import { List } from '../models/List';
import { Utterance } from './textToSpeech/Utterance';
type TextToSpeechStatusType = 'speaking' | 'paused' | 'cancelled' | 'idle';
/**
 * A class that represents a text to speech synthesizer
 * It is a wrapper around the SpeechSynthesis class, that handles multiple utterances
 */
export declare class TextToSpeech {
    synthesizer: SpeechSynthesis | null;
    selectedVoiceIndex: number;
    utterances: List<Utterance>;
    currentUtterance: Utterance | null;
    textToSpeak: string | null;
    status: TextToSpeechStatusType;
    constructor();
    get voiceList(): SpeechSynthesisVoice[] | undefined;
    get voices(): {
        label: string;
        value: number;
        details: SpeechSynthesisVoice;
    }[];
    setSelectedVoiceIndex: (voiceIndex: number) => void;
    private init;
    /**
     * This method will immediately pause any utterances that are being spoken.
     */
    pause: () => void;
    /**
     * This method will cause the browser to resume speaking an
     * utterance that was previously paused.
     */
    resume: () => void;
    /**
     * This method will immediately stop any utterances
     * that are being spoken
     */
    cancel: () => void;
    /**
     * Helper method to set a status so the status is observable
     * @param status the status to set
     */
    private setStatus;
    /**
     * Speaks the text passed in as an argument or the textToSpeak property.
     * If there is a current utterance, it will be cancelled and a new one
     * will be created. If it speaking, it will be ignored.
     * If an id is passed, it will be used to identify the utterance and speak that utterance.
     * @param text the text to speak
     */
    speak: (text?: string, id?: string) => void;
    private speakUtteranceId;
    private speakUtterance;
    restart: (utteranceId: string) => void;
    setCurrentUtterance: (utterance: Utterance) => void;
    /**
     * Method to initialize an utterance.
     * If the utterance already exists it sets it as the current utterance.
     * If it doesn't exist, it creates a new utterance and sets it as the current utterance.
     * @param {string} id the id of the utterance, must be unique
     */
    initUtterance: (id: string) => void;
    /**
     * Method to set the rate of the utterance.
     * When setting the rate, unfortunately, the speech synthesis API
     * does not allow us to set the rate of an utterance on the fly. So we
     * have to cancel the current utterance and create a new one with the new rate.
     */
    setRate: (id: string, rate: number) => void;
    /**
     * A method that sets the voice of the speech synthesis.
     * When setting a different voice, unfortunately, the speech synthesis API
     * does not allow us to set the voice of an utterance on the fly. So we
     * have to cancel the current utterance and create a new one with the new
     * voice.
     */
    setVoice: (id: string, voice: SpeechSynthesisVoice) => void;
    /**
     * Method to create a new utterance and add it to the list of utterances.
     * In addition, it also sets the current utterance to the newly created one.
     * It is used privately
     * @param id
     * @param text
     * @param options
     * @returns
     */
    private createUtterance;
    setTextToSpeak: (text: string) => void;
}
export declare const textToSpeech: TextToSpeech;
export {};