referrerpolicy=no-referrer-when-downgrade
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
// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! # Non-Interactive Staking (NIS) Pallet
//! A pallet allowing accounts to auction for being frozen and receive open-ended
//! inflation-protection in return.
//!
//! ## Overview
//!
//! Lock up tokens, for at least as long as you offer, and be free from both inflation and
//! intermediate reward or exchange until the tokens become unlocked.
//!
//! ## Design
//!
//! Queues for each of `1..QueueCount` periods, given in blocks (`Period`). Queues are limited in
//! size to something sensible, `MaxQueueLen`. A secondary storage item with `QueueCount` x `u32`
//! elements with the number of items in each queue.
//!
//! Queues are split into two parts. The first part is a priority queue based on bid size. The
//! second part is just a FIFO (the size of the second part is set with `FifoQueueLen`). Items are
//! always prepended so that removal is always O(1) since removal often happens many times under a
//! single weighed function (`on_initialize`) yet placing bids only ever happens once per weighed
//! function (`place_bid`). If the queue has a priority portion, then it remains sorted in order of
//! bid size so that smaller bids fall off as it gets too large.
//!
//! Account may enqueue a balance with some number of `Period`s lock up, up to a maximum of
//! `QueueCount`. The balance gets reserved. There's a minimum of `MinBid` to avoid dust.
//!
//! Until your bid is consolidated and you receive a receipt, you can retract it instantly and the
//! funds are unreserved.
//!
//! There's a target proportion of effective total issuance (i.e. accounting for existing receipts)
//! which the pallet attempts to have frozen at any one time. It will likely be gradually increased
//! over time by governance.
//!
//! As the proportion of effective total issuance represented by outstanding receipts drops below
//! `FrozenFraction`, then bids are taken from queues and consolidated into receipts, with the queue
//! of the greatest period taking priority. If the item in the queue's locked amount is greater than
//! the amount remaining to achieve `FrozenFraction`, then it is split up into multiple bids and
//! becomes partially consolidated.
//!
//! With the consolidation of a bid, the bid amount is taken from the owner and a receipt is issued.
//! The receipt records the proportion of the bid compared to effective total issuance at the time
//! of consolidation. The receipt has two independent elements: a "main" non-fungible receipt and
//! a second set of fungible "counterpart" tokens. The accounting functionality of the latter must
//! be provided through the `Counterpart` trait item. The main non-fungible receipt may have its
//! owner transferred through the pallet's implementation of `nonfungible::Transfer`.
//!
//! A later `thaw` function may be called in order to reduce the recorded proportion or entirely
//! remove the receipt in return for the appropriate proportion of the effective total issuance.
//! This may happen no earlier than queue's period after the point at which the receipt was issued.
//! The call must be made by the owner of both the "main" non-fungible receipt and the appropriate
//! amount of counterpart tokens.
//!
//! `NoCounterpart` may be provided as an implementation for the counterpart token system in which
//! case they are completely disregarded from the thawing logic.
//!
//! ## Terms
//!
//! - *Effective total issuance*: The total issuance of balances in the system, equal to the active
//!   issuance plus the value of all outstanding receipts, less `IgnoredIssuance`.

#![cfg_attr(not(feature = "std"), no_std)]

extern crate alloc;

use frame_support::traits::{
	fungible::{self, Inspect as FunInspect, Mutate as FunMutate},
	tokens::{DepositConsequence, Fortitude, Preservation, Provenance, WithdrawConsequence},
};
pub use pallet::*;
use sp_arithmetic::{traits::Unsigned, RationalArg};
use sp_core::TypedGet;
use sp_runtime::{
	traits::{Convert, ConvertBack},
	DispatchError, Perquintill,
};

mod benchmarking;
#[cfg(test)]
mod mock;
#[cfg(test)]
mod tests;
pub mod weights;

pub struct WithMaximumOf<A: TypedGet>(core::marker::PhantomData<A>);
impl<A: TypedGet> Convert<Perquintill, A::Type> for WithMaximumOf<A>
where
	A::Type: Clone + Unsigned + From<u64>,
	u64: TryFrom<A::Type>,
{
	fn convert(a: Perquintill) -> A::Type {
		a * A::get()
	}
}
impl<A: TypedGet> ConvertBack<Perquintill, A::Type> for WithMaximumOf<A>
where
	A::Type: RationalArg + From<u64>,
	u64: TryFrom<A::Type>,
	u128: TryFrom<A::Type>,
{
	fn convert_back(a: A::Type) -> Perquintill {
		Perquintill::from_rational(a, A::get())
	}
}

pub struct NoCounterpart<T>(core::marker::PhantomData<T>);
impl<T> FunInspect<T> for NoCounterpart<T> {
	type Balance = u32;
	fn total_issuance() -> u32 {
		0
	}
	fn minimum_balance() -> u32 {
		0
	}
	fn balance(_: &T) -> u32 {
		0
	}
	fn total_balance(_: &T) -> u32 {
		0
	}
	fn reducible_balance(_: &T, _: Preservation, _: Fortitude) -> u32 {
		0
	}
	fn can_deposit(_: &T, _: u32, _: Provenance) -> DepositConsequence {
		DepositConsequence::Success
	}
	fn can_withdraw(_: &T, _: u32) -> WithdrawConsequence<u32> {
		WithdrawConsequence::Success
	}
}
impl<T> fungible::Unbalanced<T> for NoCounterpart<T> {
	fn handle_dust(_: fungible::Dust<T, Self>) {}
	fn write_balance(_: &T, _: Self::Balance) -> Result<Option<Self::Balance>, DispatchError> {
		Ok(None)
	}
	fn set_total_issuance(_: Self::Balance) {}
}
impl<T: Eq> FunMutate<T> for NoCounterpart<T> {}
impl<T> Convert<Perquintill, u32> for NoCounterpart<T> {
	fn convert(_: Perquintill) -> u32 {
		0
	}
}

/// Setup the empty genesis state for benchmarking.
pub trait BenchmarkSetup {
	/// Create the counterpart asset. Should panic on error.
	///
	/// This is called prior to assuming that a counterpart balance exists.
	fn create_counterpart_asset();
}

impl BenchmarkSetup for () {
	fn create_counterpart_asset() {}
}

#[frame_support::pallet]
pub mod pallet {
	use super::{FunInspect, FunMutate};
	pub use crate::weights::WeightInfo;
	use alloc::{vec, vec::Vec};
	use frame_support::{
		pallet_prelude::*,
		traits::{
			fungible::{self, hold::Mutate as FunHoldMutate, Balanced as FunBalanced},
			nonfungible::{Inspect as NftInspect, Transfer as NftTransfer},
			tokens::{
				Balance,
				Fortitude::Polite,
				Precision::{BestEffort, Exact},
				Preservation::Expendable,
				Restriction::{Free, OnHold},
			},
			Defensive, DefensiveSaturating, OnUnbalanced,
		},
		PalletId,
	};
	use frame_system::pallet_prelude::*;
	use sp_arithmetic::{PerThing, Perquintill};
	use sp_runtime::{
		traits::{AccountIdConversion, Bounded, Convert, ConvertBack, Saturating, Zero},
		Rounding, TokenError,
	};

	type BalanceOf<T> =
		<<T as Config>::Currency as FunInspect<<T as frame_system::Config>::AccountId>>::Balance;
	type DebtOf<T> =
		fungible::Debt<<T as frame_system::Config>::AccountId, <T as Config>::Currency>;
	type ReceiptRecordOf<T> =
		ReceiptRecord<<T as frame_system::Config>::AccountId, BlockNumberFor<T>, BalanceOf<T>>;
	type IssuanceInfoOf<T> = IssuanceInfo<BalanceOf<T>>;
	type SummaryRecordOf<T> = SummaryRecord<BlockNumberFor<T>, BalanceOf<T>>;
	type BidOf<T> = Bid<BalanceOf<T>, <T as frame_system::Config>::AccountId>;
	type QueueTotalsTypeOf<T> = BoundedVec<(u32, BalanceOf<T>), <T as Config>::QueueCount>;

	#[pallet::config]
	pub trait Config: frame_system::Config {
		/// Information on runtime weights.
		type WeightInfo: WeightInfo;

		/// Overarching event type.
		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;

		/// The treasury's pallet id, used for deriving its sovereign account ID.
		#[pallet::constant]
		type PalletId: Get<PalletId>;

		/// Currency type that this works on.
		type Currency: FunInspect<Self::AccountId, Balance = Self::CurrencyBalance>
			+ FunMutate<Self::AccountId>
			+ FunBalanced<Self::AccountId>
			+ FunHoldMutate<Self::AccountId, Reason = Self::RuntimeHoldReason>;

		/// Overarching hold reason.
		type RuntimeHoldReason: From<HoldReason>;

		/// Just the [`Balance`] type; we have this item to allow us to constrain it to
		/// [`From<u64>`].
		type CurrencyBalance: Balance + From<u64>;

		/// Origin required for auto-funding the deficit.
		type FundOrigin: EnsureOrigin<Self::RuntimeOrigin>;

		/// The issuance to ignore. This is subtracted from the `Currency`'s `total_issuance` to get
		/// the issuance with which we determine the thawed value of a given proportion.
		type IgnoredIssuance: Get<BalanceOf<Self>>;

		/// The accounting system for the fungible counterpart tokens.
		type Counterpart: FunMutate<Self::AccountId>;

		/// The system to convert an overall proportion of issuance into a number of fungible
		/// counterpart tokens.
		///
		/// In general it's best to use `WithMaximumOf`.
		type CounterpartAmount: ConvertBack<
			Perquintill,
			<Self::Counterpart as FunInspect<Self::AccountId>>::Balance,
		>;

		/// Unbalanced handler to account for funds created (in case of a higher total issuance over
		/// freezing period).
		type Deficit: OnUnbalanced<DebtOf<Self>>;

		/// The target sum of all receipts' proportions.
		type Target: Get<Perquintill>;

		/// Number of duration queues in total. This sets the maximum duration supported, which is
		/// this value multiplied by `Period`.
		#[pallet::constant]
		type QueueCount: Get<u32>;

		/// Maximum number of items that may be in each duration queue.
		///
		/// Must be larger than zero.
		#[pallet::constant]
		type MaxQueueLen: Get<u32>;

		/// Portion of the queue which is free from ordering and just a FIFO.
		///
		/// Must be no greater than `MaxQueueLen`.
		#[pallet::constant]
		type FifoQueueLen: Get<u32>;

		/// The base period for the duration queues. This is the common multiple across all
		/// supported freezing durations that can be bid upon.
		#[pallet::constant]
		type BasePeriod: Get<BlockNumberFor<Self>>;

		/// The minimum amount of funds that may be placed in a bid. Note that this
		/// does not actually limit the amount which may be represented in a receipt since bids may
		/// be split up by the system.
		///
		/// It should be at least big enough to ensure that there is no possible storage spam attack
		/// or queue-filling attack.
		#[pallet::constant]
		type MinBid: Get<BalanceOf<Self>>;

		/// The minimum amount of funds which may intentionally be left remaining under a single
		/// receipt.
		#[pallet::constant]
		type MinReceipt: Get<Perquintill>;

		/// The number of blocks between consecutive attempts to dequeue bids and create receipts.
		///
		/// A larger value results in fewer storage hits each block, but a slower period to get to
		/// the target.
		#[pallet::constant]
		type IntakePeriod: Get<BlockNumberFor<Self>>;

		/// The maximum amount of bids that can consolidated into receipts in a single intake. A
		/// larger value here means less of the block available for transactions should there be a
		/// glut of bids.
		#[pallet::constant]
		type MaxIntakeWeight: Get<Weight>;

		/// The maximum proportion which may be thawed and the period over which it is reset.
		#[pallet::constant]
		type ThawThrottle: Get<(Perquintill, BlockNumberFor<Self>)>;

		/// Setup the state for benchmarking.
		#[cfg(feature = "runtime-benchmarks")]
		type BenchmarkSetup: crate::BenchmarkSetup;
	}

	#[pallet::pallet]
	pub struct Pallet<T>(_);

	/// A single bid, an item of a *queue* in `Queues`.
	#[derive(
		Clone, Eq, PartialEq, Default, Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen,
	)]
	pub struct Bid<Balance, AccountId> {
		/// The amount bid.
		pub amount: Balance,
		/// The owner of the bid.
		pub who: AccountId,
	}

	/// Information representing a receipt.
	#[derive(
		Clone, Eq, PartialEq, Default, Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen,
	)]
	pub struct ReceiptRecord<AccountId, BlockNumber, Balance> {
		/// The proportion of the effective total issuance.
		pub proportion: Perquintill,
		/// The account to whom this receipt belongs and the amount of funds on hold in their
		/// account for servicing this receipt. If `None`, then it is a communal receipt and
		/// fungible counterparts have been issued.
		pub owner: Option<(AccountId, Balance)>,
		/// The time after which this receipt can be thawed.
		pub expiry: BlockNumber,
	}

	/// An index for a receipt.
	pub type ReceiptIndex = u32;

	/// Overall information package on the outstanding receipts.
	///
	/// The way of determining the net issuance (i.e. after factoring in all maturing frozen funds)
	/// is:
	///
	/// `issuance - frozen + proportion * issuance`
	///
	/// where `issuance = active_issuance - IgnoredIssuance`
	#[derive(
		Clone, Eq, PartialEq, Default, Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen,
	)]
	pub struct SummaryRecord<BlockNumber, Balance> {
		/// The total proportion over all outstanding receipts.
		pub proportion_owed: Perquintill,
		/// The total number of receipts created so far.
		pub index: ReceiptIndex,
		/// The amount (as a proportion of ETI) which has been thawed in this period so far.
		pub thawed: Perquintill,
		/// The current thaw period's beginning.
		pub last_period: BlockNumber,
		/// The total amount of funds on hold for receipts. This doesn't include the pot or funds
		/// on hold for bids.
		pub receipts_on_hold: Balance,
	}

	pub struct OnEmptyQueueTotals<T>(core::marker::PhantomData<T>);
	impl<T: Config> Get<QueueTotalsTypeOf<T>> for OnEmptyQueueTotals<T> {
		fn get() -> QueueTotalsTypeOf<T> {
			BoundedVec::truncate_from(vec![
				(0, Zero::zero());
				<T as Config>::QueueCount::get() as usize
			])
		}
	}

	/// The totals of items and balances within each queue. Saves a lot of storage reads in the
	/// case of sparsely packed queues.
	///
	/// The vector is indexed by duration in `Period`s, offset by one, so information on the queue
	/// whose duration is one `Period` would be storage `0`.
	#[pallet::storage]
	pub type QueueTotals<T: Config> =
		StorageValue<_, QueueTotalsTypeOf<T>, ValueQuery, OnEmptyQueueTotals<T>>;

	/// The queues of bids. Indexed by duration (in `Period`s).
	#[pallet::storage]
	pub type Queues<T: Config> =
		StorageMap<_, Blake2_128Concat, u32, BoundedVec<BidOf<T>, T::MaxQueueLen>, ValueQuery>;

	/// Summary information over the general state.
	#[pallet::storage]
	pub type Summary<T> = StorageValue<_, SummaryRecordOf<T>, ValueQuery>;

	/// The currently outstanding receipts, indexed according to the order of creation.
	#[pallet::storage]
	pub type Receipts<T> =
		StorageMap<_, Blake2_128Concat, ReceiptIndex, ReceiptRecordOf<T>, OptionQuery>;

	#[pallet::event]
	#[pallet::generate_deposit(pub(super) fn deposit_event)]
	pub enum Event<T: Config> {
		/// A bid was successfully placed.
		BidPlaced { who: T::AccountId, amount: BalanceOf<T>, duration: u32 },
		/// A bid was successfully removed (before being accepted).
		BidRetracted { who: T::AccountId, amount: BalanceOf<T>, duration: u32 },
		/// A bid was dropped from a queue because of another, more substantial, bid was present.
		BidDropped { who: T::AccountId, amount: BalanceOf<T>, duration: u32 },
		/// A bid was accepted. The balance may not be released until expiry.
		Issued {
			/// The identity of the receipt.
			index: ReceiptIndex,
			/// The block number at which the receipt may be thawed.
			expiry: BlockNumberFor<T>,
			/// The owner of the receipt.
			who: T::AccountId,
			/// The proportion of the effective total issuance which the receipt represents.
			proportion: Perquintill,
			/// The amount of funds which were debited from the owner.
			amount: BalanceOf<T>,
		},
		/// An receipt has been (at least partially) thawed.
		Thawed {
			/// The identity of the receipt.
			index: ReceiptIndex,
			/// The owner.
			who: T::AccountId,
			/// The proportion of the effective total issuance by which the owner was debited.
			proportion: Perquintill,
			/// The amount by which the owner was credited.
			amount: BalanceOf<T>,
			/// If `true` then the receipt is done.
			dropped: bool,
		},
		/// An automatic funding of the deficit was made.
		Funded { deficit: BalanceOf<T> },
		/// A receipt was transferred.
		Transferred { from: T::AccountId, to: T::AccountId, index: ReceiptIndex },
	}

	#[pallet::error]
	pub enum Error<T> {
		/// The duration of the bid is less than one.
		DurationTooSmall,
		/// The duration is the bid is greater than the number of queues.
		DurationTooBig,
		/// The amount of the bid is less than the minimum allowed.
		AmountTooSmall,
		/// The queue for the bid's duration is full and the amount bid is too low to get in
		/// through replacing an existing bid.
		BidTooLow,
		/// Receipt index is unknown.
		UnknownReceipt,
		/// Not the owner of the receipt.
		NotOwner,
		/// Bond not yet at expiry date.
		NotExpired,
		/// The given bid for retraction is not found.
		UnknownBid,
		/// The portion supplied is beyond the value of the receipt.
		PortionTooBig,
		/// Not enough funds are held to pay out.
		Unfunded,
		/// There are enough funds for what is required.
		AlreadyFunded,
		/// The thaw throttle has been reached for this period.
		Throttled,
		/// The operation would result in a receipt worth an insignificant value.
		MakesDust,
		/// The receipt is already communal.
		AlreadyCommunal,
		/// The receipt is already private.
		AlreadyPrivate,
	}

	/// A reason for the NIS pallet placing a hold on funds.
	#[pallet::composite_enum]
	pub enum HoldReason {
		/// The NIS Pallet has reserved it for a non-fungible receipt.
		#[codec(index = 0)]
		NftReceipt,
	}

	pub(crate) struct WeightCounter {
		pub(crate) used: Weight,
		pub(crate) limit: Weight,
	}
	impl WeightCounter {
		#[allow(dead_code)]
		pub(crate) fn unlimited() -> Self {
			WeightCounter { used: Weight::zero(), limit: Weight::max_value() }
		}
		fn check_accrue(&mut self, w: Weight) -> bool {
			let test = self.used.saturating_add(w);
			if test.any_gt(self.limit) {
				false
			} else {
				self.used = test;
				true
			}
		}
		fn can_accrue(&mut self, w: Weight) -> bool {
			self.used.saturating_add(w).all_lte(self.limit)
		}
	}

	#[pallet::hooks]
	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
		fn on_initialize(n: BlockNumberFor<T>) -> Weight {
			let mut weight_counter =
				WeightCounter { used: Weight::zero(), limit: T::MaxIntakeWeight::get() };
			if T::IntakePeriod::get().is_zero() || (n % T::IntakePeriod::get()).is_zero() {
				if weight_counter.check_accrue(T::WeightInfo::process_queues()) {
					Self::process_queues(
						T::Target::get(),
						T::QueueCount::get(),
						u32::max_value(),
						&mut weight_counter,
					)
				}
			}
			weight_counter.used
		}

		fn integrity_test() {
			assert!(!T::IntakePeriod::get().is_zero());
			assert!(!T::MaxQueueLen::get().is_zero());
		}
	}

	#[pallet::call]
	impl<T: Config> Pallet<T> {
		/// Place a bid.
		///
		/// Origin must be Signed, and account must have at least `amount` in free balance.
		///
		/// - `amount`: The amount of the bid; these funds will be reserved, and if/when
		///   consolidated, removed. Must be at least `MinBid`.
		/// - `duration`: The number of periods before which the newly consolidated bid may be
		///   thawed. Must be greater than 1 and no more than `QueueCount`.
		///
		/// Complexities:
		/// - `Queues[duration].len()` (just take max).
		#[pallet::call_index(0)]
		#[pallet::weight(T::WeightInfo::place_bid_max())]
		pub fn place_bid(
			origin: OriginFor<T>,
			#[pallet::compact] amount: BalanceOf<T>,
			duration: u32,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			ensure!(amount >= T::MinBid::get(), Error::<T>::AmountTooSmall);
			let queue_count = T::QueueCount::get() as usize;
			let queue_index = duration.checked_sub(1).ok_or(Error::<T>::DurationTooSmall)? as usize;
			ensure!(queue_index < queue_count, Error::<T>::DurationTooBig);

			let net = Queues::<T>::try_mutate(
				duration,
				|q| -> Result<(u32, BalanceOf<T>), DispatchError> {
					let queue_full = q.len() == T::MaxQueueLen::get() as usize;
					ensure!(!queue_full || q[0].amount < amount, Error::<T>::BidTooLow);
					T::Currency::hold(&HoldReason::NftReceipt.into(), &who, amount)?;

					// queue is <Ordered: Lowest ... Highest><Fifo: Last ... First>
					let mut bid = Bid { amount, who: who.clone() };
					let net = if queue_full {
						core::mem::swap(&mut q[0], &mut bid);
						let _ = T::Currency::release(
							&HoldReason::NftReceipt.into(),
							&bid.who,
							bid.amount,
							BestEffort,
						);
						Self::deposit_event(Event::<T>::BidDropped {
							who: bid.who,
							amount: bid.amount,
							duration,
						});
						(0, amount - bid.amount)
					} else {
						q.try_insert(0, bid).expect("verified queue was not full above. qed.");
						(1, amount)
					};

					let sorted_item_count = q.len().saturating_sub(T::FifoQueueLen::get() as usize);
					if sorted_item_count > 1 {
						q[0..sorted_item_count].sort_by_key(|x| x.amount);
					}

					Ok(net)
				},
			)?;
			QueueTotals::<T>::mutate(|qs| {
				qs.bounded_resize(queue_count, (0, Zero::zero()));
				qs[queue_index].0 += net.0;
				qs[queue_index].1.saturating_accrue(net.1);
			});
			Self::deposit_event(Event::BidPlaced { who, amount, duration });

			Ok(())
		}

		/// Retract a previously placed bid.
		///
		/// Origin must be Signed, and the account should have previously issued a still-active bid
		/// of `amount` for `duration`.
		///
		/// - `amount`: The amount of the previous bid.
		/// - `duration`: The duration of the previous bid.
		#[pallet::call_index(1)]
		#[pallet::weight(T::WeightInfo::retract_bid(T::MaxQueueLen::get()))]
		pub fn retract_bid(
			origin: OriginFor<T>,
			#[pallet::compact] amount: BalanceOf<T>,
			duration: u32,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			let queue_count = T::QueueCount::get() as usize;
			let queue_index = duration.checked_sub(1).ok_or(Error::<T>::DurationTooSmall)? as usize;
			ensure!(queue_index < queue_count, Error::<T>::DurationTooBig);

			let bid = Bid { amount, who };

			let mut queue = Queues::<T>::get(duration);
			let pos = queue.iter().position(|i| i == &bid).ok_or(Error::<T>::UnknownBid)?;
			queue.remove(pos);
			let new_len = queue.len() as u32;

			T::Currency::release(&HoldReason::NftReceipt.into(), &bid.who, bid.amount, BestEffort)?;

			Queues::<T>::insert(duration, queue);
			QueueTotals::<T>::mutate(|qs| {
				qs.bounded_resize(queue_count, (0, Zero::zero()));
				qs[queue_index].0 = new_len;
				qs[queue_index].1.saturating_reduce(bid.amount);
			});

			Self::deposit_event(Event::BidRetracted { who: bid.who, amount: bid.amount, duration });

			Ok(())
		}

		/// Ensure we have sufficient funding for all potential payouts.
		///
		/// - `origin`: Must be accepted by `FundOrigin`.
		#[pallet::call_index(2)]
		#[pallet::weight(T::WeightInfo::fund_deficit())]
		pub fn fund_deficit(origin: OriginFor<T>) -> DispatchResult {
			T::FundOrigin::ensure_origin(origin)?;
			let summary: SummaryRecordOf<T> = Summary::<T>::get();
			let our_account = Self::account_id();
			let issuance = Self::issuance_with(&our_account, &summary);
			let deficit = issuance.required.saturating_sub(issuance.holdings);
			ensure!(!deficit.is_zero(), Error::<T>::AlreadyFunded);
			T::Deficit::on_unbalanced(T::Currency::deposit(&our_account, deficit, Exact)?);
			Self::deposit_event(Event::<T>::Funded { deficit });
			Ok(())
		}

		/// Reduce or remove an outstanding receipt, placing the according proportion of funds into
		/// the account of the owner.
		///
		/// - `origin`: Must be Signed and the account must be the owner of the receipt `index` as
		///   well as any fungible counterpart.
		/// - `index`: The index of the receipt.
		/// - `portion`: If `Some`, then only the given portion of the receipt should be thawed. If
		///   `None`, then all of it should be.
		#[pallet::call_index(3)]
		#[pallet::weight(T::WeightInfo::thaw_private())]
		pub fn thaw_private(
			origin: OriginFor<T>,
			#[pallet::compact] index: ReceiptIndex,
			maybe_proportion: Option<Perquintill>,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			// Look for `index`
			let mut receipt: ReceiptRecordOf<T> =
				Receipts::<T>::get(index).ok_or(Error::<T>::UnknownReceipt)?;
			// If found, check the owner is `who`.
			let (owner, mut on_hold) = receipt.owner.ok_or(Error::<T>::AlreadyCommunal)?;
			ensure!(owner == who, Error::<T>::NotOwner);

			let now = frame_system::Pallet::<T>::block_number();
			ensure!(now >= receipt.expiry, Error::<T>::NotExpired);

			let mut summary: SummaryRecordOf<T> = Summary::<T>::get();

			let proportion = if let Some(proportion) = maybe_proportion {
				ensure!(proportion <= receipt.proportion, Error::<T>::PortionTooBig);
				let remaining = receipt.proportion.saturating_sub(proportion);
				ensure!(
					remaining.is_zero() || remaining >= T::MinReceipt::get(),
					Error::<T>::MakesDust
				);
				proportion
			} else {
				receipt.proportion
			};

			let (throttle, throttle_period) = T::ThawThrottle::get();
			if now.saturating_sub(summary.last_period) >= throttle_period {
				summary.thawed = Zero::zero();
				summary.last_period = now;
			}
			summary.thawed.saturating_accrue(proportion);
			ensure!(summary.thawed <= throttle, Error::<T>::Throttled);

			// Multiply the proportion it is by the total issued.
			let our_account = Self::account_id();
			let effective_issuance = Self::issuance_with(&our_account, &summary).effective;
			//			let amount = proportion.mul_ceil(effective_issuance);
			let amount = proportion * effective_issuance;

			receipt.proportion.saturating_reduce(proportion);
			summary.proportion_owed.saturating_reduce(proportion);

			let dropped = receipt.proportion.is_zero();

			if amount > on_hold {
				T::Currency::release(&HoldReason::NftReceipt.into(), &who, on_hold, Exact)?;
				let deficit = amount - on_hold;
				// Try to transfer deficit from pot to receipt owner.
				summary.receipts_on_hold.saturating_reduce(on_hold);
				on_hold = Zero::zero();
				T::Currency::transfer(&our_account, &who, deficit, Expendable)
					.map_err(|_| Error::<T>::Unfunded)?;
			} else {
				on_hold.saturating_reduce(amount);
				summary.receipts_on_hold.saturating_reduce(amount);
				if dropped && !on_hold.is_zero() {
					// Reclaim any remainder:
					// Transfer excess of `on_hold` to the pot if we have now fully compensated for
					// the receipt.
					T::Currency::transfer_on_hold(
						&HoldReason::NftReceipt.into(),
						&who,
						&our_account,
						on_hold,
						Exact,
						Free,
						Polite,
					)
					.map(|_| ())
					// We ignore this error as it just means the amount we're trying to deposit is
					// dust and the beneficiary account doesn't exist.
					.or_else(|e| {
						if e == TokenError::CannotCreate.into() {
							Ok(())
						} else {
							Err(e)
						}
					})?;
					summary.receipts_on_hold.saturating_reduce(on_hold);
				}
				T::Currency::release(&HoldReason::NftReceipt.into(), &who, amount, Exact)?;
			}

			if dropped {
				Receipts::<T>::remove(index);
			} else {
				receipt.owner = Some((owner, on_hold));
				Receipts::<T>::insert(index, &receipt);
			}
			Summary::<T>::put(&summary);

			Self::deposit_event(Event::Thawed { index, who, amount, proportion, dropped });

			Ok(())
		}

		/// Reduce or remove an outstanding receipt, placing the according proportion of funds into
		/// the account of the owner.
		///
		/// - `origin`: Must be Signed and the account must be the owner of the fungible counterpart
		///   for receipt `index`.
		/// - `index`: The index of the receipt.
		#[pallet::call_index(4)]
		#[pallet::weight(T::WeightInfo::thaw_communal())]
		pub fn thaw_communal(
			origin: OriginFor<T>,
			#[pallet::compact] index: ReceiptIndex,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			// Look for `index`
			let receipt: ReceiptRecordOf<T> =
				Receipts::<T>::get(index).ok_or(Error::<T>::UnknownReceipt)?;
			// If found, check it is actually communal.
			ensure!(receipt.owner.is_none(), Error::<T>::NotOwner);
			let now = frame_system::Pallet::<T>::block_number();
			ensure!(now >= receipt.expiry, Error::<T>::NotExpired);

			let mut summary: SummaryRecordOf<T> = Summary::<T>::get();

			let (throttle, throttle_period) = T::ThawThrottle::get();
			if now.saturating_sub(summary.last_period) >= throttle_period {
				summary.thawed = Zero::zero();
				summary.last_period = now;
			}
			summary.thawed.saturating_accrue(receipt.proportion);
			ensure!(summary.thawed <= throttle, Error::<T>::Throttled);

			let cp_amount = T::CounterpartAmount::convert(receipt.proportion);
			T::Counterpart::burn_from(&who, cp_amount, Expendable, Exact, Polite)?;

			// Multiply the proportion it is by the total issued.
			let our_account = Self::account_id();
			let effective_issuance = Self::issuance_with(&our_account, &summary).effective;
			let amount = receipt.proportion * effective_issuance;

			summary.proportion_owed.saturating_reduce(receipt.proportion);

			// Try to transfer amount owed from pot to receipt owner.
			T::Currency::transfer(&our_account, &who, amount, Expendable)
				.map_err(|_| Error::<T>::Unfunded)?;

			Receipts::<T>::remove(index);
			Summary::<T>::put(&summary);

			let e =
				Event::Thawed { index, who, amount, proportion: receipt.proportion, dropped: true };
			Self::deposit_event(e);

			Ok(())
		}

		/// Make a private receipt communal and create fungible counterparts for its owner.
		#[pallet::call_index(5)]
		#[pallet::weight(T::WeightInfo::communify())]
		pub fn communify(
			origin: OriginFor<T>,
			#[pallet::compact] index: ReceiptIndex,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			// Look for `index`
			let mut receipt: ReceiptRecordOf<T> =
				Receipts::<T>::get(index).ok_or(Error::<T>::UnknownReceipt)?;

			// Check it's not already communal and make it so.
			let (owner, on_hold) = receipt.owner.take().ok_or(Error::<T>::AlreadyCommunal)?;

			// If found, check the owner is `who`.
			ensure!(owner == who, Error::<T>::NotOwner);

			// Unreserve and transfer the funds to the pot.
			let reason = HoldReason::NftReceipt.into();
			let us = Self::account_id();
			T::Currency::transfer_on_hold(&reason, &who, &us, on_hold, Exact, Free, Polite)
				.map_err(|_| Error::<T>::Unfunded)?;

			// Record that we've moved the amount reserved.
			let mut summary: SummaryRecordOf<T> = Summary::<T>::get();
			summary.receipts_on_hold.saturating_reduce(on_hold);
			Summary::<T>::put(&summary);
			Receipts::<T>::insert(index, &receipt);

			// Mint fungibles.
			let fung_eq = T::CounterpartAmount::convert(receipt.proportion);
			let _ = T::Counterpart::mint_into(&who, fung_eq).defensive();

			Ok(())
		}

		/// Make a communal receipt private and burn fungible counterparts from its owner.
		#[pallet::call_index(6)]
		#[pallet::weight(T::WeightInfo::privatize())]
		pub fn privatize(
			origin: OriginFor<T>,
			#[pallet::compact] index: ReceiptIndex,
		) -> DispatchResult {
			let who = ensure_signed(origin)?;

			// Look for `index`
			let mut receipt: ReceiptRecordOf<T> =
				Receipts::<T>::get(index).ok_or(Error::<T>::UnknownReceipt)?;

			// If found, check there is no owner.
			ensure!(receipt.owner.is_none(), Error::<T>::AlreadyPrivate);

			// Multiply the proportion it is by the total issued.
			let mut summary: SummaryRecordOf<T> = Summary::<T>::get();
			let our_account = Self::account_id();
			let effective_issuance = Self::issuance_with(&our_account, &summary).effective;
			let max_amount = receipt.proportion * effective_issuance;
			// Avoid trying to place more in the account's reserve than we have available in the pot
			let amount = max_amount.min(T::Currency::balance(&our_account));

			// Burn fungible counterparts.
			T::Counterpart::burn_from(
				&who,
				T::CounterpartAmount::convert(receipt.proportion),
				Expendable,
				Exact,
				Polite,
			)?;

			// Transfer the funds from the pot to the owner and reserve
			let reason = HoldReason::NftReceipt.into();
			let us = Self::account_id();
			T::Currency::transfer_and_hold(&reason, &us, &who, amount, Exact, Expendable, Polite)?;

			// Record that we've moved the amount reserved.
			summary.receipts_on_hold.saturating_accrue(amount);

			receipt.owner = Some((who, amount));

			Summary::<T>::put(&summary);
			Receipts::<T>::insert(index, &receipt);

			Ok(())
		}
	}

	/// Issuance information returned by `issuance()`.
	#[derive(Debug)]
	pub struct IssuanceInfo<Balance> {
		/// The balance held by this pallet instance together with the balances on hold across
		/// all receipt-owning accounts.
		pub holdings: Balance,
		/// The (non-ignored) issuance in the system, not including this pallet's account.
		pub other: Balance,
		/// The effective total issuance, hypothetically if all outstanding receipts were thawed at
		/// present.
		pub effective: Balance,
		/// The amount needed to be accessible to this pallet in case all outstanding receipts were
		/// thawed at present. If it is more than `holdings`, then the pallet will need funding.
		pub required: Balance,
	}

	impl<T: Config> NftInspect<T::AccountId> for Pallet<T> {
		type ItemId = ReceiptIndex;

		fn owner(item: &ReceiptIndex) -> Option<T::AccountId> {
			Receipts::<T>::get(item).and_then(|r| r.owner).map(|(who, _)| who)
		}

		fn attribute(item: &Self::ItemId, key: &[u8]) -> Option<Vec<u8>> {
			let item = Receipts::<T>::get(item)?;
			match key {
				b"proportion" => Some(item.proportion.encode()),
				b"expiry" => Some(item.expiry.encode()),
				b"owner" => item.owner.as_ref().map(|x| x.0.encode()),
				b"on_hold" => item.owner.as_ref().map(|x| x.1.encode()),
				_ => None,
			}
		}
	}

	impl<T: Config> NftTransfer<T::AccountId> for Pallet<T> {
		fn transfer(index: &ReceiptIndex, dest: &T::AccountId) -> DispatchResult {
			let mut item = Receipts::<T>::get(index).ok_or(TokenError::UnknownAsset)?;
			let (owner, on_hold) = item.owner.take().ok_or(Error::<T>::AlreadyCommunal)?;

			let reason = HoldReason::NftReceipt.into();
			T::Currency::transfer_on_hold(&reason, &owner, dest, on_hold, Exact, OnHold, Polite)?;

			item.owner = Some((dest.clone(), on_hold));
			Receipts::<T>::insert(&index, &item);
			Pallet::<T>::deposit_event(Event::<T>::Transferred {
				from: owner,
				to: dest.clone(),
				index: *index,
			});
			Ok(())
		}
	}

	impl<T: Config> Pallet<T> {
		/// The account ID of the reserves.
		///
		/// This actually does computation. If you need to keep using it, then make sure you cache
		/// the value and only call this once.
		pub fn account_id() -> T::AccountId {
			T::PalletId::get().into_account_truncating()
		}

		/// Returns information on the issuance within the system.
		pub fn issuance() -> IssuanceInfo<BalanceOf<T>> {
			Self::issuance_with(&Self::account_id(), &Summary::<T>::get())
		}

		/// Returns information on the issuance within the system
		///
		/// This function is equivalent to `issuance`, except that it accepts arguments rather than
		/// queries state. If the arguments are already known, then this may be slightly more
		/// performant.
		///
		/// - `our_account`: The value returned by `Self::account_id()`.
		/// - `summary`: The value returned by `Summary::<T>::get()`.
		pub fn issuance_with(
			our_account: &T::AccountId,
			summary: &SummaryRecordOf<T>,
		) -> IssuanceInfo<BalanceOf<T>> {
			let total_issuance =
				T::Currency::active_issuance().saturating_sub(T::IgnoredIssuance::get());
			let holdings =
				T::Currency::balance(our_account).saturating_add(summary.receipts_on_hold);
			let other = total_issuance.saturating_sub(holdings);
			let effective =
				summary.proportion_owed.left_from_one().saturating_reciprocal_mul(other);
			let required = summary.proportion_owed * effective;
			IssuanceInfo { holdings, other, effective, required }
		}

		/// Process some bids into receipts up to a `target` total of all receipts.
		///
		/// Touch at most `max_queues`.
		///
		/// Return the weight used.
		pub(crate) fn process_queues(
			target: Perquintill,
			max_queues: u32,
			max_bids: u32,
			weight: &mut WeightCounter,
		) {
			let mut summary: SummaryRecordOf<T> = Summary::<T>::get();
			if summary.proportion_owed >= target {
				return
			}

			let now = frame_system::Pallet::<T>::block_number();
			let our_account = Self::account_id();
			let issuance: IssuanceInfoOf<T> = Self::issuance_with(&our_account, &summary);
			let mut remaining = target.saturating_sub(summary.proportion_owed) * issuance.effective;

			let mut queues_hit = 0;
			let mut bids_hit = 0;
			let mut totals = QueueTotals::<T>::get();
			let queue_count = T::QueueCount::get();
			totals.bounded_resize(queue_count as usize, (0, Zero::zero()));
			for duration in (1..=queue_count).rev() {
				if totals[duration as usize - 1].0.is_zero() {
					continue
				}
				if remaining.is_zero() || queues_hit >= max_queues
					|| !weight.check_accrue(T::WeightInfo::process_queue())
					// No point trying to process a queue if we can't process a single bid.
					|| !weight.can_accrue(T::WeightInfo::process_bid())
				{
					break
				}

				let b = Self::process_queue(
					duration,
					now,
					&our_account,
					&issuance,
					max_bids.saturating_sub(bids_hit),
					&mut remaining,
					&mut totals[duration as usize - 1],
					&mut summary,
					weight,
				);

				bids_hit.saturating_accrue(b);
				queues_hit.saturating_inc();
			}
			QueueTotals::<T>::put(&totals);
			Summary::<T>::put(&summary);
		}

		pub(crate) fn process_queue(
			duration: u32,
			now: BlockNumberFor<T>,
			our_account: &T::AccountId,
			issuance: &IssuanceInfo<BalanceOf<T>>,
			max_bids: u32,
			remaining: &mut BalanceOf<T>,
			queue_total: &mut (u32, BalanceOf<T>),
			summary: &mut SummaryRecordOf<T>,
			weight: &mut WeightCounter,
		) -> u32 {
			let mut queue: BoundedVec<BidOf<T>, _> = Queues::<T>::get(&duration);
			let expiry = now.saturating_add(T::BasePeriod::get().saturating_mul(duration.into()));
			let mut count = 0;

			while count < max_bids &&
				!queue.is_empty() &&
				!remaining.is_zero() &&
				weight.check_accrue(T::WeightInfo::process_bid())
			{
				let bid = match queue.pop() {
					Some(b) => b,
					None => break,
				};
				if let Some(bid) = Self::process_bid(
					bid,
					expiry,
					our_account,
					issuance,
					remaining,
					&mut queue_total.1,
					summary,
				) {
					queue.try_push(bid).expect("just popped, so there must be space. qed");
					// This should exit at the next iteration (though nothing will break if it
					// doesn't).
				}
				count.saturating_inc();
			}
			queue_total.0 = queue.len() as u32;
			Queues::<T>::insert(&duration, &queue);
			count
		}

		pub(crate) fn process_bid(
			mut bid: BidOf<T>,
			expiry: BlockNumberFor<T>,
			_our_account: &T::AccountId,
			issuance: &IssuanceInfo<BalanceOf<T>>,
			remaining: &mut BalanceOf<T>,
			queue_amount: &mut BalanceOf<T>,
			summary: &mut SummaryRecordOf<T>,
		) -> Option<BidOf<T>> {
			let result = if *remaining < bid.amount {
				let overflow = bid.amount - *remaining;
				bid.amount = *remaining;
				Some(Bid { amount: overflow, who: bid.who.clone() })
			} else {
				None
			};
			let amount = bid.amount;
			summary.receipts_on_hold.saturating_accrue(amount);

			// Can never overflow due to block above.
			remaining.saturating_reduce(amount);
			// Should never underflow since it should track the total of the
			// bids exactly, but we'll be defensive.
			queue_amount.defensive_saturating_reduce(amount);

			// Now to activate the bid...
			let n = amount;
			let d = issuance.effective;
			let proportion = Perquintill::from_rational_with_rounding(n, d, Rounding::Down)
				.defensive_unwrap_or_default();
			let who = bid.who;
			let index = summary.index;
			summary.proportion_owed.defensive_saturating_accrue(proportion);
			summary.index += 1;

			let e = Event::Issued { index, expiry, who: who.clone(), amount, proportion };
			Self::deposit_event(e);
			let receipt = ReceiptRecord { proportion, owner: Some((who, amount)), expiry };
			Receipts::<T>::insert(index, receipt);

			result
		}
	}
}