Add sort_order parameter to GET endpoints for date sorting

README.md

@@ -78,6 +78,7 @@ This is a FastAPI application for generating and managing invoices. It allows yo
     - `limit`: Maximum number of records to return (default: 100)
     - `fields`: Comma-separated list of fields to include in the response (e.g., "id,invoice_number,total_amount")
     - `status`: Filter invoices by status (e.g., "PENDING", "PAID", "CANCELLED")
+    - `sort_order`: Sort by creation date, either "asc" (oldest first) or "desc" (newest first, default)
 - `GET /api/v1/invoices/{invoice_id}`: Get a specific invoice by ID
   - Query parameters:
     - `fields`: Comma-separated list of fields to include in the response (e.g., "id,invoice_number,total_amount")
@@ -194,6 +195,29 @@ To combine with other parameters:
 GET /api/v1/invoices?status=PENDING&fields=id,invoice_number,total_amount&limit=5
 ```
 
+### Sorting
+
+The API supports sorting invoices by their creation date.
+
+#### How to Use Sorting:
+
+1. Add a `sort_order` query parameter to the GET request
+2. Specify one of the allowed values:
+   - `asc`: Ascending order (oldest invoices first)
+   - `desc`: Descending order (newest invoices first, this is the default)
+
+#### Example:
+
+To get invoices in chronological order (oldest first):
+```
+GET /api/v1/invoices?sort_order=asc
+```
+
+To combine sorting with other parameters:
+```
+GET /api/v1/invoices?sort_order=desc&status=PENDING&limit=10
+```
+
 ### Available Fields:
 
 Invoices have the following fields that can be filtered:

app/api/routes/invoices.py

@@ -75,6 +75,7 @@ def get_invoices(
     limit: int = 100, 
     fields: Optional[str] = None,
     status: Optional[str] = None,
+    sort_order: Optional[str] = "desc",
     db: Session = Depends(get_db)
 ):
     """
@@ -87,6 +88,8 @@ def get_invoices(
              If not provided, all fields will be returned.
     - status: Filter invoices by status (e.g., "PENDING", "PAID", "CANCELLED")
              If not provided, all invoices regardless of status will be returned.
+    - sort_order: Sort invoices by date_created field, either "asc" for ascending or "desc" for descending order.
+                 Default is "desc" (newest first).
     """
     # Build the query with filters
     query = db.query(Invoice)
@@ -104,6 +107,25 @@ def get_invoices(
         # Apply the filter
         query = query.filter(Invoice.status == status)
     
+    # Apply sorting
+    if sort_order:
+        # Validate sort_order value
+        allowed_sort_orders = ["asc", "desc"]
+        if sort_order.lower() not in allowed_sort_orders:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Sort order must be one of {', '.join(allowed_sort_orders)}"
+            )
+        
+        # Apply sorting based on sort_order
+        if sort_order.lower() == "asc":
+            query = query.order_by(Invoice.date_created.asc())
+        else:  # Default to 'desc'
+            query = query.order_by(Invoice.date_created.desc())
+    else:
+        # Default sorting (descending - newest first)
+        query = query.order_by(Invoice.date_created.desc())
+    
     # Apply pagination
     invoices = query.offset(skip).limit(limit).all()