From 3a6d306fbff34a1fea25806279fd6e1fd4d8f1b4 Mon Sep 17 00:00:00 2001
From: Val Lorentz <progval+opdb@progval.net>
Date: Sun, 21 May 2023 14:04:44 +0200
Subject: [PATCH] Define basic architecture and pytest fixtures for SPARQL
 querying

---
 glowtables/sparql.py         | 45 ++++++++++++++++++++++++++++++++++++
 glowtables/tests/conftest.py | 39 +++++++++++++++++++++++++++++++
 pyproject.toml               |  1 +
 3 files changed, 85 insertions(+)
 create mode 100644 glowtables/sparql.py
 create mode 100644 glowtables/tests/conftest.py

diff --git a/glowtables/sparql.py b/glowtables/sparql.py
new file mode 100644
index 0000000..8c6b713
--- /dev/null
+++ b/glowtables/sparql.py
@@ -0,0 +1,45 @@
+# This file is part of the Glowtables software
+# Copyright (C) 2023  Valentin Lorentz
+#
+# This program is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Affero General Public License version 3, as published by the
+# Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License along with
+# this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Abstraction over SPARQL backends, primarily meant to be mocked by tests."""
+
+import abc
+from typing import Iterable
+
+import SPARQLWrapper
+
+
+class SparqlBackend(abc.ABC):
+    """Abstract class for SPARQL clients"""
+
+    @abc.abstractmethod
+    def query(self, query: str) -> Iterable[tuple]:
+        """Sends a SPARQL query, and returns an iterable of results."""
+
+
+class RemoteSparqlBackend(SparqlBackend):
+    """Queries a SPARQL API over HTTP."""
+
+    def __init__(self, url: str, agent: str):
+        """
+        :param url: Base URL of the endpoint
+        :param agent: User-Agent to use in HTTP requests
+        """
+        self._url = url
+        self._agent = agent
+
+    def query(self, query: str) -> Iterable[tuple]:
+        sparql = SPARQLWrapper.SPARQLWrapper(self._url, agent=self._agent)
+        sparql.setQuery(query)
+        return sparql.query()
diff --git a/glowtables/tests/conftest.py b/glowtables/tests/conftest.py
new file mode 100644
index 0000000..319f9c3
--- /dev/null
+++ b/glowtables/tests/conftest.py
@@ -0,0 +1,39 @@
+# This file is part of the Glowtables software
+# Copyright (C) 2023  Valentin Lorentz
+#
+# This program is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Affero General Public License version 3, as published by the
+# Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License along with
+# this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import Iterable
+
+import pytest
+import rdflib
+
+from glowtables.sparql import SparqlBackend
+
+
+class RdflibSparqlBackend(SparqlBackend):
+    def __init__(self, graph: rdflib.Graph):
+        self._graph = graph
+
+    def query(self, query: str) -> Iterable[tuple]:
+        ret = self._graph.query(query)
+        return ret
+
+
+@pytest.fixture()
+def rdflib_graph():
+    return rdflib.Graph()
+
+
+@pytest.fixture()
+def rdflib_sparql(rdflib_graph: rdflib.Graph):
+    return RdflibSparqlBackend(rdflib_graph)
diff --git a/pyproject.toml b/pyproject.toml
index 2160f26..afd4a04 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,6 +29,7 @@ python_version = "3.9"
 [[tool.mypy.overrides]]
 module = [
     "requests_mock",
+    "SPARQLWrapper",
 ]
 ignore_missing_imports = true