Add CsvConnector as first of internal data sources

applications/migrations/0006_unset_url_required.py

+# Generated by Django 2.0.8 on 2018-10-29 13:34
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('applications', '0005_one_to_one_group'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='application',
+            name='url',
+            field=models.URLField(blank=True),
+        ),
+    ]

core/models.py

@@ -10,6 +10,8 @@ MAX_LENGTH_NAME = 63
 
 MAX_LENGTH_API_KEY = 127
 
+MAX_LENGTH_PATH = 255
+
 
 class BaseAppDataModel(models.Model):
     #: Friendly name of this application
@@ -20,7 +22,7 @@ class BaseAppDataModel(models.Model):
     description = models.TextField(blank=True, null=False)
 
     #: Address at which the API may be accessed
-    url = models.URLField(blank=False, null=False)
+    url = models.URLField(blank=True, null=False)
 
     #: Do users require explicit permission to use this data source / application?
     access_control = models.BooleanField(default=False,

datasources/connectors/csv.py

+import typing
+
+from .base import DataSetConnector
+
+
+class DummyResponse:
+    def __init__(self,
+                 text: str,
+                 status_code: int,
+                 content_type: str):
+        self.text = text
+        self.status_code = status_code
+        self.headers = {
+            'content-type': content_type,
+        }
+
+
+class CsvConnector(DataSetConnector):
+    """
+    Data connector for retrieving data from CSV files.
+    """
+    def get_metadata(self,
+                     params: typing.Optional[typing.Mapping[str, str]] = None):
+        raise NotImplementedError('CSV does not provide metadata')
+
+    def get_data(self,
+                 params: typing.Optional[typing.Mapping[str, str]] = None):
+        raise NotImplementedError('CSV does not provide metadata')
+
+    def get_response(self,
+                     params: typing.Optional[typing.Mapping[str, str]] = None):
+        """
+        Return a dummy response from a CSV file.
+
+        :param params: Optional query parameter filters - ignored
+        :return: Requested data
+        """
+        with open(self.location, 'r') as f:
+            return DummyResponse(f.read(), 200, 'text/plain')

datasources/migrations/0008_datasource__connector_string.py

+# Generated by Django 2.0.8 on 2018-10-29 13:20
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('datasources', '0007_datasource_api_key'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='datasource',
+            name='_connector_string',
+            field=models.CharField(blank=True, max_length=255),
+        ),
+    ]

datasources/migrations/0009_unset_url_required.py

+# Generated by Django 2.0.8 on 2018-10-29 13:34
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('datasources', '0008_datasource__connector_string'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='datasource',
+            name='url',
+            field=models.URLField(blank=True),
+        ),
+    ]

datasources/models.py

@@ -7,7 +7,7 @@ from django.db import models
 from django.urls import reverse
 
 from datasources.connectors.base import BaseDataConnector
-from core.models import BaseAppDataModel, MAX_LENGTH_API_KEY, MAX_LENGTH_NAME
+from core.models import BaseAppDataModel, MAX_LENGTH_API_KEY, MAX_LENGTH_NAME, MAX_LENGTH_PATH
 
 
 class DataSource(BaseAppDataModel):
@@ -30,6 +30,10 @@ class DataSource(BaseAppDataModel):
                               related_name='datasources',
                               blank=False, null=False)
 
+    #: Information required to initialise the connector for this data source
+    _connector_string = models.CharField(max_length=MAX_LENGTH_PATH,
+                                         blank=True, null=False)
+
     #: Name of plugin which allows interaction with this data source
     plugin_name = models.CharField(max_length=MAX_LENGTH_NAME,
                                    blank=False, null=False)
@@ -42,6 +46,12 @@ class DataSource(BaseAppDataModel):
         super().__init__(*args, **kwargs)
         self._data_connector = None
 
+    @property
+    def connector_string(self):
+        if self._connector_string:
+            return self._connector_string
+        return self.url
+
     @property
     def data_connector(self) -> BaseDataConnector:
         """
@@ -62,9 +72,9 @@ class DataSource(BaseAppDataModel):
                 raise KeyError('Data source plugin not found') from e
 
             if self.api_key:
-                self._data_connector = plugin(self.url, self.api_key)
+                self._data_connector = plugin(self.connector_string, self.api_key)
             else:
-                self._data_connector = plugin(self.url)
+                self._data_connector = plugin(self.connector_string)
 
         return self._data_connector