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

/** Селект дизайн-системы: разметкой и состоянием полностью управляет React. */
export function CustomSelect({ children, ...props }) {
    const rootRef = useRef(null);
    const selectRef = useRef(null);
    const triggerRef = useRef(null);
    const listId = useId();
    const [open, setOpen] = useState(false);
    const [query, setQuery] = useState('');
    const [invalid, setInvalid] = useState(false);
    const [snapshot, setSnapshot] = useState({ options: [], selectedIndex: -1, label: '' });

    // Читаем итоговые option после commit: children могут содержать массивы и фрагменты.
    // Контролируемые value, disabled и подписи синхронизируются при каждом рендере.
    useLayoutEffect(() => {
        const select = selectRef.current;
        const next = {
            options: Array.from(select.options, option => ({
                value: option.value,
                text: option.text,
                disabled: option.disabled || Boolean(option.closest('optgroup')?.disabled)
            })),
            selectedIndex: select.selectedIndex,
            label: Array.from(select.labels || [], label => {
                const caption = label.cloneNode(true);
                caption.querySelectorAll('select, .custom-select-wrapper').forEach(node => node.remove());
                return caption.textContent.trim();
            }).join(' ')
        };
        setSnapshot(current => JSON.stringify(current) === JSON.stringify(next) ? current : next);
        if (select.validity.valid) setInvalid(false);
    });

    const expanded = open && !props.disabled;
    useEffect(() => {
        if (!expanded) return undefined;
        function closeOutside(event) {
            if (!rootRef.current?.contains(event.target)) setOpen(false);
        }
        document.addEventListener('pointerdown', closeOutside);
        return () => document.removeEventListener('pointerdown', closeOutside);
    }, [expanded]);

    const selected = snapshot.options[snapshot.selectedIndex];
    const searchable = snapshot.options.length > 6;

    function choose(index) {
        const select = selectRef.current;
        select.selectedIndex = index;
        select.dispatchEvent(new Event('change', { bubbles: true }));
        setOpen(false);
        triggerRef.current?.focus();
    }

    function toggle() {
        setQuery('');
        setOpen(current => !current);
    }

    function handleKeydown(event) {
        if (event.key === 'Escape') {
            event.preventDefault();
            event.stopPropagation();
            setOpen(false);
            triggerRef.current?.focus();
        } else if (['ArrowDown', 'ArrowUp', 'Home', 'End'].includes(event.key)) {
            event.preventDefault();
            if (!expanded) {
                setQuery('');
                setOpen(true);
                return;
            }
            const options = Array.from(rootRef.current.querySelectorAll('[role="option"]:not(:disabled)'));
            const current = options.indexOf(document.activeElement);
            const index = event.key === 'Home' ? 0
                : event.key === 'End' ? options.length - 1
                    : event.key === 'ArrowUp' ? (current < 0 ? options.length - 1 : Math.max(0, current - 1))
                        : Math.min(options.length - 1, current + 1);
            options[index]?.focus();
        }
    }

    return (
        <div
            className={`react-custom-select${expanded ? ' select-layer-active' : ''}`}
            ref={rootRef}
            onKeyDown={handleKeydown}
            onBlur={event => {
                if (!event.currentTarget.contains(event.relatedTarget)) setOpen(false);
            }}
        >
            <select
                {...props}
                ref={selectRef}
                hidden
                aria-hidden="true"
                tabIndex={-1}
                data-native-select="true"
                onInvalid={event => {
                    props.onInvalid?.(event);
                    event.preventDefault();
                    setInvalid(true);
                    triggerRef.current?.focus();
                }}
            >
                {children}
            </select>
            <div className={`custom-select-wrapper${expanded ? ' open' : ''}${props.disabled ? ' disabled' : ''}`}>
                <button
                    type="button"
                    className={`custom-select-trigger${!selected?.value ? ' placeholder-active' : ''}`}
                    ref={triggerRef}
                    disabled={props.disabled}
                    role="combobox"
                    aria-expanded={expanded}
                    aria-controls={listId}
                    aria-haspopup="listbox"
                    aria-required={props.required || undefined}
                    aria-invalid={invalid || undefined}
                    aria-describedby={invalid ? `${listId}-error` : undefined}
                    aria-label={props['aria-label'] || snapshot.label || 'Выбор значения'}
                    onClick={toggle}
                >
                    <span className="custom-select-text">{selected?.text || '—'}</span>
                    <span className="custom-select-icon" aria-hidden="true">
                        <svg width="12" height="8" viewBox="0 0 12 8" fill="none">
                            <path d="M1 1.5L6 6.5L11 1.5" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" />
                        </svg>
                    </span>
                </button>
                {expanded && (
                    <div className="custom-select-menu">
                        {searchable && (
                            <input
                                className="custom-select-search-input"
                                type="search"
                                placeholder="Поиск..."
                                aria-label="Поиск по списку"
                                value={query}
                                onChange={event => setQuery(event.target.value)}
                            />
                        )}
                        <ul className="react-select-options" role="listbox" id={listId}>
                            {snapshot.options.filter(option => option.text.toLocaleLowerCase('ru').includes(query.toLocaleLowerCase('ru'))).length === 0 && (
                                <li className="custom-select-item disabled">Ничего не найдено</li>
                            )}
                            {snapshot.options.map((option, index) => (
                                option.text.toLocaleLowerCase('ru').includes(query.toLocaleLowerCase('ru')) && (
                                    <li key={index} role="presentation">
                                        <button
                                            type="button"
                                            className={`custom-select-item${index === snapshot.selectedIndex ? ' selected' : ''}${option.disabled ? ' disabled' : ''}`}
                                            role="option"
                                            aria-selected={index === snapshot.selectedIndex}
                                            disabled={option.disabled}
                                            onClick={() => choose(index)}
                                        >
                                            {option.text}
                                        </button>
                                    </li>
                                )
                            ))}
                        </ul>
                    </div>
                )}
            </div>
            {invalid && <span id={`${listId}-error`} className="form-alert error" role="alert">Выберите значение</span>}
        </div>
    );
}