export type UrlValidation =
  | { ok: true; url: string }
  | { ok: false; error: string };

const ALLOWED_PROTOCOLS = new Set(["http:", "https:"]);

export function normalizeUrl(raw: string): string {
  const trimmed = raw.trim();
  if (trimmed === "") return trimmed;
  if (/^[a-z][a-z0-9+.-]*:/i.test(trimmed)) return trimmed;
  return `https://${trimmed}`;
}

export function validateUrl(raw: string): UrlValidation {
  const trimmed = raw.trim();
  if (trimmed === "") return { ok: false, error: "Enter a URL" };

  const candidate = normalizeUrl(trimmed);
  let parsed: URL;
  try {
    parsed = new URL(candidate);
  } catch {
    return { ok: false, error: "That doesn't look like a URL" };
  }

  if (!ALLOWED_PROTOCOLS.has(parsed.protocol)) {
    return { ok: false, error: "Only http and https URLs are allowed" };
  }
  if (!parsed.hostname) {
    return { ok: false, error: "That doesn't look like a URL" };
  }
  return { ok: true, url: parsed.toString() };
}