export type PopoReceiverType = "email" | "groupId";

/**
 * Normalize a POPO target string.
 * Supports formats:
 * - "user:email@example.com" -> "email@example.com"
 * - "group:123456" -> "123456"
 * - "email@example.com" -> "email@example.com"
 * - "123456" -> "123456"
 */
export function normalizePopoTarget(raw: string): string | null {
  const trimmed = raw.trim();
  if (!trimmed) return null;

  const lowered = trimmed.toLowerCase();
  if (lowered.startsWith("user:")) {
    return trimmed.slice("user:".length).trim() || null;
  }
  if (lowered.startsWith("group:")) {
    return trimmed.slice("group:".length).trim() || null;
  }

  return trimmed;
}

/**
 * Detect if a target is an email (P2P) or group ID.
 */
export function detectReceiverType(target: string): PopoReceiverType {
  // If it contains @ it's an email
  if (target.includes("@")) {
    return "email";
  }
  // Otherwise assume it's a group ID
  return "groupId";
}

/**
 * Format a POPO target for display.
 */
export function formatPopoTarget(id: string, type?: PopoReceiverType): string {
  const trimmed = id.trim();
  const actualType = type ?? detectReceiverType(trimmed);

  if (actualType === "email") {
    return `user:${trimmed}`;
  }
  return `group:${trimmed}`;
}

/**
 * Check if a string looks like a POPO ID.
 */
export function looksLikePopoId(raw: string): boolean {
  const trimmed = raw.trim();
  if (!trimmed) return false;

  // Has prefix
  if (/^(user|group):/i.test(trimmed)) return true;

  // Looks like an email
  if (/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(trimmed)) return true;

  // Could be a group ID (numeric string)
  if (/^\d+$/.test(trimmed)) return true;

  return false;
}