/**
 * PirpCombobox - Tippbare Dropdown-Auswahl als Ersatz für <select>
 *
 * Verwendung:
 *   new PirpCombobox(containerEl, accountOptions, {
 *       placeholder: '--Konto--',
 *       selectedValue: 'kasse_s|soll||',
 *       onSelect: function(opt) { ... }
 *   });
 *
 * accountOptions: { "Gruppenname": [ {value, label, side, rev_id, exp_id}, ... ], ... }
 */
class PirpCombobox {
    constructor(container, options, config) {
        this.container = container;
        this.options = options; // grouped: { group: [{value, label, side, rev_id, exp_id}] }
        this.config = config || {};
        this.flatOptions = [];
        this.highlighted = -1;

        // Flatten options for filtering
        for (const [group, opts] of Object.entries(this.options)) {
            for (const opt of opts) {
                this.flatOptions.push({ group, ...opt });
            }
        }

        this.build();
        this.bindEvents();

        // Set initial selection
        if (this.config.selectedValue) {
            const parts = this.config.selectedValue.split('|');
            const match = this.flatOptions.find(o =>
                o.value === parts[0] && o.side === parts[1] &&
                String(o.rev_id) === String(parts[2]) &&
                String(o.exp_id) === String(parts[3])
            );
            if (match) {
                this.input.value = match.label;
                this.selectedOpt = match;
            }
        }
    }

    build() {
        this.container.classList.add('pirp-combobox');

        this.input = document.createElement('input');
        this.input.type = 'text';
        this.input.placeholder = this.config.placeholder || '--Konto--';
        this.input.autocomplete = 'off';

        this.dropdown = document.createElement('div');
        this.dropdown.className = 'pirp-combobox-dropdown';
        this.dropdown.style.display = 'none';

        this.container.appendChild(this.input);
        this.container.appendChild(this.dropdown);

        this.selectedOpt = null;
    }

    renderDropdown(filter) {
        this.dropdown.innerHTML = '';
        this.highlighted = -1;
        const f = (filter || '').toLowerCase();
        let visibleItems = [];
        let lastGroup = null;

        for (const opt of this.flatOptions) {
            if (f && opt.label.toLowerCase().indexOf(f) === -1) continue;
            if (opt.group !== lastGroup) {
                lastGroup = opt.group;
                const groupEl = document.createElement('div');
                groupEl.className = 'pirp-combobox-group';
                groupEl.textContent = opt.group;
                this.dropdown.appendChild(groupEl);
            }
            const optEl = document.createElement('div');
            optEl.className = 'pirp-combobox-option';
            optEl.textContent = opt.label;
            optEl.dataset.index = visibleItems.length;
            visibleItems.push({ el: optEl, opt });
            this.dropdown.appendChild(optEl);
        }

        this.visibleItems = visibleItems;
    }

    open() {
        this.renderDropdown(this.input.value === (this.selectedOpt ? this.selectedOpt.label : '') ? '' : this.input.value);
        this.dropdown.style.display = 'block';
    }

    close() {
        this.dropdown.style.display = 'none';
        this.highlighted = -1;
    }

    select(opt) {
        this.selectedOpt = opt;
        this.input.value = opt.label;
        this.close();
        if (this.config.onSelect) {
            this.config.onSelect(opt);
        }
    }

    highlightIndex(idx) {
        if (!this.visibleItems || !this.visibleItems.length) return;
        if (this.highlighted >= 0 && this.highlighted < this.visibleItems.length) {
            this.visibleItems[this.highlighted].el.classList.remove('highlighted');
        }
        this.highlighted = Math.max(0, Math.min(idx, this.visibleItems.length - 1));
        this.visibleItems[this.highlighted].el.classList.add('highlighted');
        this.visibleItems[this.highlighted].el.scrollIntoView({ block: 'nearest' });
    }

    bindEvents() {
        this.input.addEventListener('focus', () => {
            this.open();
        });

        this.input.addEventListener('input', () => {
            this.renderDropdown(this.input.value);
            this.dropdown.style.display = 'block';
            if (this.visibleItems.length > 0) {
                this.highlightIndex(0);
            }
        });

        this.input.addEventListener('keydown', (e) => {
            if (this.dropdown.style.display === 'none') {
                if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
                    this.open();
                    e.preventDefault();
                }
                return;
            }

            if (e.key === 'ArrowDown') {
                e.preventDefault();
                this.highlightIndex(this.highlighted + 1);
            } else if (e.key === 'ArrowUp') {
                e.preventDefault();
                this.highlightIndex(this.highlighted - 1);
            } else if (e.key === 'Enter') {
                e.preventDefault();
                if (this.highlighted >= 0 && this.visibleItems[this.highlighted]) {
                    this.select(this.visibleItems[this.highlighted].opt);
                }
            } else if (e.key === 'Escape') {
                e.preventDefault();
                if (this.selectedOpt) {
                    this.input.value = this.selectedOpt.label;
                }
                this.close();
            }
        });

        this.input.addEventListener('blur', () => {
            // Delay to allow click on option to register
            setTimeout(() => {
                if (this.selectedOpt) {
                    this.input.value = this.selectedOpt.label;
                }
                this.close();
            }, 150);
        });

        // Use mousedown to prevent blur race condition
        this.dropdown.addEventListener('mousedown', (e) => {
            e.preventDefault(); // Prevent blur
            const optEl = e.target.closest('.pirp-combobox-option');
            if (optEl) {
                const idx = parseInt(optEl.dataset.index);
                if (this.visibleItems[idx]) {
                    this.select(this.visibleItems[idx].opt);
                }
            }
        });
    }
}