| 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 |
44×
43×
42×
41×
41×
41×
41×
41×
41×
41×
41×
41×
41×
41×
41×
507×
475×
475×
434×
434×
434×
371×
370×
369×
369×
369×
366×
366×
366×
361×
361×
361×
361×
359×
359×
359×
359×
359×
1487×
94×
94×
94×
94×
93×
92×
92×
92×
92×
88×
88×
88×
87×
86×
86×
478×
478×
86×
86×
86×
86×
86×
86×
478×
468×
468×
85×
16×
14×
9×
8×
8×
18×
16×
16×
2×
1×
33×
58×
58×
58×
58×
3×
11×
80×
79×
78×
77×
77×
86×
85×
84×
83×
83×
560×
| // SPDX-License-Identifier: BlueOak-1.0.0
pragma solidity 0.8.17;
// solhint-disable-next-line max-line-length
import "@openzeppelin/contracts-upgradeable/token/ERC20/utils/SafeERC20Upgradeable.sol";
import "../interfaces/IMain.sol";
import "../interfaces/IRToken.sol";
import "../libraries/Fixed.sol";
import "../libraries/Throttle.sol";
import "../vendor/ERC20PermitUpgradeable.sol";
import "./mixins/Component.sol";
/**
* @title RTokenP1
* An ERC20 with an elastic supply and governable exchange rate to basket units.
*/
contract RTokenP1 is ComponentP1, ERC20PermitUpgradeable, IRToken {
using FixLib for uint192;
using ThrottleLib for ThrottleLib.Throttle;
using SafeERC20Upgradeable for IERC20Upgradeable;
uint256 public constant MIN_THROTTLE_RATE_AMT = 1e18; // {qRTok}
uint256 public constant MAX_THROTTLE_RATE_AMT = 1e48; // {qRTok}
uint192 public constant MAX_THROTTLE_PCT_AMT = 1e18; // {qRTok}
uint192 public constant MIN_EXCHANGE_RATE = 1e9; // D18{BU/rTok}
uint192 public constant MAX_EXCHANGE_RATE = 1e27; // D18{BU/rTok}
/// The mandate describes what goals its governors should try to achieve. By succinctly
/// explaining the RToken’s purpose and what the RToken is intended to do, it provides common
/// ground for the governors to decide upon priorities and how to weigh tradeoffs.
///
/// Example Mandates:
///
/// - Capital preservation first. Spending power preservation second. Permissionless
/// access third.
/// - Capital preservation above all else. All revenues fund the over-collateralization pool.
/// - Risk-neutral pursuit of profit for token holders.
/// Maximize (gross revenue - payments for over-collateralization and governance).
/// - This RToken holds only FooCoin, to provide a trade for hedging against its
/// possible collapse.
///
/// The mandate may also be a URI to a longer body of text, presumably on IPFS or some other
/// immutable data store.
string public mandate;
// ==== Peer components ====
IAssetRegistry private assetRegistry;
IBasketHandler private basketHandler;
IBackingManager private backingManager;
IFurnace private furnace;
// The number of baskets that backingManager must hold
// in order for this RToken to be fully collateralized.
// The exchange rate for issuance and redemption is totalSupply()/basketsNeeded {BU}/{qRTok}.
uint192 public basketsNeeded; // D18{BU}
// === Supply throttles ===
ThrottleLib.Throttle private issuanceThrottle;
ThrottleLib.Throttle private redemptionThrottle;
function init(
IMain main_,
string calldata name_,
string calldata symbol_,
string calldata mandate_,
ThrottleLib.Params calldata issuanceThrottleParams_,
ThrottleLib.Params calldata redemptionThrottleParams_
) external initializer {
require(bytes(name_).length > 0, "name empty");
require(bytes(symbol_).length > 0, "symbol empty");
require(bytes(mandate_).length > 0, "mandate empty");
__Component_init(main_);
__ERC20_init(name_, symbol_);
__ERC20Permit_init(name_);
assetRegistry = main_.assetRegistry();
basketHandler = main_.basketHandler();
backingManager = main_.backingManager();
furnace = main_.furnace();
mandate = mandate_;
setIssuanceThrottleParams(issuanceThrottleParams_);
setRedemptionThrottleParams(redemptionThrottleParams_);
issuanceThrottle.lastTimestamp = uint48(block.timestamp);
redemptionThrottle.lastTimestamp = uint48(block.timestamp);
}
/// after fn(), assert exchangeRate in [MIN_EXCHANGE_RATE, MAX_EXCHANGE_RATE]
modifier exchangeRateIsValidAfter() {
_;
uint256 supply = totalSupply();
if (supply == 0) return;
// Note: These are D18s, even though they are uint256s. This is because
// we cannot assume we stay inside our valid range here, as that is what
// we are checking in the first place
uint256 low = (FIX_ONE_256 * basketsNeeded) / supply; // D18{BU/rTok}
uint256 high = (FIX_ONE_256 * basketsNeeded + (supply - 1)) / supply; // D18{BU/rTok}
// here we take advantage of an implicit upcast from uint192 exchange rates
require(low >= MIN_EXCHANGE_RATE && high <= MAX_EXCHANGE_RATE, "BU rate out of range");
}
/// Issue an RToken with basket collateral
/// @param amount {qTok} The quantity of RToken to issue
/// @custom:interaction nearly CEI, but see comments around handling of refunds
function issue(uint256 amount) public {
issueTo(_msgSender(), amount);
}
/// Issue an RToken with basket collateral, to a particular recipient
/// @param recipient The address to receive the issued RTokens
/// @param amount {qRTok} The quantity of RToken to issue
/// @custom:interaction
// untestable:
// `else` branch of `exchangeRateIsValidAfter` (ie. revert)
// BU exchange rate cannot decrease, and it can only increase when < FIX_ONE.
function issueTo(address recipient, uint256 amount)
public
notPausedOrFrozen
EexchangeRateIsValidAfter
{
require(amount > 0, "Cannot issue zero");
// == Refresh ==
assetRegistry.refresh();
// == Checks-effects block ==
address issuer = _msgSender(); // OK to save: it can't be changed in reentrant runs
// Ensure SOUND basket
require(basketHandler.status() == CollateralStatus.SOUND, "basket unsound");
furnace.melt();
uint256 supply = totalSupply();
// Revert if issuance exceeds either supply throttle
issuanceThrottle.useAvailable(supply, int256(amount)); // reverts on over-issuance
redemptionThrottle.useAvailable(supply, -int256(amount)); // shouldn't revert
// AT THIS POINT:
// all contract invariants hold
// furnace melting is up-to-date
// asset states are up-to-date
// throttle is up-to-date
// amtBaskets: the BU change to be recorded by this issuance
// D18{BU} = D18{BU} * {qRTok} / {qRTok}
// revert-on-overflow provided by FixLib functions
uint192 amtBaskets = supply > 0
? basketsNeeded.muluDivu(amount, supply, CEIL)
: _safeWrap(amount);
emit Issuance(issuer, recipient, amount, amtBaskets);
(address[] memory erc20s, uint256[] memory deposits) = basketHandler.quote(
amtBaskets,
CEIL
);
// Fixlib optimization:
// D18{BU} = D18{BU} + D18{BU}; uint192(+) is the same as Fix.plus
uint192 newBasketsNeeded = basketsNeeded + amtBaskets;
emit BasketsNeededChanged(basketsNeeded, newBasketsNeeded);
basketsNeeded = newBasketsNeeded;
// == Interactions: mint + transfer tokens to BackingManager ==
_mint(recipient, amount);
for (uint256 i = 0; i < erc20s.length; ++i) {
IERC20Upgradeable(erc20s[i]).safeTransferFrom(
issuer,
address(backingManager),
deposits[i]
);
}
}
/// Redeem RToken for basket collateral
/// @param amount {qTok} The quantity {qRToken} of RToken to redeem
/// @param basketNonce The nonce of the basket the redemption should be from; else reverts
/// @custom:interaction CEI
function redeem(uint256 amount, uint48 basketNonce) external {
redeemTo(_msgSender(), amount, basketNonce);
}
/// Redeem RToken for basket collateral to a particular recipient
// checks:
// amount > 0
// amount <= balanceOf(caller)
// basket is not DISABLED
//
// effects:
// (so totalSupply -= amount and balanceOf(caller) -= amount)
// basketsNeeded' / totalSupply' >== basketsNeeded / totalSupply
//
// actions:
// let erc20s = basketHandler.erc20s()
// burn(caller, amount)
// for each token in erc20s:
// let tokenAmt = (amount * basketsNeeded / totalSupply) baskets of support for token
// let prorataAmt = (amount / totalSupply) * token.balanceOf(backingManager)
// do token.transferFrom(backingManager, caller, min(tokenAmt, prorataAmt))
// untestable:
// `else` branch of `exchangeRateIsValidAfter` (ie. revert)
// BU exchange rate cannot decrease, and it can only increase when < FIX_ONE.
/// @param recipient The address to receive the backing collateral tokens
/// @param amount {qRTok} The quantity {qRToken} of RToken to redeem
/// @param basketNonce The nonce of the basket the redemption should be from; else reverts
/// @custom:interaction
function redeemTo(
address recipient,
uint256 amount,
uint48 basketNonce
) public notFrozen EexchangeRateIsValidAfter {
// == Refresh ==
assetRegistry.refresh();
// == Checks and Effects ==
address redeemer = _msgSender();
require(amount > 0, "Cannot redeem zero");
require(amount <= balanceOf(redeemer), "insufficient balance");
// Failure to melt results in a lower redemption price, so we can allow it when paused
// solhint-disable-next-line no-empty-blocks
try main.furnace().melt() {} catch {}
uint256 supply = totalSupply();
// Revert if redemption exceeds either supply throttle
issuanceThrottle.useAvailable(supply, -int256(amount));
redemptionThrottle.useAvailable(supply, int256(amount)); // reverts on over-redemption
// ==== Get basket redemption ====
// i.e, set (erc20s, amounts) = basketHandler.quote(amount * basketsNeeded / totalSupply)
// D18{BU} = D18{BU} * {qRTok} / {qRTok}
// downcast is safe: amount < totalSupply and basketsNeeded < 1e57 < 2^190 (just barely)
uint192 basketsRedeemed = basketsNeeded.muluDivu(amount, supply); // FLOOR
emit Redemption(redeemer, recipient, amount, basketsRedeemed);
require(basketHandler.nonce() == basketNonce, "non-current basket nonce");
(address[] memory erc20s, uint256[] memory amounts) = basketHandler.quote(
basketsRedeemed,
FLOOR
);
// ==== Prorate redemption ====
// i.e, set amounts = min(amounts, balances * amount / totalSupply)
// where balances[i] = erc20s[i].balanceOf(this)
// Bound each withdrawal by the prorata share, in case we're currently under-collateralized
uint256 erc20length = erc20s.length;
for (uint256 i = 0; i < erc20length; ++i) {
// {qTok} = {qTok} * {qRTok} / {qRTok}
uint256 prorata = mulDiv256(
IERC20Upgradeable(erc20s[i]).balanceOf(address(backingManager)),
amount,
supply
); // FLOOR
if (prorata < amounts[i]) amounts[i] = prorata;
}
uint192 newBasketsNeeded = basketsNeeded - basketsRedeemed;
emit BasketsNeededChanged(basketsNeeded, newBasketsNeeded);
basketsNeeded = newBasketsNeeded;
// == Interactions ==
// Accept and burn RToken, reverts if not enough balance to burn
_burn(redeemer, amount);
bool allZero = true;
for (uint256 i = 0; i < erc20length; ++i) {
if (amounts[i] == 0) continue;
if (allZero) allZero = false;
// Send withdrawal
IERC20Upgradeable(erc20s[i]).safeTransferFrom(
address(backingManager),
recipient,
amounts[i]
);
}
if (allZero) revert("empty redemption");
}
/// Mint a quantity of RToken to the `recipient`, decreasing the basket rate
/// @param recipient The recipient of the newly minted RToken
/// @param amtRToken {qRTok} The amtRToken to be minted
/// @custom:protected
// checks: unpaused; unfrozen; caller is backingManager
// effects:
// bal'[recipient] = bal[recipient] + amtRToken
// totalSupply' = totalSupply + amtRToken
//
// untestable:
// `else` branch of `exchangeRateIsValidAfter` (ie. revert) shows as uncovered
// but it is fully covered for `mint` (limitations of coverage plugin)
function mint(address recipient, uint256 amtRToken)
external
notPausedOrFrozen
EexchangeRateIsValidAfter
{
require(_msgSender() == address(backingManager), "not backing manager");
_mint(recipient, amtRToken);
}
/// Melt a quantity of RToken from the caller's account, increasing the basket rate
/// @param amtRToken {qRTok} The amtRToken to be melted
// checks: not paused or frozen
// effects:
// bal'[caller] = bal[caller] - amtRToken
// totalSupply' = totalSupply - amtRToken
//
// untestable:
// `else` branch of `exchangeRateIsValidAfter` (ie. revert) shows as uncovered
// but it is fully covered for `melt` (limitations of coverage plugin)
function melt(uint256 amtRToken) external EexchangeRateIsValidAfter {
require(_msgSender() == address(furnace), "furnace only");
_burn(_msgSender(), amtRToken);
emit Melted(amtRToken);
}
/// An affordance of last resort for Main in order to ensure re-capitalization
/// @custom:protected
// checks: unpaused; unfrozen; caller is backingManager
// effects: basketsNeeded' = basketsNeeded_
//
// untestable:
// `else` branch of `exchangeRateIsValidAfter` (ie. revert) shows as uncovered
// but it is fully covered for `setBasketsNeeded` (limitations of coverage plugin)
function setBasketsNeeded(uint192 basketsNeeded_)
external
notPausedOrFrozen
EexchangeRateIsValidAfter
{
require(_msgSender() == address(backingManager), "not backing manager");
emit BasketsNeededChanged(basketsNeeded, basketsNeeded_);
basketsNeeded = basketsNeeded_;
}
/// Sends all token balance of erc20 (if it is registered) to the BackingManager
/// @custom:interaction
function monetizeDonations(IERC20 erc20) external notPausedOrFrozen {
require(assetRegistry.isRegistered(erc20), "erc20 unregistered");
IERC20Upgradeable(address(erc20)).safeTransfer(
address(backingManager),
erc20.balanceOf(address(this))
);
}
// ==== Throttle setters/getters ====
/// @return {qRTok} The maximum issuance that can be performed in the current block
function issuanceAvailable() external view returns (uint256) {
return issuanceThrottle.currentlyAvailable(issuanceThrottle.hourlyLimit(totalSupply()));
}
/// @return available {qRTok} The maximum redemption that can be performed in the current block
function redemptionAvailable() external view returns (uint256 available) {
uint256 supply = totalSupply();
uint256 hourlyLimit = redemptionThrottle.hourlyLimit(supply);
available = redemptionThrottle.currentlyAvailable(hourlyLimit);
if (supply < available) available = supply;
}
/// @return The issuance throttle parametrization
function issuanceThrottleParams() external view returns (ThrottleLib.Params memory) {
return issuanceThrottle.params;
}
/// @return The redemption throttle parametrization
function redemptionThrottleParams() external view returns (ThrottleLib.Params memory) {
return redemptionThrottle.params;
}
/// @custom:governance
function setIssuanceThrottleParams(ThrottleLib.Params calldata params) public governance {
require(params.amtRate >= MIN_THROTTLE_RATE_AMT, "issuance amtRate too small");
require(params.amtRate <= MAX_THROTTLE_RATE_AMT, "issuance amtRate too big");
require(params.pctRate <= MAX_THROTTLE_PCT_AMT, "issuance pctRate too big");
emit IssuanceThrottleSet(issuanceThrottle.params, params);
issuanceThrottle.params = params;
}
/// @custom:governance
function setRedemptionThrottleParams(ThrottleLib.Params calldata params) public governance {
require(params.amtRate >= MIN_THROTTLE_RATE_AMT, "redemption amtRate too small");
require(params.amtRate <= MAX_THROTTLE_RATE_AMT, "redemption amtRate too big");
require(params.pctRate <= MAX_THROTTLE_PCT_AMT, "redemption pctRate too big");
emit RedemptionThrottleSet(redemptionThrottle.params, params);
redemptionThrottle.params = params;
}
// ==== Private ====
/**
* @dev Hook that is called before any transfer of tokens. This includes
* minting and burning.
*
* Calling conditions:
*
* - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
* will be transferred to `to`.
* - when `from` is zero, `amount` tokens will be minted for `to`.
* - when `to` is zero, `amount` of ``from``'s tokens will be burned.
* - `from` and `to` are never both zero.
*/
function _beforeTokenTransfer(
address,
address to,
uint256
) internal virtual override {
require(to != address(this), "RToken transfer to self");
}
/**
* @dev This empty reserved space is put in place to allow future versions to add new
* variables without shifting down storage in the inheritance chain.
* See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
*/
uint256[42] private __gap;
}
|