Changed sort to use field_metadata.search_term_to_field_key.

In the process, refactored field_metadata and LibraryDatabase2 to use the same method names for the same function (in more cases).

src/calibre/library/caches.py

@@ -334,7 +334,7 @@ class ResultCache(SearchQueryParser):
         if query and query.strip():
             # get metadata key associated with the search term. Eliminates
             # dealing with plurals and other aliases
-            location = self.field_metadata.search_term_to_key(location.lower().strip())
+            location = self.field_metadata.search_term_to_field_key(location.lower().strip())
             if isinstance(location, list):
                 if allow_recursion:
                     for loc in location:
@@ -610,12 +610,9 @@ class ResultCache(SearchQueryParser):
     # Sorting functions {{{
 
     def sanitize_sort_field_name(self, field):
-        field = field.lower().strip()
-        if field not in self.field_metadata.iterkeys():
-            if field in ('author', 'tag', 'comment'):
-                field += 's'
-        if   field == 'date': field = 'timestamp'
-        elif field == 'title': field = 'sort'
+        field = self.field_metadata.search_term_to_field_key(field.lower().strip())
+        # translate some fields to their hidden equivalent
+        if field == 'title': field = 'sort'
         elif field == 'authors': field = 'author_sort'
         return field
 

src/calibre/library/database2.py

@@ -552,10 +552,10 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         return self.field_metadata.sortable_field_keys()
 
     def searchable_fields(self):
-        return self.field_metadata.searchable_field_keys()
+        return self.field_metadata.searchable_fields()
 
     def search_term_to_field_key(self, term):
-        return self.field_metadata.search_term_to_key(term)
+        return self.field_metadata.search_term_to_field_key(term)
 
     def metadata_for_field(self, key):
         return self.field_metadata[key]

src/calibre/library/field_metadata.py

@@ -501,12 +501,12 @@ class FieldMetadata(dict):
                     raise ValueError('Attempt to add duplicate search term "%s"'%t)
                 self._search_term_map[t] = key
 
-    def search_term_to_key(self, term):
+    def search_term_to_field_key(self, term):
         if term in self._search_term_map:
             return  self._search_term_map[term]
         return term
 
-    def searchable_field_keys(self):
+    def searchable_fields(self):
         return [k for k in self._tb_cats.keys()
                 if self._tb_cats[k]['kind']=='field' and
                    len(self._tb_cats[k]['search_terms']) > 0]