Initial attempt at enabling reading the columns from the datasource

tableaudocumentapi/datasource.py

@@ -10,6 +10,7 @@
 
 from tableaudocumentapi import Connection, xfile
 from tableaudocumentapi import Field
+from tableaudocumentapi.multilookup_dict import MultiLookupDict
 
 
 def _mapping_from_xml(root_xml, column_xml):
@@ -142,4 +143,4 @@ def fields(self):
     def _get_all_fields(self):
         column_objects = (_mapping_from_xml(self._datasourceTree, xml)
                           for xml in self._datasourceTree.findall('.//column'))
-        return collections.OrderedDict([(k, v) for k, v in column_objects])
+        return MultiLookupDict({k: v for k, v in column_objects})

tableaudocumentapi/multilookup_dict.py

@@ -0,0 +1,49 @@
+def _resolve_value(key, value):
+    try:
+        retval = value.get(key, None)
+        if retval is None:
+            retval = value.getattr(key, None)
+    except AttributeError:
+        retval = None
+    return retval
+
+
+def _build_index(key, d):
+    return {_resolve_value(key, v): k
+            for k, v in d.items()
+            if _resolve_value(key, v) is not None}
+
+
+# TODO: Improve this to be more generic
+class MultiLookupDict(dict):
+    def __init__(self, args=None):
+        if args is None:
+            args = {}
+        super(MultiLookupDict, self).__init__(args)
+        self._indexes = {
+            'alias': {},
+            'caption': {}
+        }
+        self._populate_indexes()
+
+    def _populate_indexes(self):
+        self._indexes['alias'] = _build_index('alias', self)
+        self._indexes['caption'] = _build_index('caption', self)
+
+    def __setitem__(self, key, value):
+        alias = _resolve_value('alias', value)
+        caption = _resolve_value('caption', value)
+        if alias is not None:
+            self._indexes['alias'][alias] = key
+        if caption is not None:
+            self._indexes['caption'][caption] = key
+
+        dict.__setitem__(self, key, value)
+
+    def __getitem__(self, key):
+        if key in self._indexes['alias']:
+            key = self._indexes['alias'][key]
+        elif key in self._indexes['caption']:
+            key = self._indexes['caption'][key]
+
+        return dict.__getitem__(self, key)

test/test_multidict.py

@@ -0,0 +1,47 @@
+import unittest
+import os.path
+import functools
+
+from tableaudocumentapi.multilookup_dict import MultiLookupDict
+
+
+class MLDTests(unittest.TestCase):
+    def setUp(self):
+        self.mld = MultiLookupDict({
+            '[foo]': {
+                'alias': 'bar',
+                'caption': 'baz',
+                'value': 1
+            },
+            '[bar]': {
+                'caption': 'foo',
+                'value': 2
+            },
+            '[baz]': {
+                'value': 3
+            }
+        })
+
+    def test_multilookupdict_name_only(self):
+        actual = self.mld['[baz]']
+        self.assertEqual(3, actual['value'])
+
+    def test_multilookupdict_alias_overrides_everything(self):
+        actual = self.mld['bar']
+        self.assertEqual(1, actual['value'])
+
+    def test_mutlilookupdict_caption_overrides_id(self):
+        actual = self.mld['foo']
+        self.assertEqual(2, actual['value'])
+
+    def test_mutlilookupdict_can_still_find_id_even_with_alias(self):
+        actual = self.mld['[foo]']
+        self.assertEqual(1, actual['value'])
+
+    def test_mutlilookupdict_can_still_find_caption_even_with_alias(self):
+        actual = self.mld['baz']
+        self.assertEqual(1, actual['value'])
+
+    def test_mutlilookupdict_can_still_find_id_even_with_caption(self):
+        actual = self.mld['[bar]']
+        self.assertEqual(2, actual['value'])