From 5849b562d078b5cff5a91a371df609cfc97951ce Mon Sep 17 00:00:00 2001
From: Brett Smith <brettcsmith@brettcsmith.org>
Date: Thu, 5 Mar 2020 15:13:17 -0500
Subject: [PATCH] expenseAllocation: Switch to own MetadataEnum class.

Python's own enum works fine for the simple values that expenseAllocation
uses, but it won't work as well for metadata like taxImplication where
many of the values aren't legal Python identifiers. Introduce our own
MetadataEnum class with the necessary functionality, and switch to that.
---
 conservancy_beancount/plugin/core.py          | 32 ++++++++++++++++++-
 .../plugin/meta_expense_allocation.py         | 26 +++++++--------
 2 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/conservancy_beancount/plugin/core.py b/conservancy_beancount/plugin/core.py
index befa40c..d3cb6a8 100644
--- a/conservancy_beancount/plugin/core.py
+++ b/conservancy_beancount/plugin/core.py
@@ -36,6 +36,36 @@ class _GenericRange:
         return self.start <= item < self.stop
 
 
+class MetadataEnum:
+    def __init__(self, key, standard_values, aliases_map):
+        self.key = key
+        self._stdvalues = frozenset(standard_values)
+        self._aliases = dict(aliases_map)
+        self._aliases.update((v, v) for v in standard_values)
+        assert self._stdvalues == set(self._aliases.values())
+
+    def __repr__(self):
+        return "{}<{}>".format(type(self).__name__, self.key)
+
+    def __contains__(self, key):
+        return key in self._aliases
+
+    def __getitem__(self, key):
+        return self._aliases[key]
+
+    def __iter__(self):
+        return iter(self._stdvalues)
+
+    def get(self, key, default_key=None):
+        try:
+            return self[key]
+        except KeyError:
+            if default_key is None:
+                return None
+            else:
+                return self[default_key]
+
+
 class PostingChecker:
     ACCOUNTS = ('',)
     TXN_DATE_RANGE = _GenericRange(DEFAULT_START_DATE, DEFAULT_STOP_DATE)
@@ -76,7 +106,7 @@ class PostingChecker:
                 errors.append(error)
         else:
             try:
-                set_value = self.VALUES_ENUM[source_value].value
+                set_value = self.VALUES_ENUM[source_value]
             except KeyError:
                 errors.append(errormod.InvalidMetadataError(
                     txn, post, self.METADATA_KEY, source_value,
diff --git a/conservancy_beancount/plugin/meta_expense_allocation.py b/conservancy_beancount/plugin/meta_expense_allocation.py
index e1e732e..603b2d7 100644
--- a/conservancy_beancount/plugin/meta_expense_allocation.py
+++ b/conservancy_beancount/plugin/meta_expense_allocation.py
@@ -14,27 +14,23 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-import enum
-
 from . import core
 
-class ExpenseAllocations(enum.Enum):
-    administration = 'administration'
-    fundraising = 'fundraising'
-    program = 'program'
-
-    admin = administration
-
-
 class MetaExpenseAllocation(core.PostingChecker):
     ACCOUNTS = ('Expenses:',)
     METADATA_KEY = 'expenseAllocation'
-    VALUES_ENUM = ExpenseAllocations
+    VALUES_ENUM = core.MetadataEnum(METADATA_KEY, {
+        'administration',
+        'fundraising',
+        'program',
+    }, {
+        'admin': 'administration',
+    })
     DEFAULT_VALUES = {
-        'Expenses:Services:Accounting': VALUES_ENUM.administration,
-        'Expenses:Services:Administration': VALUES_ENUM.administration,
-        'Expenses:Services:Fundraising': VALUES_ENUM.fundraising,
+        'Expenses:Services:Accounting': VALUES_ENUM['administration'],
+        'Expenses:Services:Administration': VALUES_ENUM['administration'],
+        'Expenses:Services:Fundraising': VALUES_ENUM['fundraising'],
     }
 
     def _default_value(self, txn, post):
-        return self.DEFAULT_VALUES.get(post.account, self.VALUES_ENUM.program).value
+        return self.DEFAULT_VALUES.get(post.account, 'program')