1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
% The clientdatabase
-module(cldb).
-export([init/0,all/0, ask/2, login/2, decVote/1, incVote/1, register/3, check_rights/1, give_votes/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).
all() ->
F = fun() ->
mnesia:match_object({user, '_', '_', '_', '_'})
end,
{atomic, List} = mnesia:transaction(F),
List.
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) when is_list(User) ->
{atomic, [Head|_]} = ask(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;
decVote(User) ->
decVote(User#user.name).
incVote(User) ->
F = fun() ->
{atomic, [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.
|
