%%%-------------------------------------------------------------------
%%% File    : bbsOid.erl
%%% Author  : Ulf Wiger <etxuwig@ws12858>
%%% Description : 
%%%
%%% Created :  8 Mar 2006 by Ulf Wiger <etxuwig@ws12858>
%%%-------------------------------------------------------------------
-module(bbsOid).

-export([new/0,
	 incr_vsn/1,
	 add_branch/2,
	 add_peer_node/1]).

-define(MAX_SEQ, 16#ffffFFFF)

new() ->
    MyNode = node(),
    NodeId = mnesia:read_table_property(schema, {bbs_node_id,MyNode}),
    case mnesia:dirty_update_counter(bbsOid, MyNode, 1) of
	NodeSeq when NodeSeq > ?MAX_SEQ ->
	    NewNodeId  = set_new_node_id(MyNode),
	    mnesia:dirty_write({bbsOid, MyNode, 1}),
	    {NewNodeId, 1, initial_vsn()};
	NodeSeq ->
	    {NodeId, NodeSeq, initial_vsn()}
    end.

initial_vsn() ->
    [1].

%%% versions have the structure Branches ++ [integer()],
%%% where Branches :: list(binary()).
incr_vsn({NId,NSeq,V}) ->
    [I|RevT] = lists:reverse(V),
    NewV = lists:reverse([I+1|RevT]),
    {NId, NSeq, NewV}.

add_peer_node(Node) ->
    mnesia_schema:schema_transaction(
      fun() ->
	      case is_peer_node(Node) of
		  true ->
		      mnesia:abort({peer_node_exists, Node});
		  false ->
		      do_set_new_node_id(Node)
	      end
      end).

set_new_node_id(Node) ->
    mnesia_schema:schema_transaction(
      fun() ->
	      case is_peer_node(Node) of
		  true ->
		      do_set_new_node_id(Node);
		  false ->
		      mnesia:abort({not_a_peer_node, Node})
	      end
      end).

do_set_new_node_id(Node) ->
    PeerNodes = read_property(bbs_peer_nodes, ordsets:new()),
    OldCtr = read_property(bbs_node_id_ctr, 0),
    NewCtr = OldCtr + 1,
    write_property({bbs_node_id_ctr, NewCtr}),
    write_property({{bbs_node_id, Node}, NewCtr}),
    write_property({bbs_peer_nodes, 
		    ordsets:add_element(Node, PeerNodes)}),
    NewCtr.


read_property(P, Default) ->
    case mnesia_schema:do_read_table_property(
	   schema, P) of
	undefined ->
	    Default;
	Value ->
	    Value
    end.

is_peer_node(Node) ->
    Peers = read_property(bbs_peer_nodes, ordsets:new()),
    ordsets:is_element(Node, Peers).

write_property(P, Value) ->
    mnesia_schema:do_write_table_property(schema, {P, Value}).