fix: fix possible div by zero error in deposit for first depositer

Author: Teolhyn

contracts/loan_manager/src/contract.rs

@@ -778,7 +778,7 @@ mod tests {
         let positions_new_user = Positions {
             collateral: 0,
             liabilities: 0,
-            receivable_shares: 999,
+            receivable_shares: 998,
         };
         assert_eq!(
             positions_new_user,
@@ -797,54 +797,21 @@ mod tests {
         let pool_state = PoolState {
             annual_interest_rate: 200887,
             available_balance_tokens: 2000,
-            total_balance_shares: 2000,
+            total_balance_shares: 1998,
             total_balance_tokens: 2002,
         };
         assert_eq!(pool_state, pool_xlm_client.get_pool_state());
 
         let state_after_first_withdraw = pool_xlm_client.withdraw(&new_user, &1002);
         assert_eq!(state_after_first_withdraw, pool_xlm_client.get_pool_state());
-        // let test_positions_admin = Positions {
-        //     collateral: 0,
-        //     liabilities: 0,
-        //     receivable_shares: 0,
-        // };
-        // assert_eq!(
-        //     test_positions_admin,
-        //     pool_xlm_client.get_user_positions(&admin)
-        // );
-        //
-        // let test_positions_user = Positions {
-        //     collateral: 0,
-        //     liabilities: 0,
-        //     receivable_shares: 1000,
-        // };
-        // assert_eq!(
-        //     test_positions_user,
-        //     pool_xlm_client.get_user_positions(&new_user)
-        // );
-        //
-        // let test_positions_admin = Positions {
-        //     collateral: 0,
-        //     liabilities: 0,
-        //     receivable_shares: 0,
-        // };
-        // assert_eq!(
-        //     test_positions_admin,
-        //     pool_xlm_client.get_user_positions(&admin)
-        // );
-        //
-        // let pool_state = PoolState {
-        //     annual_interest_rate: 201777,
-        //     available_balance_tokens: 998,
-        //     total_balance_shares: 1000,
-        //     total_balance_tokens: 1000,
-        // };
-        // assert_eq!(pool_state, pool_xlm_client.get_pool_state());
-        //
-        // assert_eq!(1000, pool_xlm_client.get_contract_balance());
-        // pool_xlm_client.withdraw(&new_user, &998);
-        // assert_eq!(2, pool_xlm_client.get_contract_balance());
+
+        let pool_state = PoolState {
+            annual_interest_rate: 200887,
+            available_balance_tokens: 998,
+            total_balance_shares: 998,
+            total_balance_tokens: 1000,
+        };
+        assert_eq!(pool_state, pool_xlm_client.get_pool_state());
     }
 
     #[test]

contracts/loan_pool/src/contract.rs

@@ -65,20 +65,20 @@ impl LoanPoolContract {
             let client = token::Client::new(&e, &token_address);
             client.transfer(&user, &e.current_contract_address(), &amount);
 
-            storage::adjust_available_balance(&e, amount)?;
-            storage::adjust_total_shares(&e, amount)?;
-            storage::adjust_total_balance(&e, amount)?;
-
             let current_shares = Self::get_total_balance_shares(e.clone())?;
             let current_contract_balance = Self::get_contract_balance(e.clone())?;
 
-            let shares_issued = current_shares
-                .checked_mul(amount)
-                .ok_or(LoanPoolError::OverOrUnderFlow)?
-                .checked_div(current_contract_balance)
-                .ok_or(LoanPoolError::OverOrUnderFlow)?;
-            let liabilities: i128 = 0; // temp test param
-            let collateral: i128 = 0; // temp test param
+            let shares_issued = if current_contract_balance == 0 {
+                amount
+            } else {
+                current_shares
+                    .checked_mul(amount)
+                    .ok_or(LoanPoolError::OverOrUnderFlow)?
+                    .checked_div(current_contract_balance)
+                    .ok_or(LoanPoolError::OverOrUnderFlow)?
+            };
+            let liabilities: i128 = 0;
+            let collateral: i128 = 0;
             positions::increase_positions(
                 &e,
                 user.clone(),
@@ -87,6 +87,10 @@ impl LoanPoolContract {
                 collateral,
             )?;
 
+            storage::adjust_available_balance(&e, amount)?;
+            storage::adjust_total_shares(&e, shares_issued)?;
+            storage::adjust_total_balance(&e, amount)?;
+
             Ok(amount)
         }
     }
@@ -125,7 +129,12 @@ impl LoanPoolContract {
             &e,
             amount.checked_neg().ok_or(LoanPoolError::OverOrUnderFlow)?,
         )?;
-        let new_total_balance_shares = storage::adjust_total_shares(&e, shares_to_decrease)?;
+        let new_total_balance_shares = storage::adjust_total_shares(
+            &e,
+            shares_to_decrease
+                .checked_neg()
+                .ok_or(LoanPoolError::OverOrUnderFlow)?,
+        )?;
         let liabilities: i128 = 0;
         let collateral: i128 = 0;
         positions::decrease_positions(