✨(back) allow theme customnization using a configuration file

We want to customize the theme by using a configuration file. This
configuration file path can be defined using the settings
THEME_CUSTOMIZATION_FILE_PATH. If this file does not exists or is an
invalid json, an empty json object will be added in the config endpoint.

src/backend/core/api/viewsets.py

@@ -1,6 +1,7 @@
 """API endpoints"""
 # pylint: disable=too-many-lines
 
+import json
 import logging
 import uuid
 from urllib.parse import unquote, urlparse
@@ -9,6 +10,7 @@ from django.conf import settings
 from django.contrib.postgres.aggregates import ArrayAgg
 from django.contrib.postgres.fields import ArrayField
 from django.contrib.postgres.search import TrigramSimilarity
+from django.core.cache import cache
 from django.core.exceptions import ValidationError
 from django.core.files.storage import default_storage
 from django.db import connection, transaction
@@ -16,10 +18,8 @@ from django.db import models as db
 from django.db.models.expressions import RawSQL
 from django.db.models.functions import Left, Length
 from django.http import Http404, StreamingHttpResponse
-from django.utils.decorators import method_decorator
-from django.utils.text import capfirst
+from django.utils.text import capfirst, slugify
 from django.utils.translation import gettext_lazy as _
-from django.views.decorators.cache import cache_page
 
 import requests
 import rest_framework as drf
@@ -1747,23 +1747,41 @@ class ConfigView(drf.views.APIView):
             if hasattr(settings, setting):
                 dict_settings[setting] = getattr(settings, setting)
 
+        dict_settings["theme_customization"] = self._load_theme_customization()
+
         return drf.response.Response(dict_settings)
 
+    def _load_theme_customization(self):
+        if not settings.THEME_CUSTOMIZATION_FILE_PATH:
+            return {}
 
-class FooterView(drf.views.APIView):
-    """API ViewSet for sharing the footer JSON."""
-
-    permission_classes = [AllowAny]
-
-    @method_decorator(cache_page(settings.FRONTEND_FOOTER_VIEW_CACHE_TIMEOUT))
-    def get(self, request):
-        """
-        GET /api/v1.0/footer/
-            Return the footer JSON.
-        """
-        json_footer = (
-            get_footer_json(settings.FRONTEND_URL_JSON_FOOTER)
-            if settings.FRONTEND_URL_JSON_FOOTER
-            else {}
+        cache_key = (
+            f"theme_customization_{slugify(settings.THEME_CUSTOMIZATION_FILE_PATH)}"
         )
-        return drf.response.Response(json_footer)
+        theme_customization = cache.get(cache_key, {})
+        if theme_customization:
+            return theme_customization
+
+        try:
+            with open(
+                settings.THEME_CUSTOMIZATION_FILE_PATH, "r", encoding="utf-8"
+            ) as f:
+                theme_customization = json.load(f)
+        except FileNotFoundError:
+            logger.error(
+                "Configuration file not found: %s",
+                settings.THEME_CUSTOMIZATION_FILE_PATH,
+            )
+        except json.JSONDecodeError:
+            logger.error(
+                "Configuration file is not a valid JSON: %s",
+                settings.THEME_CUSTOMIZATION_FILE_PATH,
+            )
+        else:
+            cache.set(
+                cache_key,
+                theme_customization,
+                settings.THEME_CUSTOMIZATION_CACHE_TIMEOUT,
+            )
+
+        return theme_customization

src/backend/core/tests/test_api_config.py

@@ -2,6 +2,8 @@
 Test config API endpoints in the Impress core app.
 """
 
+import json
+
 from django.test import override_settings
 
 import pytest
@@ -24,6 +26,7 @@ pytestmark = pytest.mark.django_db
     MEDIA_BASE_URL="http://testserver/",
     POSTHOG_KEY={"id": "132456", "host": "https://eu.i.posthog-test.com"},
     SENTRY_DSN="https://sentry.test/123",
+    THEME_CUSTOMIZATION_FILE_PATH="",
 )
 @pytest.mark.parametrize("is_authenticated", [False, True])
 def test_api_config(is_authenticated):
@@ -56,4 +59,98 @@ def test_api_config(is_authenticated):
         "POSTHOG_KEY": {"id": "132456", "host": "https://eu.i.posthog-test.com"},
         "SENTRY_DSN": "https://sentry.test/123",
         "AI_FEATURE_ENABLED": False,
+        "theme_customization": {},
     }
+
+
+@override_settings(
+    THEME_CUSTOMIZATION_FILE_PATH="/not/existing/file.json",
+)
+@pytest.mark.parametrize("is_authenticated", [False, True])
+def test_api_config_with_invalid_theme_customization_file(is_authenticated):
+    """Anonymous users should be allowed to get the configuration."""
+    client = APIClient()
+
+    if is_authenticated:
+        user = factories.UserFactory()
+        client.force_login(user)
+
+    response = client.get("/api/v1.0/config/")
+    assert response.status_code == HTTP_200_OK
+    content = response.json()
+    assert content["theme_customization"] == {}
+
+
+@override_settings(
+    THEME_CUSTOMIZATION_FILE_PATH="/configuration/theme/invalid.json",
+)
+@pytest.mark.parametrize("is_authenticated", [False, True])
+def test_api_config_with_invalid_json_theme_customization_file(is_authenticated, fs):
+    """Anonymous users should be allowed to get the configuration."""
+    fs.create_file(
+        "/configuration/theme/invalid.json",
+        contents="invalid json",
+    )
+    client = APIClient()
+
+    if is_authenticated:
+        user = factories.UserFactory()
+        client.force_login(user)
+
+    response = client.get("/api/v1.0/config/")
+    assert response.status_code == HTTP_200_OK
+    content = response.json()
+    assert content["theme_customization"] == {}
+
+
+@override_settings(
+    THEME_CUSTOMIZATION_FILE_PATH="/configuration/theme/default.json",
+)
+@pytest.mark.parametrize("is_authenticated", [False, True])
+def test_api_config_with_theme_customization(is_authenticated, fs):
+    """Anonymous users should be allowed to get the configuration."""
+    fs.create_file(
+        "/configuration/theme/default.json",
+        contents=json.dumps(
+            {
+                "colors": {
+                    "primary": "#000000",
+                    "secondary": "#000000",
+                },
+            }
+        ),
+    )
+    client = APIClient()
+
+    if is_authenticated:
+        user = factories.UserFactory()
+        client.force_login(user)
+
+    response = client.get("/api/v1.0/config/")
+    assert response.status_code == HTTP_200_OK
+    content = response.json()
+    assert content["theme_customization"] == {
+        "colors": {
+            "primary": "#000000",
+            "secondary": "#000000",
+        },
+    }
+
+
+@pytest.mark.parametrize("is_authenticated", [False, True])
+def test_api_config_with_original_theme_customization(is_authenticated, settings):
+    """Anonymous users should be allowed to get the configuration."""
+    client = APIClient()
+
+    if is_authenticated:
+        user = factories.UserFactory()
+        client.force_login(user)
+
+    response = client.get("/api/v1.0/config/")
+    assert response.status_code == HTTP_200_OK
+    content = response.json()
+
+    with open(settings.THEME_CUSTOMIZATION_FILE_PATH, "r", encoding="utf-8") as f:
+        theme_customization = json.load(f)
+
+    assert content["theme_customization"] == theme_customization