/**
 * The embed vocabulary both sides of the wire spell.
 *
 * Its own importless module for the reason `cacheTags.ts` and `queryKeys.ts` are: the validation
 * beside it needs Zod, and `pure.ts` re-exports this so `<TaprootEmbed>` can clamp a height and read
 * a sizing mode without a consumer's bundle growing a schema library it cannot use.
 *
 * Nothing here imports anything, which is the property that makes it safe to publish.
 */
/** One embed's stored value. An address and the frame's accessible name — never markup. */
export interface EmbedValue {
    url: string;
    title: string;
}
/**
 * How an embed's frame gets its height.
 *
 * Three modes rather than one aspect ratio, because a ratio describes exactly one of the three
 * things people embed. A video is 16:9 forever and a map is whatever box you give it; a **form** is
 * 400px until somebody trips validation and then it is 900px, and no ratio says that.
 */
export declare const EMBED_SIZING_MODES: readonly ["ratio", "fixed", "auto"];
export type EmbedSizingMode = (typeof EMBED_SIZING_MODES)[number];
export type EmbedSizing = 
/** An `aspect-ratio` box. The default, and the only mode needing no JavaScript at all. */
{
    mode: 'ratio';
    ratio: number;
}
/** A stated pixel height. Covers more forms than it looks like it would. */
 | {
    mode: 'fixed';
    height: number;
}
/**
 * The frame reports its own height by `postMessage`; `minHeight` is what it stands at until one
 * arrives, and what it keeps if none ever does. Not zero — an invisible form is the failure
 * everybody ships.
 */
 | {
    mode: 'auto';
    minHeight: number;
};
/** 16:9. Every video platform's default, and why `ratio` is the default mode. */
export declare const DEFAULT_EMBED_RATIO: number;
/**
 * A ceiling on any height, stated or reported, in CSS pixels.
 *
 * Not a design opinion — a bound on what the system will carry, in the sense `requireComplete`
 * leaves alone. It stops a typo producing a frame taller than any device, and gives the message
 * handler a number to clamp against: a height arrives from another origin, so it is input.
 */
export declare const MAX_EMBED_HEIGHT = 5000;
/**
 * Whether a host is covered by a field's allowlist.
 *
 * An entry covers itself and everything under it, so `youtube.com` admits `www.youtube.com` — which
 * is what an admin typing a domain into a box means, and it avoids teaching a wildcard syntax for
 * the only case anybody needs. Three details are load-bearing:
 *
 * - The suffix test is `.${allowed}` **with the dot**. `endsWith(allowed)` would admit
 *   `evil-youtube.com`, which is the entire attack this list exists to stop.
 * - A trailing dot is stripped. `youtube.com.` is the same host to a browser and would otherwise
 *   match no entry, so an allowlist could be walked past by typing one character.
 * - A leading `*.` is stripped rather than rejected, because an admin who writes `*.youtube.com`
 *   out of habit has said exactly what this already does and should not be answered with nothing.
 */
export declare function embedHostAllowed(host: string, allowedHosts: readonly string[]): boolean;
/**
 * Read a height out of a `postMessage` payload, for `sizing.mode === 'auto'`.
 *
 * **There is no standard here, and this function is a convenience rather than a contract.**
 * iframe-resizer posts a colon-delimited string, several vendors post `{ height }`, some post a bare
 * number, and whoever built a given form posted whatever they felt like. Taproot cannot know which,
 * so `<TaprootEmbed>` takes a `parseHeight` prop and this is only what it falls back to — the same
 * split as `resolveMenu`'s `termHref` callback, and for the same reason: the CMS supplies what it
 * can know and the site supplies what only it knows.
 *
 * Returns `null` for anything it cannot read, and **null must leave the frame at its current
 * height**. Guessing zero would collapse a working embed the first time a page posted an unrelated
 * message, and pages post unrelated messages constantly.
 */
export declare function parseEmbedHeight(payload: unknown): number | null;