[Init] Initial commit - NetMesh terminal manager

domain/chatJumpNav.ts

@@ -0,0 +1,72 @@
+/**
+ * Pure helpers for AI chat in-session jump navigation (user-turn TOC).
+ */
+
+export const CHAT_JUMP_MIN_ENTRIES = 3;
+export const CHAT_JUMP_LABEL_MAX = 36;
+
+export type ChatJumpMessage = {
+  id: string;
+  role: string;
+  content?: string;
+};
+
+export type ChatJumpEntry = {
+  messageId: string;
+  label: string;
+  /** 1-based index among user turns */
+  index: number;
+};
+
+export function chatMessageDomId(messageId: string): string {
+  return `ai-chat-msg-${messageId}`;
+}
+
+export function truncateChatJumpLabel(text: string, maxLen = CHAT_JUMP_LABEL_MAX): string {
+  const normalized = text.replace(/\s+/g, ' ').trim();
+  if (!normalized) return '';
+  if (normalized.length <= maxLen) return normalized;
+  const ellipsis = '...';
+  return `${normalized.slice(0, Math.max(1, maxLen - ellipsis.length)).trimEnd()}${ellipsis}`;
+}
+
+export function buildChatJumpEntries(
+  messages: ReadonlyArray<ChatJumpMessage>,
+  options?: {
+    minEntries?: number;
+    maxLabelLen?: number;
+    emptyLabel?: string;
+  },
+): ChatJumpEntry[] {
+  const minEntries = options?.minEntries ?? CHAT_JUMP_MIN_ENTRIES;
+  const maxLabelLen = options?.maxLabelLen ?? CHAT_JUMP_LABEL_MAX;
+  const emptyLabel = options?.emptyLabel ?? '...';
+  const entries: ChatJumpEntry[] = [];
+  for (const message of messages) {
+    if (message.role !== 'user') continue;
+    const label = truncateChatJumpLabel(message.content ?? '', maxLabelLen) || emptyLabel;
+    entries.push({
+      messageId: message.id,
+      label,
+      index: entries.length + 1,
+    });
+  }
+  return entries.length >= minEntries ? entries : [];
+}
+
+/**
+ * Expand the rendered tail window so a jump target is mounted in the DOM.
+ * Call again whenever the message list grows while the jump target remains
+ * active; a one-shot expand at jump time is not enough if the tail is
+ * `slice(-count)` and later appends would otherwise slide the window forward.
+ */
+export function resolveTailCountForJumpTarget(
+  visibleMessages: ReadonlyArray<{ id: string }>,
+  targetMessageId: string,
+  currentTailCount: number,
+): number {
+  const targetIndex = visibleMessages.findIndex((message) => message.id === targetMessageId);
+  if (targetIndex < 0) return currentTailCount;
+  const requiredTail = visibleMessages.length - targetIndex;
+  return Math.max(currentTailCount, requiredTail);
+}