ore/api/src/state/market/curve.rs

use crate::error::OreError;

use super::Market;

// TODO Add weights.

impl Market {
    /// Returns the constant product invariant.
    pub(crate) fn k(&self) -> u128 {
        (self.base.liquidity() * self.quote.liquidity()).saturating_sub(1)
    }

    /// Returns the amount of base tokens that can be bought from a given amount of quote tokens.
    pub fn get_base_out(&self, quote_in: u128) -> u128 {
        let base_out = self.base.liquidity()
            - (self.k() / (self.quote.liquidity() + quote_in)).saturating_add(1);
        base_out
    }

    /// Returns the amount of quote tokens received from selling a given amount of base tokens.
    pub fn get_quote_out(&self, base_in: u128) -> u128 {
        let quote_out = self.quote.liquidity()
            - (self.k() / (self.base.liquidity() + base_in)).saturating_add(1);
        quote_out
    }

    /// Returns the amount of quote tokens needed to buy a given amount of base tokens.
    pub fn get_quote_in(&self, base_out: u128) -> Result<u128, OreError> {
        if base_out >= self.base.liquidity() {
            return Err(OreError::InsufficientVaultReserves.into());
        }
        let quote_in = (self.k() / (self.base.liquidity() - base_out)).saturating_add(1)
            - self.quote.liquidity();
        Ok(quote_in)
    }

    /// Returns the amount of base tokens which must be sold to receive a given amount of quote tokens.
    pub fn get_base_in(&self, quote_out: u128) -> Result<u128, OreError> {
        if quote_out >= self.quote.liquidity() {
            return Err(OreError::InsufficientVaultReserves.into());
        }
        let base_in = (self.k() / (self.quote.liquidity() - quote_out)).saturating_add(1)
            - self.base.liquidity();
        Ok(base_in)
    }
}