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export type SiteHostMatch =
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  | { kind: "subdomain"; slug: string; baseDomain: string }
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  | { kind: "apex"; baseDomain: string }
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  | { kind: "none" };
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export function matchSiteHost(url: URL, env: Pick<Env, "PUBLISHED_SITE_DOMAIN">): SiteHostMatch {
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  const baseDomain = env.PUBLISHED_SITE_DOMAIN?.trim().toLowerCase();
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  if (!baseDomain) return { kind: "none" };
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  const host = url.hostname.toLowerCase();
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  if (host === baseDomain) return { kind: "apex", baseDomain };
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  const suffix = "." + baseDomain;
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  if (host.endsWith(suffix)) {
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    const slug = host.slice(0, host.length - suffix.length);
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    // Reject multi-label subdomains (e.g. foo.bar.bland.site). Sites carve out
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    // exactly one label under the base domain in v1.
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    if (slug.length > 0 && !slug.includes(".")) {
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      return { kind: "subdomain", slug, baseDomain };
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    }
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  }
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  return { kind: "none" };
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}