Merge branch 'feature-caching'

Conflicts:
	docs/usage.rst

docs/configuration.rst

@@ -0,0 +1,18 @@
+============
+Configuration
+============
+
+Provided your Django project has a working cache backend, django-sheets will cache requests to the Google Sheets API for 5 minutes.
+
+ - Performance- making an extra HTTP request per page-view (or more) will lead to poor response times.
+ - Reliability- The Google Sheets API may experience failing requests- having a cached copy on your servers means this is less likely to affect you.
+ - Exceeding quota- By making excessive requests you risk exceeding the API Quota and having requests denied until the quota is refreshed, making your page unusable.
+
+If you wish to disable this cache, add to your settings file::
+
+    SHEETS_CACHE_DISABLED = True
+
+You can lower the cache timeout if you wish to sacrifice performance to lessen the chance of stale data, or extend it to improve performance and reduce server load::
+
+    # Set timeout to 1 hour
+    SHEETS_CACHE_TIMEOUT = 3600

docs/index.rst

@@ -10,6 +10,7 @@ Welcome to django-sheets's documentation!
    :maxdepth: 2
 
    installation
+   configuration
    usage
    authors
    history

docs/usage.rst

@@ -8,8 +8,15 @@ Google Sheets spreadsheet. To find it, open your sheet and select
 Click *Get sharable link* from the dialog. You'll find the 44-character key as
 part of the URL.
 
+<<<<<<< HEAD
 For example, the sample link ``https://docs.google.com/spreadsheets/d/1bJNR7SLqpzWJNvstNcFR4gtS-M7Bmn0D1X2lGTJPvGM/pubhtml``
 has key ``1bJNR7SLqpzWJNvstNcFR4gtS-M7Bmn0D1X2lGTJPvGM``
+=======
+Press Share, and select the link. You'll find the 44-character key as
+part of the link. For example, the sample link:
+
+`https://docs.google.com/spreadsheets/d/**1bJNR7SLqpzWJNvstNcFR4gtS-M7Bmn0D1X2lGTJPvGM**/pubhtml`
+>>>>>>> feature-caching
 
 Load the django-sheets template tags in your template::
 
@@ -22,9 +29,9 @@ Assign the CSV data to a variable using the ``{% csv %}`` tag::
 Try it using the sample key above::
 
     {% load sheets %}
-    {% csv "1uPsdcGUnUsf3d2xGHRGUUb7_k5IQPtBvfQY61u8Z8wE" as uk500 %}
+    {% csv "1uPsdcGUnUsf3d2xGHRGUUb7_k5IQPtBvfQY61u8Z8wE" as csv_data %}
     <table>
-    {% for row in uk500 %}
+    {% for row in csv_data %}
         <tr>
         {% for cell in row %}
             <td>{{ cell }}</td>

sheets/templatetags/sheets.py

@@ -1,6 +1,8 @@
 from __future__ import unicode_literals
 
 from django import template
+from django.conf import settings
+from django.core.cache import cache
 from django.utils.encoding import force_str, force_text
 
 import csv
@@ -13,10 +15,12 @@
 gdocs_format = \
     'https://docs.google.com/spreadsheets/d/{key}/export?format=csv&id={key}'
 
+CACHE_TIMEOUT = getattr(settings, 'SHEETS_CACHE_TIMEOUT', 300)
+CACHE_KEY = 'django-sheets-{key}'
+
 
 def get_sheet(key):
     try:
-        print(gdocs_format.format(key=key))
         response = requests.get(gdocs_format.format(key=key))
         response.raise_for_status()
         return response
@@ -33,16 +37,30 @@ def read_csv(csv_content):
     )
 
 
+class ExplicitNone:
+    pass
+
+
 @register.assignment_tag(name='csv')
 def csv_tag(key):
     if not key:
         raise RuntimeError('Sheet key not supplied')
 
+    cache_enabled = not getattr(settings, 'SHEETS_CACHE_DISABLED', False)
+
+    if cache_enabled:
+        cache_key = CACHE_KEY.format(key=key)
+        cached_output = cache.get(cache_key)
+        if cached_output is not None:
+            return cached_output
+
     response_data = get_sheet(key)
 
-    if response_data is None:
-        return None
+    if response_data:
+        reader = read_csv(response_data.content)
+        response_data = [[force_text(cell) for cell in row] for row in reader]
 
-    reader = read_csv(response_data.content)
+    if cache_enabled:
+        cache.set(cache_key, response_data, CACHE_TIMEOUT)
 
-    return [[force_text(cell) for cell in row] for row in reader]
+    return response_data

tests/test_templatetags.py

@@ -14,6 +14,8 @@
 
 from django import template
 from django.test import SimpleTestCase
+from django.test.utils import override_settings
+from django.core.cache import cache
 
 sample_template = \
     """{% spaceless %}
@@ -46,6 +48,9 @@
 
 class TestSheets(SimpleTestCase):
 
+    def setUp(self):
+        cache.clear()
+
     def test_no_key(self):
         """
         Empty keys should throw exception
@@ -83,3 +88,48 @@ def test_sample_mocked(self):
             gdocs_format.format(key=sample_key))
 
         self.assertEqual(output, open(sample_output).read())
+
+    @responses.activate
+    def test_cache(self):
+        """
+        When cache enabled, rendering tag twice should issue one request
+        """
+        responses.add(
+            responses.GET, gdocs_format.format(key=sample_key),
+            body=open(sample_response).read(),
+            match_querystring=True, status=200)
+        t = template.Template(sample_template)
+        t.render(template.Context({'key': sample_key}))
+        output = t.render(template.Context({'key': sample_key}))
+        self.assertEqual(output, open(sample_output).read())
+        self.assertEqual(1, len(responses.calls))
+
+    @responses.activate
+    @override_settings(SHEETS_CACHE_DISABLED=True)
+    def test_cache_disabled(self):
+        """
+        When cache disabled, rendering tag twice should issue two requests
+        """
+        responses.add(
+            responses.GET, gdocs_format.format(key=sample_key),
+            body=open(sample_response).read(),
+            match_querystring=True, status=200)
+        t = template.Template(sample_template)
+        t.render(template.Context({'key': sample_key}))
+        t.render(template.Context({'key': sample_key}))
+
+        self.assertEqual(2, len(responses.calls))
+
+    @responses.activate
+    def test_cache_when_empty(self):
+        """
+        Make sure that empty spreadsheets are not mistaken for cache miss
+        """
+        responses.add(
+            responses.GET, gdocs_format.format(key=sample_key),
+            body='',
+            match_querystring=True, status=200)
+        t = template.Template(sample_template)
+        t.render(template.Context({'key': sample_key}))
+        t.render(template.Context({'key': sample_key}))
+        self.assertEqual(1, len(responses.calls))