import { debounce } from './url-state.js';

export class AsyncCombobox {
    constructor(select, {
        load,
        optionValue = item => item.id,
        optionLabel = item => item.name,
        optionDescription = () => '',
        placeholder = 'Начните вводить название',
        emptyLabel = 'Ничего не найдено',
        allowEmpty = true
    }) {
        if (!select || typeof load !== 'function') throw new Error('Для поискового списка нужны select и функция загрузки');
        this.select = select;
        this.load = load;
        this.optionValue = optionValue;
        this.optionLabel = optionLabel;
        this.optionDescription = optionDescription;
        this.emptyLabel = emptyLabel;
        this.allowEmpty = allowEmpty;
        this.requestNumber = 0;
        this.items = [];

        select.dataset.nativeSelect = 'true';
        select.hidden = true;
        this.root = document.createElement('div');
        this.root.className = 'async-combobox';
        this.root.innerHTML = `
            <div class="async-combobox-control">
                <input type="search" role="combobox" aria-autocomplete="list" aria-expanded="false"
                       autocomplete="off" placeholder="${escapeText(placeholder)}">
                <button type="button" class="async-combobox-clear" aria-label="Очистить выбор" ${allowEmpty ? '' : 'hidden'}>×</button>
            </div>
            <div class="async-combobox-menu" role="listbox" hidden></div>
        `;
        select.insertAdjacentElement('afterend', this.root);
        this.input = this.root.querySelector('input');
        this.menu = this.root.querySelector('[role="listbox"]');
        this.clearButton = this.root.querySelector('.async-combobox-clear');
        this.input.setAttribute('aria-label', select.getAttribute('aria-label') || placeholder);
        this.labels = select.id
            ? [...document.querySelectorAll('label[for]')].filter(label => label.htmlFor === select.id)
            : [];
        if (select.id) {
            this.input.id = `${select.id}-search`;
            this.labels.forEach(label => { label.htmlFor = this.input.id; });
        }
        const listId = `${select.id || 'async-combobox'}-listbox`;
        this.menu.id = listId;
        this.input.setAttribute('aria-controls', listId);

        this.input.addEventListener('focus', () => this.search(this.input.value));
        this.input.addEventListener('input', debounce(() => this.search(this.input.value), 320));
        this.input.addEventListener('keydown', event => this.handleKeydown(event));
        this.clearButton.addEventListener('click', () => this.clear());
        this.menu.addEventListener('mousedown', event => event.preventDefault());
        this.menu.addEventListener('keydown', event => this.handleMenuKeydown(event));
        this.handleOutsideClick = event => {
            if (!this.root.contains(event.target)) this.close();
        };
        document.addEventListener('click', this.handleOutsideClick);
        this.syncFromSelect();
    }

    async search(query = '') {
        return this.loadMatches(query, true);
    }

    async preload(query = '') {
        return this.loadMatches(query, false);
    }

    async loadMatches(query, revealMenu) {
        const requestNumber = ++this.requestNumber;
        if (revealMenu) this.open();
        this.menu.innerHTML = '<div class="async-combobox-state"><span class="state-spinner" aria-hidden="true"></span>Поиск...</div>';
        try {
            const items = await this.load(query.trim(), this.select.value || '');
            if (requestNumber !== this.requestNumber) return;
            this.items = Array.isArray(items) ? items : [];
            this.renderItems();
        } catch (error) {
            if (requestNumber !== this.requestNumber) return;
            this.menu.innerHTML = `<div class="async-combobox-state is-error">${escapeText(error.message || 'Не удалось выполнить поиск')}</div>`;
        }
    }

    renderItems() {
        if (!this.items.length) {
            this.menu.innerHTML = `<div class="async-combobox-state">${escapeText(this.emptyLabel)}</div>`;
            return;
        }
        this.menu.innerHTML = this.items.map((item, index) => {
            const value = String(this.optionValue(item));
            const description = this.optionDescription(item);
            return `<button type="button" role="option" class="async-combobox-option" data-index="${index}"
                    aria-selected="${String(this.select.value) === value}">
                <strong>${escapeText(this.optionLabel(item))}</strong>
                ${description ? `<small>${escapeText(description)}</small>` : ''}
            </button>`;
        }).join('');
        this.menu.querySelectorAll('[data-index]').forEach(button => {
            button.addEventListener('click', () => this.choose(this.items[Number(button.dataset.index)]));
        });
    }

    choose(item) {
        const value = String(this.optionValue(item));
        const label = this.optionLabel(item);
        this.select.innerHTML = `<option value="${escapeText(value)}" selected>${escapeText(label)}</option>`;
        this.select.value = value;
        this.input.value = label;
        this.input.dataset.selectedValue = value;
        this.select.dispatchEvent(new Event('change', { bubbles: true }));
        this.close();
    }

    clear() {
        this.select.innerHTML = '<option value="" selected></option>';
        this.select.value = '';
        this.input.value = '';
        delete this.input.dataset.selectedValue;
        this.select.dispatchEvent(new Event('change', { bubbles: true }));
        this.input.focus();
        this.search('');
    }

    syncFromSelect() {
        const selected = this.select.selectedOptions?.[0];
        this.input.value = selected?.value ? selected.textContent.trim() : '';
        if (selected?.value) this.input.dataset.selectedValue = selected.value;
    }

    open() {
        this.menu.hidden = false;
        this.input.setAttribute('aria-expanded', 'true');
        this.root.classList.add('is-open');
    }

    close() {
        this.menu.hidden = true;
        this.input.setAttribute('aria-expanded', 'false');
        this.root.classList.remove('is-open');
        this.syncFromSelect();
    }

    handleKeydown(event) {
        const options = [...this.menu.querySelectorAll('[role="option"]')];
        const current = options.indexOf(document.activeElement);
        if (event.key === 'Escape') {
            this.close();
        } else if (event.key === 'ArrowDown' && options.length) {
            event.preventDefault();
            options[Math.min(current + 1, options.length - 1)].focus();
        } else if (event.key === 'ArrowUp' && options.length) {
            event.preventDefault();
            options[Math.max(current - 1, 0)].focus();
        }
    }

    handleMenuKeydown(event) {
        const options = [...this.menu.querySelectorAll('[role="option"]')];
        const current = options.indexOf(document.activeElement);
        if (event.key === 'Escape') {
            event.preventDefault();
            this.close();
            this.input.focus();
        } 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 ? this.input : options[current - 1])?.focus();
        }
    }

    destroy() {
        document.removeEventListener('click', this.handleOutsideClick);
        this.requestNumber += 1;
        this.root.remove();
        this.select.hidden = false;
        this.labels.forEach(label => { label.htmlFor = this.select.id; });
    }
}

function escapeText(value) {
    return String(value ?? '')
        .replaceAll('&', '&amp;')
        .replaceAll('<', '&lt;')
        .replaceAll('>', '&gt;')
        .replaceAll('"', '&quot;')
        .replaceAll("'", '&#039;');
}