--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/piecrust/processing/compass.py	Sun Jan 11 23:08:49 2015 -0800
@@ -0,0 +1,132 @@
+import os
+import os.path
+import logging
+import platform
+import subprocess
+from piecrust.processing.base import Processor, PRIORITY_FIRST
+from piecrust.uriutil import multi_replace
+
+
+logger = logging.getLogger(__name__)
+
+
+class CompassProcessor(Processor):
+    PROCESSOR_NAME = 'compass'
+
+    STATE_UNKNOWN = 0
+    STATE_INACTIVE = 1
+    STATE_ACTIVE = 2
+
+    def __init__(self):
+        super(CompassProcessor, self).__init__()
+        # Using a high priority is needed to get to the `.scss` files before
+        # the Sass processor.
+        self.priority = PRIORITY_FIRST
+        self.is_bypassing_structured_processing = True
+        self.is_delegating_dependency_check = False
+        self._state = self.STATE_UNKNOWN
+
+    def initialize(self, app):
+        super(CompassProcessor, self).initialize(app)
+
+    def onPipelineStart(self, pipeline):
+        super(CompassProcessor, self).onPipelineStart(pipeline)
+        self._maybeActivate(pipeline)
+
+    def onPipelineEnd(self, pipeline):
+        super(CompassProcessor, self).onPipelineEnd(pipeline)
+        self._maybeRunCompass(pipeline)
+
+    def matches(self, path):
+        if self._state != self.STATE_ACTIVE:
+            return False
+
+        _, ext = os.path.splitext(path)
+        return ext == '.scss' or ext == '.sass'
+
+    def getDependencies(self, path):
+        raise Exception("Compass processor should handle dependencies by "
+                        "itself.")
+
+    def getOutputFilenames(self, filename):
+        raise Exception("Compass processor should handle outputs by itself.")
+
+    def process(self, path, out_dir):
+        if path.startswith(self.app.theme_dir):
+            if not self._runInTheme:
+                logger.debug("Scheduling Compass execution in theme directory "
+                             "after the pipeline is done.")
+                self._runInTheme = True
+        else:
+            if not self._runInSite:
+                logger.debug("Scheduling Compass execution after the pipeline "
+                             "is done.")
+                self._runInSite = True
+
+    def _maybeActivate(self, pipeline):
+        if self._state != self.STATE_UNKNOWN:
+            return
+
+        config = self.app.config.get('compass')
+        if config is None or not config.get('enable'):
+            logger.debug("Compass processing is disabled (set "
+                         "`compass/enable` to `true` to enable it).")
+            self._state = self.STATE_INACTIVE
+            return
+
+        logger.debug("Activating Compass processing for SCSS/SASS files.")
+        self._state = self.STATE_ACTIVE
+
+        bin_path = config.get('bin', 'compass')
+
+        config_path = config.get('config_path', 'config.rb')
+        config_path = os.path.join(self.app.root_dir, config_path)
+        if not os.path.exists(config_path):
+            raise Exception("Can't find Compass configuration file: %s" %
+                            config_path)
+        self._args = '%s compile --config "%s"' % (bin_path, config_path)
+
+        frameworks = config.get('frameworks', [])
+        if not isinstance(frameworks, list):
+            frameworks = frameworks.split(',')
+        for f in frameworks:
+            self._args += ' --load %s' % f
+
+        custom_args = config.get('options')
+        if custom_args:
+            self._args += ' ' + custom_args
+
+        out_dir = pipeline.out_dir
+        tmp_dir = os.path.join(pipeline.tmp_dir, 'compass')
+        self._args = multi_replace(
+                self._args,
+                {'%out_dir%': out_dir,
+                    '%tmp_dir%': tmp_dir})
+
+        self._runInSite = False
+        self._runInTheme = False
+
+    def _maybeRunCompass(self, pipeline):
+        if self._state != self.STATE_ACTIVE:
+            return
+
+        logger.debug("Running Compass with:")
+        logger.debug(self._args)
+
+        prev_cwd = os.getcwd()
+        os.chdir(self.app.root_dir)
+        try:
+            retcode = subprocess.call(self._args, shell=True)
+        except FileNotFoundError as ex:
+            logger.error("Tried running Compass with command: %s" %
+                         self._args)
+            raise Exception("Error running Compass. "
+                            "Did you install it?") from ex
+        finally:
+            os.chdir(prev_cwd)
+
+        if retcode != 0:
+            raise Exception("Error occured in Compass. Please check "
+                            "log messages above for more information.")
+        return True
+