Merge branch 'feature/ghi-#5-dispatcher' into develop

snowsaw/dispatcher.py

@@ -0,0 +1,64 @@
+import os
+from .plugin import Plugin
+from .logging import Logger
+from .context import Context
+
+
+class Dispatcher(object):
+    """
+    Dispatches tasks to loaded plugins.
+    """
+    def __init__(self, snowblock_dir):
+        self._log = Logger()
+        self._setup_context(snowblock_dir)
+        self._load_plugins()
+
+    def _setup_context(self, snowblock_dir):
+        """
+        Sets up the plugin context for the specified snowblock.
+
+        :param snowblock_dir:  The directory of the snowblock
+        :return: The plugin context
+        """
+        path = os.path.abspath(os.path.realpath(os.path.expanduser(snowblock_dir)))
+        if not os.path.exists(path):
+            raise DispatchError("Nonexistent snowblock directory")
+        self._context = Context(path)
+
+    def dispatch(self, tasks):
+        """
+        Dispatches the specified tasks to the loaded plugins.
+
+        :param tasks: The tasks to dispatch
+        :return: True if all tasks have been handled by the loaded plugins successfully, False otherwise
+        """
+        success = True
+        for task in tasks:
+            for action in task:
+                handled = False
+                if action == "defaults":
+                    self._context.set_defaults(task[action])
+                    handled = True
+                for plugin in self._plugins:
+                    if plugin.can_handle(action):
+                        try:
+                            success &= plugin.handle(action, task[action])
+                            handled = True
+                        except Exception:
+                            self._log.error("An error was encountered while executing action \"{}\"".format(action))
+                if not handled:
+                    success = False
+                    self._log.error("Action \"{}\" not handled".format(action))
+        return success
+
+    def _load_plugins(self):
+        """
+        Loads all found plugins.
+
+        :return: None
+        """
+        self._plugins = [plugin(self._context) for plugin in Plugin.__subclasses__()]
+
+
+class DispatchError(Exception):
+    pass