import assert from "node:assert/strict";
import test from "node:test";
import type { ExtensionContext, SessionEntry } from "@earendil-works/pi-coding-agent";
import { onLiveBranch } from "../src/liveness.ts";

const STALE = "This extension ctx is stale after session replacement or reload.";

const entry = (id: string): SessionEntry =>
	({
		type: "custom",
		id,
		parentId: null,
		timestamp: "2026-09-12T00:00:00.000Z",
		customType: "unrelated",
		data: {},
	}) as SessionEntry;

const context = (branch: SessionEntry[] | (() => never)): ExtensionContext =>
	({
		get sessionManager() {
			return typeof branch === "function"
				? {
						getBranch: branch,
					}
				: { getBranch: () => branch };
		},
	}) as unknown as ExtensionContext;

test("a boundary still on the branch is live", () => {
	assert.equal(onLiveBranch(context([entry("a"), entry("b")]), "a"), true);
});

test("a boundary that left the branch is not live", () => {
	assert.equal(onLiveBranch(context([entry("a")]), "b"), false);
});

test("a replaced session is not a live branch and does not throw", () => {
	const replaced = context(() => {
		throw new Error(STALE);
	});

	assert.equal(onLiveBranch(replaced, "a"), false);
	assert.equal(onLiveBranch(replaced, null), false);
});