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
// 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.

//! The traits for putting freezes within a single fungible token class.

use crate::{ensure, traits::tokens::Fortitude};
use scale_info::TypeInfo;
use sp_arithmetic::{
	traits::{CheckedAdd, CheckedSub},
	ArithmeticError,
};
use sp_runtime::{DispatchResult, TokenError};

/// Trait for inspecting a fungible asset which can be frozen. Freezing is essentially setting a
/// minimum balance below which the total balance (inclusive of any funds placed on hold) may not
/// be normally allowed to drop. Generally, freezers will provide an "update" function such that
/// if the total balance does drop below the limit, then the freezer can update their housekeeping
/// accordingly.
pub trait Inspect<AccountId>: super::Inspect<AccountId> {
	/// An identifier for a freeze.
	type Id: codec::Encode + TypeInfo + 'static;

	/// Amount of funds held in reserve by `who` for the given `id`.
	fn balance_frozen(asset: Self::AssetId, id: &Self::Id, who: &AccountId) -> Self::Balance;

	/// The amount of the balance which can become frozen. Defaults to `total_balance()`.
	fn balance_freezable(asset: Self::AssetId, who: &AccountId) -> Self::Balance {
		Self::total_balance(asset, who)
	}

	/// Returns `true` if it's possible to introduce a freeze for the given `id` onto the
	/// account of `who`. This will be true as long as the implementor supports as many
	/// concurrent freeze locks as there are possible values of `id`.
	fn can_freeze(asset: Self::AssetId, id: &Self::Id, who: &AccountId) -> bool;
}

/// Trait for introducing, altering and removing locks to freeze an account's funds so they never
/// go below a set minimum.
pub trait Mutate<AccountId>: Inspect<AccountId> {
	/// Prevent actions which would reduce the balance of the account of `who` below the given
	/// `amount` and identify this restriction though the given `id`. Unlike `extend_freeze`, any
	/// outstanding freeze in place for `who` under the `id` are dropped.
	///
	/// If `amount` is zero, it is equivalent to using `thaw`.
	///
	/// Note that `amount` can be greater than the total balance, if desired.
	fn set_freeze(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
	) -> DispatchResult;

	/// Prevent the balance of the account of `who` from being reduced below the given `amount` and
	/// identify this restriction though the given `id`. Unlike `set_freeze`, this does not
	/// counteract any pre-existing freezes in place for `who` under the `id`. Also unlike
	/// `set_freeze`, in the case that `amount` is zero, this is no-op and never fails.
	///
	/// Note that more funds can be locked than the total balance, if desired.
	fn extend_freeze(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
	) -> DispatchResult;

	/// Remove an existing lock.
	fn thaw(asset: Self::AssetId, id: &Self::Id, who: &AccountId) -> DispatchResult;

	/// Attempt to alter the amount frozen under the given `id` to `amount`.
	///
	/// Fail if the account of `who` has fewer freezable funds than `amount`, unless `fortitude` is
	/// `Fortitude::Force`.
	fn set_frozen(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
		fortitude: Fortitude,
	) -> DispatchResult {
		let force = fortitude == Fortitude::Force;
		ensure!(
			force || Self::balance_freezable(asset.clone(), who) >= amount,
			TokenError::FundsUnavailable
		);
		Self::set_freeze(asset, id, who, amount)
	}

	/// Attempt to set the amount frozen under the given `id` to `amount`, iff this would increase
	/// the amount frozen under `id`. Do nothing otherwise.
	///
	/// Fail if the account of `who` has fewer freezable funds than `amount`, unless `fortitude` is
	/// `Fortitude::Force`.
	fn ensure_frozen(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
		fortitude: Fortitude,
	) -> DispatchResult {
		let force = fortitude == Fortitude::Force;
		ensure!(
			force || Self::balance_freezable(asset.clone(), who) >= amount,
			TokenError::FundsUnavailable
		);
		Self::extend_freeze(asset, id, who, amount)
	}

	/// Decrease the amount which is being frozen for a particular lock, failing in the case of
	/// underflow.
	fn decrease_frozen(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
	) -> DispatchResult {
		let a = Self::balance_frozen(asset.clone(), id, who)
			.checked_sub(&amount)
			.ok_or(ArithmeticError::Underflow)?;
		Self::set_frozen(asset, id, who, a, Fortitude::Polite)
	}

	/// Increase the amount which is being frozen for a particular lock, failing in the case that
	/// too little balance is available for being frozen.
	fn increase_frozen(
		asset: Self::AssetId,
		id: &Self::Id,
		who: &AccountId,
		amount: Self::Balance,
	) -> DispatchResult {
		let a = Self::balance_frozen(asset.clone(), id, who)
			.checked_add(&amount)
			.ok_or(ArithmeticError::Overflow)?;
		Self::set_frozen(asset, id, who, a, Fortitude::Polite)
	}
}