type MailAddressLookupCandidateLike = {
  display_name: string;
  email?: string | null;
};

export type MailAddressValue = {
  name?: string | null;
  email: string;
};

const EMAIL_PATTERN = /([^<>;,\s]+@[^<>;,\s]+)/g;

export function mailLookupSuggestions(candidates: readonly MailAddressLookupCandidateLike[]): MailAddressValue[] {
  const seen = new Set<string>();
  const suggestions: MailAddressValue[] = [];
  for (const candidate of candidates) {
    const email = String(candidate.email ?? "").trim().toLocaleLowerCase();
    if (!email || seen.has(email)) continue;
    seen.add(email);
    suggestions.push({ name: candidate.display_name || email, email });
  }
  return suggestions;
}

export function mailboxHeaderAddresses(value?: string | null): MailAddressValue[] {
  const input = String(value ?? "").trim();
  if (!input) return [];
  const results: MailAddressValue[] = [];
  const seen = new Set<string>();
  for (const match of input.matchAll(EMAIL_PATTERN)) {
    const email = match[1]?.replace(/[)>]+$/, "").toLocaleLowerCase();
    if (!email || seen.has(email)) continue;
    seen.add(email);
    const prefix = input.slice(Math.max(0, input.lastIndexOf(",", match.index) + 1), match.index).trim();
    const name = prefix.replace(/[<"']/g, "").trim() || undefined;
    results.push({ name, email });
  }
  return results;
}

export function mailtoHref(recipients: readonly MailAddressValue[]): string {
  const addresses = recipients.map((recipient) => recipient.email.trim()).filter(Boolean);
  return `mailto:${addresses.map(encodeURIComponent).join(",")}`;
}