Create separate endpoint for getting file upload fields.

missioncontrol/home/models.py

@@ -525,11 +525,14 @@ def get_download_url(self):
 
         return url
 
-    def get_upload_url(self):
+    @classmethod
+    def get_post_data_fields(cls, **kwargs):
+        # Create the object but don't save it
+        obj = cls(**kwargs)
         s3 = boto3.client('s3')
         post = s3.generate_presigned_post(
-            Bucket=self.bucket,
-            Key=self.key,
+            Bucket=obj.bucket,
+            Key=obj.key,
         )
 
         return post

missioncontrol/openapi/openapi.yaml

@@ -1160,6 +1160,32 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/Error'
+  /files/get_post_data_fields/:
+    get:
+      tags: ['files']
+      description: Get the fields required for uploading a new file
+      operationId: v0.files.get_post_data_fields
+      parameters:
+      - in: query
+        name: cid
+        required: true
+        description:
+            The content ID of a file (blake2b hash)
+        schema:
+          type: string
+      responses:
+        200:
+          description: The fields required for a file upload
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/PostDataFields'
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Error'
   /files/{cid}/:
     get:
       tags: ['files']
@@ -1546,7 +1572,7 @@ components:
           type: integer
           readOnly: true
 
-    PostUrlFields:
+    PostDataFields:
       properties:
         url:
           description: The url to post to

missioncontrol/tests/test_files.py

@@ -182,3 +182,26 @@ def test_version_increment(test_client, simple_file, some_hash, another_hash):
     assert result1.pop('cid') == some_hash
     assert result2.pop('cid') == another_hash
     assert result1 == result2
+
+# Still needs a database for the user setup.
+@patch('home.models.boto3')
+@pytest.mark.django_db
+def test_get_post_data_fields(boto3_mock, test_client, some_hash):
+    post_values = {
+        'url': 'https://test.example',
+        'url_fields': {},
+    }
+    boto3_mock.client.return_value.generate_presigned_post.return_value = post_values
+
+    response = test_client.get(
+        f'/api/v0/files/get_post_data_fields/',
+        query_string={'cid': some_hash}
+    )
+    assert response.status_code == 200, response.get_data()
+
+    assert response.json == post_values
+
+    boto3_mock.client.return_value.generate_presigned_post.assert_called_with(
+        Bucket=settings.FILE_STORAGE_PATH.split('/')[2],
+        Key=f'django-file-storage/{some_hash}',
+    )

missioncontrol/v0/files.py

@@ -44,4 +44,13 @@ def put(cid, file_body):
         )
     obj, created = S3File.objects.update_or_create(cid=cid, defaults=file_body)
     retval = obj.to_dict()
-    return retval, 201 if created else 200
+    return retval, 201 if created else 200
+
+def get_post_data_fields(cid):
+    if S3File.objects.filter(cid=cid).exists():
+        raise ProblemException(
+            status=409,
+            title='Conflict',
+            detail='This cid already exists in metadata',
+        )
+    return S3File.get_post_data_fields(cid=cid)