riptide-amm-math 1.0.3

#![allow(dead_code)]
use core::cmp::min;

use ethnum::I256;

#[cfg(feature = "wasm")]
use riptide_amm_macros::wasm_expose;

use borsh::{BorshDeserialize, BorshSerialize};

use super::{
    error::{CoreError, AMOUNT_EXCEEDS_MAX_U32, ARITHMETIC_OVERFLOW},
    quote::{Price, Quote, QuoteType},
    token::{a_to_b, b_to_a, deviation_per_m},
    U128,
};

mod amm;
mod book;
mod flat;
mod skew;
mod spread;

pub use amm::LiquidityType;
pub use book::BookSpacingType;
pub use skew::{SkewExponent, SkewMode};

use amm::{amm_liquidity, amm_price};
use book::{book_liquidity, new_book_liquidity, BOOK_LIQUIDITY_LEVELS};
use flat::flat_liquidity;
use skew::apply_skew_to_liquidity;
use spread::spread_liquidity;

pub(crate) const LIQUIDITY_LEVELS: usize = 32;

pub const ORACLE_DATA_LEN: usize = 276;
pub const SKEW_LEN: usize = 32;
pub const ORACLE_PAYLOAD_LEN: usize = 512;
pub const SKEW_OFFSET: usize = ORACLE_PAYLOAD_LEN - SKEW_LEN;

// Represents the liquidity on one side of the order book (price and amount of out_token).
// This is explicitly a fixed-size array to avoid heap allocation (which Vec does).
// The `len` field is the actual number of initialized elements in the array.
#[allow(clippy::len_without_is_empty)]
#[derive(Default, Debug, Clone, Copy, Eq, PartialEq)]
#[cfg_attr(feature = "wasm", wasm_expose)]
pub struct SingleSideLiquidity {
    items: [(u128, u64); LIQUIDITY_LEVELS],
    len: usize,
}

impl SingleSideLiquidity {
    pub fn new() -> Self {
        Self {
            items: [(0, 0); LIQUIDITY_LEVELS],
            len: 0,
        }
    }

    pub fn from_slice(slice: &[(u128, u64)]) -> Self {
        let mut items = [(0, 0); LIQUIDITY_LEVELS];
        items[..slice.len()].copy_from_slice(slice);
        Self {
            items,
            len: slice.len(),
        }
    }

    pub fn push(&mut self, item: (u128, u64)) -> bool {
        if self.len < 32 {
            self.items[self.len] = item;
            self.len += 1;
            true
        } else {
            false
        }
    }

    pub fn len(&self) -> usize {
        self.len
    }

    pub fn as_slice(&self) -> &[(u128, u64)] {
        &self.items[..self.len]
    }
}

#[cfg_attr(feature = "wasm", wasm_expose)]
pub const PER_CENT_DENOMINATOR: i8 = 100;

#[cfg_attr(feature = "wasm", wasm_expose)]
pub const BPS_DENOMINATOR: i16 = 10000;

#[cfg_attr(feature = "wasm", wasm_expose)]
pub const PER_M_DENOMINATOR: i32 = 1_000_000;

#[derive(Debug, Clone, Copy, Eq, PartialEq)]
#[cfg_attr(true, derive(BorshDeserialize, BorshSerialize))]
#[cfg_attr(feature = "wasm", wasm_expose)]
pub enum OracleData {
    Empty,
    FlatPrice {
        price_q64_64: u128,
    },
    SimpleSpread {
        price_q64_64: u128,
        bid_spread_per_m: i32,
        ask_spread_per_m: i32,
    },
    OrderBook {
        price_q64_64: u128,
        // The spacing between each level of liquidity
        spacing: BookSpacingType,
        // Expressed as a fraction of the total reserves
        bid_liquidity_per_m: [u32; BOOK_LIQUIDITY_LEVELS],
        ask_liquidity_per_m: [u32; BOOK_LIQUIDITY_LEVELS],
    },
    AutomatedMarketMaker {
        liquidity_type: LiquidityType,
        bid_spread_per_m: i32,
        ask_spread_per_m: i32,
    },
}

#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub struct OraclePayload {
    pub data: OracleData,
    pub skew: SkewMode,
}

impl BorshDeserialize for OraclePayload {
    fn deserialize_reader<R: borsh::io::Read>(reader: &mut R) -> borsh::io::Result<Self> {
        const _: () = assert!(ORACLE_DATA_LEN + SKEW_LEN <= ORACLE_PAYLOAD_LEN);

        let mut buf = [0u8; ORACLE_PAYLOAD_LEN];
        reader.read_exact(&mut buf)?;
        let mut data_slice = &buf[..ORACLE_DATA_LEN];
        let data = OracleData::deserialize(&mut data_slice)?;
        let mut skew_slice = &buf[SKEW_OFFSET..SKEW_OFFSET + SKEW_LEN];
        let skew = SkewMode::deserialize(&mut skew_slice)?;
        Ok(Self { data, skew })
    }
}

#[inline(never)]
fn build_base_liquidity(
    data: &OracleData,
    quote_type: QuoteType,
    reserves_a: u64,
    reserves_b: u64,
) -> Result<SingleSideLiquidity, CoreError> {
    match data {
        OracleData::Empty => Ok(SingleSideLiquidity::new()),
        OracleData::FlatPrice { price_q64_64 } => {
            flat_liquidity(*price_q64_64, quote_type, reserves_a, reserves_b)
        }
        OracleData::SimpleSpread {
            price_q64_64,
            bid_spread_per_m,
            ask_spread_per_m,
        } => spread_liquidity(
            *price_q64_64,
            *bid_spread_per_m,
            *ask_spread_per_m,
            quote_type,
            reserves_a,
            reserves_b,
        ),
        OracleData::OrderBook {
            price_q64_64,
            spacing,
            bid_liquidity_per_m,
            ask_liquidity_per_m,
        } => book_liquidity(
            quote_type,
            *price_q64_64,
            *spacing,
            bid_liquidity_per_m,
            ask_liquidity_per_m,
            reserves_a,
            reserves_b,
        ),
        OracleData::AutomatedMarketMaker {
            liquidity_type,
            bid_spread_per_m,
            ask_spread_per_m,
        } => amm_liquidity(
            *liquidity_type,
            *bid_spread_per_m,
            *ask_spread_per_m,
            quote_type,
            reserves_a,
            reserves_b,
        ),
    }
}

pub(crate) fn build_liquidity(
    payload: &OraclePayload,
    quote_type: QuoteType,
    reserves_a: u64,
    reserves_b: u64,
) -> Result<SingleSideLiquidity, CoreError> {
    let liquidity = build_base_liquidity(&payload.data, quote_type, reserves_a, reserves_b)?;

    let price = match &payload.data {
        OracleData::Empty | OracleData::AutomatedMarketMaker { .. } => return Ok(liquidity),
        OracleData::FlatPrice { price_q64_64 }
        | OracleData::SimpleSpread { price_q64_64, .. }
        | OracleData::OrderBook { price_q64_64, .. } => *price_q64_64,
    };

    let deviation = deviation_per_m(U128::from(price), reserves_a, reserves_b)?;
    let skew_per_m = payload.skew.compute_skew_per_m(deviation, quote_type)?;
    apply_skew_to_liquidity(liquidity, skew_per_m, quote_type)
}

pub(crate) fn build_price(
    liquidity: &SingleSideLiquidity,
    oracle: &OracleData,
    quote_type: QuoteType,
    reserves_a: u64,
    reserves_b: u64,
) -> Result<Price, CoreError> {
    let best_price = liquidity
        .as_slice()
        .iter()
        .find(|(_, liquidity)| *liquidity > 0)
        .map(|(price, _)| *price)
        .unwrap_or(0);

    let oracle_price = match oracle {
        OracleData::Empty => 0,
        OracleData::FlatPrice { price_q64_64 } => *price_q64_64,
        OracleData::SimpleSpread { price_q64_64, .. } => *price_q64_64,
        OracleData::OrderBook { price_q64_64, .. } => *price_q64_64,
        OracleData::AutomatedMarketMaker { liquidity_type, .. } => {
            amm_price(*liquidity_type, reserves_a, reserves_b)?
        }
    };

    let diff = if quote_type.a_to_b() {
        I256::from(oracle_price)
            .checked_sub(I256::from(best_price))
            .ok_or(ARITHMETIC_OVERFLOW)?
    } else {
        I256::from(best_price)
            .checked_sub(I256::from(oracle_price))
            .ok_or(ARITHMETIC_OVERFLOW)?
    };

    let spread = if best_price > 0 {
        diff.checked_mul(I256::from(PER_M_DENOMINATOR))
            .ok_or(ARITHMETIC_OVERFLOW)?
            .checked_div(I256::from(oracle_price))
            .ok_or(ARITHMETIC_OVERFLOW)?
            .try_into()
            .map_err(|_| AMOUNT_EXCEEDS_MAX_U32)?
    } else {
        0
    };

    Ok(Price {
        oracle_price_q64_64: oracle_price,
        best_price_q64_64: best_price,
        spread_per_m: spread,
    })
}

pub(crate) fn consume_liquidity(
    amount: u64,
    quote_type: QuoteType,
    liquidity: &SingleSideLiquidity,
) -> Result<Quote, CoreError> {
    let mut remaining_amount = amount;
    let mut other_amount: u64 = 0;

    // Start consuming the liquidity from the best price (first)
    // Stop when either the liquidity runs out or the full amount is consumed
    // `liquidity` represents the amount of output token that is available at the given price

    for (price, liquidity) in liquidity.as_slice() {
        if *price == 0 || *liquidity == 0 {
            continue;
        }

        let (step_specified_amount, step_other_amount) = if quote_type.exact_in() {
            // ExactIn
            let max_amount = if quote_type.input_is_token_a() {
                b_to_a(*liquidity, U128::from(*price), true)?
            } else {
                a_to_b(*liquidity, U128::from(*price), true)?
            };

            let step_specified_amount = min(remaining_amount, max_amount);
            let step_other_amount = if quote_type.input_is_token_a() {
                a_to_b(step_specified_amount, U128::from(*price), false)?
            } else {
                b_to_a(step_specified_amount, U128::from(*price), false)?
            };

            (step_specified_amount, min(step_other_amount, *liquidity))
        } else {
            // ExactOut

            let step_specified_amount = min(remaining_amount, *liquidity);
            let step_other_amount = if quote_type.output_is_token_a() {
                a_to_b(step_specified_amount, U128::from(*price), true)?
            } else {
                b_to_a(step_specified_amount, U128::from(*price), true)?
            };

            (step_specified_amount, step_other_amount)
        };

        remaining_amount = remaining_amount
            .checked_sub(step_specified_amount)
            .ok_or(ARITHMETIC_OVERFLOW)?;
        other_amount = other_amount
            .checked_add(step_other_amount)
            .ok_or(ARITHMETIC_OVERFLOW)?;

        if remaining_amount == 0 {
            break;
        }
    }

    let consumed_amount = amount - remaining_amount;

    let (amount_in, amount_out) = if quote_type.exact_in() {
        (consumed_amount, other_amount)
    } else {
        (other_amount, consumed_amount)
    };

    Ok(Quote {
        amount_in,
        amount_out,
        quote_type,
    })
}

pub(crate) fn new_oracle_data(
    oracle: &OracleData,
    quote: &Quote,
    reserves_a: u64,
    reserves_b: u64,
) -> Result<OracleData, CoreError> {
    match oracle {
        OracleData::Empty
        | OracleData::FlatPrice { .. }
        | OracleData::SimpleSpread { .. }
        | OracleData::AutomatedMarketMaker { .. } => Ok(*oracle),
        OracleData::OrderBook {
            price_q64_64,
            spacing,
            bid_liquidity_per_m,
            ask_liquidity_per_m,
        } => new_book_liquidity(
            quote,
            *price_q64_64,
            *spacing,
            bid_liquidity_per_m,
            ask_liquidity_per_m,
            reserves_a,
            reserves_b,
        ),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use rstest::rstest;

    #[rstest]
    fn test_empty(
        #[values(true, false)] amount_is_token_a: bool,
        #[values(true, false)] amount_is_input: bool,
    ) {
        let quote_type = QuoteType::new(amount_is_token_a, amount_is_input);
        let payload = OraclePayload {
            data: OracleData::Empty,
            skew: SkewMode::None,
        };
        let liquidity = build_liquidity(&payload, quote_type, 1000, 1000).unwrap();
        let quote = consume_liquidity(100, quote_type, &liquidity).unwrap();
        assert_eq!(
            quote,
            Quote {
                amount_in: 0,
                amount_out: 0,
                quote_type,
            }
        );
    }

    #[rstest]
    #[case(OracleData::FlatPrice { price_q64_64: 100 }, QuoteType::TokenAExactIn, 100, 100, 0)]
    #[case(OracleData::FlatPrice { price_q64_64: 100 }, QuoteType::TokenBExactIn, 100, 100, 0)]
    #[case(OracleData::SimpleSpread { price_q64_64: 100, bid_spread_per_m: 10000, ask_spread_per_m: 20000 }, QuoteType::TokenAExactIn, 100, 99, 10000)]
    #[case(OracleData::SimpleSpread { price_q64_64: 100, bid_spread_per_m: 10000, ask_spread_per_m: 20000 }, QuoteType::TokenBExactIn, 100, 102, 20000)]
    #[case(OracleData::SimpleSpread { price_q64_64: 100, bid_spread_per_m: -10000, ask_spread_per_m: -20000 }, QuoteType::TokenAExactIn, 100, 101, -10000)]
    #[case(OracleData::SimpleSpread { price_q64_64: 100, bid_spread_per_m: -10000, ask_spread_per_m: -20000 }, QuoteType::TokenBExactIn, 100, 98, -20000)]
    fn test_build_price(
        #[case] oracle: OracleData,
        #[case] quote_type: QuoteType,
        #[case] expected_oracle_price: u128,
        #[case] expected_best_price: u128,
        #[case] expected_spread_per_m: i32,
    ) {
        let reserves_a = 1_000_000;
        let reserves_b = 1_000_000;

        let payload = OraclePayload {
            data: oracle,
            skew: SkewMode::None,
        };
        let liquidity = build_liquidity(&payload, quote_type, reserves_a, reserves_b).unwrap();

        let price = build_price(&liquidity, &oracle, quote_type, reserves_a, reserves_b).unwrap();

        let expected = Price {
            oracle_price_q64_64: expected_oracle_price,
            best_price_q64_64: expected_best_price,
            spread_per_m: expected_spread_per_m,
        };

        assert_eq!(price, expected);
    }

    #[rstest]
    #[case(vec![500_000, 500_000, 0], 100, 100, 0)]
    #[case(vec![0, 500_000, 500_000], 100, 99, 10000)]
    #[case(vec![0, 0, 1_000_000], 100, 98, 20000)]
    #[case(vec![0, 0, 0], 100, 0, 0)]
    fn test_build_price_book(
        #[case] liquidity: Vec<u32>,
        #[case] expected_oracle_price: u128,
        #[case] expected_best_price: u128,
        #[case] expected_spread_per_m: i32,
    ) {
        let mut liquidity_per_m = [0u32; 32];
        liquidity_per_m[..liquidity.len()].copy_from_slice(&liquidity);
        let reserves_a = 1_000_000;
        let reserves_b = 1_000_000;
        let oracle = OracleData::OrderBook {
            price_q64_64: 100,
            spacing: BookSpacingType::Linear(10000),
            bid_liquidity_per_m: liquidity_per_m,
            ask_liquidity_per_m: [0; 32],
        };

        let payload = OraclePayload {
            data: oracle,
            skew: SkewMode::None,
        };
        let liquidity =
            build_liquidity(&payload, QuoteType::TokenAExactIn, reserves_a, reserves_b).unwrap();

        let price = build_price(
            &liquidity,
            &oracle,
            QuoteType::TokenAExactIn,
            reserves_a,
            reserves_b,
        )
        .unwrap();

        let expected = Price {
            oracle_price_q64_64: expected_oracle_price,
            best_price_q64_64: expected_best_price,
            spread_per_m: expected_spread_per_m,
        };

        assert_eq!(price, expected);
    }

    #[rstest]
    #[case(OracleData::Empty)]
    #[case(OracleData::FlatPrice { price_q64_64: 1 << 64 })]
    #[case(OracleData::SimpleSpread { price_q64_64: 1 << 64, bid_spread_per_m: 1000, ask_spread_per_m: 1000 })]
    #[case(OracleData::AutomatedMarketMaker { liquidity_type: LiquidityType::ConstantProduct, bid_spread_per_m: 1000, ask_spread_per_m: 1000 })]
    fn test_new_liquidity_unchanged(#[case] oracle: OracleData) {
        let quote = Quote {
            amount_in: 100,
            amount_out: 100,
            quote_type: QuoteType::TokenAExactIn,
        };
        let new_oracle = new_oracle_data(&oracle, &quote, 0, 0).unwrap();
        assert_eq!(new_oracle, oracle);
    }

    // Selling exact token_a. The lower the the price, the less token_b you get.
    #[rstest]
    #[case(100, Ok(Quote { amount_in: 100, amount_out: 100, quote_type: QuoteType::TokenAExactIn }))]
    #[case(500, Ok(Quote { amount_in: 500, amount_out: 300, quote_type: QuoteType::TokenAExactIn }))]
    #[case(1100, Ok(Quote { amount_in: 1100, amount_out: 600, quote_type: QuoteType::TokenAExactIn }))]
    #[case(2500, Ok(Quote { amount_in: 2500, amount_out: 950, quote_type: QuoteType::TokenAExactIn }))]
    #[case(10000, Ok(Quote { amount_in: 5100, amount_out: 1600, quote_type: QuoteType::TokenAExactIn }))]
    fn test_consume_liquidity_input_token_a(
        #[case] amount: u64,
        #[case] expected: Result<Quote, CoreError>,
    ) {
        let liquidity = SingleSideLiquidity::from_slice(&[
            (1 << 64, 100),
            ((1 << 64) / 2, 500),
            ((1 << 64) / 4, 1000),
        ]);
        let quote = consume_liquidity(amount, QuoteType::TokenAExactIn, &liquidity);
        assert_eq!(quote, expected);
    }

    // Selling exact token_b. The higher the the price, the less token_a you get.
    #[rstest]
    #[case(100, Ok(Quote { amount_in: 100, amount_out: 100, quote_type: QuoteType::TokenBExactIn }))]
    #[case(500, Ok(Quote { amount_in: 500, amount_out: 300, quote_type: QuoteType::TokenBExactIn }))]
    #[case(1100, Ok(Quote { amount_in: 1100, amount_out: 600, quote_type: QuoteType::TokenBExactIn }))]
    #[case(2500, Ok(Quote { amount_in: 2500, amount_out: 950, quote_type: QuoteType::TokenBExactIn }))]
    #[case(10000, Ok(Quote { amount_in: 5100, amount_out: 1600, quote_type: QuoteType::TokenBExactIn }))]
    fn test_consume_liquidity_input_token_b(
        #[case] amount: u64,
        #[case] expected: Result<Quote, CoreError>,
    ) {
        let liquidity =
            SingleSideLiquidity::from_slice(&[(1 << 64, 100), (2 << 64, 500), (4 << 64, 1000)]);
        let quote = consume_liquidity(amount, QuoteType::TokenBExactIn, &liquidity);
        assert_eq!(quote, expected);
    }

    // Buying exact token_a. The higher the the price, the more token_b you pay.
    #[rstest]
    #[case(100, Ok(Quote { amount_in: 100, amount_out: 100, quote_type: QuoteType::TokenAExactOut }))]
    #[case(300, Ok(Quote { amount_in: 500, amount_out: 300, quote_type: QuoteType::TokenAExactOut }))]
    #[case(600, Ok(Quote { amount_in: 1100, amount_out: 600, quote_type: QuoteType::TokenAExactOut }))]
    #[case(950, Ok(Quote { amount_in: 2500, amount_out: 950, quote_type: QuoteType::TokenAExactOut }))]
    #[case(2000, Ok(Quote { amount_in: 5100, amount_out: 1600, quote_type: QuoteType::TokenAExactOut }))]
    fn test_consume_liquidity_output_token_a(
        #[case] amount: u64,
        #[case] expected: Result<Quote, CoreError>,
    ) {
        let liquidity =
            SingleSideLiquidity::from_slice(&[(1 << 64, 100), (2 << 64, 500), (4 << 64, 1000)]);
        let quote = consume_liquidity(amount, QuoteType::TokenAExactOut, &liquidity);
        assert_eq!(quote, expected);
    }

    // Buying exact token_b. The lower the the price, the more token_a you pay.
    #[rstest]
    #[case(100, Ok(Quote { amount_in: 100, amount_out: 100, quote_type: QuoteType::TokenBExactOut }))]
    #[case(300, Ok(Quote { amount_in: 500, amount_out: 300, quote_type: QuoteType::TokenBExactOut }))]
    #[case(600, Ok(Quote { amount_in: 1100, amount_out: 600, quote_type: QuoteType::TokenBExactOut }))]
    #[case(950, Ok(Quote { amount_in: 2500, amount_out: 950, quote_type: QuoteType::TokenBExactOut }))]
    #[case(2000, Ok(Quote { amount_in: 5100, amount_out: 1600, quote_type: QuoteType::TokenBExactOut }))]
    fn test_consume_liquidity_output_token_b(
        #[case] amount: u64,
        #[case] expected: Result<Quote, CoreError>,
    ) {
        let liquidity = SingleSideLiquidity::from_slice(&[
            (1 << 64, 100),
            ((1 << 64) / 2, 500),
            ((1 << 64) / 4, 1000),
        ]);
        let quote = consume_liquidity(amount, QuoteType::TokenBExactOut, &liquidity);
        assert_eq!(quote, expected);
    }

    #[rstest]
    #[case((1 << 64) / 8, true, true, Ok(Quote { amount_in: 100, amount_out: 12, quote_type: QuoteType::TokenAExactIn }))]
    #[case((1 << 64) / 8, true, false, Ok(Quote { amount_in: 13, amount_out: 100, quote_type: QuoteType::TokenAExactOut }))]
    #[case(8 << 64, false, true, Ok(Quote { amount_in: 100, amount_out: 12, quote_type: QuoteType::TokenBExactIn }))]
    #[case(8 << 64, false, false, Ok(Quote { amount_in: 13, amount_out: 100, quote_type: QuoteType::TokenBExactOut }))]
    fn test_consume_liquidity_rounding_direction(
        #[case] price: u128,
        #[case] amount_is_token_a: bool,
        #[case] amount_is_input: bool,
        #[case] expected: Result<Quote, CoreError>,
    ) {
        let liquidity = SingleSideLiquidity::from_slice(&[(price, 1000)]);
        let quote_type = QuoteType::new(amount_is_token_a, amount_is_input);
        let result = consume_liquidity(100, quote_type, &liquidity);
        assert_eq!(result, expected);
    }

    const PRICE_ONE: u128 = 1 << 64;

    // build_liquidity applies skew to SingleSideLiquidity prices
    // adjusted_price = price * (PER_M - skew) / PER_M
    #[rstest]
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 500, 500, SkewMode::None, false)] // balanced, no skew
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 500, 500, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 500_000, negative_bid_per_m: 500_000, positive_ask_per_m: 500_000, negative_ask_per_m: 500_000 }, false)] // balanced, skew=0
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 500_000, negative_bid_per_m: 500_000, positive_ask_per_m: 500_000, negative_ask_per_m: 500_000 }, true)] // excess A, price down
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 250, 750, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 500_000, negative_bid_per_m: 500_000, positive_ask_per_m: 500_000, negative_ask_per_m: 500_000 }, false)] // excess B, price up
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 100_000, negative_bid_per_m: 100_000, positive_ask_per_m: 100_000, negative_ask_per_m: 100_000 }, true)] // low intensity, still lowers
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 1_000_000, negative_bid_per_m: 1_000_000, positive_ask_per_m: 1_000_000, negative_ask_per_m: 1_000_000 }, true)] // max intensity, stronger shift
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Quadratic, positive_bid_per_m: 500_000, negative_bid_per_m: 500_000, positive_ask_per_m: 500_000, negative_ask_per_m: 500_000 }, true)] // quadratic skew
    #[case(OracleData::FlatPrice { price_q64_64: PRICE_ONE }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 500_000, negative_bid_per_m: 500_000, positive_ask_per_m: 500_000, negative_ask_per_m: 500_000 }, true)] // FlatPrice also skewed
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 750, 250, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 100_000, negative_bid_per_m: 200_000, positive_ask_per_m: 300_000, negative_ask_per_m: 400_000 }, true)] // asymmetric, excess A
    #[case(OracleData::SimpleSpread { price_q64_64: PRICE_ONE, bid_spread_per_m: 10_000, ask_spread_per_m: 10_000 }, 250, 750, SkewMode::Polynomial { exponent: SkewExponent::Linear, positive_bid_per_m: 100_000, negative_bid_per_m: 200_000, positive_ask_per_m: 300_000, negative_ask_per_m: 400_000 }, false)] // asymmetric, excess B
    fn test_build_liquidity_skew(
        #[case] oracle: OracleData,
        #[case] reserves_a: u64,
        #[case] reserves_b: u64,
        #[case] skew_mode: SkewMode,
        #[case] price_lower: bool,
    ) {
        let payload_skew = OraclePayload {
            data: oracle,
            skew: skew_mode,
        };
        let payload_none = OraclePayload {
            data: oracle,
            skew: SkewMode::None,
        };
        let result_skew = build_liquidity(
            &payload_skew,
            QuoteType::TokenAExactIn,
            reserves_a,
            reserves_b,
        )
        .unwrap();
        let result_none = build_liquidity(
            &payload_none,
            QuoteType::TokenAExactIn,
            reserves_a,
            reserves_b,
        )
        .unwrap();
        let (skew_price, _) = result_skew.as_slice()[0];
        let (none_price, _) = result_none.as_slice()[0];
        assert_eq!(skew_price < none_price, price_lower);
    }

    #[test]
    fn test_build_liquidity_skew_empty() {
        let payload = OraclePayload {
            data: OracleData::Empty,
            skew: SkewMode::Polynomial {
                exponent: SkewExponent::Linear,
                positive_bid_per_m: 500_000,
                negative_bid_per_m: 500_000,
                positive_ask_per_m: 500_000,
                negative_ask_per_m: 500_000,
            },
        };
        let result = build_liquidity(&payload, QuoteType::TokenAExactIn, 750, 250).unwrap();
        assert_eq!(result.len(), 0);
    }
}