Basic labels support

Adds basic labels support to the registry code (V2), and the API. Note that this does not yet add any UI related support.

util/validation.py

@@ -1,5 +1,6 @@
 import string
 import re
+import json
 
 import anunidecode # Don't listen to pylint's lies. This import is required.
 
@@ -9,14 +10,21 @@ INVALID_PASSWORD_MESSAGE = 'Invalid password, password must be at least ' + \
 INVALID_USERNAME_CHARACTERS = r'[^a-z0-9_]'
 VALID_CHARACTERS = string.digits + string.lowercase
 
-MIN_LENGTH = 4
-MAX_LENGTH = 30
+MIN_USERNAME_LENGTH = 4
+MAX_USERNAME_LENGTH = 30
+
+VALID_LABEL_KEY_REGEX = r'^[a-z0-9](([a-z0-9]|[-.](?![.-]))*[a-z0-9])?$'
+
+
+def validate_label_key(label_key):
+  if len(label_key) > 255:
+    return False
+
+  return bool(re.match(VALID_LABEL_KEY_REGEX, label_key))
 
 
 def validate_email(email_address):
-  if re.match(r'[^@]+@[^@]+\.[^@]+', email_address):
-    return True
-  return False
+  return bool(re.match(r'[^@]+@[^@]+\.[^@]+', email_address))
 
 
 def validate_username(username):
@@ -25,10 +33,10 @@ def validate_username(username):
   if not regex_match:
     return (False, 'Username must match expression [a-z0-9_]+')
 
-  length_match = (len(username) >= MIN_LENGTH and len(username) <= MAX_LENGTH)
+  length_match = (len(username) >= MIN_USERNAME_LENGTH and len(username) <= MAX_USERNAME_LENGTH)
   if not length_match:
     return (False, 'Username must be between %s and %s characters in length' %
-            (MIN_LENGTH, MAX_LENGTH))
+            (MIN_USERNAME_LENGTH, MAX_USERNAME_LENGTH))
 
   return (True, '')
 
@@ -58,9 +66,20 @@ def generate_valid_usernames(input_username):
   if prefix.endswith('_'):
     prefix = prefix[0:len(prefix) - 1]
 
-  num_filler_chars = max(0, MIN_LENGTH - len(prefix))
+  num_filler_chars = max(0, MIN_USERNAME_LENGTH - len(prefix))
 
-  while num_filler_chars + len(prefix) <= MAX_LENGTH:
+  while num_filler_chars + len(prefix) <= MAX_USERNAME_LENGTH:
     for suffix in _gen_filler_chars(num_filler_chars):
       yield prefix + suffix
     num_filler_chars += 1
+
+
+def is_json(value):
+  if ((value.startswith('{') and value.endswith('}')) or
+      (value.startswith('[') and value.endswith(']'))):
+    try:
+      json.loads(value)
+      return True
+    except TypeError:
+      return False
+