refactor: 收口前端 SSE 传输层

2026-06-03 14:57:02 +08:00
parent 545ffa4b2c
commit 1eeb14c50f
10 changed files with 442 additions and 579 deletions
--- a/src/services/sseStream.ts
+++ b/src/services/sseStream.ts
@@ -0,0 +1,168 @@
+export type SseStreamEvent = {
+  eventName: string;
+  data: string;
+};
+
+export type SseJsonStreamEvent = SseStreamEvent & {
+  parsed: Record<string, unknown>;
+};
+
+type SseEventBoundary = {
+  index: number;
+  length: number;
+};
+
+type SseStreamEventHandler<TEvent extends SseStreamEvent> = (
+  event: TEvent,
+) => void | boolean;
+
+function findSseEventBoundary(buffer: string): SseEventBoundary | null {
+  const lfBoundary = buffer.indexOf('\n\n');
+  const crlfBoundary = buffer.indexOf('\r\n\r\n');
+
+  if (lfBoundary === -1 && crlfBoundary === -1) {
+    return null;
+  }
+
+  if (lfBoundary === -1) {
+    return {
+      index: crlfBoundary,
+      length: 4,
+    };
+  }
+
+  if (crlfBoundary === -1 || lfBoundary < crlfBoundary) {
+    return {
+      index: lfBoundary,
+      length: 2,
+    };
+  }
+
+  return {
+    index: crlfBoundary,
+    length: 4,
+  };
+}
+
+function parseSseEventBlock(eventBlock: string): SseStreamEvent | null {
+  let eventName = 'message';
+  const dataLines: string[] = [];
+
+  for (const rawLine of eventBlock.split(/\r?\n/u)) {
+    const line = rawLine.trim();
+
+    if (line.startsWith('event:')) {
+      eventName = line.slice(6).trim() || 'message';
+      continue;
+    }
+
+    if (line.startsWith('data:')) {
+      dataLines.push(line.slice(5).trim());
+    }
+  }
+
+  const data = dataLines.join('\n');
+  if (!data) {
+    return null;
+  }
+
+  return {
+    eventName,
+    data,
+  };
+}
+
+export function parseSseJsonObject(data: string): Record<string, unknown> | null {
+  try {
+    const parsed = JSON.parse(data) as unknown;
+    return typeof parsed === 'object' && parsed !== null
+      ? (parsed as Record<string, unknown>)
+      : null;
+  } catch {
+    return null;
+  }
+}
+
+export async function readSseStream(
+  response: Response,
+  onEvent: SseStreamEventHandler<SseStreamEvent>,
+) {
+  const streamBody = response.body;
+  if (!streamBody) {
+    throw new Error('streaming response body is unavailable');
+  }
+
+  const reader = streamBody.getReader();
+  const decoder = new TextDecoder('utf-8');
+  let buffer = '';
+  let shouldContinue = true;
+  let completed = false;
+
+  const consumeBuffer = () => {
+    for (;;) {
+      if (!shouldContinue) {
+        break;
+      }
+
+      const boundary = findSseEventBoundary(buffer);
+      if (!boundary) {
+        break;
+      }
+
+      const eventBlock = buffer.slice(0, boundary.index);
+      buffer = buffer.slice(boundary.index + boundary.length);
+      const event = parseSseEventBlock(eventBlock);
+      if (!event) {
+        continue;
+      }
+
+      if (onEvent(event) === false) {
+        shouldContinue = false;
+      }
+    }
+  };
+
+  try {
+    for (;;) {
+      const { done, value } = await reader.read();
+      if (done) {
+        break;
+      }
+
+      buffer += decoder.decode(value, { stream: true });
+      consumeBuffer();
+      if (!shouldContinue) {
+        break;
+      }
+    }
+
+    if (shouldContinue) {
+      // 流结束后 flush 解码器，避免 UTF-8 多字节字符残留在内部缓冲里。
+      buffer += decoder.decode();
+      consumeBuffer();
+      completed = true;
+    }
+  } finally {
+    if (!completed && typeof reader.cancel === 'function') {
+      await reader.cancel().catch(() => {});
+    }
+    reader.releaseLock?.();
+  }
+}
+
+export function readSseJsonStream(
+  response: Response,
+  onEvent: SseStreamEventHandler<SseJsonStreamEvent>,
+) {
+  return readSseStream(response, (event) => {
+    const parsed = parseSseJsonObject(event.data);
+    if (!parsed) {
+      return;
+    }
+
+    return onEvent({
+      ...event,
+      parsed,
+    });
+  });
+}