File size: 50,698 Bytes
f998fcd
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
// This contract is part of Zellic’s smart contract dataset, which is a collection of publicly available contract code gathered as of March 2023.

/*
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                             (@@@@(                                                  @@@@@@@@@
@@@@@@@@@@               %@@@@,         #@@@@*         (@@@@(         *@@@@@@@@@#    ,@@@@%    .@@@@&          @@@@@@@@@
@@@@@@@@@@               %@@@@,         #@@@@*    (@@@@/    /@@@@(    *@@@@@@@@@#    ,@@@@%    .@@@@&          @@@@@@@@@
@@@@@@@@@@          &@@@@,         %@@@@*         (@@@@/    /@@@@(    *@@@@@@@@@#         ,@@@@&               @@@@@@@@@
@@@@@@@@@@          &@@@@,         %@@@@*         (@@@@/    /@@@@(    *@@@@@@@@@#         ,@@@@&               @@@@@@@@@
@@@@@@@@@@               %@@@@,         #@@@@*    (@@@@/    /@@@@(    *@@@@#         ,@@@@%                    @@@@@@@@@
@@@@@@@@@@               %@@@@,         #@@@@*         (@@@@(         *@@@@#         ,@@@@%                    @@@@@@@@@
@@@@@@@@@@                                             (@@@@(                                                  @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@                                                                                                     @@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
*/

// SPDX-License-Identifier: Unlicense

pragma solidity ^0.8.15;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _setOwner(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _setOwner(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}


/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) private pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);

 * }

 * ```

 *

 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.

 */

abstract contract ERC165 is IERC165 {

    /**

     * @dev See {IERC165-supportsInterface}.

     */

    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {

        return interfaceId == type(IERC165).interfaceId;

    }

}



/**

 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension

 * @dev See https://eips.ethereum.org/EIPS/eip-721

 */

interface IERC721Metadata is IERC721 {

    /**

     * @dev Returns the token collection name.

     */

    function name() external view returns (string memory);



    /**

     * @dev Returns the token collection symbol.

     */

    function symbol() external view returns (string memory);



    /**

     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.

     */

    function tokenURI(uint256 tokenId) external view returns (string memory);

}



/**

 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including

 * the Metadata extension, but not including the Enumerable extension, which is available separately as

 * {ERC721Enumerable}.

 */

abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {

    using Address for address;

    using Strings for uint256;



    // Token name

    string private _name;



    // Token symbol

    string private _symbol;



    // Mapping from token ID to owner address

    mapping(uint256 => address) private _owners;



    // Mapping owner address to token count

    mapping(address => uint256) private _balances;



    // Mapping from token ID to approved address

    mapping(uint256 => address) private _tokenApprovals;



    // Mapping from owner to operator approvals

    mapping(address => mapping(address => bool)) private _operatorApprovals;



    /**

     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.

     */

    constructor(string memory name_, string memory symbol_) {

        _name = name_;

        _symbol = symbol_;

    }



    /**

     * @dev See {IERC165-supportsInterface}.

     */

    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {

        return

        interfaceId == type(IERC721).interfaceId ||
        interfaceId == type(IERC721Metadata).interfaceId ||
        super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }


    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),

            "ERC721: approve caller is not owner nor approved for all"

        );



        _approve(to, tokenId);

    }



    /**

     * @dev See {IERC721-getApproved}.

     */

    function getApproved(uint256 tokenId) public view virtual override returns (address) {

        require(_exists(tokenId), "ERC721: approved query for nonexistent token");



        return _tokenApprovals[tokenId];

    }



    /**

     * @dev See {IERC721-setApprovalForAll}.

     */

    function setApprovalForAll(address operator, bool approved) public virtual override {

        require(operator != _msgSender(), "ERC721: approve to caller");



        _operatorApprovals[_msgSender()][operator] = approved;

        emit ApprovalForAll(_msgSender(), operator, approved);

    }



    /**

     * @dev See {IERC721-isApprovedForAll}.

     */

    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {

        return _operatorApprovals[owner][operator];

    }



    /**

     * @dev See {IERC721-transferFrom}.

     */

    function transferFrom(

        address from,

        address to,

        uint256 tokenId

    ) public virtual override {

        //solhint-disable-next-line max-line-length

        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");



        _transfer(from, to, tokenId);

    }



    /**

     * @dev See {IERC721-safeTransferFrom}.

     */

    function safeTransferFrom(

        address from,

        address to,

        uint256 tokenId

    ) public virtual override {

        safeTransferFrom(from, to, tokenId, "");

    }



    /**

     * @dev See {IERC721-safeTransferFrom}.

     */

    function safeTransferFrom(

        address from,

        address to,

        uint256 tokenId,

        bytes memory _data

    ) public virtual override {

        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _safeTransfer(from, to, tokenId, _data);

    }



    /**

     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients

     * are aware of the ERC721 protocol to prevent tokens from being forever locked.

     *

     * `_data` is additional data, it has no specified format and it is sent in call to `to`.

     *

     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.

     * implement alternative mechanisms to perform token transfer, such as signature-based.

     *

     * Requirements:

     *

     * - `from` cannot be the zero address.

     * - `to` cannot be the zero address.

     * - `tokenId` token must exist and be owned by `from`.

     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.

     *

     * Emits a {Transfer} event.

     */

    function _safeTransfer(

        address from,

        address to,

        uint256 tokenId,

        bytes memory _data

    ) internal virtual {

        _transfer(from, to, tokenId);

        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");

    }



    /**

     * @dev Returns whether `tokenId` exists.

     *

     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.

     *

     * Tokens start existing when they are minted (`_mint`),

     * and stop existing when they are burned (`_burn`).

     */

    function _exists(uint256 tokenId) internal view virtual returns (bool) {

        return _owners[tokenId] != address(0);

    }



    /**

     * @dev Returns whether `spender` is allowed to manage `tokenId`.

     *

     * Requirements:

     *

     * - `tokenId` must exist.

     */

    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {

        require(_exists(tokenId), "ERC721: operator query for nonexistent token");

        address owner = ERC721.ownerOf(tokenId);

        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));

    }



    /**

     * @dev Safely mints `tokenId` and transfers it to `to`.

     *

     * Requirements:

     *

     * - `tokenId` must not exist.

     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.

     *

     * Emits a {Transfer} event.

     */

    function _safeMint(address to, uint256 tokenId) internal virtual {

        _safeMint(to, tokenId, "");

    }



    /**

     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is

     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.

     */

    function _safeMint(

        address to,

        uint256 tokenId,

        bytes memory _data

    ) internal virtual {

        _mint(to, tokenId);

        require(

            _checkOnERC721Received(address(0), to, tokenId, _data),

            "ERC721: transfer to non ERC721Receiver implementer"

        );

    }



    /**

     * @dev Mints `tokenId` and transfers it to `to`.

     *

     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible

     *

     * Requirements:

     *

     * - `tokenId` must not exist.

     * - `to` cannot be the zero address.

     *

     * Emits a {Transfer} event.

     */

    function _mint(address to, uint256 tokenId) internal virtual {

        require(to != address(0), "ERC721: mint to the zero address");

        require(!_exists(tokenId), "ERC721: token already minted");



        _beforeTokenTransfer(address(0), to, tokenId);



        _balances[to] += 1;

        _owners[tokenId] = to;



        emit Transfer(address(0), to, tokenId);

    }



    /**

     * @dev Destroys `tokenId`.

     * The approval is cleared when the token is burned.

     *

     * Requirements:

     *

     * - `tokenId` must exist.

     *

     * Emits a {Transfer} event.

     */

    function _burn(uint256 tokenId) internal virtual {

        address owner = ERC721.ownerOf(tokenId);



        _beforeTokenTransfer(owner, address(0), tokenId);



        // Clear approvals

        _approve(address(0), tokenId);



        _balances[owner] -= 1;

        delete _owners[tokenId];



        emit Transfer(owner, address(0), tokenId);

    }



    /**

     * @dev Transfers `tokenId` from `from` to `to`.

     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.

     *

     * Requirements:

     *

     * - `to` cannot be the zero address.

     * - `tokenId` token must be owned by `from`.

     *

     * Emits a {Transfer} event.

     */

    function _transfer(

        address from,

        address to,

        uint256 tokenId

    ) internal virtual {

        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");

        require(to != address(0), "ERC721: transfer to the zero address");



        _beforeTokenTransfer(from, to, tokenId);



        // Clear approvals from the previous owner

        _approve(address(0), tokenId);



        _balances[from] -= 1;

        _balances[to] += 1;

        _owners[tokenId] = to;



        emit Transfer(from, to, tokenId);

    }



    /**

     * @dev Approve `to` to operate on `tokenId`

     *

     * Emits a {Approval} event.

     */

    function _approve(address to, uint256 tokenId) internal virtual {

        _tokenApprovals[tokenId] = to;

        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);

    }



    /**

     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.

     * The call is not executed if the target address is not a contract.

     *

     * @param from address representing the previous owner of the given token ID

     * @param to target address that will receive the tokens

     * @param tokenId uint256 ID of the token to be transferred

     * @param _data bytes optional data to send along with the call

     * @return bool whether the call correctly returned the expected magic value

     */

    function _checkOnERC721Received(

        address from,

        address to,

        uint256 tokenId,

        bytes memory _data

    ) private returns (bool) {

        if (to.isContract()) {

            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {

                return retval == IERC721Receiver(to).onERC721Received.selector;

            } catch (bytes memory reason) {

                if (reason.length == 0) {

                    revert("ERC721: transfer to non ERC721Receiver implementer");

                } else {

                    assembly {

                        revert(add(32, reason), mload(reason))

                    }

                }

            }

        } else {

            return true;

        }

    }



    /**

     * @dev Hook that is called before any token transfer. This includes minting

     * and burning.

     *

     * Calling conditions:

     *

     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be

     * transferred to `to`.

     * - When `from` is zero, `tokenId` will be minted for `to`.

     * - When `to` is zero, ``from``'s `tokenId` will be burned.

     * - `from` and `to` are never both zero.

     *

     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].

     */

    function _beforeTokenTransfer(

        address from,

        address to,

        uint256 tokenId

    ) internal virtual {}

}



/**

 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension

 * @dev See https://eips.ethereum.org/EIPS/eip-721

 */

interface IERC721Enumerable is IERC721 {

    /**

     * @dev Returns the total amount of tokens stored by the contract.

     */

    function totalSupply() external view returns (uint256);



    /**

     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.

     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.

     */

    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);



    /**

     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.

     * Use along with {totalSupply} to enumerate all tokens.

     */

    function tokenByIndex(uint256 index) external view returns (uint256);

}



/**

 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds

 * enumerability of all the token ids in the contract as well as all token ids owned by each

 * account.

 */

abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {

    // Mapping from owner to list of owned token IDs

    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;



    // Mapping from token ID to index of the owner tokens list

    mapping(uint256 => uint256) private _ownedTokensIndex;



    // Array with all token ids, used for enumeration

    uint256[] private _allTokens;



    // Mapping from token id to position in the allTokens array

    mapping(uint256 => uint256) private _allTokensIndex;



    /**

     * @dev See {IERC165-supportsInterface}.

     */

    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {

        return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);

    }



    /**

     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.

     */

    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {

        require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");

        return _ownedTokens[owner][index];

    }



    /**

     * @dev See {IERC721Enumerable-totalSupply}.

     */

    function totalSupply() public view virtual override returns (uint256) {

        return _allTokens.length;

    }



    /**

     * @dev See {IERC721Enumerable-tokenByIndex}.

     */

    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {

        require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");

        return _allTokens[index];

    }



    /**

     * @dev Hook that is called before any token transfer. This includes minting

     * and burning.

     *

     * Calling conditions:

     *

     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be

     * transferred to `to`.

     * - When `from` is zero, `tokenId` will be minted for `to`.

     * - When `to` is zero, ``from``'s `tokenId` will be burned.

     * - `from` cannot be the zero address.

     * - `to` cannot be the zero address.

     *

     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].

     */

    function _beforeTokenTransfer(

        address from,

        address to,

        uint256 tokenId

    ) internal virtual override {

        super._beforeTokenTransfer(from, to, tokenId);



        if (from == address(0)) {

            _addTokenToAllTokensEnumeration(tokenId);

        } else if (from != to) {

            _removeTokenFromOwnerEnumeration(from, tokenId);

        }

        if (to == address(0)) {

            _removeTokenFromAllTokensEnumeration(tokenId);

        } else if (to != from) {

            _addTokenToOwnerEnumeration(to, tokenId);

        }

    }



    /**

     * @dev Private function to add a token to this extension's ownership-tracking data structures.

     * @param to address representing the new owner of the given token ID

     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address

     */

    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {

        uint256 length = ERC721.balanceOf(to);

        _ownedTokens[to][length] = tokenId;

        _ownedTokensIndex[tokenId] = length;

    }



    /**

     * @dev Private function to add a token to this extension's token tracking data structures.

     * @param tokenId uint256 ID of the token to be added to the tokens list

     */

    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {

        _allTokensIndex[tokenId] = _allTokens.length;

        _allTokens.push(tokenId);

    }



    /**

     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that

     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for

     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).

     * This has O(1) time complexity, but alters the order of the _ownedTokens array.

     * @param from address representing the previous owner of the given token ID

     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address

     */

    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {

        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and

        // then delete the last slot (swap and pop).



        uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;

        uint256 tokenIndex = _ownedTokensIndex[tokenId];



        // When the token to delete is the last token, the swap operation is unnecessary

        if (tokenIndex != lastTokenIndex) {

            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];



            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token

            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        }



        // This also deletes the contents at the last position of the array

        delete _ownedTokensIndex[tokenId];

        delete _ownedTokens[from][lastTokenIndex];

    }



    /**

     * @dev Private function to remove a token from this extension's token tracking data structures.

     * This has O(1) time complexity, but alters the order of the _allTokens array.

     * @param tokenId uint256 ID of the token to be removed from the tokens list

     */

    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {

        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and

        // then delete the last slot (swap and pop).



        uint256 lastTokenIndex = _allTokens.length - 1;

        uint256 tokenIndex = _allTokensIndex[tokenId];



        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so

        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding

        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)

        uint256 lastTokenId = _allTokens[lastTokenIndex];



        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token

        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index



        // This also deletes the contents at the last position of the array

        delete _allTokensIndex[tokenId];

        _allTokens.pop();

    }

}





/**

 * @dev String operations.

 */

library Strings {

    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";



    /**

     * @dev Converts a `uint256` to its ASCII `string` decimal representation.

     */

    function toString(uint256 value) internal pure returns (string memory) {

        // Inspired by OraclizeAPI's implementation - MIT licence

        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol



        if (value == 0) {

            return "0";

        }

        uint256 temp = value;

        uint256 digits;

        while (temp != 0) {

            digits++;

            temp /= 10;

        }

        bytes memory buffer = new bytes(digits);

        while (value != 0) {

            digits -= 1;

            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));

            value /= 10;

        }

        return string(buffer);

    }



    /**

     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.

     */

    function toHexString(uint256 value) internal pure returns (string memory) {

        if (value == 0) {

            return "0x00";

        }

        uint256 temp = value;

        uint256 length = 0;

        while (temp != 0) {

            length++;

            temp >>= 8;

        }

        return toHexString(value, length);

    }



    /**

     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.

     */

    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {

        bytes memory buffer = new bytes(2 * length + 2);

        buffer[0] = "0";

        buffer[1] = "x";

        for (uint256 i = 2 * length + 1; i > 1; --i) {

            buffer[i] = _HEX_SYMBOLS[value & 0xf];

            value >>= 4;

        }

        require(value == 0, "Strings: hex length insufficient");

        return string(buffer);

    }

}



    struct Collection {

        address token;

        string name;

        string proof;

        uint128 count;

        uint64 testMints;

        bool open;

    }



contract cc0py is ERC721, ERC721Enumerable, Ownable {



    uint256 constant public maxTestMints = 4;

    uint256 constant public maxNFTs = 6969;

    uint256 constant public maxPerCollection = 1111;

    uint256 public maxPerAddress = 2;



    Collection[] collections;



    mapping(address => uint256) public mintsByAddress;



    string private _contractURI = "data:application/json;base64,ewogICJuYW1lIjogImNjMHB5IiwKICAiZGVzY3JpcHRpb24iOiAibm8gbWludCBjb3N0LCBubyBmZWVzLCBubyBmdXR1cmUgcHJvbWlzZXMuIHNwcmVhZCB0aHJvdWdoIGRpc2NvcmQsIGNsYWltcyBsaW1pdGVkIHRvIHR3byBwZXIgYWRkcmVzcy4gY2MwcHkgbWFuaWZlc3RvIGF2YWlsYWJsZSBhcyBhIHJlYWQgZnVuY3Rpb24gb24gdGhlIGNvbnRyYWN0LiIsCiAgImltYWdlIjogImlwZnM6Ly9RbVNtYUF5NVAzQTN4bmE2TVlkNTNwcEhxeG05QTZZNWRjN0JMdW1oWnRHbzRoIiwKICAic2VsbGVyX2ZlZV9iYXNpc19wb2ludHMiOiAwLAogICJmZWVfcmVjaXBpZW50IjogIjB4MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMCIKfQ==";

    string public manifesto = "https://ipfs.io/ipfs/QmcEGGCYAVyQkQwhYXDG6n7zqFkdE3QEbJqrJvZmV7s7eD";



    constructor() ERC721("cc0py", "cc0py")  {

        _addNewCC0(0x9C8fF314C9Bc7F6e59A9d9225Fb22946427eDC03,"Nouns","https://ipfs.io/ipfs/QmUEbNwuLqd8P8WwSpuB5kqcdjbb3W3tpVh73PXr9HSUZx");

        _addNewCC0(0xd652d2633CDBfD5f27F50cdDb098e708fa8433f3,"XCOPY","https://ipfs.io/ipfs/QmTrAT3DAWNjbvwu84p8pH2UD1jEaAYaBosww3ZL2x8rqz");        

        _addNewCC0(0x23581767a106ae21c074b2276D25e5C3e136a68b,"Moonbirds","https://ipfs.io/ipfs/QmWRv8ZdgVQgVVjn2Bq9ndSN6KXiQTRLD5wFrqgtyEykqt");

        _addNewCC0(0xc143bbfcDBdBEd6d454803804752a064A622C1F3,"Grifters by XCOPY","https://ipfs.io/ipfs/QmbJ5tLsp9UpD7ySvW5wmWbtzfjfNkrnzfyfyjjRsjfTQ4");  

        _addNewCC0(0x42069ABFE407C60cf4ae4112bEDEaD391dBa1cdB,"CryptoDickbutts","https://ipfs.io/ipfs/QmSgBftSWazCMavEU5hFXoXGcjU7WztaXHNmtNdvRiZfjz");              

        _addNewCC0(0x1CB1A5e65610AEFF2551A50f76a87a7d3fB649C6,"CrypToadz by GREMPLIN","https://ipfs.io/ipfs/QmaDhapUHR5zfV4uJryAR5WBwQdsf8DUUZxiQoceSBa41L");

        _addNewCC0(0xbCe3781ae7Ca1a5e050Bd9C4c77369867eBc307e,"goblintown.wtf","https://ipfs.io/ipfs/QmQRiDKZ4XaH866yrCXexDp3AegV1CLMaCox5tWZmuVT8m");

        _addNewCC0(0x79FCDEF22feeD20eDDacbB2587640e45491b757f,"mfers","https://ipfs.io/ipfs/QmWW5XfBm2yfkyHMW4bv5bDB4MY3y9rLdxhTCZMorHXjgc");

    }



    function contractURI() public view returns (string memory) {

        return string(_contractURI);

    }



    function setContractURI(string memory newContractURI) external onlyOwner {

        _contractURI = newContractURI;

    }



    function _addNewCC0(address newContract, string memory name, string memory cc0Proof) internal {

        Collection memory collection;

        collection.token = newContract;

        collection.name = name;

        collection.proof = cc0Proof;

        collections.push(collection);

    }



    function testMint(uint256 collectionID, uint256 id) public onlyOwner {

        collections[collectionID].testMints++;

        require(collections[collectionID].testMints <= maxTestMints);



        _copyNFT(collectionID, id);

    }



    function togglePublic(uint256 collectionID, bool isOpen) public onlyOwner {

        collections[collectionID].open = isOpen;

    }



    /**

     * @notice Collection ID by Name: 0 Nouns, 1 XCOPY, 2 Moonbirds, 3 Grifters, 4 CryptoDickButts, 5 CrypToadz, 6 goblintown.WTF, 7 mfers. See Manifesto for valid ranges

     */

    function copyNFT(uint256 collectionID, uint256 id) public {

        require(collections[collectionID].open, "Not open");

        require(msg.sender == tx.origin, "Only humans");

        require(mintsByAddress[msg.sender] < maxPerAddress, "Don't be greedy!");



        mintsByAddress[msg.sender] = mintsByAddress[msg.sender] + 1;



        _copyNFT(collectionID, id);

    }



    function updateMax(uint256 _maxPerAddress) external onlyOwner {

        maxPerAddress = _maxPerAddress;

    }



    function checkClaimed(uint256 collectionID, uint256 id) public view returns (bool) {

        uint256 tokenId = toTokenId(collectionID, id);

        return _exists(tokenId);

    }



    function _copyNFT(uint256 collectionID, uint256 id) internal {

        require(totalSupply() < maxNFTs, "Max supply reached");

        require(collections[collectionID].count < maxPerCollection, "Collection max supply exceeded");



        IERC721(collections[collectionID].token).ownerOf(id);



        if(collectionID == 3) {

            require(id <= 665);

        }



        uint256 tokenId = toTokenId(collectionID, id);

        collections[collectionID].count++;



        _mint(msg.sender, tokenId);

    }



    function tokenURI(uint256 id) public view override returns (string memory URI) {

        require(_exists(id), "ERC721Metadata: URI query for nonexistent token");



        (uint256 collectionId, uint256 tokenId) = toCollectionId(id);



        string memory uri = IERC721Metadata(collections[collectionId].token).tokenURI(tokenId);



        if (collectionId == 3) {

            return string.concat("ipfs://", uri); //opensea put a bandaid on grifters to allow it to work. must be nice

        }



        return uri;

    }



    function collectionData(uint256 collectionIndex) public view returns (Collection memory) {

        return collections[collectionIndex];

    }



    function toCollectionId(uint256 id) public pure returns (uint256, uint256){

        return (

        id / 1e12,

        id % 1e12

        );

    }



    function toTokenId(uint256 collectionID, uint256 tokenId) public pure returns (uint256) {

        require(tokenId < 1e12, "Invalid tokenId");

        return (collectionID * 1e12) + tokenId;

    }



    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal override(ERC721, ERC721Enumerable) {

        super._beforeTokenTransfer(from, to, tokenId);

    }



    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC721, ERC721Enumerable) returns (bool) {

        return super.supportsInterface(interfaceId);

    }

}