feat: implement result ordering by model fields

Concerns #171.

rdfproxy/constructor.py

@@ -36,6 +36,9 @@ def __init__(
         self.group_by: str | None = self.bindings_map.get(
             model.model_config.get("group_by")
         )
+        self.order_by: str | None = self.bindings_map.get(query_parameters.order_by)
+
+        print("DEBUG: ", self.order_by)
 
     def get_items_query(self) -> str:
         """Construct a SPARQL items query for use in rdfproxy.SPARQLModelAdapter."""
@@ -118,7 +121,13 @@ def _compute_select_clause(self):
         return f"select distinct ?{self.group_by}"
 
     def _compute_order_by_value(self):
-        """Stub: Only basic logic for now."""
-        if self.group_by is None:
-            return get_query_projection(self.query)[0]
-        return f"{self.group_by}"
+        """Compute a value for ORDER BY used in RDFProxy query modification."""
+        match (self.group_by, self.order_by):
+            case None, None:
+                return f"?{get_query_projection(self.query)[0]}"
+            case group_by, None:
+                return f"?{group_by}"
+            case _, order_by:
+                return f"{'DESC' if self.query_parameters.desc else 'ASC'}(?{order_by})"
+            case _:  # pragma: no cover
+                assert False, "Unreachable case in _compute_order_by_value"

rdfproxy/utils/models.py

@@ -1,8 +1,10 @@
 """Pydantic Model definitions for rdfproxy."""
 
-from typing import Generic
+from enum import StrEnum, auto
+from typing import Any, Generic, get_origin
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, model_validator
+from pydantic.fields import FieldInfo
 from rdfproxy.utils._types import _TModelInstance
 
 
@@ -23,11 +25,39 @@ class Page(BaseModel, Generic[_TModelInstance]):
     pages: int
 
 
-class QueryParameters(BaseModel):
+class QueryParameters(
+    BaseModel,
+    Generic[_TModelInstance],
+):
     """Query parameter model for SPARQLModelAdapter.query.
 
     See https://fastapi.tiangolo.com/tutorial/query-param-models/
     """
 
     page: int = Field(default=1, gt=0)
     size: int = Field(default=100, ge=1)
+
+    order_by: str | None = Field(default=None)
+    desc: bool = Field(default=False)
+
+    @model_validator(mode="after")
+    @classmethod
+    def _check_desc_order_by_dependency(cls, data: Any) -> Any:
+        """Check the dependency of desc on order_by."""
+        _desc_defined, _order_by_defined = data.desc, data.order_by
+
+        if _desc_defined and not _order_by_defined:
+            raise ValueError("Field 'desc' requires on Field 'order_by'.")
+        return data
+
+    def __class_getitem__(cls, model: type[_TModelInstance]):
+        _order_by_fields = [
+            (k, auto())
+            for k, v in model.model_fields.items()
+            if get_origin(v.annotation) is not list
+        ]
+
+        OrderByEnum = StrEnum("OrderByEnum", _order_by_fields)
+        cls.model_fields["order_by"] = FieldInfo(annotation=OrderByEnum, default=None)
+
+        return cls