feat(web): add current-thread atom for global state management

surfsense_web/atoms/chat/current-thread.atom.ts

@@ -0,0 +1,52 @@
+import { atom } from "jotai";
+import type { ChatVisibility } from "@/lib/chat/thread-persistence";
+
+// TODO: Update `hasComments` to true when the first comment is created on a thread.
+// Currently it only updates on thread load. The gutter still works because
+// `addingCommentToMessageId` keeps it open, but the state is technically stale.
+
+// TODO: Reset `addingCommentToMessageId` to null after a comment is successfully created.
+// Currently it stays set until navigation or clicking another message's bubble.
+// Not causing issues since panel visibility is driven by per-message comment count.
+
+// TODO: Consider calling `resetCurrentThreadAtom` when unmounting the chat page
+// for explicit cleanup, though React navigation handles this implicitly.
+
+interface CurrentThreadState {
+	id: number | null;
+	visibility: ChatVisibility | null;
+	hasComments: boolean;
+	addingCommentToMessageId: number | null;
+}
+
+const initialState: CurrentThreadState = {
+	id: null,
+	visibility: null,
+	hasComments: false,
+	addingCommentToMessageId: null,
+};
+
+export const currentThreadAtom = atom<CurrentThreadState>(initialState);
+
+export const commentsEnabledAtom = atom(
+	(get) => get(currentThreadAtom).visibility === "SEARCH_SPACE"
+);
+
+export const showCommentsGutterAtom = atom((get) => {
+	const thread = get(currentThreadAtom);
+	return (
+		thread.visibility === "SEARCH_SPACE" &&
+		(thread.hasComments || thread.addingCommentToMessageId !== null)
+	);
+});
+
+export const addingCommentToMessageIdAtom = atom(
+	(get) => get(currentThreadAtom).addingCommentToMessageId,
+	(get, set, messageId: number | null) => {
+		set(currentThreadAtom, { ...get(currentThreadAtom), addingCommentToMessageId: messageId });
+	}
+);
+
+export const resetCurrentThreadAtom = atom(null, (_, set) => {
+	set(currentThreadAtom, initialState);
+});