Refactor to single parameterized datastore module

 - Work around runtime limitations of records with
helper functions for fields, queries and prestore

 - Retarget client code at single module

 - Remove separate data store modules

 - Remove use of functions in includes

 - Thank you Zed and Adam for StackOverflow help:
http://stackoverflow.com/questions/1550850/how-do-you-debug-functions-from-includes-in-erlang

src/scrumjet.app

@@ -6,10 +6,8 @@
     scrumjet_app,
     scrumjet_sup,
     scrumjet_deps,
-    scrumjet_task,
-    scrumjet_category,
+    scrumjet_datastore,
     scrumjet_category_task,
-    scrumjet_board,
     scrumjet_board_category,
     scrumjet_resource,
     scrumjet_tasks_resource,

src/scrumjet.erl

@@ -23,9 +23,7 @@ start() ->
     ensure_started(webmachine),
     mnesia:create_schema([node()]),
     ensure_started(mnesia),
-    scrumjet_task:start(),
-    scrumjet_category:start(),
-    scrumjet_board:start(),
+    scrumjet_datastore:start(),
     scrumjet_category_task:start(),
     scrumjet_board_category:start(),
     application:start(scrumjet).

src/scrumjet_board_resource.erl

@@ -23,7 +23,7 @@ init([]) -> {ok, #context{}}.
 
 resource_exists(ReqData, Context) ->
     ID = wrq:disp_path(ReqData),
-    case scrumjet_board:find({id, ID}) of
+    case scrumjet_datastore:find(scrumjet_board, {id, ID}) of
         [] -> {false, ReqData, Context#context{board=#scrumjet_board{id=ID}}};
         [Board] -> {true, ReqData, Context#context{board=Board}}
     end.
@@ -53,7 +53,7 @@ content_types_accepted(ReqData, Context) ->
 from_webform(ReqData, Context=#context{board=Board}) ->
     Params = mochiweb_util:parse_qs(wrq:req_body(ReqData)),
     Title = proplists:get_value("title", Params, ""),
-    scrumjet_board:store(Board#scrumjet_board{title=Title}),
+    scrumjet_datastore:store(Board#scrumjet_board{title=Title}),
     {true, ReqData, Context}.
 
 -spec categories(string()) -> iolist().

src/scrumjet_category_resource.erl

@@ -24,7 +24,7 @@ init([]) -> {ok, #context{}}.
 
 resource_exists(ReqData, Context) ->
     ID = wrq:disp_path(ReqData),
-    case scrumjet_category:find({id, ID}) of
+    case scrumjet_datastore:find(scrumjet_category, {id, ID}) of
         [] -> {false, ReqData, Context#context{category=
                #scrumjet_category{id=ID}}};
         [Category] -> {true, ReqData, Context#context{category=Category}}
@@ -62,7 +62,7 @@ content_types_accepted(ReqData, Context) ->
 from_webform(ReqData, Context=#context{category=Category}) ->
     Params = mochiweb_util:parse_qs(wrq:req_body(ReqData)),
     Name = proplists:get_value("name", Params, ""),
-    scrumjet_category:store(Category#scrumjet_category{name=Name}),
+    scrumjet_datastore:store(Category#scrumjet_category{name=Name}),
     {true, ReqData, Context}.
 
 -spec tasks(string()) -> iolist().

src/scrumjet_datastore.erl

@@ -0,0 +1,79 @@
+-module (scrumjet_datastore).
+
+-include("scrumjet.hrl").
+-include_lib("stdlib/include/qlc.hrl").
+
+-export([start/0, store/1, find/2, range/3]).
+
+-define (TYPES, [scrumjet_task, scrumjet_category, scrumjet_board]).
+
+%% Internal Helper Functions
+
+fields(scrumjet_task) -> record_info(fields, scrumjet_task);
+fields(scrumjet_category) -> record_info(fields, scrumjet_category);
+fields(scrumjet_board) -> record_info(fields, scrumjet_board).
+
+prestore(Record=#scrumjet_task{ctime=undefined}) ->
+    Now = erlang:now(),
+    Record#scrumjet_task{ctime=Now, mtime=Now};
+prestore(Record=#scrumjet_category{ctime=undefined}) ->
+    Now = erlang:now(),
+    Record#scrumjet_category{ctime=Now, mtime=Now};
+prestore(Record=#scrumjet_board{ctime=undefined}) ->
+    Now = erlang:now(),
+    Record#scrumjet_board{ctime=Now, mtime=Now};
+prestore(Record=#scrumjet_task{}) ->
+    Now = erlang:now(),
+    Record#scrumjet_task{mtime=Now};
+prestore(Record=#scrumjet_category{}) ->
+    Now = erlang:now(),
+    Record#scrumjet_category{mtime=Now};
+prestore(Record=#scrumjet_board{}) ->
+    Now = erlang:now(),
+    Record#scrumjet_board{mtime=Now}.
+
+select(scrumjet_task, {id, Id}) ->
+    qlc:q([M || M <- mnesia:table(scrumjet_task),
+                M#scrumjet_task.id =:= Id]);
+select(scrumjet_category, {id, Id}) ->
+    qlc:q([M || M <- mnesia:table(scrumjet_category),
+                M#scrumjet_category.id =:= Id]);
+select(scrumjet_board, {id, Id}) ->
+    qlc:q([M || M <- mnesia:table(scrumjet_board),
+                M#scrumjet_board.id =:= Id]).
+
+create_table(Type) ->
+    try
+        set = mnesia:table_info(Type, type)
+    catch
+        exit:{aborted, {no_exists, Type, type}} ->
+            {atomic, ok} = mnesia:create_table(Type,
+                [{attributes, fields(Type)},
+                {type, set},
+                {disc_copies, [node()]}])
+    end.
+
+%% Public API Functions
+
+start() -> [create_table(Type) || Type <- ?TYPES].
+
+store(Record) ->
+    F = fun() ->
+        mnesia:write(prestore(Record))
+    end,
+    mnesia:transaction(F).
+
+find(Type, Params) ->
+    F = fun() ->
+        Query = select(Type, Params),
+        qlc:eval(Query)
+    end,
+    {atomic, Records} = mnesia:transaction(F),
+    Records.
+
+range(Type, Start, End) ->
+    F = fun() ->
+        mnesia_ext:limit(Type, Start, End - Start)
+    end,
+    {atomic, Records} = mnesia:transaction(F),
+    Records.

src/scrumjet_task_resource.erl

@@ -34,7 +34,7 @@ content_types_provided(ReqData, Context) ->
 
 resource_exists(ReqData, Context) ->
     ID = wrq:disp_path(ReqData),
-    case scrumjet_task:find({id, ID}) of
+    case scrumjet_datastore:find(scrumjet_task, {id, ID}) of
         [] -> {false, ReqData, Context#context{task=#scrumjet_task{id=ID}}};
         [Task] -> {true, ReqData, Context#context{task=Task}}
     end.
@@ -73,8 +73,9 @@ from_webform(ReqData, Context=#context{task=Task}) ->
     Params = mochiweb_util:parse_qs(wrq:req_body(ReqData)),
     Headline = proplists:get_value("headline", Params, ""),
     Description = proplists:get_value("description", Params, ""),
-    scrumjet_task:store(Task#scrumjet_task{description=Description,
-                                           headline=Headline}),
+    scrumjet_datastore:store(
+        Task#scrumjet_task{description=Description,
+                           headline=Headline}),
     {true, ReqData, Context}.
 
 -spec categories(string()) -> iolist().

src/scrumjet_tasks_resource.erl

@@ -101,7 +101,7 @@ range(undefined) -> undefined.
 
 -spec tasks(integer(), integer) -> [sj_record()].
 tasks(Start, End) ->
-    scrumjet_task:range(Start, End).
+    scrumjet_datastore:range(scrumjet_task, Start, End).
 
 -spec query_range(string(), string()) -> {integer(), integer()}.
 query_range(undefined, _) -> undefined;

src/test_scrumjet_category.erl → src/test_scrumjet_datastore.erl

@@ -1,4 +1,4 @@
--module(test_scrumjet_category).
+-module(test_scrumjet_datastore).
 
 -include_lib("eunit/include/eunit.hrl").
 -include("scrumjet.hrl").
@@ -10,9 +10,9 @@ setup() ->
     mnesia:stop(),
     mnesia:delete_schema([node()]),
     mnesia:create_schema([node()]),
-    scrumjet_category:start_link().
+    scrumjet_datastore:start().
 
-cleanup(_Pid) -> catch scrumjet_category:shutdown().
+cleanup(_Pid) -> ok.
 
 happy_path_test_() ->
     {setup,
@@ -23,9 +23,9 @@ happy_path_test_() ->
 
 happy_path_generator(_Pid) ->
     {timeout, 1, [
-        fun() -> scrumjet_category:store(
+        fun() -> scrumjet_datastore:store(
             #scrumjet_category{id="family", name="Family Stuff"}) end,
-        fun() -> scrumjet_category:find({id,"family"}) end
+        fun() -> scrumjet_datastore:find(scrumjet_category, {id,"family"}) end
     ]}.
 
 % 2. Verify direct outputs of happy path
@@ -40,10 +40,10 @@ verify_happy_path_test_() ->
 
 verify_happy_path_generator(_Pid) ->
     {timeout, 1, [
-        ?_assertEqual(ok, scrumjet_category:store(
+        ?_assertEqual(ok, scrumjet_datastore:store(
             #scrumjet_category{id="family", name="Family Stuff"})),
         ?_assertMatch([#scrumjet_category{id="family", name="Family Stuff"}],
-            scrumjet_category:find({id,"family"}))
+            scrumjet_datastore:find(scrumjet_category, {id,"family"}))
     ]}.
 
 % 3. Verify Alternate Paths
@@ -58,16 +58,16 @@ verify_alternate_test_() ->
 
 verify_alternate_generator(_Pid) ->
     {timeout, 1, [
-        ?_assertMatch([], scrumjet_category:find({id,"family"})),
-        ?_assertMatch([], scrumjet_category:find({id,"work"})),
-        ?_assertEqual(ok, scrumjet_category:store(
+        ?_assertMatch([], scrumjet_datastore:find(scrumjet_category, {id,"family"})),
+        ?_assertMatch([], scrumjet_datastore:find(scrumjet_category, {id,"work"})),
+        ?_assertEqual(ok, scrumjet_datastore:store(
             #scrumjet_category{id="family", name="Family Stuff"})),
-        ?_assertEqual(ok, scrumjet_category:store(
+        ?_assertEqual(ok, scrumjet_datastore:store(
             #scrumjet_category{id="work", name="Work"})),
         ?_assertMatch([#scrumjet_category{id="family", name="Family Stuff"}],
-            scrumjet_category:find({id,"family"})),
+            scrumjet_datastore:find(scrumjet_category, {id,"family"})),
         ?_assertMatch([#scrumjet_category{id="work", name="Work"}],
-            scrumjet_category:find({id,"work"}))
+            scrumjet_datastore:find(scrumjet_category, {id,"work"}))
     ]}.
 
 % 4. Control Indirect Inputs of SUT via Test Stub