From 8855f1155be9bfbc52f35a11520a9f8164ede29b Mon Sep 17 00:00:00 2001
From: Tobi-wan Kenobi <github@tobi-wan-kenobi.at>
Date: Sun, 4 Dec 2016 16:23:44 +0100
Subject: [PATCH] [core/errors] Add custom exceptions

Add custom exceptions and add error handling to the engine's module
loading logic. I.e. when a non-existent module is loaded, an exception
is thrown now.

see #23
---
 bumblebee-status     |  6 +++++-
 bumblebee/engine.py  |  8 +++++++-
 bumblebee/error.py   | 11 +++++++++++
 tests/test_engine.py | 10 ++++++++++
 4 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 bumblebee/error.py

diff --git a/bumblebee-status b/bumblebee-status
index 4d1cfe6..fcb5679 100755
--- a/bumblebee-status
+++ b/bumblebee-status
@@ -16,6 +16,10 @@ def main():
     engine.run()
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except bumblebee.error.BaseError as error:
+        sys.stderr.write("fatal: {}\n".format(error))
+        sys.exit(1)
 
 # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/bumblebee/engine.py b/bumblebee/engine.py
index ddf6396..3c07d98 100644
--- a/bumblebee/engine.py
+++ b/bumblebee/engine.py
@@ -1,6 +1,8 @@
 """Core application engine"""
 
+import time
 import importlib
+import bumblebee.error
 
 class Module(object):
     """Module instance base class
@@ -33,7 +35,10 @@ class Engine(object):
 
     def load_module(self, module_name):
         """Load specified module and return it as object"""
-        module = importlib.import_module("bumblebee.modules.{}".format(module_name))
+        try:
+            module = importlib.import_module("bumblebee.modules.{}".format(module_name))
+        except ImportError as error:
+            raise bumblebee.error.ModuleLoadError(error)
         return getattr(module, "Module")(self)
 
     def running(self):
@@ -53,6 +58,7 @@ class Engine(object):
                 widgets += module.widgets()
             self._output.draw(widgets)
             self._output.flush()
+            time.sleep(1)
 
         self._output.stop()
 
diff --git a/bumblebee/error.py b/bumblebee/error.py
new file mode 100644
index 0000000..b07cc24
--- /dev/null
+++ b/bumblebee/error.py
@@ -0,0 +1,11 @@
+"""Collection of all exceptions raised by this tool"""
+
+class BaseError(Exception):
+    """Base class for all exceptions generated by this tool"""
+    pass
+
+class ModuleLoadError(BaseError):
+    """Raised whenever loading a module fails"""
+    pass
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4
diff --git a/tests/test_engine.py b/tests/test_engine.py
index cc5c69f..2cb5ea3 100644
--- a/tests/test_engine.py
+++ b/tests/test_engine.py
@@ -1,6 +1,7 @@
 # pylint: disable=C0103,C0111
 import unittest
 
+from bumblebee.error import ModuleLoadError
 from bumblebee.engine import Engine
 from bumblebee.config import Config
 
@@ -8,6 +9,7 @@ class TestEngine(unittest.TestCase):
     def setUp(self):
         self.engine = Engine(Config())
         self.testModule = "test"
+        self.invalidModule = "no-such-module"
         self.testModuleSpec = "bumblebee.modules.{}".format(self.testModule)
         self.testModules = [
             {"module": "test", "name": "a"},
@@ -23,6 +25,14 @@ class TestEngine(unittest.TestCase):
         module = self.engine.load_module(self.testModule)
         self.assertEquals(module.__module__, self.testModuleSpec)
 
+    def test_load_invalid_module(self):
+        with self.assertRaises(ModuleLoadError):
+            self.engine.load_module(self.invalidModule)
+
+    def test_load_none(self):
+        with self.assertRaises(ModuleLoadError):
+            self.engine.load_module(None)
+
     def test_load_modules(self):
         modules = self.engine.load_modules(self.testModules)
         self.assertEquals(len(modules), len(self.testModules))