Started on implementing OperationFactory.get_operation method.

2 files changed, 33 insertions, 0 deletions

diff --git a/obnam/oper.py b/obnam/oper.py
index eeeda01c..3d785f77 100644
--- a/obnam/oper.py
+++ b/obnam/oper.py
@@ -65,6 +65,19 @@ class Operation:
         """
 
 
+class NoArguments(obnam.ObnamException):
+
+    def __init__(self):
+        self._msg = ("Command line argument list is empty. " 
+                     "Need at least the operation name.")
+
+
+class OperationNotFound(obnam.ObnamException):
+
+    def __init__(self, name):
+        self._msg = "Unknown operation %s" % name
+
+
 class OperationFactory:
 
     """Instantiate Operation subclasses based on command line arguments."""
@@ -79,3 +92,15 @@ class OperationFactory:
             if inspect.isclass(x) and issubclass(x, Operation):
                 list.append(x)
         return list
+
+    def get_operation(self, args):
+        """Instantiate the right operation given the command line.
+        
+        If there is no corresponding operation, raise an error.
+        
+        """
+
+        if not args:
+            raise NoArguments()
+
+        raise OperationNotFound(args[0])
diff --git a/obnam/operTests.py b/obnam/operTests.py
index 120bad4d..5876acec 100644
--- a/obnam/operTests.py
+++ b/obnam/operTests.py
@@ -50,3 +50,11 @@ class OperationFactoryTests(unittest.TestCase):
     
     def testFindsOperations(self):
         self.failUnless(self.factory.find_operations())
+
+    def testRaisesErrorForNoArguments(self):
+        self.failUnlessRaises(obnam.ObnamException, 
+                              self.factory.get_operation, [])
+
+    def testRaisesErrorForUnknownArgument(self):
+        self.failUnlessRaises(obnam.ObnamException, 
+                              self.factory.get_operation, ["pink"])