refactor: 补齐草稿与SSE收口

src/services/llmClient.ts

@@ -1,5 +1,6 @@
 import type {TextStreamOptions} from './aiTypes';
 import { fetchWithApiAuth } from './apiClient';
+import { parseSseJsonObject, readSseStream } from './sseStream';
 
 const ENV: Partial<ImportMetaEnv> = import.meta.env ?? {};
 
@@ -44,6 +45,26 @@ function resolveHeaders(headers?: HeadersInit) {
   return nextHeaders;
 }
 
+function readLlmStreamDeltaContent(parsed: Record<string, unknown>) {
+  const choices = parsed.choices;
+  if (!Array.isArray(choices)) {
+    return null;
+  }
+
+  const [firstChoice] = choices;
+  if (typeof firstChoice !== 'object' || firstChoice === null) {
+    return null;
+  }
+
+  const delta = (firstChoice as {delta?: unknown}).delta;
+  if (typeof delta !== 'object' || delta === null) {
+    return null;
+  }
+
+  const content = (delta as {content?: unknown}).content;
+  return typeof content === 'string' && content.length > 0 ? content : null;
+}
+
 const NODE_ENV = getNodeEnv();
 const IS_SERVER_RUNTIME = typeof window === 'undefined';
 const SERVER_API_KEY =
@@ -291,48 +312,20 @@ export async function streamPlainTextCompletion(
       return fallbackText;
     }
 
-    const reader = response.body.getReader();
-    const decoder = new TextDecoder('utf-8');
-    let buffer = '';
     let accumulatedText = '';
 
-    for (;;) {
-      const {done, value} = await reader.read();
-      if (done) {
-        break;
+    await readSseStream(response, ({ data }) => {
+      if (data === '[DONE]') {
+        return false;
       }
 
-      buffer += decoder.decode(value, {stream: true});
-
-      while (buffer.includes('\n\n')) {
-        const boundary = buffer.indexOf('\n\n');
-        const eventBlock = buffer.slice(0, boundary);
-        buffer = buffer.slice(boundary + 2);
-
-        for (const rawLine of eventBlock.split(/\r?\n/u)) {
-          const line = rawLine.trim();
-          if (!line.startsWith('data:')) {
-            continue;
-          }
-
-          const data = line.slice(5).trim();
-          if (!data || data === '[DONE]') {
-            continue;
-          }
-
-          try {
-            const parsed = JSON.parse(data);
-            const delta = parsed?.choices?.[0]?.delta?.content;
-            if (typeof delta === 'string' && delta.length > 0) {
-              accumulatedText += delta;
-              options.onUpdate?.(accumulatedText);
-            }
-          } catch {
-            // Ignore malformed SSE frames and continue consuming the stream.
-          }
-        }
+      const parsed = parseSseJsonObject(data);
+      const delta = parsed ? readLlmStreamDeltaContent(parsed) : null;
+      if (delta) {
+        accumulatedText += delta;
+        options.onUpdate?.(accumulatedText);
       }
-    }
+    });
 
     return accumulatedText.trim();
   } catch (error) {