feat: add sessions preview rpc and menu prewarm

src/gateway/session-utils.fs.ts

@@ -3,6 +3,8 @@ import os from "node:os";
 import path from "node:path";
 
 import { resolveSessionTranscriptPath } from "../config/sessions.js";
+import { stripEnvelope } from "./chat-sanitize.js";
+import type { SessionPreviewItem } from "./session-utils.types.js";
 
 export function readSessionMessages(
   sessionId: string,
@@ -189,3 +191,202 @@ export function readLastMessagePreviewFromTranscript(
   }
   return null;
 }
+
+const PREVIEW_READ_SIZES = [64 * 1024, 256 * 1024, 1024 * 1024];
+const PREVIEW_MAX_LINES = 200;
+
+type TranscriptContentEntry = {
+  type?: string;
+  text?: string;
+  name?: string;
+};
+
+type TranscriptPreviewMessage = {
+  role?: string;
+  content?: string | TranscriptContentEntry[];
+  text?: string;
+  toolName?: string;
+  tool_name?: string;
+};
+
+function normalizeRole(role: string | undefined, isTool: boolean): SessionPreviewItem["role"] {
+  if (isTool) return "tool";
+  switch ((role ?? "").toLowerCase()) {
+    case "user":
+      return "user";
+    case "assistant":
+      return "assistant";
+    case "system":
+      return "system";
+    case "tool":
+      return "tool";
+    default:
+      return "other";
+  }
+}
+
+function truncatePreviewText(text: string, maxChars: number): string {
+  if (maxChars <= 0 || text.length <= maxChars) return text;
+  if (maxChars <= 3) return text.slice(0, maxChars);
+  return `${text.slice(0, maxChars - 3)}...`;
+}
+
+function extractPreviewText(message: TranscriptPreviewMessage): string | null {
+  if (typeof message.content === "string") {
+    const trimmed = message.content.trim();
+    return trimmed ? trimmed : null;
+  }
+  if (Array.isArray(message.content)) {
+    const parts = message.content
+      .map((entry) => (typeof entry?.text === "string" ? entry.text : ""))
+      .filter((text) => text.trim().length > 0);
+    if (parts.length > 0) {
+      return parts.join("\n").trim();
+    }
+  }
+  if (typeof message.text === "string") {
+    const trimmed = message.text.trim();
+    return trimmed ? trimmed : null;
+  }
+  return null;
+}
+
+function isToolCall(message: TranscriptPreviewMessage): boolean {
+  if (message.toolName || message.tool_name) return true;
+  if (!Array.isArray(message.content)) return false;
+  return message.content.some((entry) => {
+    if (entry?.name) return true;
+    const raw = typeof entry?.type === "string" ? entry.type.toLowerCase() : "";
+    return raw === "toolcall" || raw === "tool_call";
+  });
+}
+
+function extractToolNames(message: TranscriptPreviewMessage): string[] {
+  const names: string[] = [];
+  if (Array.isArray(message.content)) {
+    for (const entry of message.content) {
+      if (typeof entry?.name === "string" && entry.name.trim()) {
+        names.push(entry.name.trim());
+      }
+    }
+  }
+  const toolName = typeof message.toolName === "string" ? message.toolName : message.tool_name;
+  if (typeof toolName === "string" && toolName.trim()) {
+    names.push(toolName.trim());
+  }
+  return names;
+}
+
+function extractMediaSummary(message: TranscriptPreviewMessage): string | null {
+  if (!Array.isArray(message.content)) return null;
+  for (const entry of message.content) {
+    const raw = typeof entry?.type === "string" ? entry.type.trim().toLowerCase() : "";
+    if (!raw || raw === "text" || raw === "toolcall" || raw === "tool_call") continue;
+    return `[${raw}]`;
+  }
+  return null;
+}
+
+function buildPreviewItems(
+  messages: TranscriptPreviewMessage[],
+  maxItems: number,
+  maxChars: number,
+): SessionPreviewItem[] {
+  const items: SessionPreviewItem[] = [];
+  for (const message of messages) {
+    const toolCall = isToolCall(message);
+    const role = normalizeRole(message.role, toolCall);
+    let text = extractPreviewText(message);
+    if (!text) {
+      const toolNames = extractToolNames(message);
+      if (toolNames.length > 0) {
+        const shown = toolNames.slice(0, 2);
+        const overflow = toolNames.length - shown.length;
+        text = `call ${shown.join(", ")}`;
+        if (overflow > 0) text += ` +${overflow}`;
+      }
+    }
+    if (!text) {
+      text = extractMediaSummary(message);
+    }
+    if (!text) continue;
+    let trimmed = text.trim();
+    if (!trimmed) continue;
+    if (role === "user") {
+      trimmed = stripEnvelope(trimmed);
+    }
+    trimmed = truncatePreviewText(trimmed, maxChars);
+    items.push({ role, text: trimmed });
+  }
+
+  if (items.length <= maxItems) return items;
+  return items.slice(-maxItems);
+}
+
+function readRecentMessagesFromTranscript(
+  filePath: string,
+  maxMessages: number,
+  readBytes: number,
+): TranscriptPreviewMessage[] {
+  let fd: number | null = null;
+  try {
+    fd = fs.openSync(filePath, "r");
+    const stat = fs.fstatSync(fd);
+    const size = stat.size;
+    if (size === 0) return [];
+
+    const readStart = Math.max(0, size - readBytes);
+    const readLen = Math.min(size, readBytes);
+    const buf = Buffer.alloc(readLen);
+    fs.readSync(fd, buf, 0, readLen, readStart);
+
+    const chunk = buf.toString("utf-8");
+    const lines = chunk.split(/\r?\n/).filter((l) => l.trim());
+    const tailLines = lines.slice(-PREVIEW_MAX_LINES);
+
+    const collected: TranscriptPreviewMessage[] = [];
+    for (let i = tailLines.length - 1; i >= 0; i--) {
+      const line = tailLines[i];
+      try {
+        const parsed = JSON.parse(line);
+        const msg = parsed?.message as TranscriptPreviewMessage | undefined;
+        if (msg && typeof msg === "object") {
+          collected.push(msg);
+          if (collected.length >= maxMessages) break;
+        }
+      } catch {
+        // skip malformed lines
+      }
+    }
+    return collected.reverse();
+  } catch {
+    return [];
+  } finally {
+    if (fd !== null) fs.closeSync(fd);
+  }
+}
+
+export function readSessionPreviewItemsFromTranscript(
+  sessionId: string,
+  storePath: string | undefined,
+  sessionFile: string | undefined,
+  agentId: string | undefined,
+  maxItems: number,
+  maxChars: number,
+): SessionPreviewItem[] {
+  const candidates = resolveSessionTranscriptCandidates(sessionId, storePath, sessionFile, agentId);
+  const filePath = candidates.find((p) => fs.existsSync(p));
+  if (!filePath) return [];
+
+  const boundedItems = Math.max(1, Math.min(maxItems, 50));
+  const boundedChars = Math.max(20, Math.min(maxChars, 2000));
+
+  for (const readSize of PREVIEW_READ_SIZES) {
+    const messages = readRecentMessagesFromTranscript(filePath, boundedItems, readSize);
+    if (messages.length > 0 || readSize === PREVIEW_READ_SIZES[PREVIEW_READ_SIZES.length - 1]) {
+      return buildPreviewItems(messages, boundedItems, boundedChars);
+    }
+  }
+
+  return [];
+}