feat: render assistant content

apps/nextjs/src/components/assistant/assistant-markdown.ts

@@ -0,0 +1,41 @@
+const protectedMarkdownPattern = /```[\s\S]*?(?:```|$)|~~~[\s\S]*?(?:~~~|$)|`+[^`\n]*`+/gu;
+const inlineStrongListMarker = / - (?=\*\*[^*\n]{1,80}\*\*\s+(?:[—–:-]\s+)?)/gu;
+const trailingQuestion = /\s+((?:Are|Can|Could|Do|Does|How|Is|What|When|Where|Which|Why|Would)\b[^?\n]*\?)$/u;
+
+const normalizeProse = (text: string) => {
+  const withLineBreaks = text.replaceAll("\\r\\n", "\n").replaceAll("\\n", "\n");
+
+  return withLineBreaks
+    .split("\n")
+    .map((line) => {
+      const markers = [...line.matchAll(inlineStrongListMarker)];
+      if (markers.length < 2) return line;
+
+      let markerIndex = 0;
+      return line
+        .replaceAll(inlineStrongListMarker, () => (markerIndex++ === 0 ? "\n\n- " : "\n- "))
+        .replace(trailingQuestion, "\n\n$1");
+    })
+    .join("\n");
+};
+
+/**
+ * Makes common streamed model Markdown readable without changing code samples.
+ *
+ * Models occasionally emit escaped line breaks or an entire bold-label list on
+ * one line. The assistant-ui renderer receives this function through its
+ * streaming-safe `preprocess` hook, before Markdown is parsed.
+ */
+export const normalizeAssistantMarkdown = (text: string) => {
+  let offset = 0;
+  let normalized = "";
+
+  for (const match of text.matchAll(protectedMarkdownPattern)) {
+    const index = match.index;
+    normalized += normalizeProse(text.slice(offset, index));
+    normalized += match[0];
+    offset = index + match[0].length;
+  }
+
+  return normalized + normalizeProse(text.slice(offset));
+};