/**
 * The language the user is TALKING TO the assistant in (BOFF-7108).
 *
 * Separate from the app locale on purpose. A farmer whose phone and UI are in
 * English may well speak Tamil, and until now the only way to dictate Tamil was
 * to translate the entire interface — the recogniser language was derived from
 * `useI18n().locale`, so the two could not be chosen independently.
 *
 * One selection drives three things, which is the point:
 *   1. `recognition.lang` — what the recogniser is listening for;
 *   2. the reply-language directive — what the model answers in;
 *   3. the voice for reading that reply aloud.
 *
 * Deliberately NOT keyed on the app `Locale` union. That union is the set of
 * languages the INTERFACE is translated into (9, from fe-libs); this is the set
 * of languages a user might SPEAK, which is larger and grows for different
 * reasons. Tying them together is what created the problem.
 */
export interface AssistantLanguage {
    /** Primary subtag. What we persist, and what the speech-locale helpers take. */
    code: string;
    /** BCP-47 tag handed to the Web Speech APIs — region matters to acoustic models. */
    tag: string;
    /**
     * The ENDONYM — what a speaker calls their own language. Someone who reads
     * only Tamil cannot find "Tamil" in a list; they can find "தமிழ்".
     */
    label: string;
    /**
     * English name, for the model-facing directive.
     *
     * Hardcoded rather than derived from `Intl.DisplayNames` because this string
     * goes into a prompt: it must be stable and correct regardless of the reader's
     * browser, and a missing `Intl` implementation must not silently degrade an
     * instruction into a bare subtag the model may answer *about* instead of *in*.
     */
    english: string;
    /**
     * Speaking rate for this language, 1 = the engine's default.
     *
     * Nothing set a rate at all until now, so every user heard the spec default of
     * 1.0 — reported as "it reads fast", which it is: a synthesised voice at 1.0 is
     * harder to follow than a person at the same nominal speed, and harder again
     * when the listener is outdoors or hearing a second language.
     *
     * Indic and Arabic get a further reduction. Their scripts pack more syllables
     * per character than Latin, so the same nominal rate delivers noticeably more
     * speech per second.
     */
    rate?: number;
}
/** Applied when a language does not override it. */
export declare const DEFAULT_SPEECH_RATE = 0.9;
/**
 * India first and by speaker count, then the other app locales.
 *
 * Regions follow where HealthyBowl operates: `-IN` for the Indic languages,
 * because a recogniser tuned for `ur-PK` or a voice for `bn-BD` is the wrong
 * pronunciation model for this product's users.
 */
export declare const ASSISTANT_LANGUAGES: readonly AssistantLanguage[];
export declare function findAssistantLanguage(code: string | null | undefined): AssistantLanguage | null;
/**
 * Which language to use: the user's explicit choice, else the app locale, else
 * English.
 *
 * The app-locale step is what keeps this backwards-compatible — a user who never
 * touches the new control behaves exactly as before, because the value derived
 * is the one the old code derived. An app locale outside this list (or a stale
 * persisted code from a build that offered more) degrades to English rather than
 * handing the recogniser a tag it will reject.
 */
export declare function resolveAssistantLanguage(selectedCode: string | null | undefined, appLocale: string): AssistantLanguage;
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