiB
TypeScript
68 lines
2.7 KiB
TypeScript
/**
|
|
* Decode an SSE byte stream into event `data` payloads. Network reads may split UTF-8 or lines;
|
|
* CRLF, comments, non-data fields, and multi-data events are handled per SSE rules. The literal
|
|
* `[DONE]` is yielded so the caller owns final flushing, and EOF before it raises {@link LlmError}.
|
|
*
|
|
* Minimal SSE (text/event-stream) parser for the chat-completions stream.
|
|
* @module dsh-llm-deepseek/sse
|
|
*/
|
|
|
|
import { LlmError } from '@deepseek-ai/dsh-llm'
|
|
|
|
/** The terminal payload DeepSeek (and OpenAI) send after the last chunk. */
|
|
export const DONE = '[DONE]'
|
|
|
|
/** Extract the joined data payload from one raw SSE event block. */
|
|
function eventData(block: string): string | undefined {
|
|
const data: string[] = []
|
|
for (const rawLine of block.split('\n')) {
|
|
const line = rawLine.endsWith('\r') ? rawLine.slice(0, -1) : rawLine
|
|
if (line.startsWith('data:')) {
|
|
// The spec strips ONE leading space after the colon.
|
|
data.push(line.startsWith('data: ') ? line.slice(6) : line.slice(5))
|
|
}
|
|
// Comments (':…') and other fields (event:, id:, retry:) are ignored.
|
|
}
|
|
if (data.length === 0) return undefined
|
|
return data.join('\n')
|
|
}
|
|
|
|
/**
|
|
* Parse a byte stream into SSE data payloads. Yields `[DONE]` as the final
|
|
* value and returns; throws `LlmError('STREAM_CLOSED')` when the stream ends
|
|
* without it (truncated response — the model call cannot be trusted).
|
|
* @param stream - raw SSE bytes; reads may split anywhere, including mid-UTF-8 sequence.
|
|
* @returns each event's data payload in arrival order, the `[DONE]` sentinel last.
|
|
*/
|
|
export async function* parseSse(stream: AsyncIterable<Uint8Array>): AsyncGenerator<string> {
|
|
const decoder = new TextDecoder()
|
|
let buffer = ''
|
|
|
|
for await (const bytes of stream) {
|
|
buffer += decoder.decode(bytes, { stream: true })
|
|
// Events are separated by a blank line (\n\n; tolerate \r\n\r\n via the
|
|
// per-line \r strip in eventData and a normalized split here).
|
|
let boundary: number
|
|
while ((boundary = buffer.search(/\r?\n\r?\n/)) !== -1) {
|
|
const matched = /\r?\n\r?\n/.exec(buffer.slice(boundary))
|
|
const block = buffer.slice(0, boundary)
|
|
// matched cannot be null: search() just found the same pattern at 0.
|
|
buffer = buffer.slice(boundary + (matched as RegExpExecArray)[0].length)
|
|
const data = eventData(block)
|
|
if (data === undefined) continue
|
|
yield data
|
|
if (data === DONE) return
|
|
}
|
|
}
|
|
|
|
// Flush any final un-terminated event (servers usually end with \n\n, but
|
|
// a trailing block without one is still parseable).
|
|
buffer += decoder.decode()
|
|
const data = eventData(buffer)
|
|
if (data !== undefined) {
|
|
yield data
|
|
if (data === DONE) return
|
|
}
|
|
throw new LlmError('SSE stream ended without [DONE]', 'STREAM_CLOSED')
|
|
}
|