[draft] DGPF-extensible rendering of files based on public URL

globus_portal_framework/checks.py

@@ -82,3 +82,22 @@ def check_allowed_groups(app_configs, **kwargs):
                 errors.append(e)
 
     return errors
+
+
+@register
+def check_gpreview(app_configs, **kwargs):
+    """Simplistic check: GLOBUS_PREVIEW_COLLECTIONS must be a dict of {uuid: https_url}"""
+    s = getattr(settings, 'GLOBUS_PREVIEW_COLLECTIONS', {})
+
+    catchall = [
+        Error('GLOBUS_PREVIEW_COLLECTIONS must be a dict of {uuid: https_url}',
+              obj=s, id='globus_portal_framework.settings.E005')
+    ]
+
+    if not isinstance(s, dict):
+        return catchall
+
+    for k, v in s.items():
+        if len(k.replace('-', '')) != 32 or not v.startswith('https'):
+            return catchall
+    return []

globus_portal_framework/exc.py

@@ -120,6 +120,13 @@ def __init__(self, **kwargs):
         self.message = 'Preview is unable to display binary data.'
 
 
+class PreviewCollectionError(GlobusPortalException):
+    DEFAULT_MESSAGE = 'Could not determine how to access the specified collection for Preview Mode'
+    def __init__(self, message=DEFAULT_MESSAGE, **kwargs):
+        super().__init__(message=message, **kwargs)
+        self.code = 'BadPreviewConfig'
+
+
 class ExpiredGlobusToken(GlobusPortalException):
     def __init__(self, token_name='', **kwargs):
         super().__init__(**kwargs)

globus_portal_framework/gclients.py

@@ -64,7 +64,7 @@ def is_globus_user(user):
         return False
 
 
-def load_globus_access_token(user: "django.contrib.auth.models.User", token_name: str):
+def load_globus_access_token(user: "django.contrib.auth.models.User", token_name: str) -> t.Union[str, None]:
     """
     Load a globus user access token using a provided lookup by resource server.
     Scopes MUST have already been configured in settings.py, and additionally

globus_portal_framework/gpreview.py

@@ -0,0 +1,67 @@
+"""
+Functions related to the "file preview" functionality
+"""
+import logging
+import typing as t
+from urllib.parse import urljoin
+
+from django.conf import settings
+from django.urls import reverse
+
+from globus_portal_framework.exc import PreviewCollectionError
+
+log = logging.getLogger(__name__)
+
+
+def get_https_url(collection_uuid: str) -> t.Union[str, None]:
+    """
+    Get the HTTPS server URL associated with a collection UUID
+
+    Enforces an assumption that the site is only allowed to talk to (authenticated) collections that
+        are whitelisted in app settings
+    """
+    whitelist = getattr(settings, 'GLOBUS_PREVIEW_COLLECTIONS', {})
+    try:
+        return whitelist[collection_uuid]
+    except KeyError:
+        raise PreviewCollectionError(message=f'No HTTPS URL available for collection UUID {collection_uuid}')
+
+
+def get_render_options(url: str=None,
+                       collection_id: str=None, path: str=None,
+                       is_authenticated: bool=False,
+                       render_mode: str='auto'):
+    """
+    Generate "render options" used by the client-side preview feature.
+
+    Translates collection id + path into URLs based on info in app config
+    """
+    token_endpoint = None
+
+    if not url and not collection_id and not path:
+        # There's nothing to render, and it makes sense to hide the render widget on page
+        raise PreviewCollectionError(message='Please specify how to locate the file')
+
+    if (collection_id and path) and not url:
+        # Translate collection IDs into "where is the file and how to access it"
+        try:
+            base = get_https_url(collection_id)
+        except PreviewCollectionError as e:
+            log.error(f'Preview mode requested a file from unrecognized storage collection: "{collection_id}". Check GLOBUS_PREVIEW_COLLECTIONS setting.')
+            raise e
+
+        url = urljoin(base, path)
+
+        # Now that we know it's a globus collections, answer the question:
+        #  "How does the renderer get globus access credentials?" (if appropriate)
+        if is_authenticated:
+            token_endpoint = reverse('get-token', kwargs={'collection_id': collection_id})
+
+    return {
+        'url': url,
+        'render_mode': render_mode,
+
+        # null if file is public
+        'collection_id': collection_id,
+        'token_endpoint': token_endpoint,
+    }