ConstantProductLib

Title: ConstantProductLib

Authors: David Dada <daveproxy80@gmail.com> (https://github.com/dadadave80), Modified from Uniswap V2 (https://github.com/Uniswap/v2-core/blob/master/contracts/UniswapV2Pair.sol)

Library implementing a Uniswap V2-style constant-product AMM (x*y=k) as a stateless Diamond facet.

All state lives in a single ERC-7201 namespaced slot. LP shares are tracked internally (not as a separate ERC-20 token) to avoid an extra facet dependency. 0.3% swap fee (30 bps).

Constants

FEE_BPS

Swap fee in basis points (0.3%).

uint16 internal constant FEE_BPS = 30;

MINIMUM_LIQUIDITY

Minimum liquidity permanently locked on first deposit (Uniswap V2 convention).

uint256 internal constant MINIMUM_LIQUIDITY = 1000;

Functions

constantProductStorage

Returns the ConstantProduct storage struct.

function constantProductStorage() internal pure returns (ConstantProductStorage storage $);

Returns

Name	Type	Description
$	`ConstantProductStorage`

__ConstantProduct_init

Initializes the ConstantProduct pool with two ERC-20 token addresses.

Must be called inside a pre/postInitializer block. Sorts tokens so token0 < token1.

function __ConstantProduct_init(address tokenA, address tokenB) internal;

Parameters

Name	Type	Description
tokenA	`address`	One of the two pool tokens.
tokenB	`address`	The other pool token.

registerInterface

Registers support for IConstantProduct via ERC-165.

function registerInterface() internal;

token0

Returns token0 address.

function token0() internal view returns (address);

Returns

Name	Type	Description
<none>	`address`

token1

Returns token1 address.

function token1() internal view returns (address);

Returns

Name	Type	Description
<none>	`address`

getReserves

Returns the current reserves and last-update timestamp.

function getReserves() internal view returns (uint256 reserve0, uint256 reserve1, uint32 blockTimestampLast);

Returns

Name	Type	Description
reserve0	`uint256`
reserve1	`uint256`
blockTimestampLast	`uint32`

totalLpSupply

Returns the total LP share supply.

function totalLpSupply() internal view returns (uint256);

Returns

Name	Type	Description
<none>	`uint256`

lpBalanceOf

Returns the LP share balance of account.

function lpBalanceOf(address account) internal view returns (uint256);

Parameters

Name	Type	Description
account	`address`

Returns

Name	Type	Description
<none>	`uint256`

feeBps

Returns the swap fee in basis points (always 30).

function feeBps() internal pure returns (uint16);

Returns

Name	Type	Description
<none>	`uint16`

addLiquidity

Adds liquidity to the pool and mints LP shares to to.

function addLiquidity(
        uint256 amount0Desired,
        uint256 amount1Desired,
        uint256 amount0Min,
        uint256 amount1Min,
        address to
    ) internal returns (uint256 amount0, uint256 amount1, uint256 liquidity);

Parameters

Name	Type	Description
amount0Desired	`uint256`	Desired deposit of token0.
amount1Desired	`uint256`	Desired deposit of token1.
amount0Min	`uint256`	Minimum acceptable token0 deposit (slippage guard).
amount1Min	`uint256`	Minimum acceptable token1 deposit (slippage guard).
to	`address`	Recipient of minted LP shares.

Returns

Name	Type	Description
amount0	`uint256`	Actual token0 deposited.
amount1	`uint256`	Actual token1 deposited.
liquidity	`uint256`	LP shares minted to `to`.

removeLiquidity

Burns LP shares from the caller and returns underlying tokens to to.

function removeLiquidity(uint256 liquidity, uint256 amount0Min, uint256 amount1Min, address to)
        internal
        returns (uint256 amount0, uint256 amount1);

Parameters

Name	Type	Description
liquidity	`uint256`	Amount of LP shares to burn.
amount0Min	`uint256`	Minimum acceptable token0 returned (slippage guard).
amount1Min	`uint256`	Minimum acceptable token1 returned (slippage guard).
to	`address`	Recipient of the returned tokens.

Returns

Name	Type	Description
amount0	`uint256`	Amount of token0 returned.
amount1	`uint256`	Amount of token1 returned.

swapExactTokensForTokens

Swaps an exact input amount for output tokens.

function swapExactTokensForTokens(uint256 amountIn, uint256 amountOutMin, bool zeroForOne, address to)
        internal
        returns (uint256 amountOut);

Parameters

Name	Type	Description
amountIn	`uint256`	Exact input token amount to sell.
amountOutMin	`uint256`	Minimum acceptable output (slippage guard).
zeroForOne	`bool`	True = sell token0 for token1; False = sell token1 for token0.
to	`address`	Recipient of output tokens.

Returns

Name	Type	Description
amountOut	`uint256`	Output token amount sent to `to`.

_executeSwap

Internal helper that carries out the swap to avoid stack-too-deep in the public entry point. Fee-on-transfer safe: the input is pulled first and the ACTUAL received balance delta (effectiveAmountIn) drives the output, K-invariant, slippage and reserve math. For standard tokens the delta equals the requested amount, preserving existing behavior. The reentrancy guard in the caller protects the pull-before-update ordering.

function _executeSwap(
        ConstantProductStorage storage $,
        uint256 amountIn,
        uint256 amountOutMin,
        bool zeroForOne,
        address caller,
        address to
    ) private returns (uint256 amountOut);

Parameters

Name	Type	Description
$	`ConstantProductStorage`
amountIn	`uint256`
amountOutMin	`uint256`
zeroForOne	`bool`
caller	`address`
to	`address`

Returns

Name	Type	Description
amountOut	`uint256`

_checkK

Validates that the constant-product invariant holds after a swap.

function _checkK(uint256 amountIn, uint256 amountOut, uint256 reserveIn, uint256 reserveOut) private pure;

Parameters

Name	Type	Description
amountIn	`uint256`
amountOut	`uint256`
reserveIn	`uint256`
reserveOut	`uint256`

getAmountOut

Computes the output amount given an input amount and pool reserves, applying the 0.3% fee.

function getAmountOut(uint256 amountIn, uint256 reserveIn, uint256 reserveOut)
        internal
        pure
        returns (uint256 amountOut);

Parameters

Name	Type	Description
amountIn	`uint256`	The input amount.
reserveIn	`uint256`	The reserve of the input token.
reserveOut	`uint256`	The reserve of the output token.

Returns

Name	Type	Description
amountOut	`uint256`	The output amount after fee.

getAmountIn

Computes the required input to receive a specific output amount, applying the 0.3% fee.

function getAmountIn(uint256 amountOut, uint256 reserveIn, uint256 reserveOut)
        internal
        pure
        returns (uint256 amountIn);

Parameters

Name	Type	Description
amountOut	`uint256`	The desired output amount.
reserveIn	`uint256`	The reserve of the input token.
reserveOut	`uint256`	The reserve of the output token.

Returns

Name	Type	Description
amountIn	`uint256`	The required input amount (rounded up).

quote

Returns the equivalent amount of tokenB given amountA at the current pool ratio.

No fee is applied — this is used for liquidity proportion calculations.

function quote(uint256 amountA, uint256 reserveA, uint256 reserveB) internal pure returns (uint256 amountB);

Parameters

Name	Type	Description
amountA	`uint256`	Amount of tokenA.
reserveA	`uint256`	Reserve of tokenA.
reserveB	`uint256`	Reserve of tokenB.

Returns

Name	Type	Description
amountB	`uint256`	Equivalent amount of tokenB.

_sqrt

Babylonian square-root used for first-liquidity LP share calculation.

function _sqrt(uint256 y) internal pure returns (uint256 z);

Parameters

Name	Type	Description
y	`uint256`	The value to take the square root of.

Returns

Name	Type	Description
z	`uint256`	The integer square root of `y`.

_mintLp

Mints LP shares to account, updating total supply.

function _mintLp(ConstantProductStorage storage $, address account, uint256 amount) private;

Parameters

Name	Type	Description
$	`ConstantProductStorage`
account	`address`
amount	`uint256`

_burnLp

Burns LP shares from account, updating total supply.

function _burnLp(ConstantProductStorage storage $, address account, uint256 amount) private;

Parameters

Name	Type	Description
$	`ConstantProductStorage`
account	`address`
amount	`uint256`

_safeTransferFromReceived

Pulls amount of token from from into the pool and returns the ACTUAL received amount (the pool balance delta).

Fee-on-transfer / deflationary tokens deliver less than amount; the measured delta is the effective input used for reserve, LP and K math. For standard tokens the delta equals amount, preserving existing behavior. Reverts ConstantProductTransferFailed on a false return.

function _safeTransferFromReceived(address token, address from, uint256 amount) private returns (uint256 received);

Parameters

Name	Type	Description
token	`address`	The token to pull.
from	`address`	The address to pull from.
amount	`uint256`	The requested transfer amount.

Returns

Name	Type	Description
received	`uint256`	The actual amount credited to the pool (post-fee).

_safeTransfer

Calls transfer on token, reverts with ConstantProductTransferFailed on false return.

function _safeTransfer(address token, address to, uint256 amount) private;

Parameters

Name	Type	Description
token	`address`
to	`address`
amount	`uint256`