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

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