// Invoice Form Logic
    const initInvoiceForm = (searchInputId, suggestionsId, tableBodyId, grandTotalId, subtotalId, totalVatId) => {
        const searchInput = document.getElementById(searchInputId);
        const suggestions = document.getElementById(suggestionsId);
        const tableBody = document.getElementById(tableBodyId);
        const grandTotalEl = document.getElementById(grandTotalId);
        const subtotalEl = document.getElementById(subtotalId);
        const totalVatEl = document.getElementById(totalVatId);

        if (!searchInput || !tableBody) return;

        let timeout = null;
        searchInput.addEventListener('input', function() {
            clearTimeout(timeout);
            const q = this.value.trim();
            if (q.length < 2) {
                suggestions.style.display = 'none';
                return;
            }

            timeout = setTimeout(() => {
                fetch(`index.php?action=search_items&q=${encodeURIComponent(q)}`)
                    .then(res => res.ok ? res.json() : [])
                    .then(data => {
                        suggestions.innerHTML = '';
                        if (data.length > 0) {
                            data.forEach(item => {
                                const btn = document.createElement('button');
                                btn.type = 'button';
                                btn.className = 'list-group-item list-group-item-action';
                                btn.innerHTML = `
                                    <div class="d-flex justify-content-between">
                                        <span><strong>${item.sku}</strong> - ${item.name_en} / ${item.name_ar}</span>
                                        <span class="text-muted small">Stock: ${item.stock_quantity}</span>
                                    </div>
                                `;
                                btn.onclick = () => addItemToTable(item, tableBody, searchInput, suggestions, grandTotalEl, subtotalEl, totalVatEl);
                                suggestions.appendChild(btn);
                            });
                            suggestions.style.display = 'block';
                        } else {
                            suggestions.style.display = 'none';
                        }
                    });
            }, 300);
        });

        // Close suggestions when clicking outside
        document.addEventListener('click', function(e) {
            if (!searchInput.contains(e.target) && !suggestions.contains(e.target)) {
                suggestions.style.display = 'none';
            }
        });
    };

    function addItemToTable(item, tableBody, searchInput, suggestions, grandTotalEl, subtotalEl, totalVatEl, customData = null) {
        if (suggestions) suggestions.style.display = 'none';
        if (searchInput) searchInput.value = '';

        const allowZeroStock = (typeof companySettings !== 'undefined' && String(companySettings.allow_zero_stock_sell) === '1');
        const currentStock = parseFloat(item.stock_quantity) || 0;

        if (invoiceType === 'sale' && !allowZeroStock && !customData) {
            const existingInTable = Array.from(tableBody.querySelectorAll('.item-row')).find(row => row.querySelector('.item-id-input').value == item.id);
            let currentQtyInTable = 0;
            if (existingInTable) {
                currentQtyInTable = parseFloat(existingInTable.querySelector('.item-qty').value) || 0;
            }
            
            if (currentQtyInTable + 1 > currentStock) {
                alert('Insufficient stock! Available: ' + currentStock);
                return;
            }
        }
        
        const existingRow = Array.from(tableBody.querySelectorAll('.item-id-input')).find(input => input.value == item.id);
        if (existingRow && !customData) {
            const row = existingRow.closest('tr');
            const qtyInput = row.querySelector('.item-qty');
            qtyInput.value = parseFloat(qtyInput.value) + 1;
            recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl);
            return;
        }

        const row = document.createElement('tr');
        row.className = 'item-row';
        const price = customData ? customData.unit_price : (invoiceType === 'sale' ? item.sale_price : item.purchase_price);
        const qty = customData ? customData.quantity : 1;
        const vatRate = item.vat_rate || 0;
        
        row.innerHTML = `
            <td>
                <input type="hidden" name="item_ids[]" class="item-id-input" value="${item.id}">
                <input type="hidden" class="item-row-stock" value="${item.stock_quantity}">
                <input type="hidden" class="item-vat-rate" value="${vatRate}">
                <div><strong>${item.name_en}</strong></div>
                <div class="small text-muted">${item.name_ar} (${item.sku})</div>
            </td>
            <td><input type="number" step="0.001" name="quantities[]" class="form-control item-qty" value="${qty}" required></td>
            <td><input type="number" step="0.001" name="prices[]" class="form-control item-price" value="${price}" required></td>
            <td><input type="text" class="form-control bg-light" value="${parseFloat(vatRate || 0).toFixed(2)}%" readonly></td>
            <td><input type="number" step="0.001" class="form-control item-total" value="${(qty * price).toFixed(3)}" readonly></td>
            <td><button type="button" class="btn btn-outline-danger btn-sm remove-row"><i class="bi bi-trash"></i></button></td>
        `;
        
        tableBody.appendChild(row);
        attachRowListeners(row, tableBody, grandTotalEl, subtotalEl, totalVatEl);
        recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl);
    }

    function recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl) {
        let subtotal = 0;
        let totalVat = 0;
        tableBody.querySelectorAll('.item-row').forEach(row => {
            const qty = parseFloat(row.querySelector('.item-qty').value) || 0;
            const price = parseFloat(row.querySelector('.item-price').value) || 0;
            const vatRate = parseFloat(row.querySelector('.item-vat-rate').value) || 0;
            
            const total = qty * price;
            const vatAmount = total * (vatRate / 100);
            
            row.querySelector('.item-total').value = total.toFixed(3);
            subtotal += total;
            totalVat += vatAmount;
        });
        const grandTotal = subtotal + totalVat;
        
        if (subtotalEl) subtotalEl.textContent = 'OMR ' + subtotal.toFixed(3);
        if (totalVatEl) totalVatEl.textContent = 'OMR ' + totalVat.toFixed(2);
        if (grandTotalEl) grandTotalEl.textContent = 'OMR ' + grandTotal.toFixed(3);
    }

    function attachRowListeners(row, tableBody, grandTotalEl, subtotalEl, totalVatEl) {
        row.querySelector('.item-qty').addEventListener('input', function() {
            const allowZeroStock = (typeof companySettings !== 'undefined' && String(companySettings.allow_zero_stock_sell) === '1');
            if (invoiceType === 'sale' && !allowZeroStock) {
                const stock = parseFloat(row.querySelector('.item-row-stock').value) || 0;
                const qty = parseFloat(this.value) || 0;
                if (qty > stock) {
                    alert('Insufficient stock! Available: ' + stock);
                    this.value = stock;
                }
            }
            recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl);
        });
        row.querySelector('.item-price').addEventListener('input', () => recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl));
        row.querySelector('.remove-row').addEventListener('click', function() {
            row.remove();
            recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl);
        });
    }

    const invoiceType = '<?= in_array($page, ["sales", "quotations"]) ? "sale" : (in_array($page, ["purchases", "lpos"]) ? "purchase" : "") ?>';
    initInvoiceForm('productSearchInput', 'searchSuggestions', 'invoiceItemsTableBody', 'grandTotal', 'subtotal', 'totalVat');
    initInvoiceForm('editProductSearchInput', 'editSearchSuggestions', 'editInvoiceItemsTableBody', 'edit_grandTotal', 'edit_subtotal', 'edit_totalVat');