restrict html processing to a certain number of tags

setup.py

@@ -29,7 +29,7 @@ class InstallCommand(install):
 
 
 setup(name='talon',
-      version='1.3.1',
+      version='1.3.2',
       description=("Mailgun library "
                    "to extract message quotations and signatures."),
       long_description=open("README.rst").read(),

talon/quotations.py

@@ -386,7 +386,7 @@ def _extract_from_html(msg_body):
     then checking deleted checkpoints,
     then deleting necessary tags.
     """
-    if len(msg_body) > MAX_HTML_LEN:
+    if _html_too_big(msg_body):
         return msg_body
 
     if msg_body.strip() == b'':
@@ -483,3 +483,12 @@ def register_xpath_extensions():
     ns.prefix = 'mg'
     ns['text_content'] = text_content
     ns['tail'] = tail
+
+
+def _html_too_big(msg_body):
+    return msg_body.count('<') > _MAX_TAGS_COUNT
+
+
+# an extensive research shows that exceeding this limit
+# might lead to excessive processing time
+_MAX_TAGS_COUNT = 419

tests/html_quotations_test.py

@@ -385,7 +385,7 @@ def test_gmail_forwarded_msg():
     eq_(RE_WHITESPACE.sub('', msg_body), RE_WHITESPACE.sub('', extracted))
 
 
-@patch.object(quotations, 'MAX_HTML_LEN', 1)
+@patch.object(quotations, '_MAX_TAGS_COUNT', 4)
 def test_too_large_html():
     msg_body = 'Reply' \
                '<div class="gmail_quote">' \