path: root/server/cldb.erl

% The clientdatabase

-module(cldb).
-export([init/0, ask/2, login/2, decVote/1, incVote/1, register/3, check_rights/1]).
-record(user, {name, passwd, votes, rights}).

init() ->
    mnesia:create_schema([node()]),
    mnesia:start(),
    mnesia:create_table(user, [{attributes, record_info(fields, user)}]),
    io:format("Userdb up and running \n").

ask(User, Pwd) ->
    F = fun() ->
                mnesia:match_object({user, User, Pwd, '_', '_'})
        end,
    mnesia:transaction(F).

login(User, Pwd) ->
    case ask(User, Pwd) of
	{atomic, [UserRow|_]} -> {ok, UserRow};
	_-> {error}
    end.

register(User, Pwd, Root) ->
    case ask(User, '_') of
	{atomic, []} ->
	    F = fun() ->
			mnesia:write(#user{name = User, passwd = Pwd, votes = 5, rights = Root})
		end,
	    case mnesia:transaction(F) of
		{atomic, ok} ->
		    {ok, user_created};
		{atomic, Why} ->
		    {error, Why}
	    end;
	_ ->
	    {error, duplicated_user}
    end.

decVote(User) ->
    F = fun() ->
                [Head|_] = ask(User, '_'),
                Votes = Head#user.votes - 1,
                New = Head#user{votes = Votes},
                mnesia:write(New)
        end,
    mnesia:transaction(F).

incVote(User) ->
    F = fun() ->
                [Head|_] = ask(User, '_'),
                Votes = Head#user.votes + 1,
                New = Head#user{votes = Votes},
                mnesia:write(New)
        end,
    mnesia:transaction(F).

check_rights(User) ->
    {_, _, Rights} = ask(User, '_'),
    Rights.

% after a song every client gets on more vote
give_votes([Head|Rest]) -> 
	User = Head#user.name,
	incVote(User),
	give_votes(Rest);
give_votes([]) -> ok.