import { useFluent_unstable as useFluent } from '@fluentui/react-shared-contexts';
import { createPriorityQueue, useTimeout } from '@fluentui/react-utilities';
import * as React from 'react';
/** The duration the message needs to be in present in DOM for screen readers to register a change and announce */ const MESSAGE_DURATION = 500;
const VISUALLY_HIDDEN_STYLES = {
    clip: 'rect(0px, 0px, 0px, 0px)',
    height: '1px',
    margin: '-1px',
    width: '1px',
    position: 'absolute',
    overflow: 'hidden',
    textWrap: 'nowrap'
};
/* INTERNAL: implementation of the announcer using a live region element */ export const useDomAnnounce_unstable = ()=>{
    const { targetDocument } = useFluent();
    const timeoutRef = React.useRef(undefined);
    const [setAnnounceTimeout, clearAnnounceTimeout] = useTimeout();
    const elementRef = React.useRef(null);
    const order = React.useRef(0);
    // investigate alert implementation later
    // const [alertList, setAlertList] = React.useState<string[]>([]);
    const batchMessages = React.useRef([]);
    const [messageQueue] = React.useState(()=>createPriorityQueue((a, b)=>{
            if (a.priority !== b.priority) {
                return b.priority - a.priority;
            }
            return a.createdAt - b.createdAt;
        }));
    const queueMessage = React.useCallback(()=>{
        if (timeoutRef.current || !elementRef.current) {
            return;
        }
        const runCycle = ()=>{
            if (!elementRef.current) {
                return;
            }
            if (targetDocument && messageQueue.peek()) {
                // need a wrapping element for Narrator/Edge, which currently does not pick up text-only live region changes
                // consistently
                // if this is fixed, we can set textContent to the string directly
                const wrappingEl = targetDocument.createElement('span');
                wrappingEl.innerText = messageQueue.all().filter((msg)=>msg.message.trim().length > 0).reduce((prevText, currMsg)=>prevText + currMsg.message + '. ', '');
                elementRef.current.innerText = '';
                elementRef.current.appendChild(wrappingEl);
                messageQueue.clear();
                batchMessages.current = [];
                // begin new cycle to clear (or update) messages
                timeoutRef.current = setAnnounceTimeout(()=>{
                    runCycle();
                }, MESSAGE_DURATION);
            } else {
                elementRef.current.textContent = '';
                clearAnnounceTimeout();
                timeoutRef.current = undefined;
            }
        };
        runCycle();
    }, [
        clearAnnounceTimeout,
        messageQueue,
        setAnnounceTimeout,
        targetDocument
    ]);
    const announce = React.useCallback((message, options = {})=>{
        const { alert = false, priority = 0, batchId } = options;
        // check if message is an alert
        if (alert) {
        // TODO: alert implementation
        // setAlertList([...alertList, message]);
        }
        const liveMessage = {
            message,
            createdAt: order.current++,
            priority,
            batchId
        };
        // check if batchId exists
        if (batchId) {
            // update associated msg if it does
            const batchMessage = batchMessages.current.find((msg)=>msg.batchId === batchId);
            if (batchMessage) {
                // replace existing message in queue
                messageQueue.remove(batchMessage.message);
                // update list of existing batchIds w/ most recent message
                batchMessage.message = liveMessage;
            } else {
                // update list of existing batchIds, add new if doesn't already exist
                batchMessages.current = [
                    ...batchMessages.current,
                    {
                        batchId,
                        message: liveMessage
                    }
                ];
            }
        }
        // add new message
        messageQueue.enqueue(liveMessage);
        queueMessage();
    }, [
        messageQueue,
        queueMessage
    ]);
    React.useEffect(()=>{
        if (!targetDocument) {
            return;
        }
        const element = targetDocument.createElement('div');
        element.setAttribute('aria-live', 'assertive');
        Object.assign(element.style, VISUALLY_HIDDEN_STYLES);
        targetDocument.body.append(element);
        elementRef.current = element;
        return ()=>{
            element.remove();
            elementRef.current = null;
            clearAnnounceTimeout();
            timeoutRef.current = undefined;
        };
    }, [
        clearAnnounceTimeout,
        targetDocument
    ]);
    return announce;
};