Add basic Validation for URITemplates

Closes #33

tests/test_validator.py

@@ -0,0 +1,43 @@
+"""Tests for the uritemplate.Validator class."""
+import uritemplate
+from uritemplate import exceptions
+
+import pytest
+
+
+@pytest.mark.parametrize('template', [
+    'https://github.com{/user}',
+    'https://github.com/sigmavirus24{/repository}',
+    '{foo}',
+    '?{bar}',
+    'https://example.com',
+])
+def test_valid_uris(template):
+    """Verify we don't raise an exception."""
+    urit = uritemplate.URITemplate(template)
+    uritemplate.Validator().validate(urit)
+
+
+@pytest.mark.parametrize('template', [
+    'https://github.com{/user',
+    'https://github.com/sigmavirus24/repository}',
+    '{foo}}',
+    '?{{bar}',
+])
+def test_invalid_uris(template):
+    """Verify we catch invalid URITemplates."""
+    urit = uritemplate.URITemplate(template)
+    with pytest.raises(exceptions.InvalidTemplate):
+        uritemplate.Validator().validate(urit)
+
+
+@pytest.mark.parametrize('template', [
+    'https://github.com{/user',
+    'https://github.com/sigmavirus24/repository}',
+    '{foo}}',
+    '?{{bar}',
+])
+def test_allow_invalid_uris(template):
+    """Verify we allow invalid URITemplates."""
+    urit = uritemplate.URITemplate(template)
+    uritemplate.Validator().allow_unbalanced_braces().validate(urit)

uritemplate/__init__.py

@@ -16,11 +16,12 @@
 __author__ = 'Ian Cordasco'
 __license__ = 'Modified BSD or Apache License, Version 2.0'
 __copyright__ = 'Copyright 2013 Ian Cordasco'
-__version__ = '3.0.0'
+__version__ = '3.1.0'
 __version_info__ = tuple(int(i) for i in __version__.split('.') if i.isdigit())
 
 from uritemplate.api import (
     URITemplate, expand, partial, variables  # noqa: E402
 )
+from uritemplate.validator import Validator  # noqa: E402
 
-__all__ = ('URITemplate', 'expand', 'partial', 'variables')
+__all__ = ('URITemplate', 'Validator', 'expand', 'partial', 'variables')

uritemplate/exceptions.py

@@ -0,0 +1,31 @@
+"""Module containing all exceptions for the uritemplate module."""
+
+
+class TemplateException(Exception):
+    """Base Exception class for all uritemplate exceptions."""
+
+    pass
+
+
+class InvalidTemplate(TemplateException):
+    """Base class for template validation."""
+
+    message = "The URI template ({}) is invalid."
+
+    def __init__(self, uri, *args):
+        """Initialize our exception."""
+        super(InvalidTemplate, self).__init__(self.message.format(uri, *args))
+        self.uri = uri
+
+
+class UnbalancedBraces(InvalidTemplate):
+    """The template has unbalanced braces."""
+
+    message = "The URI template ({}) has more {} braces than {} braces."
+
+    def __init__(self, uri, left_braces_count, right_braces_count):
+        """Initialize our exception."""
+        more, less = 'left', 'right'
+        if left_braces_count < right_braces_count:
+            more, less = less, more
+        super(UnbalancedBraces, self).__init__(uri, more, less)

uritemplate/validator.py

@@ -0,0 +1,58 @@
+"""Module containing all the validation logic for uritemplate."""
+from uritemplate import exceptions as exc
+
+
+class Validator(object):
+    """Provide configurable validation of URITemplate objects.
+
+    .. versionadded:: 3.1.0
+
+    .. code-block::
+
+        from uritemplate import URITemplate, Validator
+
+
+    """
+
+    def __init__(self):
+        """Initialize our validator."""
+        self.enforcing_unbalanced_braces = True
+
+    def allow_unbalanced_braces(self):
+        """Allow a template to have unbalanced braces.
+
+        .. versionadded:: 3.1.0
+
+        Returns the validator instance.
+        """
+        self.enforcing_unbalanced_braces = False
+        return self
+
+    def force_balanced_braces(self):
+        """Force a template to have balanced braces.
+
+        .. versionadded:: 3.1.0
+
+        Returns the validator instance.
+        """
+        self.enforcing_unbalanced_braces = True
+        return self
+
+    def validate(self, template):
+        """Validate that a template meets the parameters.
+
+        .. versionadded:: 3.1.0
+
+        :raises: uritemplate.exceptions.InvalidTemplate
+        :raises: uritemplate.exceptions.UnbalancedBraces
+        """
+        if self.enforcing_unbalanced_braces:
+            _enforce_balanced_braces(template)
+
+
+def _enforce_balanced_braces(template):
+    uri = template.uri
+    left_braces = uri.count('{')
+    right_braces = uri.count('}')
+    if left_braces != right_braces:
+        raise exc.UnbalancedBraces(uri, left_braces, right_braces)