From d8ee20c402cd10863858402b5c8b3b488273fff0 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Fri, 7 Jun 2019 17:30:50 +0000
Subject: [PATCH] Add ShouldNeverHappen exception

---
 cheuph/__init__.py         | 2 ++
 cheuph/cursor_rendering.py | 9 ++++-----
 cheuph/exceptions.py       | 8 +++++++-
 should_never_happens.txt   | 3 +++
 4 files changed, 16 insertions(+), 6 deletions(-)
 create mode 100644 should_never_happens.txt

diff --git a/cheuph/__init__.py b/cheuph/__init__.py
index 5c12663..c63ff02 100644
--- a/cheuph/__init__.py
+++ b/cheuph/__init__.py
@@ -7,6 +7,7 @@ from .cursor_rendering import *
 from .cursor_tree_widget import *
 from .element import *
 from .element_supply import *
+from .exceptions import *
 from .markup import *
 from .rendered_element_cache import *
 
@@ -19,5 +20,6 @@ __all__ += cursor_rendering.__all__
 __all__ += cursor_tree_widget.__all__
 __all__ += element.__all__
 __all__ += element_supply.__all__
+__all__ += exceptions.__all__
 __all__ += markup.__all__
 __all__ += rendered_element_cache.__all__
diff --git a/cheuph/cursor_rendering.py b/cheuph/cursor_rendering.py
index bcf1a25..e059a4c 100644
--- a/cheuph/cursor_rendering.py
+++ b/cheuph/cursor_rendering.py
@@ -6,6 +6,7 @@ from typing import Generic, List, Optional, Tuple, TypeVar
 from .attributed_lines import AttributedLines
 from .element import Element, Id, Message, RenderedElement, RenderedMessage
 from .element_supply import ElementSupply
+from .exceptions import ShouldNeverHappen
 from .markup import AT, AttributedText, Attributes
 from .rendered_element_cache import RenderedElementCache
 
@@ -408,11 +409,9 @@ class CursorTreeRenderer(Generic[E]):
             return 0, middle_index
 
         if middle_index < self.lines.upper_offset:
-            raise Exception()
             attrs, _ = lines[0]
             index = self.lines.upper_offset
         elif middle_index > self.lines.lower_offset:
-            raise Exception()
             attrs, _ = lines[-1]
             index = self.lines.lower_offset
         else:
@@ -535,7 +534,7 @@ class CursorTreeRenderer(Generic[E]):
                 message = self._cache.get(mid)
 
             if message is None:
-                raise Exception() # TODO use better exception
+                raise ShouldNeverHappen(1)
 
             height += len(message.lines)
 
@@ -553,7 +552,7 @@ class CursorTreeRenderer(Generic[E]):
         below_new = self._element_id_below_cursor(new_cursor_id)
 
         if above_old is None:
-            raise Exception() # TODO use better exception
+            raise ShouldNeverHappen(2)
 
         # Moving horizontally at the bottom of the supply
         if below_new is None:
@@ -579,7 +578,7 @@ class CursorTreeRenderer(Generic[E]):
         above_new = self._element_id_above_cursor(new_cursor_id)
 
         if above_new is None:
-            raise Exception() # TODO use better exception
+            raise ShouldNeverHappen(3)
 
         # Moving horizontally at the bottom of the supply
         if below_old is None:
diff --git a/cheuph/exceptions.py b/cheuph/exceptions.py
index 5c990ae..c113f41 100644
--- a/cheuph/exceptions.py
+++ b/cheuph/exceptions.py
@@ -1,4 +1,10 @@
-__all__ = ["MessageSupplyException"]
+__all__ = ["MessageSupplyException", "ShouldNeverHappen"]
 
 class MessageSupplyException(Exception):
     pass
+
+class ShouldNeverHappen(Exception):
+    def __init__(self, number: int) -> None:
+        message = (f"SNV{number:05} - please contact @Garmy with the code on"
+                " the left if you see this")
+        super().__init__(message)
diff --git a/should_never_happens.txt b/should_never_happens.txt
new file mode 100644
index 0000000..4e8a7dd
--- /dev/null
+++ b/should_never_happens.txt
@@ -0,0 +1,3 @@
+SNH0001 - cursor_rendering.py
+SNH0002 - cursor_rendering.py
+SNH0003 - cursor_rendering.py