70 lines
1.9 KiB
TypeScript
70 lines
1.9 KiB
TypeScript
/**
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* 极简 SSE（text/event-stream）解析器。
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*
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* 只依赖 Web 标准的 ReadableStream，可直接消费 fetch 响应体。
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* 上游既可能是标准 SSE，也可能在末尾缺少空行，因此以「块边界」为准做收尾。
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*/
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export interface SseEvent {
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event?: string
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data: string
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}
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export async function* parseSse(
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stream: ReadableStream<Uint8Array>
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): AsyncGenerator<SseEvent, void, void> {
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const reader = stream.getReader()
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const decoder = new TextDecoder()
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let buffer = ''
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try {
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for (;;) {
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const { done, value } = await reader.read()
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if (done) break
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buffer += decoder.decode(value, { stream: true })
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let index: number
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// 事件之间以空行分隔，兼容 \r\n 与 \n
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while ((index = findBoundary(buffer)) !== -1) {
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const raw = buffer.slice(0, index)
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buffer = buffer.slice(index).replace(/^(\r?\n){2}/, '')
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const parsed = parseBlock(raw)
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if (parsed) yield parsed
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}
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}
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// 收尾：流结束时可能残留最后一个事件
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buffer += decoder.decode()
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const tail = parseBlock(buffer)
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if (tail) yield tail
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} finally {
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reader.releaseLock()
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}
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}
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function findBoundary(buffer: string): number {
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const a = buffer.indexOf('\n\n')
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const b = buffer.indexOf('\r\n\r\n')
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if (a === -1) return b
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if (b === -1) return a
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return Math.min(a, b)
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}
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function parseBlock(block: string): SseEvent | null {
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const lines = block.split(/\r?\n/)
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const dataLines: string[] = []
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let event: string | undefined
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for (const line of lines) {
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if (!line || line.startsWith(':')) continue
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if (line.startsWith('event:')) {
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event = line.slice(6).trim()
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} else if (line.startsWith('data:')) {
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dataLines.push(line.slice(5).replace(/^ /, ''))
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}
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}
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if (dataLines.length === 0) return null
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return { event, data: dataLines.join('\n') }
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}
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