/**
 * Determine whether a platform ID needs a channel-type prefix.
 *
 * Chat SDK adapters (Telegram, Discord, Slack, Teams, etc.) namespace their
 * platform IDs with a channel prefix: "telegram:123456", "discord:guild:chan".
 * The router stores channel_type and platform_id in separate columns, but
 * Chat SDK adapters send the prefixed form as the platform_id — so any code
 * that writes messaging_groups rows must produce the same shape the adapter
 * will later emit as event.platformId, or router lookups miss and messages
 * get silently dropped.
 *
 * Native adapters (Signal, WhatsApp, iMessage) use their own ID formats and
 * send them as-is — no channel prefix. WhatsApp/iMessage emit JIDs/emails
 * containing '@'. Signal emits raw phone numbers ('+15551234567') for DMs
 * and 'group:<id>' for group chats. Prefixing any of these would cause a
 * mismatch with what the adapter later emits.
 */
export function namespacedPlatformId(channel: string, raw: string): string {
  if (raw.startsWith(`${channel}:`)) return raw;
  if (raw.includes('@')) return raw;
  if (raw.startsWith('+') || raw.startsWith('group:')) return raw;
  return `${channel}:${raw}`;
}