Add crudkit!

crudkit/service.py

@@ -0,0 +1,52 @@
+from sqlalchemy import func
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session
+
+from .dsl import QuerySpec, build_query
+from .eager import default_eager_policy
+
+class CrudService:
+    def __init__(self, session: Session, eager_policy=default_eager_policy):
+        self.s = session
+        self.eager_policy = eager_policy
+
+    def create(self, Model, data, *, before=None, after=None):
+        if before: data = before(data) or data
+        obj = Model(**data)
+        self.s.add(obj)
+        self.s.flush()
+        if after: after(obj)
+        return obj
+
+    def get(self, Model, id, spec: QuerySpec | None = None):
+        spec = spec or QuerySpec()
+        stmt = build_query(Model, spec, self.eager_policy).where(Model.id == id)
+        return self.s.execute(stmt).scalars().first()
+
+    def list(self, Model, spec: QuerySpec):
+        stmt = build_query(Model, spec, self.eager_policy)
+        count_stmt = stmt.with_only_columns(func.count()).order_by(None)
+        total = self.s.execute(count_stmt).scalar_one()
+        if spec.page and spec.per_page:
+            stmt = stmt.limit(spec.per_page).offset((spec.page - 1) * spec.per_page)
+        rows = self.s.execute(stmt).scalars().all()
+        return rows, total
+
+    def update(self, obj, data, *, before=None, after=None):
+        if obj.is_deleted: raise ValueError("Cannot update a deleted record")
+        if before: data = before(obj, data) or data
+        for k, v in data.items(): setattr(obj, k, v)
+        obj.version += 1
+        if after: after(obj)
+        return obj
+
+    def soft_delete(self, obj, *, cascade=False, guard=None):
+        if guard and not guard(obj): raise ValueError("Delete blocked by guard")
+        # optionsl FK hygiene checks go here
+        obj.mark_deleted()
+        return obj
+
+    def undelete(self, obj):
+        obj.deleted = False
+        obj.version += 1
+        return obj