Extend edX API utility to support retrieval of specific resources

This will be used to retrieve data for the program detail page. Part of ECOM-4415.

openedx/core/lib/edx_api_utils.py

@@ -11,23 +11,25 @@ from openedx.core.lib.token_utils import get_id_token
 log = logging.getLogger(__name__)
 
 
-def get_edx_api_data(api_config, user, resource, querystring=None, cache_key=None):
-    """Fetch data from an API using provided API configuration and resource
-        name.
+def get_edx_api_data(api_config, user, resource, resource_id=None, querystring=None, cache_key=None):
+    """GET data from an edX REST API.
+
+    DRY utility for handling caching and pagination.
 
     Arguments:
-        api_config (ConfigurationModel): The configuration model governing
-            interaction with the API.
+        api_config (ConfigurationModel): The configuration model governing interaction with the API.
         user (User): The user to authenticate as when requesting data.
-        resource(str): Name of the API resource for which data is being
-            requested.
-        querystring(dict): Querystring parameters that might be required to
-            request data.
-        cache_key(str): Where to cache retrieved data. Omitting this will cause the
-            cache to be bypassed.
+        resource (str): Name of the API resource being requested.
+
+    Keyword Arguments:
+        resource_id (int or str): Identifies a specific resource to be retrieved.
+        querystring (dict): Optional query string parameters.
+        cache_key (str): Where to cache retrieved data. The cache will be ignored if this is omitted
+            (neither inspected nor updated).
 
     Returns:
-        list of dict, representing data returned by the API.
+        Data returned by the API. When hitting a list endpoint, extracts "results" (list of dict)
+        returned by DRF-powered APIs.
     """
     no_data = []
 
@@ -36,30 +38,29 @@ def get_edx_api_data(api_config, user, resource, querystring=None, cache_key=Non
         return no_data
 
     if cache_key:
+        cache_key = '{}.{}'.format(cache_key, resource_id) if resource_id else cache_key
+
         cached = cache.get(cache_key)
-        if cached is not None:
+        if cached:
             return cached
 
     try:
         jwt = get_id_token(user, api_config.OAUTH2_CLIENT_NAME)
         api = EdxRestApiClient(api_config.internal_api_url, jwt=jwt)
-    except Exception:  # pylint: disable=broad-except
+    except:  # pylint: disable=bare-except
         log.exception('Failed to initialize the %s API client.', api_config.API_NAME)
         return no_data
 
     try:
-        querystring = {} if not querystring else querystring
-        response = getattr(api, resource).get(**querystring)
-        results = response.get('results', no_data)
-        page = 1
-        next_page = response.get('next', None)
-        while next_page:
-            page += 1
-            querystring['page'] = page
-            response = getattr(api, resource).get(**querystring)
-            results += response.get('results', no_data)
-            next_page = response.get('next', None)
-    except Exception:  # pylint: disable=broad-except
+        endpoint = getattr(api, resource)
+        querystring = querystring if querystring else {}
+        response = endpoint(resource_id).get(**querystring)
+
+        if resource_id:
+            results = response
+        else:
+            results = _traverse_pagination(response, endpoint, querystring, no_data)
+    except:  # pylint: disable=bare-except
         log.exception('Failed to retrieve data from the %s API.', api_config.API_NAME)
         return no_data
 
@@ -67,3 +68,22 @@ def get_edx_api_data(api_config, user, resource, querystring=None, cache_key=Non
         cache.set(cache_key, results, api_config.cache_ttl)
 
     return results
+
+
+def _traverse_pagination(response, endpoint, querystring, no_data):
+    """Traverse a paginated API response.
+
+    Extracts and concatenates "results" (list of dict) returned by DRF-powered APIs.
+    """
+    results = response.get('results', no_data)
+
+    page = 1
+    next_page = response.get('next')
+    while next_page:
+        page += 1
+        querystring['page'] = page
+        response = endpoint.get(**querystring)
+        results += response.get('results', no_data)
+        next_page = response.get('next')
+
+    return results