Extensions docs server: Design changes, partial template support.

chrome/common/extensions/docs/server2/template_data_source.py

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import json
+import logging
+import os
+import time
+
+from third_party.handlebar import Handlebar
+
+class TemplateDataSource(object):
+  def __init__(self, fetcher, base_paths, cache_timeout_seconds):
+    logging.info('Template data source created: %s %d' %
+        (' '.join(base_paths), cache_timeout_seconds))
+    self._fetcher = fetcher
+    self._template_cache = {}
+    self._base_paths = base_paths
+    self._cache_timeout_seconds = cache_timeout_seconds
+
+  def Render(self, template_name, context):
+    template = self.get(template_name)
+    if not template:
+      return ''
+      # TODO error handling
+    return template.render(json.loads(context), {'templates': self}).text

[not at google - send to devlin, 2012/06/08 01:42:53]

nice!

You should add a quick comment around here somewhere explaining this behaviour.
I think just on Render will be fine.

[cduvall, 2012/06/08 02:18:06]

Done.

+
+  class _CachedTemplate(object):
+    def __init__(self, template, cache_timeout_seconds):
+      self.template = template
+      self._expiry = time.time() + cache_timeout_seconds

[not at google - send to devlin, 2012/06/08 01:42:53]

I think that we should inject the expiry directly (i.e. pass through the expiry
time, not the cache timeout).  Because the cache timeout is a property of the
TemplateDataSource, and the expiry is a property of CachedTemplate.

[cduvall, 2012/06/08 02:18:06]

Done.

+
+    def HasExpired(self):
+      return time.time() > self._expiry
+
+  def __getitem__(self, key):
+    return self.get(key)
+
+  def get(self, key):
+    index = key.rfind('.html')
+    if index > 0:
+      key = key[:index]
+    path = key + '.html'
+    if key in self._template_cache:
+      if self._template_cache[key].HasExpired():
+        self._template_cache.pop(key)
+    if key not in self._template_cache:
+      logging.info('Template cache miss for: ' + path)
+      compiled_template = None
+      for base_path in self._base_paths:
+        try:
+          template = self._fetcher.FetchResource(base_path + path).content
+          compiled_template = Handlebar(template)
+          self._template_cache[key] = self._CachedTemplate(
+              compiled_template,
+              self._cache_timeout_seconds)
+          break
+        except:
+          pass
+
+    return compiled_template