import type { StoredMessage } from 'tinode-sdk';

/**
 * Two different "message is gone" protocol paths render differently (confirmed against the old
 * app's chat-message.jsx, a real, previously-hit gap): `msg.hi` is the server's own soft-delete
 * marker (renders as a centered system-style line, no bubble at all); Tinode's recall protocol
 * instead nulls out `content` on an otherwise-normal message (still a regular aligned bubble, just
 * with placeholder text). Getting these swapped either crashes on a null content or silently
 * misrenders a recalled message as a deleted-system-line.
 */
export function isServerDeleted(msg: StoredMessage): boolean {
  return !!(msg as StoredMessage & { hi?: boolean }).hi;
}

export function isRecalled(msg: StoredMessage): boolean {
  return !isServerDeleted(msg) && msg.content == null;
}

interface SystemNoticeContent {
  text: string;
}

function isSystemNoticeContent(content: unknown): content is SystemNoticeContent {
  return !!content && typeof content === 'object' && typeof (content as SystemNoticeContent).text === 'string';
}

/**
 * Plain centered system-event text (e.g. "你们已成为好友，现在可以开始聊天了") -- backend-custom
 * `head['x-im-type']`, not a Drafty content type. Doesn't yet cover the actionable group-invitation
 * card variant (same head type, but with a real join button) since that's group-chat territory
 * (Phase 3); when that lands it needs to be excluded here the same way the old app excludes it.
 */
export function systemNoticeText(msg: StoredMessage): string | null {
  const headType = msg.head?.['x-im-type'];
  if (headType !== 'system_notice' && headType !== 'system_action') return null;
  return isSystemNoticeContent(msg.content) ? msg.content.text : null;
}