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
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
// Copyright 2017-2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.

//! `V1` Primitives.

use bitvec::vec::BitVec;
use parity_scale_codec::{Decode, Encode};
use scale_info::TypeInfo;
use sp_std::{
	marker::PhantomData,
	prelude::*,
	slice::{Iter, IterMut},
	vec::IntoIter,
};

use application_crypto::KeyTypeId;
use inherents::InherentIdentifier;
use primitives::RuntimeDebug;
use runtime_primitives::traits::{AppVerify, Header as HeaderT};
use sp_arithmetic::traits::{BaseArithmetic, Saturating};

pub use runtime_primitives::traits::{BlakeTwo256, Hash as HashT};

// Export some core primitives.
pub use polkadot_core_primitives::v2::{
	AccountId, AccountIndex, AccountPublic, Balance, Block, BlockId, BlockNumber, CandidateHash,
	ChainId, DownwardMessage, Hash, Header, InboundDownwardMessage, InboundHrmpMessage, Moment,
	Nonce, OutboundHrmpMessage, Remark, Signature, UncheckedExtrinsic,
};

// Export some polkadot-parachain primitives
pub use polkadot_parachain::primitives::{
	HeadData, HrmpChannelId, Id, UpwardMessage, ValidationCode, ValidationCodeHash,
	LOWEST_PUBLIC_ID, LOWEST_USER_ID,
};

#[cfg(feature = "std")]
use serde::{Deserialize, Serialize};

pub use sp_authority_discovery::AuthorityId as AuthorityDiscoveryId;
pub use sp_consensus_slots::Slot;
pub use sp_staking::SessionIndex;

/// Signed data.
mod signed;
pub use signed::{EncodeAs, Signed, UncheckedSigned};

mod metrics;
pub use metrics::{
	metric_definitions, RuntimeMetricLabel, RuntimeMetricLabelValue, RuntimeMetricLabelValues,
	RuntimeMetricLabels, RuntimeMetricOp, RuntimeMetricUpdate,
};

/// The key type ID for a collator key.
pub const COLLATOR_KEY_TYPE_ID: KeyTypeId = KeyTypeId(*b"coll");

mod collator_app {
	use application_crypto::{app_crypto, sr25519};
	app_crypto!(sr25519, super::COLLATOR_KEY_TYPE_ID);
}

/// Identity that collators use.
pub type CollatorId = collator_app::Public;

/// A Parachain collator keypair.
#[cfg(feature = "std")]
pub type CollatorPair = collator_app::Pair;

/// Signature on candidate's block data by a collator.
pub type CollatorSignature = collator_app::Signature;

/// The key type ID for a parachain validator key.
pub const PARACHAIN_KEY_TYPE_ID: KeyTypeId = KeyTypeId(*b"para");

mod validator_app {
	use application_crypto::{app_crypto, sr25519};
	app_crypto!(sr25519, super::PARACHAIN_KEY_TYPE_ID);
}

/// Identity that parachain validators use when signing validation messages.
///
/// For now we assert that parachain validator set is exactly equivalent to the authority set, and
/// so we define it to be the same type as `SessionKey`. In the future it may have different crypto.
pub type ValidatorId = validator_app::Public;

/// Trait required for type specific indices e.g. `ValidatorIndex` and `GroupIndex`
pub trait TypeIndex {
	/// Returns the index associated to this value.
	fn type_index(&self) -> usize;
}

/// Index of the validator is used as a lightweight replacement of the `ValidatorId` when appropriate.
#[derive(Eq, Ord, PartialEq, PartialOrd, Copy, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Hash))]
pub struct ValidatorIndex(pub u32);

// We should really get https://github.com/paritytech/polkadot/issues/2403 going ..
impl From<u32> for ValidatorIndex {
	fn from(n: u32) -> Self {
		ValidatorIndex(n)
	}
}

impl TypeIndex for ValidatorIndex {
	fn type_index(&self) -> usize {
		self.0 as usize
	}
}

application_crypto::with_pair! {
	/// A Parachain validator keypair.
	pub type ValidatorPair = validator_app::Pair;
}

/// Signature with which parachain validators sign blocks.
///
/// For now we assert that parachain validator set is exactly equivalent to the authority set, and
/// so we define it to be the same type as `SessionKey`. In the future it may have different crypto.
pub type ValidatorSignature = validator_app::Signature;

/// A declarations of storage keys where an external observer can find some interesting data.
pub mod well_known_keys {
	use super::{HrmpChannelId, Id};
	use hex_literal::hex;
	use parity_scale_codec::Encode as _;
	use sp_io::hashing::twox_64;
	use sp_std::prelude::*;

	// A note on generating these magic values below:
	//
	// The `StorageValue`, such as `ACTIVE_CONFIG` was obtained by calling:
	//
	//     <Self as Store>::ActiveConfig::hashed_key()
	//
	// The `StorageMap` values require `prefix`, and for example for `hrmp_egress_channel_index`,
	// it could be obtained like:
	//
	//     <Hrmp as Store>::HrmpEgressChannelsIndex::prefix_hash();
	//

	/// The current epoch index.
	///
	/// The storage item should be access as a `u64` encoded value.
	pub const EPOCH_INDEX: &[u8] =
		&hex!["1cb6f36e027abb2091cfb5110ab5087f38316cbf8fa0da822a20ac1c55bf1be3"];

	/// The current relay chain block randomness
	///
	/// The storage item should be accessed as a `schnorrkel::Randomness` encoded value.
	pub const CURRENT_BLOCK_RANDOMNESS: &[u8] =
		&hex!["1cb6f36e027abb2091cfb5110ab5087fd077dfdb8adb10f78f10a5df8742c545"];

	/// The randomness for one epoch ago
	///
	/// The storage item should be accessed as a `schnorrkel::Randomness` encoded value.
	pub const ONE_EPOCH_AGO_RANDOMNESS: &[u8] =
		&hex!["1cb6f36e027abb2091cfb5110ab5087f7ce678799d3eff024253b90e84927cc6"];

	/// The randomness for two epochs ago
	///
	/// The storage item should be accessed as a `schnorrkel::Randomness` encoded value.
	pub const TWO_EPOCHS_AGO_RANDOMNESS: &[u8] =
		&hex!["1cb6f36e027abb2091cfb5110ab5087f7a414cb008e0e61e46722aa60abdd672"];

	/// The current slot number.
	///
	/// The storage entry should be accessed as a `Slot` encoded value.
	pub const CURRENT_SLOT: &[u8] =
		&hex!["1cb6f36e027abb2091cfb5110ab5087f06155b3cd9a8c9e5e9a23fd5dc13a5ed"];

	/// The currently active host configuration.
	///
	/// The storage entry should be accessed as an `AbridgedHostConfiguration` encoded value.
	pub const ACTIVE_CONFIG: &[u8] =
		&hex!["06de3d8a54d27e44a9d5ce189618f22db4b49d95320d9021994c850f25b8e385"];

	/// The upward message dispatch queue for the given para id.
	///
	/// The storage entry stores a tuple of two values:
	///
	/// - `count: u32`, the number of messages currently in the queue for given para,
	/// - `total_size: u32`, the total size of all messages in the queue.
	pub fn relay_dispatch_queue_size(para_id: Id) -> Vec<u8> {
		let prefix = hex!["f5207f03cfdce586301014700e2c2593fad157e461d71fd4c1f936839a5f1f3e"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}

	/// The HRMP channel for the given identifier.
	///
	/// The storage entry should be accessed as an `AbridgedHrmpChannel` encoded value.
	pub fn hrmp_channels(channel: HrmpChannelId) -> Vec<u8> {
		let prefix = hex!["6a0da05ca59913bc38a8630590f2627cb6604cff828a6e3f579ca6c59ace013d"];

		channel.using_encoded(|channel: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(channel).iter())
				.chain(channel.iter())
				.cloned()
				.collect()
		})
	}

	/// The list of inbound channels for the given para.
	///
	/// The storage entry stores a `Vec<ParaId>`
	pub fn hrmp_ingress_channel_index(para_id: Id) -> Vec<u8> {
		let prefix = hex!["6a0da05ca59913bc38a8630590f2627c1d3719f5b0b12c7105c073c507445948"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}

	/// The list of outbound channels for the given para.
	///
	/// The storage entry stores a `Vec<ParaId>`
	pub fn hrmp_egress_channel_index(para_id: Id) -> Vec<u8> {
		let prefix = hex!["6a0da05ca59913bc38a8630590f2627cf12b746dcf32e843354583c9702cc020"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}

	/// The MQC head for the downward message queue of the given para. See more in the `Dmp` module.
	///
	/// The storage entry stores a `Hash`. This is polkadot hash which is at the moment
	/// `blake2b-256`.
	pub fn dmq_mqc_head(para_id: Id) -> Vec<u8> {
		let prefix = hex!["63f78c98723ddc9073523ef3beefda0c4d7fefc408aac59dbfe80a72ac8e3ce5"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}

	/// The signal that indicates whether the parachain should go-ahead with the proposed validation
	/// code upgrade.
	///
	/// The storage entry stores a value of `UpgradeGoAhead` type.
	pub fn upgrade_go_ahead_signal(para_id: Id) -> Vec<u8> {
		let prefix = hex!["cd710b30bd2eab0352ddcc26417aa1949e94c040f5e73d9b7addd6cb603d15d3"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}

	/// The signal that indicates whether the parachain is disallowed to signal an upgrade at this
	/// relay-parent.
	///
	/// The storage entry stores a value of `UpgradeRestriction` type.
	pub fn upgrade_restriction_signal(para_id: Id) -> Vec<u8> {
		let prefix = hex!["cd710b30bd2eab0352ddcc26417aa194f27bbb460270642b5bcaf032ea04d56a"];

		para_id.using_encoded(|para_id: &[u8]| {
			prefix
				.as_ref()
				.iter()
				.chain(twox_64(para_id).iter())
				.chain(para_id.iter())
				.cloned()
				.collect()
		})
	}
}

/// Unique identifier for the Parachains Inherent
pub const PARACHAINS_INHERENT_IDENTIFIER: InherentIdentifier = *b"parachn0";

/// The key type ID for parachain assignment key.
pub const ASSIGNMENT_KEY_TYPE_ID: KeyTypeId = KeyTypeId(*b"asgn");

/// Maximum compressed code size we support right now.
/// At the moment we have runtime upgrade on chain, which restricts scalability severely. If we want
/// to have bigger values, we should fix that first.
///
/// Used for:
/// * initial genesis for the Parachains configuration
/// * checking updates to this stored runtime configuration do not exceed this limit
/// * when detecting a code decompression bomb in the client
// NOTE: This value is used in the runtime so be careful when changing it.
pub const MAX_CODE_SIZE: u32 = 3 * 1024 * 1024;

/// Maximum head data size we support right now.
///
/// Used for:
/// * initial genesis for the Parachains configuration
/// * checking updates to this stored runtime configuration do not exceed this limit
// NOTE: This value is used in the runtime so be careful when changing it.
pub const MAX_HEAD_DATA_SIZE: u32 = 1 * 1024 * 1024;

/// Maximum PoV size we support right now.
///
/// Used for:
/// * initial genesis for the Parachains configuration
/// * checking updates to this stored runtime configuration do not exceed this limit
/// * when detecting a PoV decompression bomb in the client
// NOTE: This value is used in the runtime so be careful when changing it.
pub const MAX_POV_SIZE: u32 = 5 * 1024 * 1024;

// The public key of a keypair used by a validator for determining assignments
/// to approve included parachain candidates.
mod assignment_app {
	use application_crypto::{app_crypto, sr25519};
	app_crypto!(sr25519, super::ASSIGNMENT_KEY_TYPE_ID);
}

/// The public key of a keypair used by a validator for determining assignments
/// to approve included parachain candidates.
pub type AssignmentId = assignment_app::Public;

application_crypto::with_pair! {
	/// The full keypair used by a validator for determining assignments to approve included
	/// parachain candidates.
	pub type AssignmentPair = assignment_app::Pair;
}

/// The index of the candidate in the list of candidates fully included as-of the block.
pub type CandidateIndex = u32;

/// Get a collator signature payload on a relay-parent, block-data combo.
pub fn collator_signature_payload<H: AsRef<[u8]>>(
	relay_parent: &H,
	para_id: &Id,
	persisted_validation_data_hash: &Hash,
	pov_hash: &Hash,
	validation_code_hash: &ValidationCodeHash,
) -> [u8; 132] {
	// 32-byte hash length is protected in a test below.
	let mut payload = [0u8; 132];

	payload[0..32].copy_from_slice(relay_parent.as_ref());
	u32::from(*para_id).using_encoded(|s| payload[32..32 + s.len()].copy_from_slice(s));
	payload[36..68].copy_from_slice(persisted_validation_data_hash.as_ref());
	payload[68..100].copy_from_slice(pov_hash.as_ref());
	payload[100..132].copy_from_slice(validation_code_hash.as_ref());

	payload
}

fn check_collator_signature<H: AsRef<[u8]>>(
	relay_parent: &H,
	para_id: &Id,
	persisted_validation_data_hash: &Hash,
	pov_hash: &Hash,
	validation_code_hash: &ValidationCodeHash,
	collator: &CollatorId,
	signature: &CollatorSignature,
) -> Result<(), ()> {
	let payload = collator_signature_payload(
		relay_parent,
		para_id,
		persisted_validation_data_hash,
		pov_hash,
		validation_code_hash,
	);

	if signature.verify(&payload[..], collator) {
		Ok(())
	} else {
		Err(())
	}
}

/// A unique descriptor of the candidate receipt.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Hash))]
pub struct CandidateDescriptor<H = Hash> {
	/// The ID of the para this is a candidate for.
	pub para_id: Id,
	/// The hash of the relay-chain block this is executed in the context of.
	pub relay_parent: H,
	/// The collator's sr25519 public key.
	pub collator: CollatorId,
	/// The blake2-256 hash of the persisted validation data. This is extra data derived from
	/// relay-chain state which may vary based on bitfields included before the candidate.
	/// Thus it cannot be derived entirely from the relay-parent.
	pub persisted_validation_data_hash: Hash,
	/// The blake2-256 hash of the PoV.
	pub pov_hash: Hash,
	/// The root of a block's erasure encoding Merkle tree.
	pub erasure_root: Hash,
	/// Signature on blake2-256 of components of this receipt:
	/// The parachain index, the relay parent, the validation data hash, and the `pov_hash`.
	pub signature: CollatorSignature,
	/// Hash of the para header that is being generated by this candidate.
	pub para_head: Hash,
	/// The blake2-256 hash of the validation code bytes.
	pub validation_code_hash: ValidationCodeHash,
}

impl<H: AsRef<[u8]>> CandidateDescriptor<H> {
	/// Check the signature of the collator within this descriptor.
	pub fn check_collator_signature(&self) -> Result<(), ()> {
		check_collator_signature(
			&self.relay_parent,
			&self.para_id,
			&self.persisted_validation_data_hash,
			&self.pov_hash,
			&self.validation_code_hash,
			&self.collator,
			&self.signature,
		)
	}
}

/// A candidate-receipt.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
pub struct CandidateReceipt<H = Hash> {
	/// The descriptor of the candidate.
	pub descriptor: CandidateDescriptor<H>,
	/// The hash of the encoded commitments made as a result of candidate execution.
	pub commitments_hash: Hash,
}

impl<H> CandidateReceipt<H> {
	/// Get a reference to the candidate descriptor.
	pub fn descriptor(&self) -> &CandidateDescriptor<H> {
		&self.descriptor
	}

	/// Computes the blake2-256 hash of the receipt.
	pub fn hash(&self) -> CandidateHash
	where
		H: Encode,
	{
		CandidateHash(BlakeTwo256::hash_of(self))
	}
}

/// All data pertaining to the execution of a para candidate.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
pub struct FullCandidateReceipt<H = Hash, N = BlockNumber> {
	/// The inner candidate receipt.
	pub inner: CandidateReceipt<H>,
	/// The validation data derived from the relay-chain state at that
	/// point. The hash of the persisted validation data should
	/// match the `persisted_validation_data_hash` in the descriptor
	/// of the receipt.
	pub validation_data: PersistedValidationData<H, N>,
}

/// A candidate-receipt with commitments directly included.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Hash))]
pub struct CommittedCandidateReceipt<H = Hash> {
	/// The descriptor of the candidate.
	pub descriptor: CandidateDescriptor<H>,
	/// The commitments of the candidate receipt.
	pub commitments: CandidateCommitments,
}

impl<H> CommittedCandidateReceipt<H> {
	/// Get a reference to the candidate descriptor.
	pub fn descriptor(&self) -> &CandidateDescriptor<H> {
		&self.descriptor
	}
}

impl<H: Clone> CommittedCandidateReceipt<H> {
	/// Transforms this into a plain `CandidateReceipt`.
	pub fn to_plain(&self) -> CandidateReceipt<H> {
		CandidateReceipt {
			descriptor: self.descriptor.clone(),
			commitments_hash: self.commitments.hash(),
		}
	}

	/// Computes the hash of the committed candidate receipt.
	///
	/// This computes the canonical hash, not the hash of the directly encoded data.
	/// Thus this is a shortcut for `candidate.to_plain().hash()`.
	pub fn hash(&self) -> CandidateHash
	where
		H: Encode,
	{
		self.to_plain().hash()
	}

	/// Does this committed candidate receipt corresponds to the given [`CandidateReceipt`]?
	pub fn corresponds_to(&self, receipt: &CandidateReceipt<H>) -> bool
	where
		H: PartialEq,
	{
		receipt.descriptor == self.descriptor && receipt.commitments_hash == self.commitments.hash()
	}
}

impl PartialOrd for CommittedCandidateReceipt {
	fn partial_cmp(&self, other: &Self) -> Option<sp_std::cmp::Ordering> {
		Some(self.cmp(other))
	}
}

impl Ord for CommittedCandidateReceipt {
	fn cmp(&self, other: &Self) -> sp_std::cmp::Ordering {
		// TODO: compare signatures or something more sane
		// https://github.com/paritytech/polkadot/issues/222
		self.descriptor()
			.para_id
			.cmp(&other.descriptor().para_id)
			.then_with(|| self.commitments.head_data.cmp(&other.commitments.head_data))
	}
}

/// The validation data provides information about how to create the inputs for validation of a candidate.
/// This information is derived from the chain state and will vary from para to para, although some
/// fields may be the same for every para.
///
/// Since this data is used to form inputs to the validation function, it needs to be persisted by the
/// availability system to avoid dependence on availability of the relay-chain state.
///
/// Furthermore, the validation data acts as a way to authorize the additional data the collator needs
/// to pass to the validation function. For example, the validation function can check whether the incoming
/// messages (e.g. downward messages) were actually sent by using the data provided in the validation data
/// using so called MQC heads.
///
/// Since the commitments of the validation function are checked by the relay-chain, secondary checkers
/// can rely on the invariant that the relay-chain only includes para-blocks for which these checks have
/// already been done. As such, there is no need for the validation data used to inform validators and
/// collators about the checks the relay-chain will perform to be persisted by the availability system.
///
/// The `PersistedValidationData` should be relatively lightweight primarily because it is constructed
/// during inclusion for each candidate and therefore lies on the critical path of inclusion.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Default))]
pub struct PersistedValidationData<H = Hash, N = BlockNumber> {
	/// The parent head-data.
	pub parent_head: HeadData,
	/// The relay-chain block number this is in the context of.
	pub relay_parent_number: N,
	/// The relay-chain block storage root this is in the context of.
	pub relay_parent_storage_root: H,
	/// The maximum legal size of a POV block, in bytes.
	pub max_pov_size: u32,
}

impl<H: Encode, N: Encode> PersistedValidationData<H, N> {
	/// Compute the blake2-256 hash of the persisted validation data.
	pub fn hash(&self) -> Hash {
		BlakeTwo256::hash_of(self)
	}
}

/// Commitments made in a `CandidateReceipt`. Many of these are outputs of validation.
#[derive(PartialEq, Eq, Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Hash, Default))]
pub struct CandidateCommitments<N = BlockNumber> {
	/// Messages destined to be interpreted by the Relay chain itself.
	pub upward_messages: Vec<UpwardMessage>,
	/// Horizontal messages sent by the parachain.
	pub horizontal_messages: Vec<OutboundHrmpMessage<Id>>,
	/// New validation code.
	pub new_validation_code: Option<ValidationCode>,
	/// The head-data produced as a result of execution.
	pub head_data: HeadData,
	/// The number of messages processed from the DMQ.
	pub processed_downward_messages: u32,
	/// The mark which specifies the block number up to which all inbound HRMP messages are processed.
	pub hrmp_watermark: N,
}

impl CandidateCommitments {
	/// Compute the blake2-256 hash of the commitments.
	pub fn hash(&self) -> Hash {
		BlakeTwo256::hash_of(self)
	}
}

/// A bitfield concerning availability of backed candidates.
///
/// Every bit refers to an availability core index.
#[derive(PartialEq, Eq, Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
pub struct AvailabilityBitfield(pub BitVec<u8, bitvec::order::Lsb0>);

impl From<BitVec<u8, bitvec::order::Lsb0>> for AvailabilityBitfield {
	fn from(inner: BitVec<u8, bitvec::order::Lsb0>) -> Self {
		AvailabilityBitfield(inner)
	}
}

/// A signed compact statement, suitable to be sent to the chain.
pub type SignedStatement = Signed<CompactStatement>;
/// A signed compact statement, with signature not yet checked.
pub type UncheckedSignedStatement = UncheckedSigned<CompactStatement>;

/// A bitfield signed by a particular validator about the availability of pending candidates.
pub type SignedAvailabilityBitfield = Signed<AvailabilityBitfield>;
/// A signed bitfield with signature not yet checked.
pub type UncheckedSignedAvailabilityBitfield = UncheckedSigned<AvailabilityBitfield>;

/// A set of signed availability bitfields. Should be sorted by validator index, ascending.
pub type SignedAvailabilityBitfields = Vec<SignedAvailabilityBitfield>;
/// A set of unchecked signed availability bitfields. Should be sorted by validator index, ascending.
pub type UncheckedSignedAvailabilityBitfields = Vec<UncheckedSignedAvailabilityBitfield>;

/// A backed (or backable, depending on context) candidate.
#[derive(Encode, Decode, Clone, PartialEq, Eq, RuntimeDebug, TypeInfo)]
pub struct BackedCandidate<H = Hash> {
	/// The candidate referred to.
	pub candidate: CommittedCandidateReceipt<H>,
	/// The validity votes themselves, expressed as signatures.
	pub validity_votes: Vec<ValidityAttestation>,
	/// The indices of the validators within the group, expressed as a bitfield.
	pub validator_indices: BitVec<u8, bitvec::order::Lsb0>,
}

impl<H> BackedCandidate<H> {
	/// Get a reference to the descriptor of the para.
	pub fn descriptor(&self) -> &CandidateDescriptor<H> {
		&self.candidate.descriptor
	}

	/// Compute this candidate's hash.
	pub fn hash(&self) -> CandidateHash
	where
		H: Clone + Encode,
	{
		self.candidate.hash()
	}

	/// Get this candidate's receipt.
	pub fn receipt(&self) -> CandidateReceipt<H>
	where
		H: Clone,
	{
		self.candidate.to_plain()
	}
}

/// Verify the backing of the given candidate.
///
/// Provide a lookup from the index of a validator within the group assigned to this para,
/// as opposed to the index of the validator within the overall validator set, as well as
/// the number of validators in the group.
///
/// Also provide the signing context.
///
/// Returns either an error, indicating that one of the signatures was invalid or that the index
/// was out-of-bounds, or the number of signatures checked.
pub fn check_candidate_backing<H: AsRef<[u8]> + Clone + Encode>(
	backed: &BackedCandidate<H>,
	signing_context: &SigningContext<H>,
	group_len: usize,
	validator_lookup: impl Fn(usize) -> Option<ValidatorId>,
) -> Result<usize, ()> {
	if backed.validator_indices.len() != group_len {
		return Err(())
	}

	if backed.validity_votes.len() > group_len {
		return Err(())
	}

	// this is known, even in runtime, to be blake2-256.
	let hash = backed.candidate.hash();

	let mut signed = 0;
	for ((val_in_group_idx, _), attestation) in backed
		.validator_indices
		.iter()
		.enumerate()
		.filter(|(_, signed)| **signed)
		.zip(backed.validity_votes.iter())
	{
		let validator_id = validator_lookup(val_in_group_idx).ok_or(())?;
		let payload = attestation.signed_payload(hash, signing_context);
		let sig = attestation.signature();

		if sig.verify(&payload[..], &validator_id) {
			signed += 1;
		} else {
			return Err(())
		}
	}

	if signed != backed.validity_votes.len() {
		return Err(())
	}

	Ok(signed)
}

/// The unique (during session) index of a core.
#[derive(
	Encode, Decode, Default, PartialOrd, Ord, Eq, PartialEq, Clone, Copy, TypeInfo, RuntimeDebug,
)]
#[cfg_attr(feature = "std", derive(Hash))]
pub struct CoreIndex(pub u32);

impl From<u32> for CoreIndex {
	fn from(i: u32) -> CoreIndex {
		CoreIndex(i)
	}
}

impl TypeIndex for CoreIndex {
	fn type_index(&self) -> usize {
		self.0 as usize
	}
}

/// The unique (during session) index of a validator group.
#[derive(Encode, Decode, Default, Clone, Copy, Debug, PartialEq, Eq, TypeInfo)]
#[cfg_attr(feature = "std", derive(Hash))]
pub struct GroupIndex(pub u32);

impl From<u32> for GroupIndex {
	fn from(i: u32) -> GroupIndex {
		GroupIndex(i)
	}
}

impl TypeIndex for GroupIndex {
	fn type_index(&self) -> usize {
		self.0 as usize
	}
}

/// A claim on authoring the next block for a given parathread.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct ParathreadClaim(pub Id, pub CollatorId);

/// An entry tracking a claim to ensure it does not pass the maximum number of retries.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct ParathreadEntry {
	/// The claim.
	pub claim: ParathreadClaim,
	/// Number of retries.
	pub retries: u32,
}

/// What is occupying a specific availability core.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub enum CoreOccupied {
	/// A parathread.
	Parathread(ParathreadEntry),
	/// A parachain.
	Parachain,
}

/// A helper data-type for tracking validator-group rotations.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct GroupRotationInfo<N = BlockNumber> {
	/// The block number where the session started.
	pub session_start_block: N,
	/// How often groups rotate. 0 means never.
	pub group_rotation_frequency: N,
	/// The current block number.
	pub now: N,
}

impl GroupRotationInfo {
	/// Returns the index of the group needed to validate the core at the given index, assuming
	/// the given number of cores.
	///
	/// `core_index` should be less than `cores`, which is capped at `u32::max()`.
	pub fn group_for_core(&self, core_index: CoreIndex, cores: usize) -> GroupIndex {
		if self.group_rotation_frequency == 0 {
			return GroupIndex(core_index.0)
		}
		if cores == 0 {
			return GroupIndex(0)
		}

		let cores = sp_std::cmp::min(cores, u32::MAX as usize);
		let blocks_since_start = self.now.saturating_sub(self.session_start_block);
		let rotations = blocks_since_start / self.group_rotation_frequency;

		// g = c + r mod cores

		let idx = (core_index.0 as usize + rotations as usize) % cores;
		GroupIndex(idx as u32)
	}

	/// Returns the index of the group assigned to the given core. This does no checking or
	/// whether the group index is in-bounds.
	///
	/// `core_index` should be less than `cores`, which is capped at `u32::max()`.
	pub fn core_for_group(&self, group_index: GroupIndex, cores: usize) -> CoreIndex {
		if self.group_rotation_frequency == 0 {
			return CoreIndex(group_index.0)
		}
		if cores == 0 {
			return CoreIndex(0)
		}

		let cores = sp_std::cmp::min(cores, u32::MAX as usize);
		let blocks_since_start = self.now.saturating_sub(self.session_start_block);
		let rotations = blocks_since_start / self.group_rotation_frequency;
		let rotations = rotations % cores as u32;

		// g = c + r mod cores
		// c = g - r mod cores
		// x = x + cores mod cores
		// c = (g + cores) - r mod cores

		let idx = (group_index.0 as usize + cores - rotations as usize) % cores;
		CoreIndex(idx as u32)
	}

	/// Create a new `GroupRotationInfo` with one further rotation applied.
	pub fn bump_rotation(&self) -> Self {
		GroupRotationInfo {
			session_start_block: self.session_start_block,
			group_rotation_frequency: self.group_rotation_frequency,
			now: self.next_rotation_at(),
		}
	}
}

impl<N: Saturating + BaseArithmetic + Copy> GroupRotationInfo<N> {
	/// Returns the block number of the next rotation after the current block. If the current block
	/// is 10 and the rotation frequency is 5, this should return 15.
	pub fn next_rotation_at(&self) -> N {
		let cycle_once = self.now + self.group_rotation_frequency;
		cycle_once -
			(cycle_once.saturating_sub(self.session_start_block) % self.group_rotation_frequency)
	}

	/// Returns the block number of the last rotation before or including the current block. If the
	/// current block is 10 and the rotation frequency is 5, this should return 10.
	pub fn last_rotation_at(&self) -> N {
		self.now -
			(self.now.saturating_sub(self.session_start_block) % self.group_rotation_frequency)
	}
}

/// Information about a core which is currently occupied.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct OccupiedCore<H = Hash, N = BlockNumber> {
	// NOTE: this has no ParaId as it can be deduced from the candidate descriptor.
	/// If this core is freed by availability, this is the assignment that is next up on this
	/// core, if any. None if there is nothing queued for this core.
	pub next_up_on_available: Option<ScheduledCore>,
	/// The relay-chain block number this began occupying the core at.
	pub occupied_since: N,
	/// The relay-chain block this will time-out at, if any.
	pub time_out_at: N,
	/// If this core is freed by being timed-out, this is the assignment that is next up on this
	/// core. None if there is nothing queued for this core or there is no possibility of timing
	/// out.
	pub next_up_on_time_out: Option<ScheduledCore>,
	/// A bitfield with 1 bit for each validator in the set. `1` bits mean that the corresponding
	/// validators has attested to availability on-chain. A 2/3+ majority of `1` bits means that
	/// this will be available.
	pub availability: BitVec<u8, bitvec::order::Lsb0>,
	/// The group assigned to distribute availability pieces of this candidate.
	pub group_responsible: GroupIndex,
	/// The hash of the candidate occupying the core.
	pub candidate_hash: CandidateHash,
	/// The descriptor of the candidate occupying the core.
	pub candidate_descriptor: CandidateDescriptor<H>,
}

impl<H, N> OccupiedCore<H, N> {
	/// Get the Para currently occupying this core.
	pub fn para_id(&self) -> Id {
		self.candidate_descriptor.para_id
	}
}

/// Information about a core which is currently occupied.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct ScheduledCore {
	/// The ID of a para scheduled.
	pub para_id: Id,
	/// The collator required to author the block, if any.
	pub collator: Option<CollatorId>,
}

/// The state of a particular availability core.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub enum CoreState<H = Hash, N = BlockNumber> {
	/// The core is currently occupied.
	#[codec(index = 0)]
	Occupied(OccupiedCore<H, N>),
	/// The core is currently free, with a para scheduled and given the opportunity
	/// to occupy.
	///
	/// If a particular Collator is required to author this block, that is also present in this
	/// variant.
	#[codec(index = 1)]
	Scheduled(ScheduledCore),
	/// The core is currently free and there is nothing scheduled. This can be the case for parathread
	/// cores when there are no parathread blocks queued. Parachain cores will never be left idle.
	#[codec(index = 2)]
	Free,
}

impl<N> CoreState<N> {
	/// If this core state has a `para_id`, return it.
	pub fn para_id(&self) -> Option<Id> {
		match self {
			Self::Occupied(ref core) => Some(core.para_id()),
			Self::Scheduled(ScheduledCore { para_id, .. }) => Some(*para_id),
			Self::Free => None,
		}
	}

	/// Is this core state `Self::Occupied`?
	pub fn is_occupied(&self) -> bool {
		matches!(self, Self::Occupied(_))
	}
}

/// An assumption being made about the state of an occupied core.
#[derive(Clone, Copy, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq, Eq, Hash))]
pub enum OccupiedCoreAssumption {
	/// The candidate occupying the core was made available and included to free the core.
	#[codec(index = 0)]
	Included,
	/// The candidate occupying the core timed out and freed the core without advancing the para.
	#[codec(index = 1)]
	TimedOut,
	/// The core was not occupied to begin with.
	#[codec(index = 2)]
	Free,
}

/// An even concerning a candidate.
#[derive(Clone, Encode, Decode, TypeInfo, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub enum CandidateEvent<H = Hash> {
	/// This candidate receipt was backed in the most recent block.
	/// This includes the core index the candidate is now occupying.
	#[codec(index = 0)]
	CandidateBacked(CandidateReceipt<H>, HeadData, CoreIndex, GroupIndex),
	/// This candidate receipt was included and became a parablock at the most recent block.
	/// This includes the core index the candidate was occupying as well as the group responsible
	/// for backing the candidate.
	#[codec(index = 1)]
	CandidateIncluded(CandidateReceipt<H>, HeadData, CoreIndex, GroupIndex),
	/// This candidate receipt was not made available in time and timed out.
	/// This includes the core index the candidate was occupying.
	#[codec(index = 2)]
	CandidateTimedOut(CandidateReceipt<H>, HeadData, CoreIndex),
}

/// Scraped runtime backing votes and resolved disputes.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct ScrapedOnChainVotes<H: Encode + Decode = Hash> {
	/// The session in which the block was included.
	pub session: SessionIndex,
	/// Set of backing validators for each candidate, represented by its candidate
	/// receipt.
	pub backing_validators_per_candidate:
		Vec<(CandidateReceipt<H>, Vec<(ValidatorIndex, ValidityAttestation)>)>,
	/// On-chain-recorded set of disputes.
	/// Note that the above `backing_validators` are
	/// unrelated to the backers of the disputes candidates.
	pub disputes: MultiDisputeStatementSet,
}

/// A vote of approval on a candidate.
#[derive(Clone, RuntimeDebug)]
pub struct ApprovalVote(pub CandidateHash);

impl ApprovalVote {
	/// Yields the signing payload for this approval vote.
	pub fn signing_payload(&self, session_index: SessionIndex) -> Vec<u8> {
		const MAGIC: [u8; 4] = *b"APPR";

		(MAGIC, &self.0, session_index).encode()
	}
}

/// Custom validity errors used in Polkadot while validating transactions.
#[repr(u8)]
pub enum ValidityError {
	/// The Ethereum signature is invalid.
	InvalidEthereumSignature = 0,
	/// The signer has no claim.
	SignerHasNoClaim = 1,
	/// No permission to execute the call.
	NoPermission = 2,
	/// An invalid statement was made for a claim.
	InvalidStatement = 3,
}

impl From<ValidityError> for u8 {
	fn from(err: ValidityError) -> Self {
		err as u8
	}
}

/// Abridged version of `HostConfiguration` (from the `Configuration` parachains host runtime module)
/// meant to be used by a parachain or PDK such as cumulus.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct AbridgedHostConfiguration {
	/// The maximum validation code size, in bytes.
	pub max_code_size: u32,
	/// The maximum head-data size, in bytes.
	pub max_head_data_size: u32,
	/// Total number of individual messages allowed in the parachain -> relay-chain message queue.
	pub max_upward_queue_count: u32,
	/// Total size of messages allowed in the parachain -> relay-chain message queue before which
	/// no further messages may be added to it. If it exceeds this then the queue may contain only
	/// a single message.
	pub max_upward_queue_size: u32,
	/// The maximum size of an upward message that can be sent by a candidate.
	///
	/// This parameter affects the size upper bound of the `CandidateCommitments`.
	pub max_upward_message_size: u32,
	/// The maximum number of messages that a candidate can contain.
	///
	/// This parameter affects the size upper bound of the `CandidateCommitments`.
	pub max_upward_message_num_per_candidate: u32,
	/// The maximum number of outbound HRMP messages can be sent by a candidate.
	///
	/// This parameter affects the upper bound of size of `CandidateCommitments`.
	pub hrmp_max_message_num_per_candidate: u32,
	/// The minimum period, in blocks, between which parachains can update their validation code.
	pub validation_upgrade_cooldown: BlockNumber,
	/// The delay, in blocks, before a validation upgrade is applied.
	pub validation_upgrade_delay: BlockNumber,
}

/// Abridged version of `HrmpChannel` (from the `Hrmp` parachains host runtime module) meant to be
/// used by a parachain or PDK such as cumulus.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct AbridgedHrmpChannel {
	/// The maximum number of messages that can be pending in the channel at once.
	pub max_capacity: u32,
	/// The maximum total size of the messages that can be pending in the channel at once.
	pub max_total_size: u32,
	/// The maximum message size that could be put into the channel.
	pub max_message_size: u32,
	/// The current number of messages pending in the channel.
	/// Invariant: should be less or equal to `max_capacity`.s`.
	pub msg_count: u32,
	/// The total size in bytes of all message payloads in the channel.
	/// Invariant: should be less or equal to `max_total_size`.
	pub total_size: u32,
	/// A head of the Message Queue Chain for this channel. Each link in this chain has a form:
	/// `(prev_head, B, H(M))`, where
	/// - `prev_head`: is the previous value of `mqc_head` or zero if none.
	/// - `B`: is the [relay-chain] block number in which a message was appended
	/// - `H(M)`: is the hash of the message being appended.
	/// This value is initialized to a special value that consists of all zeroes which indicates
	/// that no messages were previously added.
	pub mqc_head: Option<Hash>,
}

/// A possible upgrade restriction that prevents a parachain from performing an upgrade.
#[derive(Copy, Clone, Encode, Decode, PartialEq, RuntimeDebug, TypeInfo)]
pub enum UpgradeRestriction {
	/// There is an upgrade restriction and there are no details about its specifics nor how long
	/// it could last.
	#[codec(index = 0)]
	Present,
}

/// A struct that the relay-chain communicates to a parachain indicating what course of action the
/// parachain should take in the coordinated parachain validation code upgrade process.
///
/// This data type appears in the last step of the upgrade process. After the parachain observes it
/// and reacts to it the upgrade process concludes.
#[derive(Copy, Clone, Encode, Decode, PartialEq, RuntimeDebug, TypeInfo)]
pub enum UpgradeGoAhead {
	/// Abort the upgrade process. There is something wrong with the validation code previously
	/// submitted by the parachain. This variant can also be used to prevent upgrades by the governance
	/// should an emergency emerge.
	///
	/// The expected reaction on this variant is that the parachain will admit this message and
	/// remove all the data about the pending upgrade. Depending on the nature of the problem (to
	/// be examined offchain for now), it can try to send another validation code or just retry later.
	#[codec(index = 0)]
	Abort,
	/// Apply the pending code change. The parablock that is built on a relay-parent that is descendant
	/// of the relay-parent where the parachain observed this signal must use the upgraded validation
	/// code.
	#[codec(index = 1)]
	GoAhead,
}

/// Consensus engine id for polkadot v1 consensus engine.
pub const POLKADOT_ENGINE_ID: runtime_primitives::ConsensusEngineId = *b"POL1";

/// A consensus log item for polkadot validation. To be used with [`POLKADOT_ENGINE_ID`].
#[derive(Decode, Encode, Clone, PartialEq, Eq)]
pub enum ConsensusLog {
	/// A parachain or parathread upgraded its code.
	#[codec(index = 1)]
	ParaUpgradeCode(Id, ValidationCodeHash),
	/// A parachain or parathread scheduled a code upgrade.
	#[codec(index = 2)]
	ParaScheduleUpgradeCode(Id, ValidationCodeHash, BlockNumber),
	/// Governance requests to auto-approve every candidate included up to the given block
	/// number in the current chain, inclusive.
	#[codec(index = 3)]
	ForceApprove(BlockNumber),
	/// A signal to revert the block number in the same chain as the
	/// header this digest is part of and all of its descendants.
	///
	/// It is a no-op for a block to contain a revert digest targeting
	/// its own number or a higher number.
	///
	/// In practice, these are issued when on-chain logic has detected an
	/// invalid parachain block within its own chain, due to a dispute.
	#[codec(index = 4)]
	Revert(BlockNumber),
}

impl ConsensusLog {
	/// Attempt to convert a reference to a generic digest item into a consensus log.
	pub fn from_digest_item(
		digest_item: &runtime_primitives::DigestItem,
	) -> Result<Option<Self>, parity_scale_codec::Error> {
		match digest_item {
			runtime_primitives::DigestItem::Consensus(id, encoded) if id == &POLKADOT_ENGINE_ID =>
				Ok(Some(Self::decode(&mut &encoded[..])?)),
			_ => Ok(None),
		}
	}
}

impl From<ConsensusLog> for runtime_primitives::DigestItem {
	fn from(c: ConsensusLog) -> runtime_primitives::DigestItem {
		Self::Consensus(POLKADOT_ENGINE_ID, c.encode())
	}
}

/// A statement about a candidate, to be used within the dispute resolution process.
///
/// Statements are either in favor of the candidate's validity or against it.
#[derive(Encode, Decode, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub enum DisputeStatement {
	/// A valid statement, of the given kind.
	#[codec(index = 0)]
	Valid(ValidDisputeStatementKind),
	/// An invalid statement, of the given kind.
	#[codec(index = 1)]
	Invalid(InvalidDisputeStatementKind),
}

impl DisputeStatement {
	/// Get the payload data for this type of dispute statement.
	pub fn payload_data(&self, candidate_hash: CandidateHash, session: SessionIndex) -> Vec<u8> {
		match *self {
			DisputeStatement::Valid(ValidDisputeStatementKind::Explicit) =>
				ExplicitDisputeStatement { valid: true, candidate_hash, session }.signing_payload(),
			DisputeStatement::Valid(ValidDisputeStatementKind::BackingSeconded(
				inclusion_parent,
			)) => CompactStatement::Seconded(candidate_hash).signing_payload(&SigningContext {
				session_index: session,
				parent_hash: inclusion_parent,
			}),
			DisputeStatement::Valid(ValidDisputeStatementKind::BackingValid(inclusion_parent)) =>
				CompactStatement::Valid(candidate_hash).signing_payload(&SigningContext {
					session_index: session,
					parent_hash: inclusion_parent,
				}),
			DisputeStatement::Valid(ValidDisputeStatementKind::ApprovalChecking) =>
				ApprovalVote(candidate_hash).signing_payload(session),
			DisputeStatement::Invalid(InvalidDisputeStatementKind::Explicit) =>
				ExplicitDisputeStatement { valid: false, candidate_hash, session }.signing_payload(),
		}
	}

	/// Check the signature on a dispute statement.
	pub fn check_signature(
		&self,
		validator_public: &ValidatorId,
		candidate_hash: CandidateHash,
		session: SessionIndex,
		validator_signature: &ValidatorSignature,
	) -> Result<(), ()> {
		let payload = self.payload_data(candidate_hash, session);

		if validator_signature.verify(&payload[..], &validator_public) {
			Ok(())
		} else {
			Err(())
		}
	}

	/// Whether the statement indicates validity.
	pub fn indicates_validity(&self) -> bool {
		match *self {
			DisputeStatement::Valid(_) => true,
			DisputeStatement::Invalid(_) => false,
		}
	}

	/// Whether the statement indicates invalidity.
	pub fn indicates_invalidity(&self) -> bool {
		match *self {
			DisputeStatement::Valid(_) => false,
			DisputeStatement::Invalid(_) => true,
		}
	}

	/// Statement is backing statement.
	pub fn is_backing(&self) -> bool {
		match *self {
			Self::Valid(ValidDisputeStatementKind::BackingSeconded(_)) |
			Self::Valid(ValidDisputeStatementKind::BackingValid(_)) => true,
			Self::Valid(ValidDisputeStatementKind::Explicit) |
			Self::Valid(ValidDisputeStatementKind::ApprovalChecking) |
			Self::Invalid(_) => false,
		}
	}
}

/// Different kinds of statements of validity on  a candidate.
#[derive(Encode, Decode, Copy, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub enum ValidDisputeStatementKind {
	/// An explicit statement issued as part of a dispute.
	#[codec(index = 0)]
	Explicit,
	/// A seconded statement on a candidate from the backing phase.
	#[codec(index = 1)]
	BackingSeconded(Hash),
	/// A valid statement on a candidate from the backing phase.
	#[codec(index = 2)]
	BackingValid(Hash),
	/// An approval vote from the approval checking phase.
	#[codec(index = 3)]
	ApprovalChecking,
}

/// Different kinds of statements of invalidity on a candidate.
#[derive(Encode, Decode, Copy, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub enum InvalidDisputeStatementKind {
	/// An explicit statement issued as part of a dispute.
	#[codec(index = 0)]
	Explicit,
}

/// An explicit statement on a candidate issued as part of a dispute.
#[derive(Clone, PartialEq, RuntimeDebug)]
pub struct ExplicitDisputeStatement {
	/// Whether the candidate is valid
	pub valid: bool,
	/// The candidate hash.
	pub candidate_hash: CandidateHash,
	/// The session index of the candidate.
	pub session: SessionIndex,
}

impl ExplicitDisputeStatement {
	/// Produce the payload used for signing this type of statement.
	pub fn signing_payload(&self) -> Vec<u8> {
		const MAGIC: [u8; 4] = *b"DISP";

		(MAGIC, self.valid, self.candidate_hash, self.session).encode()
	}
}

/// A set of statements about a specific candidate.
#[derive(Encode, Decode, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub struct DisputeStatementSet {
	/// The candidate referenced by this set.
	pub candidate_hash: CandidateHash,
	/// The session index of the candidate.
	pub session: SessionIndex,
	/// Statements about the candidate.
	pub statements: Vec<(DisputeStatement, ValidatorIndex, ValidatorSignature)>,
}

impl From<CheckedDisputeStatementSet> for DisputeStatementSet {
	fn from(other: CheckedDisputeStatementSet) -> Self {
		other.0
	}
}

impl AsRef<DisputeStatementSet> for DisputeStatementSet {
	fn as_ref(&self) -> &DisputeStatementSet {
		&self
	}
}

/// A set of dispute statements.
pub type MultiDisputeStatementSet = Vec<DisputeStatementSet>;

/// A _checked_ set of dispute statements.
#[derive(Clone, PartialEq, RuntimeDebug)]
pub struct CheckedDisputeStatementSet(DisputeStatementSet);

impl AsRef<DisputeStatementSet> for CheckedDisputeStatementSet {
	fn as_ref(&self) -> &DisputeStatementSet {
		&self.0
	}
}

impl core::cmp::PartialEq<DisputeStatementSet> for CheckedDisputeStatementSet {
	fn eq(&self, other: &DisputeStatementSet) -> bool {
		self.0.eq(other)
	}
}

impl CheckedDisputeStatementSet {
	/// Convert from an unchecked, the verification of correctness of the `unchecked` statement set
	/// _must_ be done before calling this function!
	pub fn unchecked_from_unchecked(unchecked: DisputeStatementSet) -> Self {
		Self(unchecked)
	}
}

/// A set of _checked_ dispute statements.
pub type CheckedMultiDisputeStatementSet = Vec<CheckedDisputeStatementSet>;

/// The entire state of a dispute.
#[derive(Encode, Decode, Clone, RuntimeDebug, PartialEq, TypeInfo)]
pub struct DisputeState<N = BlockNumber> {
	/// A bitfield indicating all validators for the candidate.
	pub validators_for: BitVec<u8, bitvec::order::Lsb0>, // one bit per validator.
	/// A bitfield indicating all validators against the candidate.
	pub validators_against: BitVec<u8, bitvec::order::Lsb0>, // one bit per validator.
	/// The block number at which the dispute started on-chain.
	pub start: N,
	/// The block number at which the dispute concluded on-chain.
	pub concluded_at: Option<N>,
}

/// Parachains inherent-data passed into the runtime by a block author
#[derive(Encode, Decode, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub struct InherentData<HDR: HeaderT = Header> {
	/// Signed bitfields by validators about availability.
	pub bitfields: UncheckedSignedAvailabilityBitfields,
	/// Backed candidates for inclusion in the block.
	pub backed_candidates: Vec<BackedCandidate<HDR::Hash>>,
	/// Sets of dispute votes for inclusion,
	pub disputes: MultiDisputeStatementSet,
	/// The parent block header. Used for checking state proofs.
	pub parent_header: HDR,
}

/// An either implicit or explicit attestation to the validity of a parachain
/// candidate.
#[derive(Clone, Eq, PartialEq, Decode, Encode, RuntimeDebug, TypeInfo)]
pub enum ValidityAttestation {
	/// Implicit validity attestation by issuing.
	/// This corresponds to issuance of a `Candidate` statement.
	#[codec(index = 1)]
	Implicit(ValidatorSignature),
	/// An explicit attestation. This corresponds to issuance of a
	/// `Valid` statement.
	#[codec(index = 2)]
	Explicit(ValidatorSignature),
}

impl ValidityAttestation {
	/// Produce the underlying signed payload of the attestation, given the hash of the candidate,
	/// which should be known in context.
	pub fn to_compact_statement(&self, candidate_hash: CandidateHash) -> CompactStatement {
		// Explicit and implicit map directly from
		// `ValidityVote::Valid` and `ValidityVote::Issued`, and hence there is a
		// `1:1` relationshow which enables the conversion.
		match *self {
			ValidityAttestation::Implicit(_) => CompactStatement::Seconded(candidate_hash),
			ValidityAttestation::Explicit(_) => CompactStatement::Valid(candidate_hash),
		}
	}

	/// Get a reference to the signature.
	pub fn signature(&self) -> &ValidatorSignature {
		match *self {
			ValidityAttestation::Implicit(ref sig) => sig,
			ValidityAttestation::Explicit(ref sig) => sig,
		}
	}

	/// Produce the underlying signed payload of the attestation, given the hash of the candidate,
	/// which should be known in context.
	pub fn signed_payload<H: Encode>(
		&self,
		candidate_hash: CandidateHash,
		signing_context: &SigningContext<H>,
	) -> Vec<u8> {
		match *self {
			ValidityAttestation::Implicit(_) =>
				(CompactStatement::Seconded(candidate_hash), signing_context).encode(),
			ValidityAttestation::Explicit(_) =>
				(CompactStatement::Valid(candidate_hash), signing_context).encode(),
		}
	}
}

/// A type returned by runtime with current session index and a parent hash.
#[derive(Clone, Eq, PartialEq, Default, Decode, Encode, RuntimeDebug)]
pub struct SigningContext<H = Hash> {
	/// Current session index.
	pub session_index: sp_staking::SessionIndex,
	/// Hash of the parent.
	pub parent_hash: H,
}

const BACKING_STATEMENT_MAGIC: [u8; 4] = *b"BKNG";

/// Statements that can be made about parachain candidates. These are the
/// actual values that are signed.
#[derive(Clone, PartialEq, Eq, RuntimeDebug)]
#[cfg_attr(feature = "std", derive(Hash))]
pub enum CompactStatement {
	/// Proposal of a parachain candidate.
	Seconded(CandidateHash),
	/// State that a parachain candidate is valid.
	Valid(CandidateHash),
}

impl CompactStatement {
	/// Yields the payload used for validator signatures on this kind
	/// of statement.
	pub fn signing_payload(&self, context: &SigningContext) -> Vec<u8> {
		(self, context).encode()
	}
}

// Inner helper for codec on `CompactStatement`.
#[derive(Encode, Decode, TypeInfo)]
enum CompactStatementInner {
	#[codec(index = 1)]
	Seconded(CandidateHash),
	#[codec(index = 2)]
	Valid(CandidateHash),
}

impl From<CompactStatement> for CompactStatementInner {
	fn from(s: CompactStatement) -> Self {
		match s {
			CompactStatement::Seconded(h) => CompactStatementInner::Seconded(h),
			CompactStatement::Valid(h) => CompactStatementInner::Valid(h),
		}
	}
}

impl parity_scale_codec::Encode for CompactStatement {
	fn size_hint(&self) -> usize {
		// magic + discriminant + payload
		4 + 1 + 32
	}

	fn encode_to<T: parity_scale_codec::Output + ?Sized>(&self, dest: &mut T) {
		dest.write(&BACKING_STATEMENT_MAGIC);
		CompactStatementInner::from(self.clone()).encode_to(dest)
	}
}

impl parity_scale_codec::Decode for CompactStatement {
	fn decode<I: parity_scale_codec::Input>(
		input: &mut I,
	) -> Result<Self, parity_scale_codec::Error> {
		let maybe_magic = <[u8; 4]>::decode(input)?;
		if maybe_magic != BACKING_STATEMENT_MAGIC {
			return Err(parity_scale_codec::Error::from("invalid magic string"))
		}

		Ok(match CompactStatementInner::decode(input)? {
			CompactStatementInner::Seconded(h) => CompactStatement::Seconded(h),
			CompactStatementInner::Valid(h) => CompactStatement::Valid(h),
		})
	}
}

impl CompactStatement {
	/// Get the underlying candidate hash this references.
	pub fn candidate_hash(&self) -> &CandidateHash {
		match *self {
			CompactStatement::Seconded(ref h) | CompactStatement::Valid(ref h) => h,
		}
	}
}

/// `IndexedVec` struct indexed by type specific indices.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct IndexedVec<K, V>(Vec<V>, PhantomData<fn(K) -> K>);

impl<K, V> Default for IndexedVec<K, V> {
	fn default() -> Self {
		Self(vec![], PhantomData)
	}
}

impl<K, V> From<Vec<V>> for IndexedVec<K, V> {
	fn from(validators: Vec<V>) -> Self {
		Self(validators, PhantomData)
	}
}

impl<K, V> FromIterator<V> for IndexedVec<K, V> {
	fn from_iter<T: IntoIterator<Item = V>>(iter: T) -> Self {
		Self(Vec::from_iter(iter), PhantomData)
	}
}

impl<K, V> IndexedVec<K, V>
where
	V: Clone,
{
	/// Returns a reference to an element indexed using `K`.
	pub fn get(&self, index: K) -> Option<&V>
	where
		K: TypeIndex,
	{
		self.0.get(index.type_index())
	}

	/// Returns number of elements in vector.
	pub fn len(&self) -> usize {
		self.0.len()
	}

	/// Returns contained vector.
	pub fn to_vec(&self) -> Vec<V> {
		self.0.clone()
	}

	/// Returns an iterator over the underlying vector.
	pub fn iter(&self) -> Iter<'_, V> {
		self.0.iter()
	}

	/// Returns a mutable iterator over the underlying vector.
	pub fn iter_mut(&mut self) -> IterMut<'_, V> {
		self.0.iter_mut()
	}

	/// Creates a consuming iterator.
	pub fn into_iter(self) -> IntoIter<V> {
		self.0.into_iter()
	}

	/// Returns true if the underlying container is empty.
	pub fn is_empty(&self) -> bool {
		self.0.is_empty()
	}
}

/// The maximum number of validators `f` which may safely be faulty.
///
/// The total number of validators is `n = 3f + e` where `e in { 1, 2, 3 }`.
pub fn byzantine_threshold(n: usize) -> usize {
	n.saturating_sub(1) / 3
}

/// The supermajority threshold of validators which represents a subset
/// guaranteed to have at least f+1 honest validators.
pub fn supermajority_threshold(n: usize) -> usize {
	n - byzantine_threshold(n)
}

/// Information about validator sets of a session.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct SessionInfo {
	/****** New in v2 *******/
	/// All the validators actively participating in parachain consensus.
	/// Indices are into the broader validator set.
	pub active_validator_indices: Vec<ValidatorIndex>,
	/// A secure random seed for the session, gathered from BABE.
	pub random_seed: [u8; 32],
	/// The amount of sessions to keep for disputes.
	pub dispute_period: SessionIndex,

	/****** Old fields ******/
	/// Validators in canonical ordering.
	///
	/// NOTE: There might be more authorities in the current session, than `validators` participating
	/// in parachain consensus. See
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
	///
	/// `SessionInfo::validators` will be limited to to `max_validators` when set.
	pub validators: IndexedVec<ValidatorIndex, ValidatorId>,
	/// Validators' authority discovery keys for the session in canonical ordering.
	///
	/// NOTE: The first `validators.len()` entries will match the corresponding validators in
	/// `validators`, afterwards any remaining authorities can be found. This is any authorities not
	/// participating in parachain consensus - see
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148)
	pub discovery_keys: Vec<AuthorityDiscoveryId>,
	/// The assignment keys for validators.
	///
	/// NOTE: There might be more authorities in the current session, than validators participating
	/// in parachain consensus. See
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
	///
	/// Therefore:
	/// ```ignore
	///		assignment_keys.len() == validators.len() && validators.len() <= discovery_keys.len()
	///	```
	pub assignment_keys: Vec<AssignmentId>,
	/// Validators in shuffled ordering - these are the validator groups as produced
	/// by the `Scheduler` module for the session and are typically referred to by
	/// `GroupIndex`.
	pub validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
	/// The number of availability cores used by the protocol during this session.
	pub n_cores: u32,
	/// The zeroth delay tranche width.
	pub zeroth_delay_tranche_width: u32,
	/// The number of samples we do of `relay_vrf_modulo`.
	pub relay_vrf_modulo_samples: u32,
	/// The number of delay tranches in total.
	pub n_delay_tranches: u32,
	/// How many slots (BABE / SASSAFRAS) must pass before an assignment is considered a
	/// no-show.
	pub no_show_slots: u32,
	/// The number of validators needed to approve a block.
	pub needed_approvals: u32,
}

/// A statement from the specified validator whether the given validation code passes PVF
/// pre-checking or not anchored to the given session index.
#[derive(Encode, Decode, Clone, PartialEq, RuntimeDebug, TypeInfo)]
pub struct PvfCheckStatement {
	/// `true` if the subject passed pre-checking and `false` otherwise.
	pub accept: bool,
	/// The validation code hash that was checked.
	pub subject: ValidationCodeHash,
	/// The index of a session during which this statement is considered valid.
	pub session_index: SessionIndex,
	/// The index of the validator from which this statement originates.
	pub validator_index: ValidatorIndex,
}

impl PvfCheckStatement {
	/// Produce the payload used for signing this type of statement.
	///
	/// It is expected that it will be signed by the validator at `validator_index` in the
	/// `session_index`.
	pub fn signing_payload(&self) -> Vec<u8> {
		const MAGIC: [u8; 4] = *b"VCPC"; // for "validation code pre-checking"
		(MAGIC, self.accept, self.subject, self.session_index, self.validator_index).encode()
	}
}

/// Old, v1-style info about session info. Only needed for limited
/// backwards-compatibility.
#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
#[cfg_attr(feature = "std", derive(PartialEq))]
pub struct OldV1SessionInfo {
	/// Validators in canonical ordering.
	///
	/// NOTE: There might be more authorities in the current session, than `validators` participating
	/// in parachain consensus. See
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
	///
	/// `SessionInfo::validators` will be limited to to `max_validators` when set.
	pub validators: IndexedVec<ValidatorIndex, ValidatorId>,
	/// Validators' authority discovery keys for the session in canonical ordering.
	///
	/// NOTE: The first `validators.len()` entries will match the corresponding validators in
	/// `validators`, afterwards any remaining authorities can be found. This is any authorities not
	/// participating in parachain consensus - see
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148)
	pub discovery_keys: Vec<AuthorityDiscoveryId>,
	/// The assignment keys for validators.
	///
	/// NOTE: There might be more authorities in the current session, than validators participating
	/// in parachain consensus. See
	/// [`max_validators`](https://github.com/paritytech/polkadot/blob/a52dca2be7840b23c19c153cf7e110b1e3e475f8/runtime/parachains/src/configuration.rs#L148).
	///
	/// Therefore:
	/// ```ignore
	///		assignment_keys.len() == validators.len() && validators.len() <= discovery_keys.len()
	///	```
	pub assignment_keys: Vec<AssignmentId>,
	/// Validators in shuffled ordering - these are the validator groups as produced
	/// by the `Scheduler` module for the session and are typically referred to by
	/// `GroupIndex`.
	pub validator_groups: IndexedVec<GroupIndex, Vec<ValidatorIndex>>,
	/// The number of availability cores used by the protocol during this session.
	pub n_cores: u32,
	/// The zeroth delay tranche width.
	pub zeroth_delay_tranche_width: u32,
	/// The number of samples we do of `relay_vrf_modulo`.
	pub relay_vrf_modulo_samples: u32,
	/// The number of delay tranches in total.
	pub n_delay_tranches: u32,
	/// How many slots (BABE / SASSAFRAS) must pass before an assignment is considered a
	/// no-show.
	pub no_show_slots: u32,
	/// The number of validators needed to approve a block.
	pub needed_approvals: u32,
}

impl From<OldV1SessionInfo> for SessionInfo {
	fn from(old: OldV1SessionInfo) -> SessionInfo {
		SessionInfo {
			// new fields
			active_validator_indices: Vec::new(),
			random_seed: [0u8; 32],
			dispute_period: 6,
			// old fields
			validators: old.validators,
			discovery_keys: old.discovery_keys,
			assignment_keys: old.assignment_keys,
			validator_groups: old.validator_groups,
			n_cores: old.n_cores,
			zeroth_delay_tranche_width: old.zeroth_delay_tranche_width,
			relay_vrf_modulo_samples: old.relay_vrf_modulo_samples,
			n_delay_tranches: old.n_delay_tranches,
			no_show_slots: old.no_show_slots,
			needed_approvals: old.needed_approvals,
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;

	#[test]
	fn group_rotation_info_calculations() {
		let info =
			GroupRotationInfo { session_start_block: 10u32, now: 15, group_rotation_frequency: 5 };

		assert_eq!(info.next_rotation_at(), 20);
		assert_eq!(info.last_rotation_at(), 15);
	}

	#[test]
	fn group_for_core_is_core_for_group() {
		for cores in 1..=256 {
			for rotations in 0..(cores * 2) {
				let info = GroupRotationInfo {
					session_start_block: 0u32,
					now: rotations,
					group_rotation_frequency: 1,
				};

				for core in 0..cores {
					let group = info.group_for_core(CoreIndex(core), cores as usize);
					assert_eq!(info.core_for_group(group, cores as usize).0, core);
				}
			}
		}
	}

	#[test]
	fn collator_signature_payload_is_valid() {
		// if this fails, collator signature verification code has to be updated.
		let h = Hash::default();
		assert_eq!(h.as_ref().len(), 32);

		let _payload = collator_signature_payload(
			&Hash::repeat_byte(1),
			&5u32.into(),
			&Hash::repeat_byte(2),
			&Hash::repeat_byte(3),
			&Hash::repeat_byte(4).into(),
		);
	}

	#[test]
	fn test_byzantine_threshold() {
		assert_eq!(byzantine_threshold(0), 0);
		assert_eq!(byzantine_threshold(1), 0);
		assert_eq!(byzantine_threshold(2), 0);
		assert_eq!(byzantine_threshold(3), 0);
		assert_eq!(byzantine_threshold(4), 1);
		assert_eq!(byzantine_threshold(5), 1);
		assert_eq!(byzantine_threshold(6), 1);
		assert_eq!(byzantine_threshold(7), 2);
	}

	#[test]
	fn test_supermajority_threshold() {
		assert_eq!(supermajority_threshold(0), 0);
		assert_eq!(supermajority_threshold(1), 1);
		assert_eq!(supermajority_threshold(2), 2);
		assert_eq!(supermajority_threshold(3), 3);
		assert_eq!(supermajority_threshold(4), 3);
		assert_eq!(supermajority_threshold(5), 4);
		assert_eq!(supermajority_threshold(6), 5);
		assert_eq!(supermajority_threshold(7), 5);
	}

	#[test]
	fn balance_bigger_than_usize() {
		let zero_b: Balance = 0;
		let zero_u: usize = 0;

		assert!(zero_b.leading_zeros() >= zero_u.leading_zeros());
	}
}