Enforce safety limits while borrowing, while computing max swap source, and max spot order base/quote (#642)

* --wip-- [skip ci]

* enforce safety limits while borrowing

Signed-off-by: microwavedcola1 <microwavedcola@gmail.com>

* --wip-- [skip ci]

* --wip-- [skip ci]

* --wip-- [skip ci]

* Fixes from review

Signed-off-by: microwavedcola1 <microwavedcola@gmail.com>

* Fixes from review

Signed-off-by: microwavedcola1 <microwavedcola@gmail.com>

---------

Signed-off-by: microwavedcola1 <microwavedcola@gmail.com>

ts/client/src/accounts/bank.ts

@@ -1,7 +1,7 @@
 import { BN } from '@coral-xyz/anchor';
 import { utf8 } from '@coral-xyz/anchor/dist/cjs/utils/bytes';
 import { PublicKey } from '@solana/web3.js';
-import { I80F48, I80F48Dto, ZERO_I80F48 } from '../numbers/I80F48';
+import { I80F48, I80F48Dto, ONE_I80F48, ZERO_I80F48 } from '../numbers/I80F48';
 import { As, toUiDecimals } from '../utils';
 import { OracleProvider } from './oracle';
 
@@ -397,17 +397,11 @@ export class Bank implements BankForHealth {
   }
 
   uiDeposits(): number {
-    return toUiDecimals(
-      this.indexedDeposits.mul(this.depositIndex),
-      this.mintDecimals,
-    );
+    return toUiDecimals(this.nativeDeposits(), this.mintDecimals);
   }
 
   uiBorrows(): number {
-    return toUiDecimals(
-      this.indexedBorrows.mul(this.borrowIndex),
-      this.mintDecimals,
-    );
+    return toUiDecimals(this.nativeBorrows(), this.mintDecimals);
   }
 
   /**
@@ -481,6 +475,48 @@ export class Bank implements BankForHealth {
   getDepositRateUi(): number {
     return this.getDepositRate().toNumber() * 100;
   }
+
+  getNetBorrowLimitPerWindow(): I80F48 {
+    return I80F48.fromI64(this.netBorrowLimitPerWindowQuote).div(this.price);
+  }
+
+  getBorrowLimitLeftInWindow(): I80F48 {
+    return this.getNetBorrowLimitPerWindow()
+      .sub(I80F48.fromI64(this.netBorrowsInWindow))
+      .max(ZERO_I80F48());
+  }
+
+  getNetBorrowLimitPerWindowUi(): number {
+    return toUiDecimals(this.getNetBorrowLimitPerWindow(), this.mintDecimals);
+  }
+
+  getMaxWithdraw(vaultBalance: BN, userDeposits = ZERO_I80F48()): I80F48 {
+    userDeposits = userDeposits.max(ZERO_I80F48());
+
+    // any borrow must respect the minVaultToDepositsRatio
+    const minVaultBalanceRequired = this.nativeDeposits().mul(
+      I80F48.fromNumber(this.minVaultToDepositsRatio),
+    );
+    const maxBorrowFromVault = I80F48.fromI64(vaultBalance)
+      .sub(minVaultBalanceRequired)
+      .max(ZERO_I80F48());
+    // User deposits can exceed maxWithdrawFromVault
+    let maxBorrow = maxBorrowFromVault.sub(userDeposits).max(ZERO_I80F48());
+    // any borrow must respect the limit left in window
+    maxBorrow = maxBorrow.min(this.getBorrowLimitLeftInWindow());
+    // borrows would be applied a fee
+    maxBorrow = maxBorrow.div(ONE_I80F48().add(this.loanOriginationFeeRate));
+
+    // user deposits can always be withdrawn
+    // even if vaults can be depleted
+    return maxBorrow.add(userDeposits).min(I80F48.fromI64(vaultBalance));
+  }
+
+  getTimeToNextBorrowLimitWindowStartsTs(): number {
+    return this.netBorrowLimitWindowSizeTs
+      .sub(new BN(Date.now() / 1000).sub(this.lastNetBorrowsWindowStartTs))
+      .toNumber();
+  }
 }
 
 export class MintInfo {

ts/client/src/accounts/group.ts

@@ -488,12 +488,7 @@ export class Group {
     return this.getFirstBankByTokenIndex(0 as TokenIndex);
   }
 
-  /**
-   *
-   * @param mintPk
-   * @returns sum of ui balances of vaults for all banks for a token
-   */
-  public getTokenVaultBalanceByMintUi(mintPk: PublicKey): number {
+  public getTokenVaultBalanceByMint(mintPk: PublicKey): BN {
     const banks = this.banksMapByMint.get(mintPk.toBase58());
     if (!banks) {
       throw new Error(`No bank found for mint ${mintPk}!`);
@@ -509,7 +504,19 @@ export class Group {
       totalAmount.iadd(amount);
     }
 
-    return toUiDecimals(totalAmount, this.getMintDecimals(mintPk));
+    return totalAmount;
+  }
+
+  /**
+   *
+   * @param mintPk
+   * @returns sum of ui balances of vaults for all banks for a token
+   */
+  public getTokenVaultBalanceByMintUi(mintPk: PublicKey): number {
+    return toUiDecimals(
+      this.getTokenVaultBalanceByMint(mintPk),
+      this.getMintDecimals(mintPk),
+    );
   }
 
   public getSerum3MarketByMarketIndex(marketIndex: MarketIndex): Serum3Market {

ts/client/src/accounts/mangoAccount.ts

@@ -594,22 +594,11 @@ export class MangoAccount {
       ),
     );
     const sourceBalance = this.getEffectiveTokenBalance(group, sourceBank);
-    if (maxSource.gt(sourceBalance)) {
-      // Cannot borrow more than the window limit
-      let sourceBorrow = maxSource.sub(sourceBalance);
-      const netBorrowLimitPerWindow = I80F48.fromI64(
-        sourceBank.netBorrowLimitPerWindowQuote,
-      ).div(sourceBank.price);
-      sourceBorrow = sourceBorrow.min(netBorrowLimitPerWindow);
-
-      maxSource = sourceBalance.add(
-        sourceBorrow.div(ONE_I80F48().add(sourceBank.loanOriginationFeeRate)),
-      );
-    }
-
-    // Cannot swap more than total deposits in mango for the token
-    maxSource = maxSource.min(sourceBank.nativeDeposits());
-
+    const maxWithdrawNative = sourceBank.getMaxWithdraw(
+      group.getTokenVaultBalanceByMint(sourceBank.mint),
+      sourceBalance,
+    );
+    maxSource = maxSource.min(maxWithdrawNative);
     return toUiDecimals(maxSource, group.getMintDecimals(sourceMintPk));
   }
 
@@ -740,12 +729,11 @@ export class MangoAccount {
     // If its a bid then the reserved fund and potential loan is in base
     // also keep some buffer for fees, use taker fees for worst case simulation.
     const quoteBalance = this.getEffectiveTokenBalance(group, quoteBank);
-    if (quoteAmount.gt(quoteBalance)) {
-      const quoteBorrow = quoteAmount.sub(quoteBalance);
-      quoteAmount = quoteBalance.add(
-        quoteBorrow.div(ONE_I80F48().add(quoteBank.loanOriginationFeeRate)),
-      );
-    }
+    const maxWithdrawNative = quoteBank.getMaxWithdraw(
+      group.getTokenVaultBalanceByMint(quoteBank.mint),
+      quoteBalance,
+    );
+    quoteAmount = quoteAmount.min(maxWithdrawNative);
     quoteAmount = quoteAmount.div(
       ONE_I80F48().add(I80F48.fromNumber(serum3Market.getFeeRates(true))),
     );
@@ -782,12 +770,11 @@ export class MangoAccount {
     // If its a ask then the reserved fund and potential loan is in base
     // also keep some buffer for fees, use taker fees for worst case simulation.
     const baseBalance = this.getEffectiveTokenBalance(group, baseBank);
-    if (baseAmount.gt(baseBalance)) {
-      const baseBorrow = baseAmount.sub(baseBalance);
-      baseAmount = baseBalance.add(
-        baseBorrow.div(ONE_I80F48().add(baseBank.loanOriginationFeeRate)),
-      );
-    }
+    const maxWithdrawNative = baseBank.getMaxWithdraw(
+      group.getTokenVaultBalanceByMint(baseBank.mint),
+      baseBalance,
+    );
+    baseAmount = baseAmount.min(maxWithdrawNative);
     baseAmount = baseAmount.div(
       ONE_I80F48().add(I80F48.fromNumber(serum3Market.getFeeRates(true))),
     );