Further updates to page. Small update to internal API.

Internal API update functions now accept partial updates, allowing one to
selectively update only some fields of a particular record.

src/ts_common.erl

@@ -1,5 +1,5 @@
 -module(ts_common).
--export([new/1, update/1, list/3, order_datetimes/2]).
+-export([new/1, update/1, update_record/2, list/3, order_datetimes/2]).
 
 -include_lib("stdlib/include/qlc.hrl").
 
@@ -25,9 +25,22 @@ update(Record) ->
         % record does not exist, cannot update
         [] -> no_record;
         % record does exist, update
-        [_ExistingRecord] -> mnesia:dirty_write(Record)
+        [ExistingRecord] ->
+            mnesia:dirty_write(update_record(ExistingRecord, Record))
     end.
 
+update_record(Record, UpdateData) ->
+    update_record(tuple_to_list(Record), tuple_to_list(UpdateData), []).
+    
+update_record([], [], Updated) -> list_to_tuple(lists:reverse(Updated));
+update_record([Field|RecordFields], [FieldReplacement|UpdateData], Acc) ->
+    UpdatedField = case FieldReplacement of
+        undefined -> Field;
+        NewValue -> NewValue
+    end,
+
+    update_record(RecordFields, UpdateData, [UpdatedField|Acc]).
+
 %% list <Length> number of records, skipping the first <Start>
 list(Table, Start, Length)
 when is_atom(Table) and is_integer(Start) and is_integer(Length) ->

src/ts_entry.erl

@@ -25,7 +25,8 @@ update(ER = #ts_entry{}) ->
         % record does not exist
         [] -> no_record;
         % record exists, update it
-        [_Record] -> mnesia:dirty_write(ER)
+        [ExistingRecord] ->
+            mnesia:dirty_write(ts_common:update_record(ExistingRecord, ER))
     end.
 
 lookup(Username, TimelineId, EntryId) ->

src/ts_json.erl

@@ -47,7 +47,7 @@ ejson_to_record(_Empty=#ts_timeline{}, EJSON) ->
     {struct, Fields} = EJSON,
 
     #ts_timeline{
-        ref = {undef, undef},
+        ref = {undefined, undefined},
         created = decode_datetime(element(2, lists:keyfind(created, 1, Fields))),
         desc = element(2, lists:keyfind(description, 1, Fields))};
 
@@ -55,7 +55,7 @@ ejson_to_record(_Empty=#ts_entry{}, EJSON) ->
     {struct, Fields} = EJSON,
 
     #ts_entry{
-        ref = {undef, undef, undef},
+        ref = {undefined, undefined, undefined},
         timestamp = calendar:datetime_to_gregorian_seconds(decode_datetime(
             element(2, lists:keyfind(timestamp, 1, Fields)))),
         mark = element(2, lists:keyfind(mark, 1, Fields)),