aboutsummaryrefslogtreecommitdiffstats
path: root/lib/diameter/src/base/diameter_gen.erl
blob: 4879ad8f6c3f4fd634acddca18dcfa08be78396f (plain) (blame)
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
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2017. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%

%%
%% This file contains code that encode/decode modules generated by
%% diameter_codegen.erl calls to implement the functionality. This
%% code does most of the work, the generated code being kept simple.
%%

-module(diameter_gen).

-export([encode_avps/3,
         decode_avps/3,
         grouped_avp/4,
         empty_group/2,
         empty/2]).

-include_lib("diameter/include/diameter.hrl").

-define(THROW(T), throw({?MODULE, T})).

-type parent_name()   :: atom().  %% parent = Message or AVP
-type parent_record() :: tuple(). %%
-type avp_name()   :: atom().
-type avp_record() :: tuple().
-type avp_values() :: [{avp_name(), term()}].

-type non_grouped_avp() :: #diameter_avp{}.
-type grouped_avp() :: nonempty_improper_list(#diameter_avp{}, [avp()]).
-type avp() :: non_grouped_avp() | grouped_avp().

%% ---------------------------------------------------------------------------
%% # encode_avps/3
%% ---------------------------------------------------------------------------

-spec encode_avps(parent_name(), parent_record() | avp_values(), map())
   -> iolist()
    | no_return().

encode_avps(Name, Vals, #{module := Mod} = Opts) ->
    try
        encode(Name, Vals, Opts, Mod)
    catch
        throw: {?MODULE, Reason} ->
            diameter_lib:log({encode, error},
                             ?MODULE,
                             ?LINE,
                             {Reason, Name, Vals, Mod}),
            erlang:error(list_to_tuple(Reason ++ [Name]));
        error: Reason ->
            Stack = erlang:get_stacktrace(),
            diameter_lib:log({encode, failure},
                             ?MODULE,
                             ?LINE,
                             {Reason, Name, Vals, Mod, Stack}),
            erlang:error({encode_failure, Reason, Name, Stack})
    end.

%% encode/4

encode(Name, Vals, #{ordered_encode := false} = Opts, Mod)
  when is_list(Vals) ->
    lists:map(fun({F,V}) -> encode(Name, F, V, Opts, Mod) end, Vals);

encode(Name, Vals, Opts, Mod)
  when is_list(Vals) ->
    encode(Name, Mod:'#set-'(Vals, newrec(Mod, Name)), Opts, Mod);

encode(Name, Rec, Opts, Mod) ->
    [encode(Name, F, V, Opts, Mod) || {F,V} <- Mod:'#get-'(Rec)].

%% encode/5

encode(Name, AvpName, Values, Opts, Mod) ->
    enc(Name, AvpName, Mod:avp_arity(Name, AvpName), Values, Opts, Mod).

%% enc/6

enc(_, AvpName, 1, undefined, _, _) ->
    ?THROW([mandatory_avp_missing, AvpName]);

enc(Name, AvpName, 1, Value, Opts, Mod) ->
    enc(Name, AvpName, [Value], Opts, Mod);

enc(_, _, {0,_}, [], _, _) ->
    [];

enc(_, AvpName, _, T, _, _)
  when not is_list(T) ->
    ?THROW([repeated_avp_as_non_list, AvpName, T]);

enc(_, AvpName, {Min, _}, L, _, _)
  when length(L) < Min ->
    ?THROW([repeated_avp_insufficient_arity, AvpName, Min, L]);

enc(_, AvpName, {_, Max}, L, _, _)
  when Max < length(L) ->
    ?THROW([repeated_avp_excessive_arity, AvpName, Max, L]);

enc(Name, AvpName, _, Values, Opts, Mod) ->
    enc(Name, AvpName, Values, Opts, Mod).

%% enc/5

enc(Name, 'AVP', Values, Opts, Mod) ->
    [enc_AVP(Name, A, Opts, Mod) || A <- Values];

enc(_, AvpName, Values, Opts, Mod) ->
    enc(AvpName, Values, Opts, Mod).

%% enc/4

enc(AvpName, Values, Opts, Mod) ->
    H = Mod:avp_header(AvpName),
    [diameter_codec:pack_data(H, Mod:avp(encode, V, AvpName, Opts))
     || V <- Values].

%% enc_AVP/4

%% No value: assume AVP data is already encoded. The normal case will
%% be when this is passed back from #diameter_packet.errors as a
%% consequence of a failed decode. Any AVP can be encoded this way
%% however, which side-steps any arity checks for known AVP's and
%% could potentially encode something unfortunate.
enc_AVP(_, #diameter_avp{value = undefined} = A, Opts, _) ->
    diameter_codec:pack_avp(A, Opts);

%% Missing name for value encode.
enc_AVP(_, #diameter_avp{name = N, value = V}, _, _)
  when N == undefined;
       N == 'AVP' ->
    ?THROW([value_with_nameless_avp, N, V]);

%% Or not. Ensure that 'AVP' is the appropriate field. Note that if we
%% don't know this AVP at all then the encode will fail.
enc_AVP(Name, #diameter_avp{name = AvpName, value = Data}, Opts, Mod) ->
    0 == Mod:avp_arity(Name, AvpName)
        orelse ?THROW([known_avp_as_AVP, Name, AvpName, Data]),
    enc(AvpName, [Data], Opts, Mod);

%% The backdoor ...
enc_AVP(_, {AvpName, Value}, Opts, Mod) ->
    enc(AvpName, [Value], Opts, Mod);

%% ... and the side door.
enc_AVP(_Name, {_Dict, _AvpName, _Data} = T, Opts, _) ->
    diameter_codec:pack_avp(#diameter_avp{data = T}, Opts).

%% ---------------------------------------------------------------------------
%% # decode_avps/3
%% ---------------------------------------------------------------------------

-spec decode_avps(parent_name(), [#diameter_avp{}], map())
   -> {parent_record(), [avp()], Failed}
 when Failed :: [{5000..5999, #diameter_avp{}}].

decode_avps(Name, Recs, #{module := Mod} = Opts) ->
    {Avps, {Rec, AM, Failed}}
        = mapfoldl(fun(T,A) -> decode(Name, Opts, Mod, T, A) end,
                   {newrec(Mod, Name, Opts), #{}, []},
                   Recs),
    %% AM counts the number of top-level AVPs, which missing/4 then
    %% uses when adding 5005 errors.
    {Rec, Avps, Failed ++ missing(Name, Opts, Mod, AM)}.

%% Append 5005 errors so that errors are reported in the order
%% encountered. Failed-AVP should typically contain the first
%% error encountered.

%% mapfoldl/3
%%
%% Like lists:mapfoldl/3, but don't reverse the list.

mapfoldl(F, Acc, List) ->
    mapfoldl(F, Acc, List, []).

mapfoldl(F, Acc0, [T|Rest], List) ->
    {B, Acc} = F(T, Acc0),
    mapfoldl(F, Acc, Rest, [B|List]);
mapfoldl(_, Acc, [], List) ->
    {List, Acc}.

%% missing/4

%% 3588:
%%
%%   DIAMETER_MISSING_AVP               5005
%%      The request did not contain an AVP that is required by the Command
%%      Code definition.  If this value is sent in the Result-Code AVP, a
%%      Failed-AVP AVP SHOULD be included in the message.  The Failed-AVP
%%      AVP MUST contain an example of the missing AVP complete with the
%%      Vendor-Id if applicable.  The value field of the missing AVP
%%      should be of correct minimum length and contain zeros.

missing(Name, Opts, Mod, AM) ->
    lists:foldl(fun(T,A) -> missing(T, AM, Opts, Mod, A) end,
                [],
                Mod:avp_arity(Name)).

%% missing/5

missing({Name, Arity}, AM, Opts, Mod, Acc) ->
    case missing(Name, Arity, AM) of
        true  -> [{5005, empty_avp(Name, Opts, Mod)} | Acc];
        false -> Acc
    end.

%% missing/3

missing(Name, Arity, AM) ->
    'AVP' /= Name andalso too_few(Name, Arity, AM).

%% too_few/3
%%
%% Maximum arities have already been checked during the decode.

too_few(_, {0, _}, _) ->
    false;

too_few(FieldName, 1, AM) ->
    not maps:is_key(FieldName, AM);

too_few(FieldName, {M, _}, AM) ->
    maps:get(FieldName, AM, 0) < M.

%% empty_avp/3

empty_avp(Name, Opts, Mod) ->
    {Code, Flags, VId} = Mod:avp_header(Name),
    {Name, Type} = Mod:avp_name(Code, VId),
    #diameter_avp{name = Name,
                  code = Code,
                  vendor_id = VId,
                  is_mandatory = 0 /= (Flags band 2#01000000),
                  need_encryption = 0 /= (Flags band 2#00100000),
                  data = Mod:empty_value(Name, Opts),
                  type = Type}.

%% 3588, ch 7:
%%
%%   The Result-Code AVP describes the error that the Diameter node
%%   encountered in its processing.  In case there are multiple errors,
%%   the Diameter node MUST report only the first error it encountered
%%   (detected possibly in some implementation dependent order).  The
%%   specific errors that can be described by this AVP are described in
%%   the following section.

%% decode/5

decode(Name,
       Opts,
       Mod,
       #diameter_avp{code = Code, vendor_id = Vid}
       = Avp,
       {Rec, AM, Failed}) ->
    T = Mod:avp_name(Code, Vid),
    decode(Name, Opts, Mod, T, Avp, {Rec, incr(field(T), AM), Failed}).

%% field/1

field({AvpName, _Type}) ->
    AvpName;

field('AVP' = A) ->
    A.

%% incr/2

incr(Key, Map) ->
    maps:update_with(Key, fun incr/1, 1, Map).

%% incr/1

incr(N) ->
    N + 1.

%% decode/6

%% AVP not in dictionary.
decode(Name, Opts, Mod, 'AVP', Avp, Acc) ->
    decode_AVP(Name, Avp, Opts, Mod, Acc);

%% 6733, 4.4:
%%
%%   Receivers of a Grouped AVP that does not have the 'M' (mandatory)
%%   bit set and one or more of the encapsulated AVPs within the group
%%   has the 'M' (mandatory) bit set MAY simply be ignored if the
%%   Grouped AVP itself is unrecognized. The rule applies even if the
%%   encapsulated AVP with its 'M' (mandatory) bit set is further
%%   encapsulated within other sub-groups, i.e., other Grouped AVPs
%%   embedded within the Grouped AVP.
%%
%% The first sentence is slightly mangled, but take it to mean this:
%%
%%   An unrecognized AVP of type Grouped that does not set the 'M' bit
%%   MAY be ignored even if one of its encapsulated AVPs sets the 'M'
%%   bit.
%%
%% The text above is a change from RFC 3588, which instead says this:
%%
%%   Further, if any of the AVPs encapsulated within a Grouped AVP has
%%   the 'M' (mandatory) bit set, the Grouped AVP itself MUST also
%%   include the 'M' bit set.
%%
%% Both of these texts have problems. If the AVP is unknown then its
%% type is unknown since the type isn't sent over the wire, so the
%% 6733 text becomes a non-statement: don't know that the AVP not
%% setting the M-bit is of type Grouped, therefore can't know that its
%% data consists of encapsulated AVPs, therefore can't but ignore that
%% one of these might set the M-bit. It should be no worse if we know
%% the AVP to have type Grouped.
%%
%% Similarly, for the 3588 text: if we receive an AVP that doesn't set
%% the M-bit and don't know that the AVP has type Grouped then we
%% can't realize that its data contains an AVP that sets the M-bit, so
%% can't regard the AVP as erroneous on this account. Again, it should
%% be no worse if the type is known to be Grouped, but in this case
%% the RFC forces us to regard the AVP as erroneous. This is
%% inconsistent, and the 3588 text has never been enforced.
%%
%% So, if an AVP doesn't set the M-bit then we're free to ignore it,
%% regardless of the AVP's type. If we know the type to be Grouped
%% then we must ignore the M-bit on an encapsulated AVP. That means
%% packing such an encapsulated AVP into an 'AVP' field if need be,
%% not regarding the lack of a specific field as an error as is
%% otherwise the case. (The lack of an AVP-specific field being how we
%% defined the RFC's "unrecognized", which is slightly stronger than
%% "not defined".)

decode(Name, Opts0, Mod, {AvpName, Type}, Avp, Acc) ->
    #diameter_avp{data = Data, is_mandatory = M}
        = Avp,

    %% Whether or not to ignore an M-bit on an encapsulated AVP, or on
    %% all AVPs with the service_opt() strict_mbit.
    Opts1 = set_strict(Type, M, Opts0),

    %% Whether or not we're decoding within Failed-AVP and should
    %% ignore decode errors.
    #{dictionary := AppMod, failed_avp := Failed}
        = Opts
        = set_failed(Name, Opts1), %% Not AvpName or else a failed Failed-AVP
                                   %% decode is packed into 'AVP'.

    %% Reset the dictionary for best-effort decode of Failed-AVP.
    DecMod = if Failed -> AppMod;
                true   -> Mod
             end,

    %% A Grouped AVP is represented as a #diameter_avp{} list with AVP
    %% as head and component AVPs as tail. On encode, data can be a
    %% list of component AVPs.

    try avp_decode(Data, AvpName, Opts, DecMod, Mod) of
        {Rec, As} when Type == 'Grouped' ->
            A = Avp#diameter_avp{name = AvpName,
                                 value = Rec,
                                 type = Type},
            {[A|As], pack_avp(Name, A, Opts, Mod, Acc)};

        V when Type /= 'Grouped' ->
            A = Avp#diameter_avp{name = AvpName,
                                 value = V,
                                 type = Type},
            {A, pack_avp(Name, A, Opts, Mod, Acc)}
    catch
        throw: {?MODULE, {grouped, Error, ComponentAvps}} ->
            decode_error(Name,
                         Error,
                         ComponentAvps,
                         Opts,
                         Mod,
                         Avp#diameter_avp{name = AvpName,
                                          data = trim(Avp#diameter_avp.data),
                                          type = Type},
                         Acc);

        error: Reason ->
            decode_error(Name,
                         Reason,
                         Opts,
                         Mod,
                         Avp#diameter_avp{name = AvpName,
                                          data = trim(Avp#diameter_avp.data),
                                          type = Type},
                         Acc)
    end.

%% avp_decode/5

avp_decode(Data, AvpName, Opts, Mod, Mod) ->
    Mod:avp(decode, Data, AvpName, Opts);

avp_decode(Data, AvpName, Opts, Mod, _) ->
    Mod:avp(decode, Data, AvpName, Opts, Mod).

%% trim/1
%%
%% Remove any extra bit that was added in diameter_codec to induce a
%% 5014 error.

trim(#diameter_avp{data = Data} = Avp) ->
    Avp#diameter_avp{data = trim(Data)};

trim({5014, Bin}) ->
    Bin;

trim(Avps)
  when is_list(Avps) ->
    lists:map(fun trim/1, Avps);

trim(Avp) ->
    Avp.

%% decode_error/7

decode_error(Name, [_|Rec], _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
    decode_AVP(Name, Avp#diameter_avp{value = Rec}, Opts, Mod, Acc);

decode_error(Name, _, _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
    decode_AVP(Name, Avp, Opts, Mod, Acc);

decode_error(_, [Error | _], ComponentAvps, _, _, Avp, Acc) ->
    decode_error(Error, Avp, Acc, ComponentAvps);

decode_error(_, Error, ComponentAvps, _, _, Avp, Acc) ->
    decode_error(Error, Avp, Acc, ComponentAvps).

%% decode_error/6

decode_error(Name, _Reason, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
    decode_AVP(Name, Avp, Opts, Mod, Acc);

decode_error(Name, Reason, Opts, Mod, Avp, {Rec, AM, Failed}) ->
    Stack = diameter_lib:get_stacktrace(),
    AvpName = Avp#diameter_avp.name,
    diameter_lib:log(decode_error,
                     ?MODULE,
                     ?LINE,
                     {Reason, Name, AvpName, Mod, Stack}),
    {Avp, {Rec, AM, [rc(Reason, Avp, Opts, Mod) | Failed]}}.

%% decode_error/4

decode_error({RC, ErrorData}, Avp, {Rec, AM, Failed}, ComponentAvps) ->
    E = Avp#diameter_avp{data = [ErrorData]},
    {[Avp | trim(ComponentAvps)], {Rec, AM, [{RC, E} | Failed]}}.

%% set_strict/3

%% Set false as soon as we see a Grouped AVP that doesn't set the
%% M-bit, to ignore the M-bit on an encapsulated AVP.
set_strict('Grouped', false = M, #{strict_mbit := true} = Opts) ->
    Opts#{strict_mbit := M};
set_strict(_, _, Opts) ->
    Opts.

%% set_failed/2
%%
%% Set true as soon as we see Failed-AVP. Matching on 'Failed-AVP'
%% assumes that this is the RFC AVP. Strictly, this doesn't need to be
%% the case.

set_failed('Failed-AVP', #{failed_avp := false} = Opts) ->
    Opts#{failed_avp := true};
set_failed(_, Opts) ->
    Opts.

%% decode_AVP/5
%%
%% Don't know this AVP: see if it can be packed in an 'AVP' field
%% undecoded. Note that the type field is 'undefined' in this case.

decode_AVP(Name, Avp, Opts, Mod, Acc) ->
    {trim(Avp), pack_AVP(Name, Avp, Opts, Mod, Acc)}.

%% rc/2

%% diameter_types will raise an error of this form to communicate
%% DIAMETER_INVALID_AVP_LENGTH (5014). A module specified to a
%% @custom_types tag in a dictionary file can also raise an error of
%% this form.
rc({'DIAMETER', 5014 = RC, _}, #diameter_avp{name = AvpName} = A, Opts, Mod) ->
    {RC, A#diameter_avp{data = Mod:empty_value(AvpName, Opts)}};

%% 3588:
%%
%%   DIAMETER_INVALID_AVP_VALUE         5004
%%      The request contained an AVP with an invalid value in its data
%%      portion.  A Diameter message indicating this error MUST include
%%      the offending AVPs within a Failed-AVP AVP.
rc(_, Avp, _, _) ->
    {5004, Avp}.

%% pack_avp/5

pack_avp(Name, #diameter_avp{name = AvpName} = Avp, Opts, Mod, Acc) ->
    pack_avp(Name, Mod:avp_arity(Name, AvpName), Avp, Opts, Mod, Acc).

%% pack_avp/6

pack_avp(Name, 0, Avp, Opts, Mod, Acc) ->
    pack_AVP(Name, Avp, Opts, Mod, Acc);

pack_avp(_, Arity, #diameter_avp{name = AvpName} = Avp, _Opts, Mod, Acc) ->
    pack(Arity, AvpName, Avp, Mod, Acc).

%% pack_AVP/5

%% Length failure was induced because of a header/payload length
%% mismatch. The AVP Length is reset to match the received data if
%% this AVP is encoded in an answer message, since the length is
%% computed.
%%
%% Data is a truncated header if command_code = undefined, otherwise
%% payload bytes. The former is padded to the length of a header if
%% the AVP reaches an outgoing encode in diameter_codec.
%%
%% RFC 6733 says that an AVP returned with 5014 can contain a minimal
%% payload for the AVP's type, but in this case we don't know the
%% type.

pack_AVP(_, #diameter_avp{data = {5014 = RC, Data}} = Avp, _, _, Acc) ->
    {Rec, AM, Failed} = Acc,
    {Rec, AM, [{RC, Avp#diameter_avp{data = Data}} | Failed]};

pack_AVP(Name, Avp, Opts, Mod, Acc) ->
    Arity = pack_arity(Name, Opts, Mod, Avp),
    if 0 == Arity ->
            M = Avp#diameter_avp.is_mandatory,
            {Rec, AM, Failed} = Acc,
            {Rec, AM, [{if M -> 5001; true -> 5008 end, Avp} | Failed]};
       true ->
            pack(Arity, 'AVP', Avp, Mod, Acc)
    end.

%% 3588:
%%
%%   DIAMETER_AVP_UNSUPPORTED           5001
%%      The peer received a message that contained an AVP that is not
%%      recognized or supported and was marked with the Mandatory bit.  A
%%      Diameter message with this error MUST contain one or more Failed-
%%      AVP AVP containing the AVPs that caused the failure.
%%
%%   DIAMETER_AVP_NOT_ALLOWED           5008
%%      A message was received with an AVP that MUST NOT be present.  The
%%      Failed-AVP AVP MUST be included and contain a copy of the
%%      offending AVP.

%% pack_arity/4

%% Give Failed-AVP special treatment since (1) it'll contain any
%% unrecognized mandatory AVP's and (2) the RFC 3588 grammar failed to
%% allow for Failed-AVP in an answer-message.

pack_arity(Name,
           #{strict_mbit := Strict,
             failed_avp := Failed},
           Mod,
           #diameter_avp{is_mandatory = M,
                         name = AvpName}) ->

    %% Not testing just Name /= 'Failed-AVP' means we're changing the
    %% packing of AVPs nested within Failed-AVP, but the point of
    %% ignoring errors within Failed-AVP is to decode as much as
    %% possible, and failing because a mandatory AVP couldn't be
    %% packed into a dedicated field defeats that point.

    if Failed == true;
       Name == 'Failed-AVP';
       Name == 'answer-message', AvpName == 'Failed-AVP';
       not M;
       not Strict ->
            Mod:avp_arity(Name, 'AVP');
       true ->
            0
    end.

%% pack/5

pack(Arity, F, Avp, Mod, {Rec, AM, Failed}) ->
    case too_many(F, Arity, AM) of
        true  -> {Rec, AM, [{5009, Avp} | Failed]};
        false -> {set(Arity, F, value(F, Avp), Mod, Rec), AM, Failed}
    end.

%% 3588:
%%
%%   DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
%%      A message was received that included an AVP that appeared more
%%      often than permitted in the message definition.  The Failed-AVP
%%      AVP MUST be included and contain a copy of the first instance of
%%      the offending AVP that exceeded the maximum number of occurrences
%%

%% too_many/3

too_many(_, {_, '*'}, _) ->
    false;

too_many(FieldName, {_, M}, Map) ->
    too_many(FieldName, M, Map);

too_many(FieldName, M, Map) ->
    #{FieldName := N} = Map,
    M < N.

%% set/5

set(_, _, _, _, undefined = No) ->
    No;

set(1, F, Value, Mod, Rec) ->
    Mod:'#set-'({F, Value}, Rec);

set(_, F, V, Mod, Rec) ->
    Vs = Mod:'#get-'(F, Rec),
    Mod:'#set-'({F, [V|Vs]}, Rec).

%% value/2

value('AVP', Avp) ->
    Avp;

value(_, #diameter_avp{value = V}) ->
    V.

%% ---------------------------------------------------------------------------
%% # grouped_avp/3
%% ---------------------------------------------------------------------------

-spec grouped_avp(decode, avp_name(), binary() | {5014, binary()}, term())
   -> {avp_record(), [avp()]};
                 (encode, avp_name(), avp_record() | avp_values(), term())
   -> iolist()
    | no_return().

%% Length error induced by diameter_codec:collect_avps/1: the AVP
%% length in the header was too short (insufficient for the extracted
%% header) or too long (past the end of the message). An empty payload
%% is sufficient according to the RFC text for 5014.
grouped_avp(decode, _Name, {5014 = RC, _Bin}, _) ->
    ?THROW({grouped, {RC, []}, []});

grouped_avp(decode, Name, Data, Opts) ->
    grouped_decode(Name, diameter_codec:collect_avps(Data), Opts);

grouped_avp(encode, Name, Data, Opts) ->
    encode_avps(Name, Data, Opts).

%% grouped_decode/2
%%
%% Note that Grouped is the only AVP type that doesn't just return a
%% decoded value, also returning the list of component diameter_avp
%% records.

%% Length error in trailing component AVP.
grouped_decode(_Name, {Error, Acc}, _) ->
    {5014, Avp} = Error,
    ?THROW({grouped, Error, [Avp | Acc]});

%% 7.5.  Failed-AVP AVP

%%    In the case where the offending AVP is embedded within a Grouped AVP,
%%    the Failed-AVP MAY contain the grouped AVP, which in turn contains
%%    the single offending AVP.  The same method MAY be employed if the
%%    grouped AVP itself is embedded in yet another grouped AVP and so on.
%%    In this case, the Failed-AVP MAY contain the grouped AVP hierarchy up
%%    to the single offending AVP.  This enables the recipient to detect
%%    the location of the offending AVP when embedded in a group.

%% An error in decoding a component AVP throws the first faulty
%% component, which the catch in d/3 wraps in the Grouped AVP in
%% question. A partially decoded record is only used when ignoring
%% errors in Failed-AVP.
grouped_decode(Name, ComponentAvps, Opts) ->
    {Rec, Avps, Es} = decode_avps(Name, ComponentAvps, Opts),
    [] == Es orelse ?THROW({grouped, [{_,_} = hd(Es) | Rec], Avps}),
    {Rec, Avps}.

%% ---------------------------------------------------------------------------
%% # empty_group/2
%% ---------------------------------------------------------------------------

empty_group(Name, #{module := Mod} = Opts) ->
    list_to_binary([z(F, A, Opts, Mod) || {F,A} <- Mod:avp_arity(Name)]).

z(Name, 1, Opts, Mod) ->
    z(Name, Opts, Mod);
z(_, {0,_}, _, _) ->
    [];
z(Name, {Min, _}, Opts, Mod) ->
    binary:copy(z(Name, Opts, Mod), Min).

z('AVP', _, _) ->
    <<0:64>>;  %% minimal header
z(Name, Opts, Mod) ->
    Bin = diameter_codec:pack_data(Mod:avp_header(Name),
                                   Mod:empty_value(Name, Opts)),
    Sz = iolist_size(Bin),
    <<0:Sz/unit:8>>.

%% ---------------------------------------------------------------------------
%% # empty/2
%% ---------------------------------------------------------------------------

empty(Name, #{module := Mod} = Opts) ->
    Mod:avp(encode, zero, Name, Opts).

%% ------------------------------------------------------------------------------

%% newrec/3

newrec(_, _, #{record_decode := false}) ->
    undefined;

newrec(Mod, Name, _) ->
    newrec(Mod, Name).

%% newrec/2

newrec(Mod, Name) ->
    Mod:'#new-'(Mod:name2rec(Name)).