Add a CleverCSS plugin.

CleverCSS [1] is a Python-based preprocessor for CSS. It is not quite
as powerful as LessCSS and doesn't seem to get much updates, but the
advantage is that it only requires Python (which you'd already have for
Hyde) and you don't need node.js or some client-side JS.

[1] http://sandbox.pocoo.org/clevercss/

hyde/ext/plugins/css.py

@@ -3,7 +3,9 @@
 CSS plugins
 """
 
-from hyde.plugin import CLTransformer
+
+from hyde.plugin import CLTransformer, Plugin
+from hyde.exceptions import HydeException
 
 import re
 import subprocess
@@ -227,3 +229,80 @@ class StylusPlugin(CLTransformer):
                     "processing [%s]" % (stylus.name, resource.source_file))
         return target.read_all()
 
+
+#
+# Clever CSS
+#
+
+class CleverCSSPlugin(Plugin):
+    """
+    The plugin class for CleverCSS
+    """
+
+    def __init__(self, site):
+        super(CleverCSSPlugin, self).__init__(site)
+        try:
+            import clevercss
+        except ImportError, e:
+            raise HydeException('Unable to import CleverCSS: ' + e.message)
+        else:
+            self.clevercss = clevercss
+
+    def _should_parse_resource(self, resource):
+        """
+        Check user defined
+        """
+        return resource.source_file.kind == 'ccss' and \
+               getattr(resource, 'meta', {}).get('parse', True)
+
+    def _should_replace_imports(self, resource):
+        return getattr(resource, 'meta', {}).get('uses_template', True)
+
+    def begin_site(self):
+        """
+        Find all the clevercss files and set their relative deploy path.
+        """
+        for resource in self.site.content.walk_resources():
+            if self._should_parse_resource(resource):
+                new_name = resource.source_file.name_without_extension + ".css"
+                target_folder = File(resource.relative_deploy_path).parent
+                resource.relative_deploy_path = target_folder.child(new_name)
+
+    def begin_text_resource(self, resource, text):
+        """
+        Replace @import statements with {% include %} statements.
+        """
+
+        if not self._should_parse_resource(resource) or \
+           not self._should_replace_imports(resource):
+            return text
+
+        import_finder = re.compile(
+                            '^\\s*@import\s+(?:\'|\")([^\'\"]*)(?:\'|\")\s*\;\s*$',
+                            re.MULTILINE)
+
+        def import_to_include(match):
+            if not match.lastindex:
+                return ''
+            path = match.groups(1)[0]
+            afile = File(resource.source_file.parent.child(path))
+            if len(afile.kind.strip()) == 0:
+                afile = File(afile.path + '.ccss')
+            ref = self.site.content.resource_from_path(afile.path)
+            if not ref:
+                raise self.template.exception_class(
+                        "Cannot import from path [%s]" % afile.path)
+            ref.is_processable = False
+            return self.template.get_include_statement(ref.relative_path)
+        text = import_finder.sub(import_to_include, text)
+        return text
+
+    def text_resource_complete(self, resource, text):
+        """
+        Run clevercss compiler on text.
+        """
+        if not self._should_parse_resource(resource):
+            return
+
+        return self.clevercss.convert(text, self.settings)
+