const NAME_CONTROL_CHARACTERS = /[\u0000-\u001f\u007f]/;
const TEXT_CONTROL_CHARACTERS = /[\u0000-\u0008\u000b\u000c\u000e-\u001f\u007f]/;

export function validateGroupDetails(nameValue: unknown, descriptionValue: unknown) {
  const name = String(nameValue ?? "").trim();
  const description = String(descriptionValue ?? "").trim();
  if (
    name.length < 1 ||
    name.length > 50 ||
    NAME_CONTROL_CHARACTERS.test(name) ||
    description.length > 500 ||
    TEXT_CONTROL_CHARACTERS.test(description)
  ) return null;
  return { name, description };
}

export function adminGroupReturnPath(
  value: unknown,
  result: "saved=group" | "error=invalid-group-assignment",
) {
  const requested = String(value ?? "");
  let pathname = "/admin/users";
  const parameters = new URLSearchParams();
  if (requested.startsWith("/")) {
    const url = new URL(requested, "http://internal");
    if (url.pathname === "/admin/users") {
      const search = url.searchParams.get("q")?.trim().slice(0, 100);
      if (search) parameters.set("q", search);
    } else if (/^\/admin\/groups\/[0-9a-f-]{36}$/i.test(url.pathname)) {
      pathname = url.pathname;
    }
  }
  const [key, resultValue] = result.split("=", 2) as ["saved" | "error", string];
  parameters.set(key, resultValue);
  return `${pathname}?${parameters.toString()}`;
}

export function editableGroupName(currentName: string, isDefault: boolean, requestedName: string) {
  return isDefault ? currentName : requestedName;
}

export function effectiveGroupMemberCount(
  totalUsers: number,
  assignedGroupIds: string[],
  group: { id: string; isDefault: boolean },
) {
  return group.isDefault
    ? Math.max(0, totalUsers - assignedGroupIds.length)
    : assignedGroupIds.filter((groupId) => groupId === group.id).length;
}

export function isEffectiveGroupMember(
  userId: string,
  assignmentByUser: Record<string, string>,
  group: { id: string; isDefault: boolean },
) {
  return group.isDefault ? !assignmentByUser[userId] : assignmentByUser[userId] === group.id;
}

export function groupSlug(name: string, existingSlugs: Set<string>) {
  const normalized = name
    .normalize("NFKD")
    .replace(/[\u0300-\u036f]/g, "")
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "") || "group";
  const base = normalized.slice(0, 50).replace(/-+$/g, "") || "group";
  if (!existingSlugs.has(base)) return base;
  for (let suffix = 2; suffix < 10_000; suffix += 1) {
    const suffixText = `-${suffix}`;
    const candidate = `${base.slice(0, 50 - suffixText.length).replace(/-+$/g, "")}${suffixText}`;
    if (!existingSlugs.has(candidate)) return candidate;
  }
  throw new Error("Could not generate a unique group slug");
}