// In-memory cache of the most-recently-rendered messages for each
// conversation. Survives React component unmount/remount (used by
// `useConversationMessages` to initialize state synchronously when
// ConversationPage is remounted on chat switch). Session-scoped — lost
// on full app reload. The SQLite cache (`messageCache.ts`) is still the
// source of truth for cross-session persistence; this layer just shaves
// off the round-trip-to-disk spinner flash.
//
// Two-tier semantics:
//   * `hasCachedMessages(id)` returns true even for a known-empty chat
//     so the hook can suppress the loading spinner on re-entry.
//   * `getCachedMessages(id)` returns a defensive copy so callers can't
//     mutate the cached array.

import type { DecryptedMessage } from '@chat-app/shared/chat';

const cache = new Map<string, DecryptedMessage[]>();

export function getCachedMessages(conversationId: string): DecryptedMessage[] {
  const stored = cache.get(conversationId);
  return stored ? stored.slice() : [];
}

export function hasCachedMessages(conversationId: string): boolean {
  return cache.has(conversationId);
}

export function setCachedMessages(
  conversationId: string,
  messages: DecryptedMessage[],
): void {
  cache.set(conversationId, messages.slice());
}

export function __resetForTests(): void {
  cache.clear();
}