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import type { SiteDocumentAssets } from "@/sites/types";
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type PreloadKind = "script" | "style";
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function createPreloadLinkHeaderValue(href: string, kind: PreloadKind): string {
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  return `<${href}>; rel=preload; as=${kind}`;
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}
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function withSitesPreloadHeaders(
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  headersInit: HeadersInit,
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  assets: SiteDocumentAssets,
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  scriptHrefs: readonly string[],
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): Record<string, string> {
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  const headers = new Headers(headersInit);
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  const seen = new Set<string>();
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  function append(href: string | null | undefined, kind: PreloadKind): void {
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    if (!href) return;
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    const value = createPreloadLinkHeaderValue(href, kind);
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    if (seen.has(value)) return;
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    seen.add(value);
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    headers.append("Link", value);
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  }
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  append(assets.stylesheetHref, "style");
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  append(assets.fontStylesheetHref, "style");
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  for (const href of scriptHrefs) append(href, "script");
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  return Object.fromEntries(headers.entries());
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}
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export function withSitesStaticDocumentPreloadHeaders(
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  headersInit: HeadersInit,
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  assets: SiteDocumentAssets,
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): Record<string, string> {
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  return withSitesPreloadHeaders(headersInit, assets, []);
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}
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export function withSitesPageDocumentPreloadHeaders(
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  headersInit: HeadersInit,
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  assets: SiteDocumentAssets,
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): Record<string, string> {
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  return withSitesPreloadHeaders(headersInit, assets, [
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    ...(assets.scriptSrc ? [assets.scriptSrc] : []),
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    ...assets.modulePreloadHrefs,
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  ]);
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}