Add calculate_fee_rate_and_remainder (#28)

CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.2.1] - 2014-04-30
+
+### Added
+
+- Add `calculate_fee_rate_and_remainder`
+
 ## [0.2.0] - 2014-04-29
 
 ### Added
@@ -100,3 +106,7 @@ and this project adheres to
 [0.0.7]: https://github.com/margined-protocol/vaultenator/0.0.6...0.0.7
 [0.0.8]: https://github.com/margined-protocol/vaultenator/0.0.7...0.0.8
 [0.0.9]: https://github.com/margined-protocol/vaultenator/0.0.8...0.0.9
+[0.1.0]: https://github.com/margined-protocol/vaultenator/0.0.9...0.1.0
+[0.1.1]: https://github.com/margined-protocol/vaultenator/0.1.0...0.1.1
+[0.2.0]: https://github.com/margined-protocol/vaultenator/0.1.1...0.2.0
+[0.2.1]: https://github.com/margined-protocol/vaultenator/0.2.0...0.2.1

Cargo.toml

@@ -12,7 +12,7 @@ readme       = "README.md"
 repository   = "https://github.com/margined-protocol/vaultenator"
 resolver     = "2"
 rust-version = "1.77.2"
-version      = "0.2.0"
+version      = "0.2.1"
 
 [lib]
 crate-type = ["cdylib", "rlib"]

src/maths.rs

@@ -1,4 +1,4 @@
-use cosmwasm_std::{StdError, Uint128};
+use cosmwasm_std::{Decimal, StdError, StdResult, Uint128};
 
 pub const DEFAULT_STRATEGY_TOKENS_PER_DEPOSITED_BASE_TOKEN: Uint128 = Uint128::new(1_000_000);
 
@@ -16,8 +16,19 @@ pub fn calculate_strategy_tokens(
     Ok(strategy_tokens)
 }
 
+pub fn calculate_fee_and_remainder(
+    amount: Uint128,
+    fee_rate: Decimal,
+) -> StdResult<(Uint128, Uint128)> {
+    let remainder = amount * (Decimal::one() - fee_rate);
+    let fee = amount.checked_sub(remainder)?;
+    Ok((fee, remainder))
+}
+
 #[cfg(test)]
 mod tests {
+    use std::str::FromStr;
+
     use super::*;
 
     #[test]
@@ -55,4 +66,48 @@ mod tests {
                 .unwrap();
         assert_eq!(result, Uint128::new(1_000_000)); // Should match the strategy token supply because ratio is 1:1
     }
+
+    #[test]
+    fn test_calculate_fee_and_remainder_with_basic_fee() {
+        let fee_rate = Decimal::percent(10);
+        let amount = Uint128::new(1000);
+        let expected_fee = Uint128::new(100);
+        let expected_remainder = Uint128::new(900);
+        let (fee, remainder) = calculate_fee_and_remainder(amount, fee_rate).unwrap();
+        assert_eq!(fee, expected_fee);
+        assert_eq!(remainder, expected_remainder);
+    }
+
+    #[test]
+    fn test_calculate_fee_and_remainder_with_zero_fee_rate() {
+        let fee_rate = Decimal::zero();
+        let amount = Uint128::new(1000);
+        let expected_fee = Uint128::new(0);
+        let expected_remainder = Uint128::new(1000);
+        let (fee, remainder) = calculate_fee_and_remainder(amount, fee_rate).unwrap();
+        assert_eq!(fee, expected_fee);
+        assert_eq!(remainder, expected_remainder);
+    }
+
+    #[test]
+    fn test_calculate_fee_and_remainder_with_100_percent_fee_rate() {
+        let fee_rate = Decimal::percent(100);
+        let amount = Uint128::new(1000);
+        let expected_fee = Uint128::new(1000);
+        let expected_remainder = Uint128::zero();
+        let (fee, remainder) = calculate_fee_and_remainder(amount, fee_rate).unwrap();
+        assert_eq!(fee, expected_fee);
+        assert_eq!(remainder, expected_remainder);
+    }
+
+    #[test]
+    fn test_calculate_fee_and_remainder_with_small_fractional_fee_rate() {
+        let fee_rate = Decimal::from_str("0.05").unwrap();
+        let amount = Uint128::new(1000);
+        let expected_fee = Uint128::new(50);
+        let expected_remainder = Uint128::new(950);
+        let (fee, remainder) = calculate_fee_and_remainder(amount, fee_rate).unwrap();
+        assert_eq!(fee, expected_fee);
+        assert_eq!(remainder, expected_remainder);
+    }
 }