From cfb1905ad3add8561a7fb09f09a5ad624f3da025 Mon Sep 17 00:00:00 2001
From: Denali Marsh <denali@kava.io>
Date: Wed, 11 Nov 2020 16:05:17 +0100
Subject: [PATCH] Harvest: borrows capped by utilization (#714)

* wrap error borrow exceeds mod acc balance

* address revisions
---
 x/harvest/keeper/borrow.go      | 15 ++++++++++++++-
 x/harvest/keeper/borrow_test.go | 21 +++++++++++++++++++++
 x/harvest/types/errors.go       |  2 ++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/x/harvest/keeper/borrow.go b/x/harvest/keeper/borrow.go
index 58977471..f56a6b69 100644
--- a/x/harvest/keeper/borrow.go
+++ b/x/harvest/keeper/borrow.go
@@ -1,6 +1,8 @@
 package keeper
 
 import (
+	"strings"
+
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 
@@ -16,7 +18,18 @@ func (k Keeper) Borrow(ctx sdk.Context, borrower sdk.AccAddress, coins sdk.Coins
 
 	err = k.supplyKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleAccountName, borrower, coins)
 	if err != nil {
-		return err
+		if strings.Contains(err.Error(), "insufficient account funds") {
+			modAccCoins := k.supplyKeeper.GetModuleAccount(ctx, types.ModuleAccountName).GetCoins()
+			for _, coin := range coins {
+				_, isNegative := modAccCoins.SafeSub(sdk.NewCoins(coin))
+				if isNegative {
+					return sdkerrors.Wrapf(types.ErrBorrowExceedsAvailableBalance,
+						"the requested borrow amount of %s exceeds the total amount of %s%s available to borrow",
+						coin, modAccCoins.AmountOf(coin.Denom), coin.Denom,
+					)
+				}
+			}
+		}
 	}
 
 	borrow, found := k.GetBorrow(ctx, borrower)
diff --git a/x/harvest/keeper/borrow_test.go b/x/harvest/keeper/borrow_test.go
index 3e1de3bb..bb8fa330 100644
--- a/x/harvest/keeper/borrow_test.go
+++ b/x/harvest/keeper/borrow_test.go
@@ -192,6 +192,27 @@ func (suite *KeeperTestSuite) TestBorrow() {
 				contains:   "no price found for market",
 			},
 		},
+		{
+			"invalid: borrow exceed module account balance",
+			args{
+				priceKAVA:                 sdk.MustNewDecFromStr("2.00"),
+				loanToValueKAVA:           sdk.MustNewDecFromStr("0.8"),
+				priceBTCB:                 sdk.MustNewDecFromStr("0.00"),
+				loanToValueBTCB:           sdk.MustNewDecFromStr("0.01"),
+				priceBNB:                  sdk.MustNewDecFromStr("0.00"),
+				loanToValueBNB:            sdk.MustNewDecFromStr("0.01"),
+				borrower:                  sdk.AccAddress(crypto.AddressHash([]byte("test"))),
+				depositCoins:              []sdk.Coin{sdk.NewCoin("ukava", sdk.NewInt(100*KAVA_CF))},
+				previousBorrowCoins:       sdk.NewCoins(),
+				borrowCoins:               sdk.NewCoins(sdk.NewCoin("busd", sdk.NewInt(101*BUSD_CF))),
+				expectedAccountBalance:    sdk.NewCoins(),
+				expectedModAccountBalance: sdk.NewCoins(),
+			},
+			errArgs{
+				expectPass: false,
+				contains:   "exceeds module account balance:",
+			},
+		},
 	}
 	for _, tc := range testCases {
 		suite.Run(tc.name, func() {
diff --git a/x/harvest/types/errors.go b/x/harvest/types/errors.go
index 55ea0d83..9c09cb17 100644
--- a/x/harvest/types/errors.go
+++ b/x/harvest/types/errors.go
@@ -45,4 +45,6 @@ var (
 	ErrMarketNotFound = sdkerrors.Register(ModuleName, 19, "no market found for denom")
 	// ErrPriceNotFound error for when a price for the input market is not found
 	ErrPriceNotFound = sdkerrors.Register(ModuleName, 20, "no price found for market")
+	// ErrBorrowExceedsAvailableBalance for when a requested borrow exceeds available module acc balances
+	ErrBorrowExceedsAvailableBalance = sdkerrors.Register(ModuleName, 21, "exceeds module account balance")
 )