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@benesjan
benesjan committed Oct 10, 2024
1 parent 6874b55 commit d33c3fe
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Showing 2 changed files with 67 additions and 33 deletions.
10 changes: 10 additions & 0 deletions noir-projects/noir-contracts/contracts/dex_contract/src/lib.nr
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Original file line number Diff line number Diff line change
Expand Up @@ -16,3 +16,13 @@ pub fn get_amount_out(amount_in: u64, reserve_in: u64, reserve_out: u64) -> u64
let denominator = reserve_in * 1000 + amount_in_with_fee;
numerator / denominator
}

// given an output amount of an asset and pair reserves, returns a required input amount of the other asset
// copy of https://github.com/Uniswap/v2-periphery/blob/0335e8f7e1bd1e8d8329fd300aea2ef2f36dd19f/contracts/libraries/UniswapV2Library.sol#L53
pub fn get_amount_in(amount_out: u64, reserve_in: u64, reserve_out: u64) -> u64 {
assert(amount_out > 0, "INSUFFICIENT_OUTPUT_AMOUNT");
assert((reserve_in > 0) & (reserve_out > 0), "INSUFFICIENT_LIQUIDITY");
let numerator = reserve_in * amount_out * 1000;
let denominator = (reserve_out - amount_out) * 997;
(numerator / denominator) + 1
}
90 changes: 57 additions & 33 deletions noir-projects/noir-contracts/contracts/dex_contract/src/main.nr
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use dep::aztec::macros::aztec;
// A Noir implementation of a simplified Uniswap v2 pool.
#[aztec]
contract DEX {
use crate::lib::{get_quote, get_amount_out};
use crate::lib::{get_quote, get_amount_out, get_amount_in};
use dep::aztec::{
macros::{storage::storage, events::event, functions::{private, public, view, internal, initializer}},
prelude::{AztecAddress, SharedImmutable}, protocol_types::traits::Serialize
Expand Down Expand Up @@ -173,6 +173,7 @@ contract DEX {
let token0 = Token::at(state.token0);
let token1 = Token::at(state.token1);

// We transfer the liquidity tokens to the DEX and prepare partial notes for the output tokens.
liquidity_token.transfer_to_public(msg.sender, context.this_address(), liquidity, nonce).call(&mut context);
let token0_slot_commitment = token0.prepare_transfer_to_private(context.this_address(), msg.sender, nonce).call(&mut context);
let token1_slot_commitment = token1.prepare_transfer_to_private(context.this_address(), msg.sender, nonce).call(&mut context);
Expand Down Expand Up @@ -206,17 +207,19 @@ contract DEX {
let token1 = Token::at(state.token1);
let liquidity_token = Token::at(state.liquidity_token);

// Calculate the amounts to be removed from the pool
let mut balance0 = token0.balance_of_public(context.this_address()).view(&mut context);
let mut balance1 = token1.balance_of_public(context.this_address()).view(&mut context);
// We get the reserves and the liquidity token total supply.
let reserve0 = token0.balance_of_public(context.this_address()).view(&mut context) as u64;
let reserve1 = token1.balance_of_public(context.this_address()).view(&mut context) as u64;
let total_supply = liquidity_token.total_supply().view(&mut context) as u64;

let total_supply = liquidity_token.total_supply().view(&mut context);
// We calculate the amounts of token0 and token1 the user is entitled to based on the amount of liquidity they
// are removing.
let amount0 = liquidity * reserve0 / total_supply;
let amount1 = liquidity * reserve1 / total_supply;

let amount0 = liquidity * balance0 / total_supply;
let amount1 = liquidity * balance1 / total_supply;
// TODO: Nuke these castings. Ideally make Token return integer and not Field.
assert(amount0 as u64 >= amount0_min, "INSUFFICIENT_0_AMOUNT");
assert(amount1 as u64 >= amount1_min, "INSUFFICIENT_1_AMOUNT");
// We check if the amounts are greater than the minimum amounts the user is willing to accept.
assert(amount0 >= amount0_min, "INSUFFICIENT_0_AMOUNT");
assert(amount1 >= amount1_min, "INSUFFICIENT_1_AMOUNT");

// At last we burn the liquidity tokens and transfer the token0 and token1 to the user.
liquidity_token.burn_public(context.this_address(), liquidity, 0).call(&mut context);
Expand All @@ -240,6 +243,7 @@ contract DEX {
let token_in = Token::at(token_address_in);
let token_out = Token::at(token_address_out);

// We transfer the `amount_in` to the DEX and we prepare partial note for the output token.
token_in.transfer_to_public(msg.sender, context.this_address(), amount_in, nonce).call(&mut context);
let token_out_slot_commitment = token_out.prepare_transfer_to_private(context.this_address(), msg.sender).call(&mut context);

Expand Down Expand Up @@ -268,16 +272,22 @@ contract DEX {
let token_in = Token::at(token_address_in);
let token_out = Token::at(token_address_out);

// We get the reserves. The `amount_in` was already transferred to the DEX so we need to subtract it.
let reserve_in_with_amount_in = token_in.balance_of_public(context.this_address()).view(&mut context) as u64;
let reserve_in = reserve_in_with_amount_in - amount_in;
let reserve_out = token_out.balance_of_public(context.this_address()).view(&mut context) as u64;

// Calculate the amount of output token we will get.
let amount_out = get_amount_out(amount_in, reserve_in, reserve_out);
assert(amount_out >= amount_out_min, "INSUFFICIENT_OUTPUT_AMOUNT");

// Transfer the output token to the user.
token_out.finalize_transfer_to_private(token_out_slot_commitment, amount_out).call(&mut context);
}

// Swaps `amount_out` of `token_out` for at most `amount_in_max` of `token_in`. The `from_0_to_1` flag indicates
// whether we are swapping `token0` for `token1` or vice versa. `nonce` can be arbitrary non-zero value and its
// purpose is to isolate authwits to this specific call.
#[private]
fn swap_tokens_for_exact_tokens(amount_out: u64, amount_in_max: u64, from_0_to_1: bool, nonce: Field) {
let state = storage.state.read_private();
Expand All @@ -291,6 +301,7 @@ contract DEX {
let token_in = Token::at(token_address_in);
let token_out = Token::at(token_address_out);

// We transfer the `amount_in_max` to the DEX and we prepare partial notes for refund and for the output token.
token_in.transfer_to_public(msg.sender, context.this_address(), amount_in_max, nonce).call(&mut context);
let refund_token_in_slot_commitment = token_in.prepare_transfer_to_private(msg.sender, context.this_address(), nonce).call(&mut context);
let token_out_slot_commitment = token_out.prepare_transfer_to_private(context.this_address(), msg.sender).call(&mut context);
Expand All @@ -304,27 +315,40 @@ contract DEX {
token_address_out
).enqueue(&mut context);
}
// #[public]
// #[internal]
// fn _swap_tokens_for_exact_tokens(
// refund_token_in_slot_commitment: Field,
// token_out_slot_commitment: Field,
// amount_out: u64,
// amount_in_max: u64,
// token_address_in: AztecAddress,
// token_address_out: AztecAddress,
// ) {
// // We don't need any kind of reentrancy guard here because the only way to enter this public function is from
// // `swap_tokens_for_exact_tokens` which is private and since public functions cannot call private ones
// // it's impossible to reenter this function.
// let token_in = Token::at(token_address_in);
// let token_out = Token::at(token_address_out);
// let reserve_in_with_amount_in_max = token_in.balance_of_public(context.this_address()).view(&mut context) as u64;
// let reserve_in = reserve_in_with_amount_in_max - amount_in_max;
// let reserve_out = token_out.balance_of_public(context.this_address()).view(&mut context) as u64;
// let amount_in = get_amount_in(amount_out, reserve_in, reserve_out);
// assert(amount_in <= amount_in_max, "EXCESSIVE_INPUT_AMOUNT");
// token_in.finalize_transfer_to_public_with_refund(refund_token_in_slot_commitment, amount_in).call(&mut context);
// token_out.finalize_transfer_to_private(token_out_slot_commitment, amount_out).call(&mut context);
// }

#[public]
#[internal]
fn _swap_tokens_for_exact_tokens(
refund_token_in_slot_commitment: Field,
token_out_slot_commitment: Field,
amount_out: u64,
amount_in_max: u64,
token_address_in: AztecAddress,
token_address_out: AztecAddress
) {
// We don't need any kind of reentrancy guard here because the only way to enter this public function is from
// `swap_tokens_for_exact_tokens` which is private and since public functions cannot call private ones
// it's impossible to reenter this function.

let token_in = Token::at(token_address_in);
let token_out = Token::at(token_address_out);

// We get the reserves. The `amount_in_max` was already transferred to the DEX so we need to subtract it.
let reserve_in_with_amount_in_max = token_in.balance_of_public(context.this_address()).view(&mut context) as u64;
let reserve_in = reserve_in_with_amount_in_max - amount_in_max;
let reserve_out = token_out.balance_of_public(context.this_address()).view(&mut context) as u64;

// Calculate the amount of input token needed to get the desired amount of output token.
let amount_in = get_amount_in(amount_out, reserve_in, reserve_out);
assert(amount_in <= amount_in_max, "EXCESSIVE_INPUT_AMOUNT");

// If less than amount_in_max of input token was needed we refund the difference.
let refund_amount = amount_in_max - amount_in;
if (refund_amount > 0) {
token_in.finalize_transfer_to_private(refund_token_in_slot_commitment, refund_amount).call(&mut context);
}

// Transfer the output token to the user.
token_out.finalize_transfer_to_private(token_out_slot_commitment, amount_out).call(&mut context);
}
}

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