import { useCallback } from 'react';
import { useLocalStorage } from '@/hooks/useLocalStorage';
import { useCurrentUser } from '@/hooks/useCurrentUser';

/**
 * Per-conversation "last read" timestamps (unix seconds) for direct messages,
 * stored per-pubkey in localStorage. A conversation counts as unread when its
 * latest message (from the OTHER person) is newer than this timestamp.
 *
 * Local-only by design: this is a lightweight "have I seen it" convenience, not
 * a synced read-receipt broadcast to anyone. Nothing here leaves the device.
 *
 * NIP-17 note: gift-wrapped DMs are decrypted client-side, so we compare against
 * the message's own `created_at`. (Gift-wrap timestamps can be slightly fuzzed,
 * but the inner rumor's `created_at` — what we store on DirectMessage — is the
 * sender's real time, so this comparison is reliable for read state.)
 */
export function useDMRead() {
  const { user } = useCurrentUser();
  const key = user ? `dm-last-read:${user.pubkey}` : 'dm-last-read:anon';
  const [map, setMap] = useLocalStorage<Record<string, number>>(key, {});

  /** Mark a conversation (keyed by the other party's pubkey) read as of `ts`. */
  const markRead = useCallback(
    (conversationWith: string, ts?: number) => {
      const at = ts ?? Math.floor(Date.now() / 1000);
      setMap((prev) => {
        const key = conversationWith.toLowerCase();
        if ((prev[key] ?? 0) >= at) return prev; // never move backwards
        return { ...prev, [key]: at };
      });
    },
    [setMap],
  );

  /** Last-read unix seconds for a conversation, or 0 if never opened. */
  const getLastRead = useCallback(
    (conversationWith: string) => map[conversationWith.toLowerCase()] ?? 0,
    [map],
  );

  return { lastReadMap: map, markRead, getLastRead };
}