import { useEffect, useId, useRef, useState } from 'react';

const SEARCH_DEBOUNCE_MS = 320;

export function AsyncCombobox({
    allowClear = true,
    ariaLabel = 'Поисковый список',
    emptyLabel = 'Ничего не найдено',
    load,
    onSelect,
    optionDescription = () => '',
    optionLabel = item => item.name,
    optionValue = item => item.id,
    placeholder = 'Начните вводить название',
    selectedLabel = '',
    selectedValue = ''
}) {
    const rootRef = useRef(null);
    const inputRef = useRef(null);
    const debounceTimer = useRef(null);
    const requestNumber = useRef(0);
    const restoringFocus = useRef(false);
    const [open, setOpen] = useState(false);
    const [query, setQuery] = useState('');
    const [items, setItems] = useState([]);
    const [loading, setLoading] = useState(false);
    const [error, setError] = useState('');
    const listId = useId();

    useEffect(() => () => {
        window.clearTimeout(debounceTimer.current);
        requestNumber.current += 1;
    }, []);

    useEffect(() => {
        if (!open) return undefined;
        const handlePointerDown = event => {
            if (rootRef.current && !rootRef.current.contains(event.target)) {
                close();
            }
        };
        document.addEventListener('pointerdown', handlePointerDown);
        return () => document.removeEventListener('pointerdown', handlePointerDown);
    });

    async function search(nextQuery) {
        const currentRequest = requestNumber.current + 1;
        requestNumber.current = currentRequest;
        setOpen(true);
        setLoading(true);
        setError('');
        try {
            const result = await load(String(nextQuery || '').trim(), selectedValue || '');
            if (requestNumber.current !== currentRequest) return;
            setItems(Array.isArray(result) ? result : []);
            setLoading(false);
        } catch {
            if (requestNumber.current !== currentRequest) return;
            setError('Не удалось выполнить поиск');
            setLoading(false);
        }
    }

    function close() {
        window.clearTimeout(debounceTimer.current);
        requestNumber.current += 1;
        setOpen(false);
        setQuery('');
        setItems([]);
        setError('');
        setLoading(false);
    }

    function choose(item) {
        onSelect(item);
        close();
        restoreInputFocus();
    }

    function restoreInputFocus() {
        restoringFocus.current = true;
        inputRef.current?.focus();
        restoringFocus.current = false;
    }

    function clear() {
        onSelect(null);
        setQuery('');
        restoreInputFocus();
        void search('');
    }

    function handleFocus() {
        if (restoringFocus.current || open) return;
        setQuery(selectedLabel);
        void search(selectedLabel);
    }

    function handleInput(event) {
        const value = event.target.value;
        setQuery(value);
        // Старый ответ не должен стать доступен во время задержки нового поиска.
        requestNumber.current += 1;
        setOpen(true);
        setItems([]);
        setLoading(true);
        setError('');
        window.clearTimeout(debounceTimer.current);
        debounceTimer.current = window.setTimeout(() => {
            void search(value);
        }, SEARCH_DEBOUNCE_MS);
    }

    function handleInputKeydown(event) {
        if (event.key === 'Escape') {
            event.preventDefault();
            close();
        } else if (event.key === 'ArrowDown') {
            event.preventDefault();
            rootRef.current?.querySelector('[role="option"]')?.focus();
        }
    }

    function handleMenuKeydown(event) {
        const options = Array.from(rootRef.current?.querySelectorAll('[role="option"]') || []);
        const current = options.indexOf(document.activeElement);
        if (event.key === 'Escape') {
            event.preventDefault();
            close();
            restoreInputFocus();
        } else if (event.key === 'ArrowDown' && current >= 0) {
            event.preventDefault();
            options[Math.min(current + 1, options.length - 1)]?.focus();
        } else if (event.key === 'ArrowUp' && current >= 0) {
            event.preventDefault();
            (current === 0 ? inputRef.current : options[current - 1])?.focus();
        }
    }

    return (
        <div
            className={`async-combobox${open ? ' is-open' : ''}`}
            ref={rootRef}
            onBlur={event => {
                if (!event.currentTarget.contains(event.relatedTarget)) close();
            }}
        >
            <div className="async-combobox-control">
                <input
                    type="search"
                    role="combobox"
                    aria-autocomplete="list"
                    aria-expanded={open}
                    aria-controls={listId}
                    aria-label={ariaLabel}
                    autoComplete="off"
                    placeholder={placeholder}
                    value={open ? query : selectedLabel}
                    onChange={handleInput}
                    onFocus={handleFocus}
                    onKeyDown={handleInputKeydown}
                    ref={inputRef}
                />
                {allowClear && (
                    <button type="button" className="async-combobox-clear" aria-label="Очистить выбор" onClick={clear}>×</button>
                )}
            </div>
            <div className="async-combobox-menu" role="listbox" id={listId} hidden={!open} onKeyDown={handleMenuKeydown}>
                {open && (
                    loading ? (
                        <div className="async-combobox-state"><span className="state-spinner" aria-hidden="true" />Поиск...</div>
                    ) : error ? (
                        <div className="async-combobox-state is-error">{error}</div>
                    ) : items.length === 0 ? (
                        <div className="async-combobox-state">{emptyLabel}</div>
                    ) : items.map(item => {
                        const value = String(optionValue(item));
                        const description = optionDescription(item);
                        return (
                            <button
                                key={value}
                                type="button"
                                role="option"
                                className="async-combobox-option"
                                aria-selected={String(selectedValue) === value}
                                onClick={() => choose(item)}
                            >
                                <strong>{optionLabel(item)}</strong>
                                {description ? <small>{description}</small> : null}
                            </button>
                        );
                    })
                )}
            </div>
        </div>
    );
}