feat: sessions api, view & resume prev sessions (#1453)

* Centralize session files to goose::session module
* Write session metadata and messages in jsonl
* Refactor CLI build_session to use goose::session functions
* Track session's token usage by adding optional session_id in agent.reply(...)
* NOTE: Only sessions saved through the updates goose::session functions will show up in GUI

Co-authored-by: Bradley Axen <baxen@squareup.com>

ui/desktop/src/sessions.ts

@@ -0,0 +1,110 @@
+import { getApiUrl, getSecretKey } from './config';
+
+export interface SessionMetadata {
+  description: string;
+  message_count: number;
+  total_tokens: number | null;
+}
+
+export interface Session {
+  id: string;
+  path: string;
+  modified: string;
+  metadata: SessionMetadata;
+}
+
+export interface SessionsResponse {
+  sessions: Session[];
+}
+
+export interface SessionMessage {
+  role: 'user' | 'assistant';
+  created: number;
+  content: {
+    type: string;
+    text: string;
+  }[];
+}
+
+export interface SessionDetails {
+  session_id: string;
+  metadata: SessionMetadata;
+  messages: SessionMessage[];
+}
+
+/**
+ * Generate a session ID in the format yyyymmdd_hhmmss
+ */
+export function generateSessionId(): string {
+  const now = new Date();
+  const year = now.getFullYear();
+  const month = String(now.getMonth() + 1).padStart(2, '0');
+  const day = String(now.getDate()).padStart(2, '0');
+  const hours = String(now.getHours()).padStart(2, '0');
+  const minutes = String(now.getMinutes()).padStart(2, '0');
+  const seconds = String(now.getSeconds()).padStart(2, '0');
+
+  return `${year}${month}${day}_${hours}${minutes}${seconds}`;
+}
+
+/**
+ * Fetches all available sessions from the API
+ * @returns Promise with sessions data
+ */
+export async function fetchSessions(): Promise<SessionsResponse> {
+  try {
+    const response = await fetch(getApiUrl('/sessions'), {
+      method: 'GET',
+      headers: {
+        'Content-Type': 'application/json',
+        'X-Secret-Key': getSecretKey(),
+      },
+    });
+
+    if (!response.ok) {
+      throw new Error(`Failed to fetch sessions: ${response.status} ${response.statusText}`);
+    }
+
+    // TODO: remove this logic once everyone migrates to the new sessions format
+    // for now, filter out sessions whose description is empty (old CLI sessions)
+    const sessions = (await response.json()).sessions.filter(
+      (session: Session) => session.metadata.description !== ''
+    );
+
+    // order sessions by 'modified' date descending
+    sessions.sort(
+      (a: Session, b: Session) => new Date(b.modified).getTime() - new Date(a.modified).getTime()
+    );
+
+    return { sessions };
+  } catch (error) {
+    console.error('Error fetching sessions:', error);
+    throw error;
+  }
+}
+
+/**
+ * Fetches details for a specific session
+ * @param sessionId The ID of the session to fetch
+ * @returns Promise with session details
+ */
+export async function fetchSessionDetails(sessionId: string): Promise<SessionDetails> {
+  try {
+    const response = await fetch(getApiUrl(`/sessions/${sessionId}`), {
+      method: 'GET',
+      headers: {
+        'Content-Type': 'application/json',
+        'X-Secret-Key': getSecretKey(),
+      },
+    });
+
+    if (!response.ok) {
+      throw new Error(`Failed to fetch session details: ${response.status} ${response.statusText}`);
+    }
+
+    return await response.json();
+  } catch (error) {
+    console.error(`Error fetching session details for ${sessionId}:`, error);
+    throw error;
+  }
+}