program: add-spot-borrow-insurance-limits

programs/drift/src/instructions/admin.rs

@@ -128,7 +128,7 @@ pub fn handle_initialize_spot_market(
         return Err(ErrorCode::InvalidInsuranceFundAuthority.into());
     }
 
-    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate)?;
+    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate, 0)?;
 
     let spot_market_index = get_then_update_id!(state, number_of_spot_markets);
 
@@ -278,7 +278,9 @@ pub fn handle_initialize_spot_market(
         flash_loan_initial_token_amount: 0,
         total_swap_fee: 0,
         scale_initial_asset_weight_start,
-        padding: [0; 48],
+        max_token_borrows: 0,
+        min_borrow_rate: 0,
+        padding: [0; 36],
         insurance_fund: InsuranceFund {
             vault: *ctx.accounts.insurance_fund_vault.to_account_info().key,
             unstaking_period: THIRTEEN_DAY,
@@ -2243,9 +2245,15 @@ pub fn handle_update_spot_market_borrow_rate(
     optimal_utilization: u32,
     optimal_borrow_rate: u32,
     max_borrow_rate: u32,
+    min_borrow_rate: Option<u32>,
 ) -> Result<()> {
     let spot_market = &mut load_mut!(ctx.accounts.spot_market)?;
-    validate_borrow_rate(optimal_utilization, optimal_borrow_rate, max_borrow_rate)?;
+    validate_borrow_rate(
+        optimal_utilization,
+        optimal_borrow_rate,
+        max_borrow_rate,
+        min_borrow_rate.unwrap_or(spot_market.min_borrow_rate),
+    )?;
 
     msg!(
         "spot_market.optimal_utilization: {:?} -> {:?}",
@@ -2268,6 +2276,11 @@ pub fn handle_update_spot_market_borrow_rate(
     spot_market.optimal_utilization = optimal_utilization;
     spot_market.optimal_borrow_rate = optimal_borrow_rate;
     spot_market.max_borrow_rate = max_borrow_rate;
+
+    if min_borrow_rate.is_some() {
+        spot_market.min_borrow_rate = min_borrow_rate.unwrap();
+    }
+
     Ok(())
 }
 
@@ -2290,6 +2303,35 @@ pub fn handle_update_spot_market_max_token_deposits(
     Ok(())
 }
 
+#[access_control(
+    spot_market_valid(&ctx.accounts.spot_market)
+)]
+pub fn handle_update_spot_market_max_token_borrows(
+    ctx: Context<AdminUpdateSpotMarket>,
+    max_token_borrows: u64,
+) -> Result<()> {
+    let spot_market = &mut load_mut!(ctx.accounts.spot_market)?;
+
+    msg!(
+        "spot_market.max_token_borrows: {:?} -> {:?}",
+        spot_market.max_token_borrows,
+        max_token_borrows
+    );
+
+    let current_spot_tokens_borrows: u64 = spot_market.get_borrows()?.cast()?;
+
+    validate!(
+        current_spot_tokens_borrows <= max_token_borrows,
+        ErrorCode::InvalidSpotMarketInitialization,
+        "spot borrows {} > max_token_borrows {}",
+        current_spot_tokens_borrows,
+        max_token_borrows
+    )?;
+
+    spot_market.max_token_borrows = max_token_borrows;
+    Ok(())
+}
+
 #[access_control(
 spot_market_valid(&ctx.accounts.spot_market)
 )]

programs/drift/src/lib.rs

@@ -874,12 +874,14 @@ pub mod drift {
         optimal_utilization: u32,
         optimal_borrow_rate: u32,
         max_borrow_rate: u32,
+        min_borrow_rate: Option<u32>,
     ) -> Result<()> {
         handle_update_spot_market_borrow_rate(
             ctx,
             optimal_utilization,
             optimal_borrow_rate,
             max_borrow_rate,
+            min_borrow_rate,
         )
     }
 

programs/drift/src/math/spot_balance.rs

@@ -158,7 +158,8 @@ pub fn calculate_accumulated_interest(
         utilization
             .safe_mul(borrow_rate_slope)?
             .safe_div(SPOT_UTILIZATION_PRECISION)?
-    };
+    }
+    .max(spot_market.min_borrow_rate.cast()?);
 
     let time_since_last_update = now
         .cast::<u64>()

programs/drift/src/state/spot_market.rs

@@ -178,7 +178,14 @@ pub struct SpotMarket {
     /// disabled when 0
     /// precision: QUOTE_PRECISION
     pub scale_initial_asset_weight_start: u64,
-    pub padding: [u8; 48],
+    /// When to begin scaling down the initial asset weight
+    /// disabled when 0
+    /// precision: QUOTE_PRECISION
+    pub max_token_borrows: u64,
+    /// The min borrow rate for this market when the market regardless of utilization
+    /// precision: SPOT_RATE_PRECISION
+    pub min_borrow_rate: u32,
+    pub padding: [u8; 36],
 }
 
 impl Default for SpotMarket {
@@ -239,7 +246,9 @@ impl Default for SpotMarket {
             flash_loan_initial_token_amount: 0,
             total_swap_fee: 0,
             scale_initial_asset_weight_start: 0,
-            padding: [0; 48],
+            max_token_borrows: 0,
+            min_borrow_rate: 0,
+            padding: [0; 36],
         }
     }
 }
@@ -426,6 +435,19 @@ impl SpotMarket {
             deposits,
         )?;
 
+        if self.max_token_borrows > 0 {
+            let borrows = self.get_borrows()?;
+            let max_token_borrows = self.max_token_borrows.cast::<u128>()?;
+
+            validate!(
+                max_token_borrows == 0 || borrows <= max_token_borrows,
+                ErrorCode::MaxDeposit,
+                "max token amount ({}) < borrows ({})",
+                max_token_borrows,
+                borrows,
+            )?;
+        }
+
         Ok(())
     }
 

programs/drift/src/validation/spot_market.rs

@@ -7,6 +7,7 @@ pub fn validate_borrow_rate(
     optimal_utilization: u32,
     optimal_borrow_rate: u32,
     max_borrow_rate: u32,
+    min_borrow_rate: u32,
 ) -> DriftResult {
     validate!(
         optimal_utilization <= SPOT_UTILIZATION_PRECISION_U32,
@@ -18,10 +19,18 @@ pub fn validate_borrow_rate(
     validate!(
         optimal_borrow_rate <= max_borrow_rate,
         ErrorCode::InvalidSpotMarketInitialization,
-        "For spot market, optimal borrow rate ({}) must be <  max borrow rate ({})",
+        "For spot market, optimal borrow rate ({}) must be <=  max borrow rate ({})",
         optimal_borrow_rate,
         max_borrow_rate
     )?;
 
+    validate!(
+        optimal_borrow_rate >= min_borrow_rate,
+        ErrorCode::InvalidSpotMarketInitialization,
+        "For spot market, optimal borrow rate ({}) must be >= min borrow rate ({})",
+        optimal_borrow_rate,
+        min_borrow_rate
+    )?;
+
     Ok(())
 }