compute store flow path based on user_data folder

There are some enviroments whe erlang-red is running as a non-privileged
user. Thus, if erlang-red is installed on /usr/ path it will not have
the correct permissions when writing flows to disk.

This change allows erlang-red compute a store flow path based on:

1. if flow_store application property has been configured, erlang-red
   will use that value. Otherwise:

2. get `user_data` [1] from filename:basedir/2 as a base folder for
   storing flows. e.g.: in my host (linux based) the store folder is
   /home/joaohf/.local/share/erlang-red/

1: https://www.erlang.org/doc/apps/stdlib/filename.html#basedir/3

Author: joaohf

src/ered_flow_store.erl

@@ -0,0 +1,19 @@
+-module(ered_flow_store).
+
+-export([store_flow/0, store_flow_id/1, store_main_flow/0]).
+
+store_flow_id(FlowId) when is_binary(FlowId) ->
+    store_flow_id(binary_to_list(FlowId));
+store_flow_id(FlowId) when is_list(FlowId) ->
+    filename:join([get_store_flow(), FlowId, "flows.json"]).
+
+store_flow() ->
+    get_store_flow().
+
+store_main_flow() ->
+    filename:join([get_store_flow(), "flows.json"]).
+
+get_store_flow() ->
+    application:get_env(
+        erlang_red, flow_store, filename:basedir(user_data, "erlang-red")
+    ).

src/nodes/ered_node_flowhub_pull.erl

@@ -69,10 +69,7 @@ handle_msg(_, NodeDef) ->
 %%
 
 handle_flowid(FlowId, Msg, #{<<"wires">> := [WiresPort1 | _]} = NodeDef) ->
-    FileName = io_lib:format(
-        "~s/testflows/~s/flows.json",
-        [code:priv_dir(erlang_red), FlowId]
-    ),
+    FileName = ered_flow_store:store_flow_id(FlowId),
 
     case file:read_file(FileName) of
         {ok, FileData} ->

src/servers/ered_credentials_store.erl

@@ -134,7 +134,8 @@ terminate(Event, _State) ->
 %% ----------------- helpers
 %%
 load_initial_credentials() ->
-    FileName = io_lib:format("~s/flows_cred.json", [code:priv_dir(erlang_red)]),
+    FileName = filename:join(ered_flow_store:store_flow(), "flows_cred.json"),
+
     case filelib:is_regular(FileName) of
         false ->
             #{store => #{}};
@@ -144,7 +145,7 @@ load_initial_credentials() ->
     end.
 
 store_credentials_to_disk(#{store := Hsh} = _State) ->
-    FileName = io_lib:format("~s/flows_cred.json", [code:priv_dir(erlang_red)]),
+    FileName = filename:join(ered_flow_store:store_flow(), "flows_cred.json"),
 
     case file:write_file(FileName, json:encode(Hsh)) of
         ok ->

src/servers/ered_flow_store_server.erl

@@ -122,10 +122,7 @@ handle_call({filename, FlowId}, _From, FlowStore) ->
             {reply, error, FlowStore}
     end;
 handle_call({retrieve_main_flow}, _From, FlowStore) ->
-    SrcFileName = io_lib:format(
-        "~s/flows.json",
-        [code:priv_dir(erlang_red)]
-    ),
+    SrcFileName = ered_flow_store:store_main_flow(),
 
     {reply, file:read_file(SrcFileName), FlowStore};
 handle_call(_Msg, _From, FlowStore) ->
@@ -146,10 +143,7 @@ handle_info({store_main_flow, FlowData}, State) ->
     %% remove any reference to <<"credentials">>
     NodeAry = remove_credentials(NodeAryWithCreds),
 
-    DestFileName = io_lib:format(
-        "~s/flows.json",
-        [code:priv_dir(erlang_red)]
-    ),
+    DestFileName = ered_flow_store:store_main_flow(),
 
     filelib:ensure_dir(DestFileName),
     case file:write_file(DestFileName, encode_json(NodeAry)) of
@@ -170,10 +164,7 @@ handle_info({store_flow, FlowId, JsonText}, FlowStore) ->
     %% remove any reference to <<"credentials">>
     NodeAry = remove_credentials(json:decode(NodeAryWithCreds)),
 
-    DestFileName = io_lib:format(
-        "~s/testflows/~s/flows.json",
-        [code:priv_dir(erlang_red), FlowId]
-    ),
+    DestFileName = ered_flow_store:store_flow_id(FlowId),
 
     filelib:ensure_dir(DestFileName),
     case file:write_file(DestFileName, encode_json(NodeAry)) of
@@ -237,12 +228,10 @@ remove_credentials([NodeDef | Rest], Store) ->
 compile_file_list() ->
     {ok, MP} = re:compile("([A-Z0-9]{16})/flows.json", [caseless]),
 
-    TestFlowDir = io_lib:format("~s/testflows/", [code:priv_dir(erlang_red)]),
+    TestFlowDir = filename:join(code:priv_dir(erlang_red), "testflows"),
+    StoreFlowDir = ered_flow_store:store_flow(),
 
-    FileNames = filelib:fold_files(
-        TestFlowDir,
-        "flows.json",
-        true,
+    Fun =
         fun(Fname, Acc) ->
             case re:run(Fname, MP) of
                 {match, [{_, _}, {S, L}]} ->
@@ -251,9 +240,11 @@ compile_file_list() ->
                     Acc
             end
         end,
-        []
-    ),
-    FileNames.
+
+    FileNames0 = filelib:fold_files(TestFlowDir, "flows.json", true, Fun, []),
+    FileNames1 = filelib:fold_files(StoreFlowDir, "flows.json", true, Fun, []),
+
+    FileNames0 ++ FileNames1.
 
 %% erlfmt:ignore lining stuff up
 compile_file_store([], FileStore) ->