Add allow_zero_price_sales toggle: config UI, POS enforcement and backend validation

pos/blueprints/config_bp.py

@@ -1130,6 +1130,39 @@ def update_counter_remission_config():
     return jsonify({'enabled': enabled == 'true'})
 
 
+@config_bp.route('/sales-settings', methods=['GET'])
+@require_auth('pos.view')
+def get_sales_settings():
+    """Get sales-related settings (zero-price sales, etc.)."""
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute("SELECT value FROM tenant_config WHERE key = 'allow_zero_price_sales'")
+    row = cur.fetchone()
+    cur.close(); conn.close()
+    # Default to true to avoid breaking existing tenants that sell at $0.
+    allow = True
+    if row:
+        allow = str(row[0]).lower() in ('true', '1', 'yes')
+    return jsonify({'allow_zero_price_sales': allow})
+
+
+@config_bp.route('/sales-settings', methods=['PUT'])
+@require_auth('config.edit')
+def update_sales_settings():
+    """Update sales-related settings."""
+    data = request.get_json() or {}
+    allow = 'true' if data.get('allow_zero_price_sales') else 'false'
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute("""
+        INSERT INTO tenant_config (key, value) VALUES (%s, %s)
+        ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value
+    """, ('allow_zero_price_sales', allow))
+    conn.commit()
+    cur.close(); conn.close()
+    return jsonify({'allow_zero_price_sales': allow == 'true'})
+
+
 @config_bp.route('/onboarding-status', methods=['GET'])
 @require_auth('pos.view')
 def get_onboarding_status():

pos/blueprints/pos_bp.py

@@ -32,6 +32,29 @@ def _tenant_allows_negative_stock(conn):
     return row is not None and str(row[0]).lower() in ('true', '1', 'yes')
 
 
+def _tenant_allows_zero_price(conn):
+    """Return True if the tenant allows selling items at $0. Defaults to True."""
+    cur = conn.cursor()
+    cur.execute("SELECT value FROM tenant_config WHERE key = 'allow_zero_price_sales'")
+    row = cur.fetchone()
+    cur.close()
+    return str(row[0]).lower() in ('true', '1', 'yes') if row else True
+
+
+def _validate_zero_price(conn, items):
+    """Raise ValueError if any item line would be <= $0 and the tenant forbids it."""
+    if _tenant_allows_zero_price(conn):
+        return
+    for item in items:
+        unit_price = float(item.get('unit_price', 0) or 0)
+        quantity = float(item.get('quantity', 1) or 1)
+        discount_pct = float(item.get('discount_pct', 0) or 0)
+        line_total = unit_price * quantity * (1 - discount_pct / 100)
+        if line_total <= 0:
+            name = item.get('name') or item.get('part_number') or item.get('inventory_id')
+            raise ValueError(f"No está permitido vender artículos en $0 ({name})")
+
+
 def _enrich_items(cur, items, customer_id=None):
     """Look up inventory data for items that lack unit_price/tax_rate.
 
@@ -129,6 +152,7 @@ def create_sale():
                     }), 400
 
     try:
+        _validate_zero_price(conn, data.get('items', []))
         sale = process_sale(conn, data)
         conn.commit()
         conn.close()
@@ -164,6 +188,7 @@ def create_remission():
                     }), 400
 
     try:
+        _validate_zero_price(conn, data.get('items', []))
         sale = create_remission_note(conn, {
             'tenant_id': g.tenant_id,
             'branch_id': branch_id,
@@ -728,6 +753,7 @@ def create_quotation():
     # Enrich items with inventory data (price, tax, etc.)
     try:
         enriched = _enrich_items(cur, items, data.get('customer_id'))
+        _validate_zero_price(conn, enriched)
     except ValueError as e:
         cur.close(); conn.close()
         return jsonify({'error': str(e)}), 400
@@ -1116,6 +1142,7 @@ def update_quotation(quot_id):
 
     try:
         enriched = _enrich_items(cur, items, data.get('customer_id'))
+        _validate_zero_price(conn, enriched)
     except ValueError as e:
         cur.close(); conn.close()
         return jsonify({'error': str(e)}), 400
@@ -1602,6 +1629,7 @@ def convert_quotation(quot_id):
     }
 
     try:
+        _validate_zero_price(conn, items)
         sale = process_sale(conn, sale_data)
 
         # Mark quotation as converted
@@ -1760,6 +1788,7 @@ def create_layaway():
     # Enrich items with inventory data
     try:
         enriched = _enrich_items(cur, items, customer_id)
+        _validate_zero_price(conn, enriched)
     except ValueError as e:
         cur.close(); conn.close()
         return jsonify({'error': str(e)}), 400

pos/blueprints/service_order_bp.py

@@ -38,6 +38,29 @@ from blueprints.config_bp import _get_workshop_permissions, _DEFAULT_WORKSHOP_PE
 service_order_bp = Blueprint('service_orders', __name__, url_prefix='/pos/api/service-orders')
 
 
+def _tenant_allows_zero_price(conn):
+    """Return True if the tenant allows selling items at $0. Defaults to True."""
+    cur = conn.cursor()
+    cur.execute("SELECT value FROM tenant_config WHERE key = 'allow_zero_price_sales'")
+    row = cur.fetchone()
+    cur.close()
+    return str(row[0]).lower() in ('true', '1', 'yes') if row else True
+
+
+def _validate_zero_price(conn, items):
+    """Raise ValueError if any item line would be <= $0 and the tenant forbids it."""
+    if _tenant_allows_zero_price(conn):
+        return
+    for item in items:
+        unit_price = float(item.get('unit_price', 0) or 0)
+        quantity = float(item.get('quantity', 1) or 1)
+        discount_pct = float(item.get('discount_pct', 0) or 0)
+        line_total = unit_price * quantity * (1 - discount_pct / 100)
+        if line_total <= 0:
+            name = item.get('name') or item.get('part_number') or item.get('inventory_id')
+            raise ValueError(f"No está permitido vender artículos en $0 ({name})")
+
+
 # Roles allowed to access the workshop module at all.
 _WORKSHOP_VIEW_ROLES = {'owner', 'admin', 'counter', 'cashier', 'workshop', 'mechanic'}
 
@@ -174,6 +197,7 @@ def create_order_from_pos():
     )
     conn = get_tenant_conn(g.tenant_id)
     try:
+        _validate_zero_price(conn, items)
         result = create_service_order(conn, {
             'tenant_id': g.tenant_id,
             'branch_id': data.get('branch_id', g.branch_id),

pos/static/js/config.js

@@ -625,6 +625,7 @@ const Config = (() => {
             await saveVehicleCompatSource();
             await saveAllowedBrands();
             await saveModules();
+            await saveSalesSettings();
             await saveReceiptConfig();
             toast('Configuración guardada', 'ok');
         } catch (e) {
@@ -1015,6 +1016,37 @@ const Config = (() => {
         }
     }
 
+    async function loadSalesSettings() {
+        try {
+            var res = await fetch(API + '/sales-settings', { headers: headers() });
+            if (!res.ok) return;
+            var data = await res.json();
+            var cb = document.getElementById('cfg-allow-zero-price');
+            if (cb) cb.checked = data.allow_zero_price_sales !== false;
+        } catch (e) {
+            console.error('Config.loadSalesSettings:', e);
+        }
+    }
+
+    async function saveSalesSettings() {
+        var cb = document.getElementById('cfg-allow-zero-price');
+        if (!cb) return;
+        try {
+            var res = await fetch(API + '/sales-settings', {
+                method: 'PUT',
+                headers: headers(),
+                body: JSON.stringify({ allow_zero_price_sales: cb.checked })
+            });
+            if (!res.ok) {
+                var err = await res.json().catch(function() { return { error: res.statusText }; });
+                throw new Error(err.error || 'Save failed');
+            }
+        } catch (e) {
+            toast(e.message, 'error');
+            throw e;
+        }
+    }
+
     // -------------------------------------------------------------------------
     // Tab navigation
     // -------------------------------------------------------------------------
@@ -1277,6 +1309,7 @@ const Config = (() => {
         loadVehicleCompatSource();
         loadAllowedBrands();
         loadModules();
+        loadSalesSettings();
         loadReceiptConfig();
         if (isAdmin) {
             loadRolePermissions();

pos/static/js/pos.js

@@ -32,6 +32,7 @@ const POS = (() => {
     let canCreateLayaway = false;
     let canCreateRemission = false;
     let counterRemissionEnabled = false;
+    let allowZeroPriceSales = true;
     let currentPerms = [];
     let receiptConfig = {};
     let couriers = [];
@@ -142,6 +143,13 @@ const POS = (() => {
             } catch (e) {
                 counterRemissionEnabled = false;
             }
+            // Sales settings (zero-price sales toggle)
+            try {
+                const ssCfg = await api('/pos/api/config/sales-settings');
+                allowZeroPriceSales = ssCfg.allow_zero_price_sales !== false;
+            } catch (e) {
+                allowZeroPriceSales = true;
+            }
             // Counter remission workflow applies only to the counter role.
             canCreateRemission = counterRemissionEnabled && employeeRole === 'counter' && perms.includes('pos.remission');
 
@@ -442,6 +450,18 @@ const POS = (() => {
         }
     }
 
+    function isZeroPriceItem(item) {
+        const unitPrice = parseFloat(item.unit_price || 0);
+        const qty = parseFloat(item.quantity || 1);
+        const discount = parseFloat(item.discount_pct || 0);
+        return (unitPrice * qty * (1 - discount / 100)) <= 0;
+    }
+
+    function findZeroPriceItem() {
+        if (allowZeroPriceSales) return null;
+        return cart.find(isZeroPriceItem) || null;
+    }
+
     function modifyPrice() {
         if (!canEditPrice) { showToast('No tienes permiso para modificar precios'); return; }
         if (selectedRow < 0 || selectedRow >= cart.length) {
@@ -451,12 +471,15 @@ const POS = (() => {
         const p = prompt('Nuevo precio unitario:', cart[selectedRow].unit_price);
         if (p !== null) {
             const n = parseFloat(p);
-            if (n >= 0) {
+            if (n < 0) { showToast('Precio no válido'); return; }
+            if (!allowZeroPriceSales && n === 0) {
+                showToast('No está permitido dejar el precio en $0');
+                return;
+            }
             cart[selectedRow].unit_price = n;
             renderCart();
         }
     }
-    }
 
     // Wire confirm-cancel button
     document.addEventListener('DOMContentLoaded', function() {
@@ -1052,6 +1075,12 @@ const POS = (() => {
             generate_cfdi: document.getElementById('cfdiCheck').checked,
         };
 
+        const zeroItem = findZeroPriceItem();
+        if (zeroItem) {
+            showToast('No está permitido vender artículos en $0: ' + (zeroItem.name || zeroItem.part_number));
+            return;
+        }
+
         const confirmBtn = document.getElementById('btnConfirmPayment');
         confirmBtn.disabled = true;
         confirmBtn.textContent = 'Procesando...';
@@ -1105,6 +1134,11 @@ const POS = (() => {
     async function createRemissionNote() {
         if (cart.length === 0) { showToast('Carrito vacio'); return; }
         if (!canCreateRemission) { showToast('No tienes permiso para generar notas de remision'); return; }
+        const zeroItem = findZeroPriceItem();
+        if (zeroItem) {
+            showToast('No está permitido vender artículos en $0: ' + (zeroItem.name || zeroItem.part_number));
+            return;
+        }
 
         const total = getTotal();
         const noteData = {
@@ -1262,6 +1296,11 @@ const POS = (() => {
     // ─── Quotation ───────────────────────
     async function saveQuotation() {
         if (cart.length === 0) { showToast('Carrito vacio'); return; }
+        const zeroItem = findZeroPriceItem();
+        if (zeroItem) {
+            showToast('No está permitido cotizar artículos en $0: ' + (zeroItem.name || zeroItem.part_number));
+            return;
+        }
 
         const body = {
             items: cart.map(item => ({
@@ -1302,6 +1341,11 @@ const POS = (() => {
     async function createLayaway() {
         if (!canCreateLayaway) { showToast('No tienes permiso para crear apartados'); return; }
         if (cart.length === 0) { alert('Carrito vacio'); return; }
+        const zeroItem = findZeroPriceItem();
+        if (zeroItem) {
+            alert('No está permitido apartar artículos en $0: ' + (zeroItem.name || zeroItem.part_number));
+            return;
+        }
         if (!currentCustomer) { alert('Seleccione un cliente para apartado'); return; }
 
         const total = getTotal();
@@ -1345,6 +1389,11 @@ const POS = (() => {
     function createServiceOrder() {
         if (!canCreateWorkshopOrder) { showToast('No tienes permiso para ordenes de taller'); return; }
         if (cart.length === 0) { showToast('Carrito vacio'); return; }
+        const zeroItem = findZeroPriceItem();
+        if (zeroItem) {
+            showToast('No está permitido generar orden con artículos en $0: ' + (zeroItem.name || zeroItem.part_number));
+            return;
+        }
         const custInput = document.getElementById('soCustomer');
         if (custInput) custInput.value = currentCustomer ? currentCustomer.name : 'Publico General';
         document.getElementById('serviceOrderModal').classList.add('open');

pos/static/pwa/sw.js

@@ -6,7 +6,7 @@
 // The fetch handler normalizes static asset URLs (strips ?v= query strings)
 // so templates can use cache-busting query params freely.
 
-const VERSION = 43;
+const VERSION = 44;
 const CACHE_NAME = 'nexus-pos-v' + VERSION;
 
 const APP_SHELL = [

pos/templates/config.html

@@ -736,6 +736,16 @@
                 <span class="toggle__slider"></span>
               </label>
             </div>
+            <div class="toggle-row">
+              <div class="toggle-row__info">
+                <span class="toggle-row__label">Permitir ventas en $0</span>
+                <span class="toggle-row__desc">Permite vender artículos con precio unitario o total de línea igual a $0</span>
+              </div>
+              <label class="toggle">
+                <input type="checkbox" id="cfg-allow-zero-price" checked />
+                <span class="toggle__slider"></span>
+              </label>
+            </div>
           </div>
         </div>