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),