(Broken) Working on DB item ID generation...

3 files changed, 213 insertions, 1 deletions

diff --git a/src/db/db_node.erl b/src/db/db_node.erl
index 309adc0..30a29e2 100644
--- a/src/db/db_node.erl
+++ b/src/db/db_node.erl
@@ -32,5 +32,9 @@ start () ->
    db_model:add_db(map_db, Mnesia),
    db_model:add_db(player_db, Mnesia),
    db_model:add_db(roster_db, Mnesia),
+   db_model:add_db(inventory_db, Mnesia),
+
+   ok = db_item_ids_manager:start(),
+
    wait_for_stop(),
    ok.
diff --git a/src/db/logic/db_access.erl b/src/db/logic/db_access.erl
index d62e4ec..39019a6 100644
--- a/src/db/logic/db_access.erl
+++ b/src/db/logic/db_access.erl
@@ -88,7 +88,7 @@ insert_at (DB, ID, ReadPerm, WritePerm, Value) ->
       any())
    -> ({'aborted', any()} | {'atomic', {'ok', binary()}}).
 insert (DB, ReadPerm, WritePerm, Value) ->
-   ID = <<"?">>, %% TODO [FUNCTION: db][HIGH]: gen new ID.
+   ID = db_item_ids_manager:allocate(DB),
    case insert_at(DB, ID, ReadPerm, WritePerm, Value) of
       {'atomic', 'ok'} -> {'atomic', {'ok', ID}};
       {aborted, Val} -> {aborted, Val}
diff --git a/src/db/struct/db_item_ids_manager.erl b/src/db/struct/db_item_ids_manager.erl
new file mode 100644
index 0000000..999a047
--- /dev/null
+++ b/src/db/struct/db_item_ids_manager.erl
@@ -0,0 +1,208 @@
+-module(db_item_ids_manager).
+-behavior(gen_server).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% TYPES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+-record
+(
+   entry,
+   {
+      last_id :: binary(),
+      freed_ids :: list(binary())
+   }
+).
+
+-type entry() :: #entry{}.
+
+%% FIXME: IDs should be generated in a decentralized fashion.
+%% TODO: How to handle IDs management with the redundancy DBs?
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% EXPORTS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%% 'gen_server' Exports
+-export
+(
+   [
+      init/1,
+      handle_cast/2,
+      handle_call/3, %% No reply will ever be given.
+      terminate/2,
+      code_change/3,
+      format_status/2,
+      handle_info/2
+   ]
+).
+
+%%%% Actual Interface
+-export
+(
+   [
+      allocate/1,
+      free/2,
+      start/0
+   ]
+).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% LOCAL FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+-spec next_char (integer()) -> integer().
+next_char ($9) -> $a;
+next_char ($z) -> $A;
+next_char ($Z) -> $0;
+next_char (C) -> (C + 1).
+
+-spec next_id_internal
+   (
+      list(integer()),
+      boolean(),
+      list(integer())
+   )
+   -> list(integer()).
+next_id_internal ([], true, Result) -> [$0|Result];
+next_id_internal ([], false, Result) -> Result;
+next_id_internal ([$Z|Next], true, Result) ->
+   next_id_internal(Next, true, [$0|Result]);
+next_id_internal ([Char|Next], true, Result) ->
+   next_id_internal(Next, false, [next_char(Char)|Result]);
+next_id_internal ([Char|Next], false, Result) ->
+   next_id_internal(Next, false, [Char|Result]).
+
+-spec next_id (binary()) -> binary().
+next_id (ID) ->
+   list_to_binary
+   (
+      next_id_internal
+      (
+         lists:reverse(binary:bin_to_list(ID)),
+         true,
+         []
+      )
+   ).
+
+-spec new_entry () -> entry().
+new_entry () ->
+   #entry
+   {
+      last_id = <<"">>,
+      freed_ids = []
+   }.
+
+-spec allocate_id_in_entry (entry()) -> {entry(), binary()}.
+allocate_id_in_entry (Entry) ->
+   case Entry#entry.freed_ids of
+      [] ->
+         NewID = next_id(Entry#entry.last_id),
+         {
+            Entry#entry{ last_id = NewID },
+            NewID
+         };
+
+      [OldID|OtherOldIDs] ->
+         {
+            Entry#entry{ freed_ids = OtherOldIDs },
+            OldID
+         }
+   end.
+
+-spec allocate_id
+   (
+      atom(),
+      dict:dict(atom(), entry())
+   )
+   -> {dict:dict(atom(), entry()), binary()}.
+allocate_id (DB, State) ->
+   S0Entry =
+      case dict:find(DB, State) of
+         {ok, Value} -> Value;
+         error -> new_entry()
+      end,
+
+   {S1Entry, NewID} = allocate_id_in_entry(S0Entry),
+
+   S0State = dict:store(DB, S1Entry, State),
+
+   {S0State, NewID}.
+
+-spec free_id
+   (
+      binary(),
+      atom(),
+      dict:dict(atom(), entry())
+   )
+   -> dict:dict(atom(), entry()).
+free_id (ID, DB, State) ->
+   Entry =
+      case dict:find(DB, State) of
+         {ok, Value} -> Value;
+         error -> new_entry()
+      end,
+
+   EntryFreedIDs = Entry#entry.freed_ids,
+
+   case lists:member(ID, EntryFreedIDs) of
+      true -> State;
+      false ->
+         Result =
+            dict:store
+            (
+               DB,
+               Entry#entry{ freed_ids = [ID|EntryFreedIDs] },
+               State
+            ),
+
+         Result
+   end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% EXPORTED FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%% 'gen_server' functions
+init (_) -> {ok, dict:new()}.
+
+handle_call ({allocate, DB}, _, State) ->
+   {NewState, NewID} = allocate_id(DB, State),
+   {reply, {allocated_id, NewID}, NewState};
+handle_call ({free, ID, DB}, _, State) ->
+   {noreply, free_id(ID, DB, State)}.
+
+handle_cast ({allocate, _DB}, State) ->
+   {noreply, State};
+handle_cast ({free, ID, DB}, State) ->
+   {noreply, free_id(ID, DB, State)}.
+
+terminate (_, _) -> ok.
+
+code_change (_, State, _) ->
+   {ok, State}.
+
+format_status (_, [_, State]) ->
+   [{data, [{"State", State}]}].
+
+handle_info(_, State) ->
+   {noreply, State}.
+
+%%%% Interface Functions
+-spec allocate (atom()) -> binary().
+allocate (DB) ->
+   gen_server:call({global, db_item_ids_manager}, {allocate, DB}),
+
+   receive
+      {allocated_id, Result} ->
+         io:format("~n[DB: ~p] Item ID ~p allocated.~n", [DB, Result]),
+         Result
+   end.
+
+-spec free (binary(), atom()) -> 'ok'.
+free (ID, DB) ->
+   gen_server:cast({global, db_item_ids_manager}, {free, ID, DB}),
+
+   ok.
+
+-spec start () -> 'ok'.
+start () ->
+   {ok, _} = gen_server:start({global, db_item_ids_manager}, ?MODULE, none, []),
+
+   ok.