PB-1677: sort extension - Add sortby query param

app/stac_api/pagination.py

@@ -171,7 +171,25 @@ def get_page_size(self, request):
         )
 
 
-class GetPostCursorPagination(CursorPagination):
+class SortedCursorPagination(CursorPagination):
+    '''Pagination class that supports sorting via the sortby parameter'''
+    ordering = 'name'
+
+    def get_ordering(self, request, queryset, view):
+        '''Get the ordering from the sortby query parameter if present.'''
+        sort_fields = getattr(view, 'sort_fields', None)
+        if not sort_fields:
+            return super().get_ordering(request, queryset, view)
+
+        ordering = []
+        for model_field, is_ascending in sort_fields:
+            if not is_ascending:
+                model_field = "-" + model_field
+            ordering.append(model_field)
+        return ordering
+
+
+class GetPostCursorPagination(SortedCursorPagination):
     '''Pagination to be used for the GET/POST /search endpoint where the
     pagination is either in query or in payload depending on the method.
     '''

app/stac_api/utils.py

@@ -20,6 +20,7 @@
 from django.conf import settings
 from django.contrib.gis.geos import Point
 from django.contrib.gis.geos import Polygon
+from django.core.exceptions import ValidationError
 from django.core.management import call_command
 from django.core.management.base import BaseCommand
 from django.core.management.base import CommandParser
@@ -629,3 +630,125 @@ def parse_cache_control_header(cache_control_header):
     parts = [i.strip() for i in cache_control_header.split(',')]
     args = {i.split('=')[0].strip(): i.split('=')[-1].strip() for i in parts if i}
     return {k: True if v == k else v for k, v in args.items()}
+
+
+# Maps sortby parameter values to Django model field
+SORTABLE_FIELDS = {
+    'id': 'name',
+    'collection': 'collection__name',
+    'datetime': 'properties_datetime',
+    'title': 'properties_title',
+    'created': 'created',
+    'updated': 'updated',
+}
+
+
+def parse_sortby_get(sortby_param, sortable_fields):
+    '''Parse and validate the GET (string) format of the sortby parameter.
+
+    The sortby parameter is a comma-separated string of fields prefixed with '+'
+    (ascending, default) or '-' (descending).
+
+    Example: "-created,title".
+
+    Args:
+        sortby_param: string
+            Comma-separated list of fields prefixed with '+' or '-'
+        sortable_fields: dict
+            Mapping of allowed sortby field names to Django model fields
+
+    Returns:
+        list: List of tuples (field, direction) where `direction` is True for ascending,
+              False for descending and `field` is the Django model field corresponding to
+              the given input field. Returns empty list if sortby_param is None or empty.
+
+    Raises:
+        ValidationError: If an invalid field is specified
+    '''
+    if not sortby_param:
+        return []
+
+    sort_fields = []
+    for sort_field in sortby_param.split(','):
+        sort_field = sort_field.strip()
+        if not sort_field:
+            continue
+
+        if sort_field.startswith('-'):
+            is_ascending = False
+            field_name = sort_field[1:]
+        elif sort_field.startswith('+'):
+            is_ascending = True
+            field_name = sort_field[1:]
+        else:
+            is_ascending = True
+            field_name = sort_field
+
+        internal_field = _resolve_sort_field(field_name, sortable_fields)
+        sort_fields.append((internal_field, is_ascending))
+    return sort_fields
+
+
+def parse_sortby_post(sortby_param, sortable_fields):
+    '''Parse the POST (list of objects) format of the sortby parameter.
+
+    The sortby parameter in the request body is a list of objects with a 'field'
+    and a 'direction' ('asc' or 'desc') property.
+
+    Example: [{"field": "created", "direction": "desc"}].
+
+    Args:
+        sortby_param: list
+            List of {"field": ..., "direction": ...} objects
+        sortable_fields: dict
+            Mapping of allowed sortby field names to Django model fields
+
+    Returns:
+        list: List of tuples (field, direction) where `direction` is True for ascending,
+              False for descending and `field` is the Django model field corresponding to
+              the given input field. Returns empty list if sortby_param is None or empty.
+
+    Raises:
+        ValidationError: If an invalid field or direction is specified
+    '''
+    sort_fields = []
+    for sort_item in sortby_param:
+        if not isinstance(sort_item, dict) or 'field' not in sort_item:
+            raise ValidationError("Each sortby entry must be an object with a 'field' property")
+        field_name = sort_item['field']
+        direction = str(sort_item.get('direction', 'asc')).lower()
+        if direction == 'asc':
+            is_ascending = True
+        elif direction == 'desc':
+            is_ascending = False
+        else:
+            raise ValidationError(
+                f"Invalid sort direction '{direction}'. "
+                f"Allowed values are: 'asc', 'desc'"
+            )
+        internal_field = _resolve_sort_field(field_name, sortable_fields)
+        sort_fields.append((internal_field, is_ascending))
+    return sort_fields
+
+
+def _resolve_sort_field(field_name, sortable_fields):
+    '''Resolve a sortby field name to its Django model field, validating it.
+
+    Args:
+        field_name: string
+            The field name provided in the sortby parameter
+        sortable_fields: dict
+            Mapping of allowed sortby field names to Django model fields
+
+    Returns:
+        string: The Django model field corresponding to the given field name
+
+    Raises:
+        ValidationError: If the field name is not allowed for sorting
+    '''
+    if field_name not in sortable_fields:
+        raise ValidationError(
+            f"Invalid sort field '{field_name}'. "
+            f"Allowed fields are: {', '.join(sortable_fields.keys())}"
+        )
+    return sortable_fields[field_name]

app/stac_api/validators_serializer.py

@@ -3,15 +3,19 @@
 
 from django.contrib.gis.gdal.error import GDALException
 from django.contrib.gis.geos import GEOSGeometry
+from django.core.exceptions import ValidationError as DjangoValidationError
 from django.db import IntegrityError
 from django.db import transaction
 from django.utils.translation import gettext_lazy as _
 
 from rest_framework import serializers
 
+from stac_api.utils import SORTABLE_FIELDS
 from stac_api.utils import fromisoformat
 from stac_api.utils import geometry_from_bbox
 from stac_api.utils import harmonize_post_get_for_search
+from stac_api.utils import parse_sortby_get
+from stac_api.utils import parse_sortby_post
 from stac_api.validators import validate_geometry
 
 logger = logging.getLogger(__name__)
@@ -72,7 +76,7 @@ def __init__(self):
         self.queriable_date_fields = ['created', 'updated']
         self.queriable_str_fields = ['title', 'cf:standard_name', 'unit']
 
-    def validate(self, request):
+    def validate(self, request):  # pylint: disable=too-many-branches
         '''Validates the request of the search endpoint
 
         This function validates the request of the search endpoint. As a simplification the
@@ -93,6 +97,15 @@ def validate(self, request):
         if request.method == "POST":
             self.validate_query_parameters_post_search(query_param)
 
+        try:
+            if 'sortby' in query_param:
+                if request.method == "POST":
+                    request.sort_fields = parse_sortby_post(query_param['sortby'], SORTABLE_FIELDS)
+                else:
+                    request.sort_fields = parse_sortby_get(query_param['sortby'], SORTABLE_FIELDS)
+        except DjangoValidationError as error:
+            self.errors['sortby'] = _(error.message)
+
         if 'bbox' in query_param:
             self.validate_bbox(query_param['bbox'])
         if 'datetime' in query_param:
@@ -366,6 +379,7 @@ def validate_query_parameters_post_search(self, query_param):
             "limit",
             "cursor",
             "query",
+            "sortby",
             "forecast:reference_datetime",
             "forecast:horizon",
             "forecast:duration",

app/stac_api/views/general.py

@@ -69,6 +69,8 @@ class SearchList(generics.GenericAPIView, mixins.ListModelMixin):
     # search overall collections and that the item name is only unique within a collection
     # we must use the pk as ordering attribute, otherwise the cursor pagination will not work
     ordering = ['pk']
+    # Resolved sortby fields. None means no sortby was provided and the default ordering is used.
+    sort_fields = None
 
     # pylint: disable=too-many-branches
     def get_queryset(self):
@@ -121,6 +123,7 @@ def list(self, request, *args, **kwargs):
 
         validate_search_request = ValidateSearchRequest()
         validate_search_request.validate(request)  # validate the search request
+        self.sort_fields = getattr(request, 'sort_fields', None)
         queryset = self.filter_queryset(self.get_queryset())
 
         page = self.paginate_queryset(queryset)

app/stac_api/views/item.py

@@ -18,12 +18,15 @@
 from stac_api.models.collection import Collection
 from stac_api.models.item import Asset
 from stac_api.models.item import Item
+from stac_api.pagination import SortedCursorPagination
 from stac_api.serializers.item import AssetSerializer
 from stac_api.serializers.item import ItemDetailSerializer
 from stac_api.serializers.item import ItemListSerializer
 from stac_api.serializers.item import ItemSerializer
 from stac_api.serializers.utils import get_relation_links
+from stac_api.utils import SORTABLE_FIELDS
 from stac_api.utils import get_asset_path
+from stac_api.utils import parse_sortby_get
 from stac_api.validators_view import validate_collection
 from stac_api.validators_view import validate_item
 from stac_api.validators_view import validate_renaming
@@ -89,8 +92,10 @@ def get_asset_etag(request, *args, **kwargs):
 
 class ItemsList(generics.GenericAPIView):
     serializer_class = ItemSerializer
-    ordering = ['name']
+    pagination_class = SortedCursorPagination
     name = 'items-list'  # this name must match the name in urls.py
+    # Resolved sortby fields. None means no sortby was provided and the default ordering is used.
+    sort_fields = None
 
     def get_queryset(self):
         # filter based on the url
@@ -122,6 +127,11 @@ def get_queryset(self):
 
     def list(self, request, *args, **kwargs):
         validate_collection(self.kwargs)
+
+        sort_fields = request.query_params.get('sortby')
+        if sort_fields:
+            self.sort_fields = parse_sortby_get(sort_fields, SORTABLE_FIELDS)
+
         queryset = self.filter_queryset(self.get_queryset())
         page = self.paginate_queryset(queryset)
         if page is not None:

app/tests/tests_10/test_items_endpoint.py

@@ -188,6 +188,102 @@ def test_items_endpoint_non_existing_collection(self):
         response = self.client.get(f"/{STAC_BASE_V}/collections/non-existing-collection/items")
         self.assertStatusCode(404, response)
 
+    def test_sortby_id_ascending(self):
+        response = self.client.get(
+            f"/{STAC_BASE_V}/collections/{self.collection.name}/items?sortby=id"
+        )
+
+        self.assertStatusCode(200, response)
+        item_ids = [item['id'] for item in response.json()['features']]
+        self.assertEqual(item_ids, ["item-1", "item-2"])
+
+    def test_sortby_id_descending(self):
+        response = self.client.get(
+            f"/{STAC_BASE_V}/collections/{self.collection.name}/items?sortby=-id"
+        )
+        self.assertStatusCode(200, response)
+        item_ids = [item['id'] for item in response.json()['features']]
+        self.assertEqual(item_ids, ["item-2", "item-1"])
+
+    def test_sortby_properties_datetime(self):
+
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-dt-1',
+            properties_datetime=timezone.now() + timedelta(days=2),
+            db_create=True
+        )
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-dt-2',
+            properties_datetime=timezone.now() + timedelta(days=1),
+            db_create=True
+        )
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-dt-3',
+            properties_datetime=timezone.now() + timedelta(days=3),
+            db_create=True
+        )
+
+        # Test ascending sort
+        response = self.client.get(
+            f"/{STAC_BASE_V}/collections/{self.collection.name}/items?sortby=datetime"
+        )
+
+        self.assertStatusCode(200, response)
+        item_ids = [item['id'] for item in response.json()['features']]
+        self.assertEqual(item_ids, ['item-1', 'item-2', 'item-dt-2', 'item-dt-1', 'item-dt-3'])
+
+        # Test descending sort
+        response = self.client.get(
+            f"/{STAC_BASE_V}/collections/{self.collection.name}/items?sortby=-datetime"
+        )
+        self.assertStatusCode(200, response)
+        item_ids = [item['id'] for item in response.json()['features']]
+        self.assertEqual(item_ids, ['item-dt-3', 'item-dt-1', 'item-dt-2', 'item-1', 'item-2'])
+
+    def test_sortby_multiple_fields(self):
+        tomorrow = timezone.now() + timedelta(days=1)
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-multi-1',
+            properties_datetime=tomorrow,
+            properties_title='AAA',
+            db_create=True
+        )
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-multi-2',
+            properties_datetime=tomorrow,
+            properties_title='BBB',
+            db_create=True
+        )
+        self.factory.create_item_sample(
+            self.collection,
+            name='item-multi-3',
+            properties_datetime=tomorrow + timedelta(days=1),
+            properties_title='CCC',
+            db_create=True
+        )
+
+        # Sort by datetime ascending, then by title descending
+        response = self.client.get(
+            (f"/{STAC_BASE_V}/collections/{self.collection.name}/items?"
+             f"sortby=datetime,-title")
+        )
+        self.assertStatusCode(200, response)
+        item_ids = [item['id'] for item in response.json()['features']]
+        self.assertEqual(
+            item_ids, ['item-1', 'item-2', 'item-multi-2', 'item-multi-1', 'item-multi-3']
+        )
+
+    def test_sortby_invalid_field(self):
+        response = self.client.get(
+            f"/{STAC_BASE_V}/collections/{self.collection.name}/items?sortby=expires"
+        )
+        self.assertStatusCode(400, response)
+
 
 class ItemsDatetimeQueryEndpointTestCase(StacBaseTestCase):