%% The client database
-module(cldb).
-export([init/0, all/0, find/1, login/2, dec_vote/1, inc_vote/1, register/3, check_rights/1, update_votes/0, logout/1, set_client_pid/2, get_votes/1]).
-record(user, {name, passwd, votes, logged_in, pid, rights}).
%% Initialisation of the mnesia database
init() ->
mnesia:create_schema([node()]),
mnesia:start(),
mnesia:create_table(user, [{attributes, record_info(fields, user)}]),
io:format("Userdb up and running \n").
%% The basic search operations on the database
find(User) when is_list(User) ->
find(User, '_');
find(User) ->
find(User#user.name, '_').
find(User, Pwd) ->
F = fun() ->
mnesia:match_object({user, User, Pwd, '_', '_', '_', '_'})
end,
mnesia:transaction(F).
find_logged_in_user() ->
F = fun() ->
mnesia:match_object({user, '_', '_', '_', true, '_', '_'})
end,
case mnesia:transaction(F) of
{atomic, List} -> {ok, List};
_ -> {error}
end.
find_user_by_pid(Pid) ->
F = fun() ->
mnesia:match_object({user, '_', '_', '_', '_', Pid, '_'})
end,
case mnesia:transaction(F) of
{atomic, List} -> {ok, List};
_ -> {error}
end.
%% Retrieve all entries
all() ->
F = fun() ->
mnesia:match_object({user, '_', '_', '_', '_', '_', '_'})
end,
case mnesia:transaction(F) of
{atomic, List} -> {ok, List};
_ -> {error}
end.
%% Perform the login operation of a user into the database.
login(User, Pwd) when is_list(User) and is_list(Pwd) ->
case find(User, Pwd) of
{atomic, [UserRow|_]} ->
NewUserRow = UserRow#user{logged_in = true},
F = fun() ->
mnesia:write(NewUserRow)
end,
case mnesia:transaction(F) of
{atomic, ok} ->
{ok, NewUserRow};
{atomic, Why} ->
{error, Why}
end;
_-> {error}
end;
login(_, _) ->
{error}.
%% In order to log out the client after its process has died.
set_client_pid(User, Pid) ->
case find(User) of
{atomic, [UserRow|_]} ->
NewUserRow = UserRow#user{pid = Pid},
F = fun() ->
mnesia:write(NewUserRow)
end,
case mnesia:transaction(F) of
{atomic, ok} ->
{ok, pid_updated};
{atomic, Why} ->
{error, Why}
end;
_ ->
{error, user_not_found}
end.
%% Change the database to log out a user by PID
logout(Pid) ->
case find_user_by_pid(Pid) of
{atomic, [UserRow|_]} ->
F = fun() ->
New = UserRow#user{logged_in = false},
mnesia:write(New)
end,
case mnesia:transaction(F) of
{atomic, ok} ->
{ok, logged_out};
{atomic, Why} ->
{error, Why}
end;
_ ->
{error, invalid_user}
end.
%% Adds an entry into the database for this user.
%% If he is already registered, this will return an error.
%% In order to vote, users arer required to log in after registering.
register(User, Pwd, Root) when is_list(User) and is_list(Pwd) ->
case find(User) of
{atomic, []} ->
F = fun() ->
mnesia:write(#user{name = User, passwd = Pwd, votes = 5, logged_in = false, pid = undef, rights = Root})
end,
case mnesia:transaction(F) of
{atomic, ok} ->
io:format("User created: ~s~n", [User]),
{ok, user_created};
{atomic, Why} ->
{error, Why}
end;
_ ->
{error, duplicated_user}
end;
register(_,_,_) ->
{error, invalid_username}.
%% functions to de- and increment the amount of votes a user has left.
dec_vote(User) when is_list(User) ->
{atomic, [Head|_]} = find(User),
if Head#user.votes > 0 ->
F = fun() ->
Votes = Head#user.votes - 1,
New = Head#user{votes = Votes},
mnesia:write(New)
end,
mnesia:transaction(F),
{ok};
true -> {error}
end;
dec_vote(User) ->
dec_vote(User#user.name).
inc_vote(User) ->
F = fun() ->
{atomic, [Head|_]} = find(User),
Votes = Head#user.votes + 1,
New = Head#user{votes = Votes},
mnesia:write(New)
end,
mnesia:transaction(F).
%% Return rights of a user (admin or nan).
check_rights(User) ->
{atomic, [UserRow|_]} = find(User),
UserRow#user.rights.
update_votes() ->
%% after a song every logged in client gets one more vote to spend
case find_logged_in_user() of
{ok, List} ->
give_votes(List);
_ -> error
end.
%% Increment the votes of every user.
%% This is called when a song has ended.
give_votes([User|Rest]) ->
inc_vote(User#user.name),
give_votes(Rest);
give_votes([]) -> ok.
%% Returns the amount of votes a specific user has.
get_votes(User) ->
case find(User) of
{atomic, [UserRow|_]} ->
{ok, UserRow#user.votes};
_ ->
{error, user_not_found}
end.
