refactor(agent): isolate node filesystem session dependencies

packages/agent/src/harness/session/memory-repo.ts

@@ -0,0 +1,51 @@
+import type { Session, SessionMetadata, SessionRepo } from "../types.js";
+import { InMemorySessionStorage } from "./memory-storage.js";
+import { createSessionId, createTimestamp, getEntriesToFork, toSession } from "./repo-utils.js";
+
+export class InMemorySessionRepo implements SessionRepo<SessionMetadata, { id?: string }, void> {
+	private sessions = new Map<string, Session<SessionMetadata>>();
+
+	async create(options: { id?: string } = {}): Promise<Session<SessionMetadata>> {
+		const metadata: SessionMetadata = {
+			id: options.id ?? createSessionId(),
+			createdAt: createTimestamp(),
+		};
+		const storage = new InMemorySessionStorage({ metadata });
+		const session = toSession(storage);
+		this.sessions.set(metadata.id, session);
+		return session;
+	}
+
+	async open(metadata: SessionMetadata): Promise<Session<SessionMetadata>> {
+		const session = this.sessions.get(metadata.id);
+		if (!session) {
+			throw new Error(`Session not found: ${metadata.id}`);
+		}
+		return session;
+	}
+
+	async list(): Promise<SessionMetadata[]> {
+		return Promise.all([...this.sessions.values()].map((session) => session.getMetadata()));
+	}
+
+	async delete(metadata: SessionMetadata): Promise<void> {
+		this.sessions.delete(metadata.id);
+	}
+
+	async fork(
+		sourceMetadata: SessionMetadata,
+		options: { entryId?: string; position?: "before" | "at"; id?: string },
+	): Promise<Session<SessionMetadata>> {
+		const source = await this.open(sourceMetadata);
+		const forkedEntries = await getEntriesToFork(source.getStorage(), options);
+		const metadata: SessionMetadata = {
+			id: options.id ?? createSessionId(),
+			createdAt: createTimestamp(),
+		};
+		const leafId = forkedEntries[forkedEntries.length - 1]?.id ?? null;
+		const storage = new InMemorySessionStorage({ metadata, entries: forkedEntries, leafId });
+		const session = toSession(storage);
+		this.sessions.set(metadata.id, session);
+		return session;
+	}
+}