--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/piecrust/processing/less.py	Sun Aug 10 23:43:16 2014 -0700
@@ -0,0 +1,77 @@
+import os
+import os.path
+import json
+import hashlib
+import logging
+import subprocess
+from piecrust.processing.base import SimpleFileProcessor
+from piecrust.processing.tree import FORCE_BUILD
+
+
+logger = logging.getLogger(__name__)
+
+
+class LessProcessor(SimpleFileProcessor):
+    PROCESSOR_NAME = 'less'
+
+    def __init__(self):
+        super(LessProcessor, self).__init__({'less': 'css'})
+        self._conf = None
+        self._map_dir = None
+
+    def onPipelineStart(self, pipeline):
+        self._map_dir = os.path.join(pipeline.tmp_dir, 'less')
+        if not os.path.isdir(self._map_dir):
+            os.makedirs(self._map_dir)
+
+    def getDependencies(self, path):
+        map_path = self._getMapPath(path)
+        try:
+            with open(map_path, 'r') as f:
+                dep_map = json.load(f)
+            source = dep_map.get('sources')
+            # The last one is always the file itself, so skip that. Also,
+            # make all paths absolute.
+            path_dir = os.path.dirname(path)
+            def _makeAbs(p):
+                return os.path.join(path_dir, p)
+            return map(_makeAbs, source[:-1])
+        except IOError:
+            # Map file not found... rebuild.
+            logger.debug("No map file found for LESS file '%s' at '%s'. "
+                         "Rebuilding" % (path, map_path))
+            return FORCE_BUILD
+
+    def _doProcess(self, in_path, out_path):
+        self._ensureInitialized()
+
+        map_path = self._getMapPath(in_path)
+        map_path = os.path.relpath(map_path)
+        args = [self._conf['bin'], '--source-map=%s' % map_path]
+        args += self._conf['options']
+        args.append(in_path)
+        args.append(out_path)
+        logger.debug("Processing LESS file: %s" % args)
+        retcode = subprocess.call(args)
+        if retcode != 0:
+            raise Exception("Error occured in LESS compiler. Please check "
+                            "log messages above for more information.")
+        return True
+
+    def _ensureInitialized(self):
+        if self._conf is not None:
+            return
+
+        self._conf = self.app.config.get('less') or {}
+        self._conf.setdefault('bin', 'lessc')
+        self._conf.setdefault('options',
+                ['--compress'])
+        if not isinstance(self._conf['options'], list):
+            raise Exception("The `less/options` configuration setting "
+                            "must be an array of arguments.")
+
+    def _getMapPath(self, path):
+        map_name = "%s.map" % hashlib.md5(path).hexdigest()
+        map_path = os.path.join(self._map_dir, map_name)
+        return map_path
+