WIP: minimal write-once projection store in FLU

prototype/poc-machi/src/machi_flu0.erl

@@ -3,7 +3,8 @@
 -behaviour(gen_server).
 
 -export([start_link/1, stop/1,
-         write/2, get/1, trim/1]).
+         write/2, get/1, trim/1,
+         proj_write/3, proj_read/2, proj_get_latest_num/1, proj_read_latest/1]).
 -ifdef(TEST).
 -compile(export_all).
 -endif.
@@ -28,7 +29,8 @@
 
 -record(state, {
           name :: list(),
-          register = 'unwritten' :: register()
+          register = 'unwritten' :: register(),
+          proj_store :: dict()
          }).
 
 start_link(Name) when is_list(Name) ->
@@ -46,10 +48,22 @@ write(Pid, Bin) when is_binary(Bin) ->
 trim(Pid) ->
     gen_server:call(Pid, {trim}, ?LONG_TIME).
 
+proj_write(Pid, Num, Proj) ->
+    gen_server:call(Pid, {proj_write, Num, Proj}, ?LONG_TIME).
+
+proj_read(Pid, Num) ->
+    gen_server:call(Pid, {proj_read, Num}, ?LONG_TIME).
+
+proj_get_latest_num(Pid) ->
+    gen_server:call(Pid, {proj_get_latest_num}, ?LONG_TIME).
+
+proj_read_latest(Pid) ->
+    gen_server:call(Pid, {proj_read_latest}, ?LONG_TIME).
+
 %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%%
 
 init([Name]) ->
-    {ok, #state{name=Name}}.
+    {ok, #state{name=Name, proj_store=orddict:new()}}.
 
 handle_call({write, Bin}, _From, #state{register=unwritten} = S) ->
     {reply, ok, S#state{register=Bin}};
@@ -65,6 +79,23 @@ handle_call({trim}, _From, #state{register=B} = S) when is_binary(B) ->
     {reply, ok, S#state{register=trimmed}};
 handle_call({trim}, _From, #state{register=trimmed} = S) ->
     {reply, error_trimmed, S};
+handle_call({proj_write, Num, Proj}, _From, S) ->
+    {Reply, NewS} = do_proj_write(Num, Proj, S),
+    {reply, Reply, NewS};
+handle_call({proj_read, Num}, _From, S) ->
+    {Reply, NewS} = do_proj_read(Num, S),
+    {reply, Reply, NewS};
+handle_call({proj_get_latest_num}, _From, S) ->
+    {Reply, NewS} = do_proj_get_latest_num(S),
+    {reply, Reply, NewS};
+handle_call({proj_read_latest}, _From, S) ->
+    case do_proj_get_latest_num(S) of
+        {error_unwritten, _S} ->
+            {reply, error_unwritten, S};
+        {{ok, Num}, _S} ->
+            Proj = orddict:fetch(Num, S#state.proj_store),
+            {reply, {ok, Proj}, S}
+    end;
 handle_call(stop, _From, MLP) ->
     {stop, normal, ok, MLP};
 handle_call(_Request, _From, MLP) ->
@@ -85,3 +116,28 @@ code_change(_OldVsn, MLP, _Extra) ->
 
 %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%% %%%%
 
+do_proj_write(Num, Proj, #state{proj_store=D} = S) ->
+    case orddict:find(Num, D) of
+        error ->
+            D2 = orddict:store(Num, Proj, D),
+            {ok, S#state{proj_store=D2}};
+        {ok, _} ->
+            {error_written, S}
+    end.
+
+do_proj_read(Num, #state{proj_store=D} = S) ->
+    case orddict:find(Num, D) of
+        error ->
+            {error_unwritten, S};
+        {ok, Proj} ->
+            {{ok, Proj}, S}
+    end.
+
+do_proj_get_latest_num(#state{proj_store=D} = S) ->
+    case lists:sort(orddict:to_list(D)) of
+        [] ->
+            {error_unwritten, S};
+        L ->
+            {Num, _Proj} = lists:last(L),
+            {{ok, Num}, S}
+    end.

prototype/poc-machi/test/machi_flu0_test.erl

@@ -61,6 +61,21 @@ concuerror4_test() ->
     ok = machi_flu0:stop(F1),
     ok.
     
+proj_store_test() ->
+    {ok, F1} = machi_flu0:start_link("one"),
+
+    error_unwritten = machi_flu0:proj_get_latest_num(F1),
+    error_unwritten = machi_flu0:proj_read_latest(F1),
+
+    Proj1 = whatever1,
+    ok = machi_flu0:proj_write(F1, 1, Proj1),
+    error_written = machi_flu0:proj_write(F1, 1, Proj1),
+    {ok, Proj1} = machi_flu0:proj_read(F1, 1),
+    {ok, 1} = machi_flu0:proj_get_latest_num(F1),
+    {ok, Proj1} = machi_flu0:proj_read_latest(F1),
+
+    ok = machi_flu0:stop(F1),
+    ok.
 
 -endif.
 -endif.