From 0815bee4e6d0b67bcf55e977acc53e26eda9d86a Mon Sep 17 00:00:00 2001
From: Ian Ward <ian@excess.org>
Date: Fri, 6 Jan 2017 16:20:49 -0500
Subject: [PATCH] [#3390] datastore dump format=json

---
 ckanext/datastore/controller.py |  5 ++-
 ckanext/datastore/writer.py     | 58 +++++++++++++++++++++++++++++++--
 doc/maintaining/datastore.rst   |  8 +++--
 3 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/ckanext/datastore/controller.py b/ckanext/datastore/controller.py
index 559a1d2dfb7..821c5a97ab0 100644
--- a/ckanext/datastore/controller.py
+++ b/ckanext/datastore/controller.py
@@ -18,12 +18,13 @@
 from ckanext.datastore.writer import (
     csv_writer,
     tsv_writer,
+    json_writer,
 )
 
 int_validator = get_validator('int_validator')
 boolean_validator = get_validator('boolean_validator')
 
-DUMP_FORMATS = 'csv', 'tsv'
+DUMP_FORMATS = 'csv', 'tsv', 'json'
 PAGINATE_BY = 10000
 
 
@@ -45,6 +46,8 @@ def start_writer(columns):
                 return csv_writer(response, columns, resource_id, bom)
             if fmt == 'tsv':
                 return tsv_writer(response, columns, resource_id, bom)
+            if fmt == 'json':
+                return json_writer(response, columns, resource_id, bom)
             abort(400, _(
                 u'format: must be one of %s') % u', '.join(DUMP_FORMATS))
 
diff --git a/ckanext/datastore/writer.py b/ckanext/datastore/writer.py
index b767220ad5a..910337124ba 100644
--- a/ckanext/datastore/writer.py
+++ b/ckanext/datastore/writer.py
@@ -1,4 +1,6 @@
 from contextlib import contextmanager
+from email.utils import encode_rfc2231
+import json
 
 import unicodecsv
 
@@ -24,7 +26,8 @@ def csv_writer(response, columns, name=None, bom=False):
         response.headers['Content-Type'] = 'text/csv; charset=utf-8'
         if name:
             response.headers['Content-disposition'] = (
-                'attachment; filename="{name}.csv"'.format(name=name))
+                'attachment; filename="{name}.csv"'.format(
+                    name=encode_rfc2231(name)))
     wr = unicodecsv.writer(response, encoding='utf-8')
     if bom:
         response.write(UTF8_BOM)
@@ -49,13 +52,62 @@ def tsv_writer(response, columns, name=None, bom=False):
 
     if hasattr(response, 'headers'):
         response.headers['Content-Type'] = (
-            'text/csv;tab-separated-values charset=utf-8')
+            'text/tab-separated-values; charset=utf-8')
         if name:
             response.headers['Content-disposition'] = (
-                'attachment; filename="{name}.tsv"'.format(name=name))
+                'attachment; filename="{name}.tsv"'.format(
+                    name=encode_rfc2231(name)))
     wr = unicodecsv.writer(
         response, encoding='utf-8', dialect=unicodecsv.excel_tab)
     if bom:
         response.write(UTF8_BOM)
     wr.writerow(columns)
     yield wr
+
+
+@contextmanager
+def json_writer(response, columns, name=None, bom=False):
+    u'''Context manager for writing UTF-8 JSON data to response
+
+    :param response: file-like or response-like object for writing
+        data and headers (response-like objects only)
+    :param columns: list of column names
+    :param name: file name (for headers, response-like objects only)
+    :param bom: True to include a UTF-8 BOM at the start of the file
+
+    >>> with json_writer(response, fields) as d:
+    >>>    d.writerow(row1)
+    >>>    d.writerow(row2)
+    '''
+
+    if hasattr(response, 'headers'):
+        response.headers['Content-Type'] = (
+            'application/json; charset=utf-8')
+        if name:
+            response.headers['Content-disposition'] = (
+                'attachment; filename="{name}.json"'.format(
+                    name=encode_rfc2231(name)))
+    if bom:
+        response.write(UTF8_BOM)
+    response.write(b'{\n  "data": [')
+    yield JSONWriter(response, columns)
+    response.write(b'\n]}\n')
+
+
+class JSONWriter(object):
+    def __init__(self, response, columns):
+        self.response = response
+        self.columns = columns
+        self.first = True
+
+    def writerow(self, row):
+        if self.first:
+            self.first = False
+            self.response.write(b'\n    ')
+        else:
+            self.response.write(b',\n    ')
+        self.response.write(json.dumps(
+            {k: v for (k, v) in zip(self.columns, row)},
+            ensure_ascii=False,
+            separators=(',', ':'),
+            sort_keys=True).encode('utf-8'))
diff --git a/doc/maintaining/datastore.rst b/doc/maintaining/datastore.rst
index a19294f6c9b..11689ad4b82 100644
--- a/doc/maintaining/datastore.rst
+++ b/doc/maintaining/datastore.rst
@@ -275,14 +275,16 @@ API reference
 
 .. _dump:
 
-Download resource as CSV
-------------------------
+Download resource
+-----------------
 
 A DataStore resource can be downloaded in the `CSV`_ file format from ``{CKAN-URL}/datastore/dump/{RESOURCE-ID}``.
 
 For an Excel-compatible CSV file use ``{CKAN-URL}/datastore/dump/{RESOURCE-ID}?bom=true``.
 
-For tab-separated values use ``{CKAN-URL}/datastore/dump/{RESOURCE-ID}?format=tsv``.
+Other formats are also supported. For tab-separated values use
+``{CKAN-URL}/datastore/dump/{RESOURCE-ID}?format=tsv`` and for JSON use
+``{CKAN-URL}/datastore/dump/{RESOURCE-ID}?format=json``.
 
 .. _CSV: https://en.wikipedia.org/wiki/Comma-separated_values