Use Spreadsheet class to generate example CSVs

This means not repeating a bunch of `with StringIO` blocks all
over the place.

app/main/views/send.py

@@ -112,7 +112,7 @@ def send_messages(service_id, template_id):
         try:
             upload_id = s3upload(
                 service_id,
-                Spreadsheet.from_file(form.file.data.filename, form.file.data).as_dict,
+                Spreadsheet.from_file(form.file.data, filename=form.file.data.filename).as_dict,
                 current_app.config['AWS_REGION']
             )
             session['upload_data'] = {
@@ -142,16 +142,13 @@ def send_messages(service_id, template_id):
 @user_has_permissions('send_texts', 'send_emails', 'send_letters', 'manage_templates', any_=True)
 def get_example_csv(service_id, template_id):
     template = Template(service_api_client.get_service_template(service_id, template_id)['data'])
-    with io.StringIO() as output:
-        writer = csv.writer(output)
-        writer.writerows([
-            [first_column_heading[template.template_type]] + list(template.placeholders),
-            get_example_csv_rows(template)
-        ])
-        return output.getvalue(), 200, {
-            'Content-Type': 'text/csv; charset=utf-8',
-            'Content-Disposition': 'inline; filename="{}.csv"'.format(template.name)
-        }
+    return Spreadsheet.from_rows([
+        [first_column_heading[template.template_type]] + list(template.placeholders),
+        get_example_csv_rows(template)
+    ]).as_csv_data, 200, {
+        'Content-Type': 'text/csv; charset=utf-8',
+        'Content-Disposition': 'inline; filename="{}.csv"'.format(template.name)
+    }
 
 
 @main.route("/services/<service_id>/send/<template_id>/test", methods=['GET', 'POST'])
@@ -167,31 +164,28 @@ def send_test(service_id, template_id):
     )
 
     if len(template.placeholders) == 0 or request.method == 'POST':
-        with io.StringIO() as output:
-            writer = csv.writer(output)
-            writer.writerows([
-                [first_column_heading[template.template_type]] + list(template.placeholders),
-                get_example_csv_rows(template, use_example_as_example=False, submitted_fields=request.form)
-            ])
-            upload_id = s3upload(
-                service_id,
-                {
-                    'file_name': file_name,
-                    'data': output.getvalue()
-                },
-                current_app.config['AWS_REGION']
-            )
-            session['upload_data'] = {
-                "template_id": template_id,
-                "original_file_name": file_name
-            }
-            return redirect(url_for(
-                '.check_messages',
-                upload_id=upload_id,
-                service_id=service_id,
-                template_type=template.template_type,
-                from_test=True
-            ))
+        upload_id = s3upload(
+            service_id,
+            {
+                'file_name': file_name,
+                'data': Spreadsheet.from_rows([
+                    [first_column_heading[template.template_type]] + list(template.placeholders),
+                    get_example_csv_rows(template, use_example_as_example=False, submitted_fields=request.form)
+                ]).as_csv_data
+            },
+            current_app.config['AWS_REGION']
+        )
+        session['upload_data'] = {
+            "template_id": template_id,
+            "original_file_name": file_name
+        }
+        return redirect(url_for(
+            '.check_messages',
+            upload_id=upload_id,
+            service_id=service_id,
+            template_type=template.template_type,
+            from_test=True
+        ))
 
     return render_template(
         'views/send-test.html',

app/utils.py

@@ -143,7 +143,7 @@ class Spreadsheet():
 
     allowed_file_extensions = ['csv', 'xlsx', 'xls', 'ods', 'xlsm', 'tsv']
 
-    def __init__(self, filename, csv_data):
+    def __init__(self, csv_data, filename=''):
         self.filename = filename
         self.as_csv_data = csv_data
         self.as_dict = {
@@ -164,24 +164,28 @@ class Spreadsheet():
         return '\r\n'.join(file_content.getvalue().decode('utf-8').splitlines())
 
     @classmethod
-    def from_file(cls, filename, file_content):
+    def from_rows(cls, rows, filename=''):
+
+        with StringIO() as converted:
+            output = csv.writer(converted)
+
+            for row in rows:
+                output.writerow(row)
+
+            return cls(converted.getvalue(), filename)
+
+    @classmethod
+    def from_file(cls, file_content, filename=''):
 
         extension = cls.get_extension(filename)
 
         if extension == 'csv':
-            return cls(filename, Spreadsheet.normalise_newlines(file_content))
+            return cls(Spreadsheet.normalise_newlines(file_content), filename)
 
         if extension == 'tsv':
             file_content = StringIO(Spreadsheet.normalise_newlines(file_content))
 
-        with StringIO() as converted:
-
-            output = csv.writer(converted)
-
-            for row in pyexcel.get_sheet(
-                file_type=extension,
-                file_content=file_content.getvalue()
-            ).to_array():
-                output.writerow(row)
-
-            return cls(filename, converted.getvalue())
+        return cls.from_rows(pyexcel.get_sheet(
+            file_type=extension,
+            file_content=file_content.getvalue()
+        ).to_array(), filename)