/** # SwapPair # Author: Increment Labs */ import FungibleToken from 0xf233dcee88fe0abe import SwapInterfaces from 0xb78ef7afa52ff906 import SwapConfig from 0xb78ef7afa52ff906 import SwapError from 0xb78ef7afa52ff906 import SwapFactory from 0xb063c16cac85dbd1 pub contract SwapPair: FungibleToken { /// Total supply of pair lpTokens in existence pub var totalSupply: UFix64 /// Two vaults for the trading pair. access(self) let token0Vault: @FungibleToken.Vault access(self) let token1Vault: @FungibleToken.Vault pub let token0VaultType: Type pub let token1VaultType: Type pub let token0Key: String pub let token1Key: String /// TWAP: last cumulative price pub var blockTimestampLast: UFix64 pub var price0CumulativeLastScaled: UInt256 pub var price1CumulativeLastScaled: UInt256 /// Transaction lock access(self) var lock: Bool /// √(reserve0 * reserve1) for volatile pool, or √√[(r0^3 * r1 + r0 * r1^3) / 2] for stable pool, as of immediately after the most recent liquidity event pub var rootKLast: UFix64 /// Reserved parameter fields: {ParamName: Value} /// Used fields: /// |__ 1. "isStableSwap" -> Bool access(self) let _reservedFields: {String: AnyStruct} /// Event that is emitted when the contract is created pub event TokensInitialized(initialSupply: UFix64) /// Event that is emitted when tokens are withdrawn from a Vault pub event TokensWithdrawn(amount: UFix64, from: Address?) /// Event that is emitted when tokens are deposited to a Vault pub event TokensDeposited(amount: UFix64, to: Address?) /// Event that is emitted when new tokens are minted pub event TokensMinted(amount: UFix64) /// Event that is emitted when tokens are destroyed pub event TokensBurned(amount: UFix64) /// Event that is emitted when a swap trade happenes to this trading pair /// direction: 0 - in self.token0 swapped to out self.token1 /// 1 - in self.token1 swapped to out self.token0 pub event Swap(inTokenAmount: UFix64, outTokenAmount: UFix64, direction: UInt8) /// Event that is emitted when a flashloan is originated from this SwapPair pool pub event Flashloan(executor: Address, executorType: Type, originator: Address, requestedTokenKey: String, amount: UFix64) /// Lptoken Vault /// pub resource Vault: FungibleToken.Provider, FungibleToken.Receiver, FungibleToken.Balance { /// Holds the balance of a users tokens pub var balance: UFix64 /// Initialize the balance at resource creation time init(balance: UFix64) { self.balance = balance } /// withdraw /// /// Function that takes an integer amount as an argument /// and withdraws that amount from the Vault. /// It creates a new temporary Vault that is used to hold /// the money that is being transferred. It returns the newly /// created Vault to the context that called so it can be deposited /// elsewhere. /// pub fun withdraw(amount: UFix64): @FungibleToken.Vault { self.balance = self.balance - amount emit TokensWithdrawn(amount: amount, from: self.owner?.address) return <-create Vault(balance: amount) } /// deposit /// /// Function that takes a Vault object as an argument and adds /// its balance to the balance of the owners Vault. /// It is allowed to destroy the sent Vault because the Vault /// was a temporary holder of the tokens. The Vault's balance has /// been consumed and therefore can be destroyed. /// pub fun deposit(from: @FungibleToken.Vault) { let vault <- from as! @SwapPair.Vault self.balance = self.balance + vault.balance emit TokensDeposited(amount: vault.balance, to: self.owner?.address) vault.balance = 0.0 destroy vault } destroy() { SwapPair.totalSupply = SwapPair.totalSupply - self.balance } } /// createEmptyVault // /// Function that creates a new Vault with a balance of zero /// and returns it to the calling context. A user must call this function /// and store the returned Vault in their storage in order to allow their /// account to be able to receive deposits of this token type. /// pub fun createEmptyVault(): @FungibleToken.Vault { return <-create Vault(balance: 0.0) } /// Permanently lock the first small amount lpTokens access(self) fun donateInitialMinimumLpToken(donateLpBalance: UFix64) { self.totalSupply = self.totalSupply + donateLpBalance emit TokensMinted(amount: donateLpBalance) } /// Mint lpTokens access(self) fun mintLpToken(amount: UFix64): @SwapPair.Vault { self.totalSupply = self.totalSupply + amount emit TokensMinted(amount: amount) return <- create Vault(balance: amount) } /// Burn lpTokens access(self) fun burnLpToken(from: @SwapPair.Vault) { let amount = from.balance destroy from emit TokensBurned(amount: amount) } /// Add liquidity /// pub fun addLiquidity(tokenAVault: @FungibleToken.Vault, tokenBVault: @FungibleToken.Vault): @FungibleToken.Vault { pre { tokenAVault.balance > 0.0 && tokenBVault.balance > 0.0: SwapError.ErrorEncode( msg: "SwapPair: added zero liquidity", err: SwapError.ErrorCode.ADD_ZERO_LIQUIDITY ) (tokenAVault.isInstance(self.token0VaultType) && tokenBVault.isInstance(self.token1VaultType)) || (tokenBVault.isInstance(self.token0VaultType) && tokenAVault.isInstance(self.token1VaultType)): SwapError.ErrorEncode( msg: "SwapPair: added incompatible liquidity pair vaults", err: SwapError.ErrorCode.INVALID_PARAMETERS ) self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } post { self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } self.lock = true let reserve0LastScaled = SwapConfig.UFix64ToScaledUInt256(self.token0Vault.balance) let reserve1LastScaled = SwapConfig.UFix64ToScaledUInt256(self.token1Vault.balance) /// Update twap at the first transaction in one block with the last block balance self._update(reserve0Last: self.token0Vault.balance, reserve1Last: self.token1Vault.balance) /// Mint fee let feeOn = self._mintFee(reserve0: self.token0Vault.balance, reserve1: self.token1Vault.balance) var liquidity = 0.0 if (self.totalSupply == 0.0) { var donateLpBalance = 0.0 if self.isStableSwap() { donateLpBalance = 0.0001 // 1e-4 } else { donateLpBalance = 0.000001 // 1e-6 } // When adding initial liquidity, the balance should not be below certain minimum amount assert(tokenAVault.balance > donateLpBalance && tokenBVault.balance > donateLpBalance, message: SwapError.ErrorEncode( msg: "SwapPair: less than initial minimum liquidity", err: SwapError.ErrorCode.BELOW_MINIMUM_INITIAL_LIQUIDITY ) ) /// Add initial liquidity if (tokenAVault.isInstance(self.token0VaultType)) { self.token0Vault.deposit(from: <-tokenAVault) self.token1Vault.deposit(from: <-tokenBVault) } else { self.token0Vault.deposit(from: <-tokenBVault) self.token1Vault.deposit(from: <-tokenAVault) } /// Mint initial liquidity token and donate initial minimum liquidity token let initialLpAmount = self._rootK(balance0: self.token0Vault.balance, balance1: self.token1Vault.balance) self.donateInitialMinimumLpToken(donateLpBalance: donateLpBalance) liquidity = initialLpAmount - donateLpBalance } else { var lptokenMintAmount0Scaled: UInt256 = 0 var lptokenMintAmount1Scaled: UInt256 = 0 /// Use UFIx64ToUInt256 in division & multiply to solve precision issues let inAmountAScaled = SwapConfig.UFix64ToScaledUInt256(tokenAVault.balance) let inAmountBScaled = SwapConfig.UFix64ToScaledUInt256(tokenBVault.balance) let totalSupplyScaled = SwapConfig.UFix64ToScaledUInt256(self.totalSupply) if (tokenAVault.isInstance(self.token0VaultType)) { lptokenMintAmount0Scaled = inAmountAScaled * totalSupplyScaled / reserve0LastScaled lptokenMintAmount1Scaled = inAmountBScaled * totalSupplyScaled / reserve1LastScaled self.token0Vault.deposit(from: <-tokenAVault) self.token1Vault.deposit(from: <-tokenBVault) } else { lptokenMintAmount0Scaled = inAmountBScaled * totalSupplyScaled / reserve0LastScaled lptokenMintAmount1Scaled = inAmountAScaled * totalSupplyScaled / reserve1LastScaled self.token0Vault.deposit(from: <-tokenBVault) self.token1Vault.deposit(from: <-tokenAVault) } /// Note: User should add proportional liquidity as any extra is added into pool. let mintLptokenAmountScaled = lptokenMintAmount0Scaled < lptokenMintAmount1Scaled ? lptokenMintAmount0Scaled : lptokenMintAmount1Scaled /// Mint liquidity token pro rata liquidity = SwapConfig.ScaledUInt256ToUFix64(mintLptokenAmountScaled) } /// Mint lpTokens let lpTokenVault <-self.mintLpToken(amount: liquidity) if feeOn { self.rootKLast = self._rootK(balance0: self.token0Vault.balance, balance1: self.token1Vault.balance) } self.lock = false return <-lpTokenVault } /// Remove Liquidity /// /// @Return: @[FungibleToken.Vault; 2] /// pub fun removeLiquidity(lpTokenVault: @FungibleToken.Vault) : @[FungibleToken.Vault] { pre { lpTokenVault.balance > 0.0: SwapError.ErrorEncode( msg: "SwapPair: removed zero liquidity", err: SwapError.ErrorCode.INVALID_PARAMETERS ) lpTokenVault.isInstance(Type<@SwapPair.Vault>()): SwapError.ErrorEncode( msg: "SwapPair: input vault type mismatch with lpTokenVault type", err: SwapError.ErrorCode.MISMATCH_LPTOKEN_VAULT ) self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } post { self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } self.lock = true let reserve0LastScaled = SwapConfig.UFix64ToScaledUInt256(self.token0Vault.balance) let reserve1LastScaled = SwapConfig.UFix64ToScaledUInt256(self.token1Vault.balance) /// Update twap self._update(reserve0Last: self.token0Vault.balance, reserve1Last: self.token1Vault.balance) /// Mint fee let feeOn = self._mintFee(reserve0: self.token0Vault.balance, reserve1: self.token1Vault.balance) /// Use UFIx64ToUInt256 in division & multiply to solve precision issues let removeAmountScaled = SwapConfig.UFix64ToScaledUInt256(lpTokenVault.balance) let totalSupplyScaled = SwapConfig.UFix64ToScaledUInt256(self.totalSupply) let token0AmountScaled = removeAmountScaled * reserve0LastScaled / totalSupplyScaled let token1AmountScaled = removeAmountScaled * reserve1LastScaled / totalSupplyScaled let token0Amount = SwapConfig.ScaledUInt256ToUFix64(token0AmountScaled) let token1Amount = SwapConfig.ScaledUInt256ToUFix64(token1AmountScaled) let withdrawnToken0 <- self.token0Vault.withdraw(amount: token0Amount) let withdrawnToken1 <- self.token1Vault.withdraw(amount: token1Amount) /// Burn lpTokens self.burnLpToken(from: <- (lpTokenVault as! @SwapPair.Vault)) if feeOn { self.rootKLast = self._rootK(balance0: self.token0Vault.balance, balance1: self.token1Vault.balance) } self.lock = false return <- [<-withdrawnToken0, <-withdrawnToken1] } /// Swap /// pub fun swap(vaultIn: @FungibleToken.Vault, exactAmountOut: UFix64?): @FungibleToken.Vault { pre { vaultIn.balance > 0.0: SwapError.ErrorEncode(msg: "SwapPair: zero in balance", err: SwapError.ErrorCode.INVALID_PARAMETERS) vaultIn.isInstance(self.token0VaultType) || vaultIn.isInstance(self.token1VaultType): SwapError.ErrorEncode( msg: "SwapPair: incompatible in token vault", err: SwapError.ErrorCode.INVALID_PARAMETERS ) self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } post { self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } self.lock = true self._update(reserve0Last: self.token0Vault.balance, reserve1Last: self.token1Vault.balance) var amountOut = 0.0 /// Calculate the swap result if (vaultIn.isInstance(self.token0VaultType)) { if self.isStableSwap() { amountOut = SwapConfig.getAmountOutStable(amountIn: vaultIn.balance, reserveIn: self.token0Vault.balance, reserveOut: self.token1Vault.balance, p: self.getStableCurveP(), swapFeeRateBps: self.getSwapFeeBps()) } else { amountOut = SwapConfig.getAmountOutVolatile(amountIn: vaultIn.balance, reserveIn: self.token0Vault.balance, reserveOut: self.token1Vault.balance, swapFeeRateBps: self.getSwapFeeBps()) } } else { if self.isStableSwap() { amountOut = SwapConfig.getAmountOutStable(amountIn: vaultIn.balance, reserveIn: self.token1Vault.balance, reserveOut: self.token0Vault.balance, p: 1.0/self.getStableCurveP(), swapFeeRateBps: self.getSwapFeeBps()) } else { amountOut = SwapConfig.getAmountOutVolatile(amountIn: vaultIn.balance, reserveIn: self.token1Vault.balance, reserveOut: self.token0Vault.balance, swapFeeRateBps: self.getSwapFeeBps()) } } /// Check and swap exact output amount if specified in argument if exactAmountOut != nil { assert(amountOut >= exactAmountOut!, message: SwapError.ErrorEncode( msg: "SwapPair: INSUFFICIENT_OUTPUT_AMOUNT", err: SwapError.ErrorCode.INSUFFICIENT_OUTPUT_AMOUNT ) ) amountOut = exactAmountOut! } if (vaultIn.isInstance(self.token0VaultType)) { emit Swap(inTokenAmount: vaultIn.balance, outTokenAmount: amountOut, direction: 0) self.token0Vault.deposit(from: <-vaultIn) self.lock = false return <- self.token1Vault.withdraw(amount: amountOut) } else { emit Swap(inTokenAmount: vaultIn.balance, outTokenAmount: amountOut, direction: 1) self.token1Vault.deposit(from: <-vaultIn) self.lock = false return <- self.token0Vault.withdraw(amount: amountOut) } } /// An executor contract can request to use the whole liquidity of current SwapPair and perform custom operations (like arbitrage, liquidation, et al.), as long as: /// 1. executor implements FlashLoanExecutor resource interface and sets up corresponding resource to receive & process requested tokens, and /// 2. executor repays back requested amount + fees (dominated by 'flashloanRateBps x amount'), and /// all in one atomic function call. /// @params: User-definited extra data passed to executor for further auth/check/decode /// pub fun flashloan(executorCap: Capability<&{SwapInterfaces.FlashLoanExecutor}>, requestedTokenVaultType: Type, requestedAmount: UFix64, params: {String: AnyStruct}) { pre { requestedTokenVaultType == self.token0VaultType || requestedTokenVaultType == self.token1VaultType: SwapError.ErrorEncode( msg: "SwapPair: flashloan invalid requested token type", err: SwapError.ErrorCode.INVALID_PARAMETERS ) (requestedTokenVaultType == self.token0VaultType && requestedAmount > 0.0 && requestedAmount < self.token0Vault.balance) || (requestedTokenVaultType == self.token1VaultType && requestedAmount > 0.0 && requestedAmount < self.token1Vault.balance) : SwapError.ErrorEncode( msg: "SwapPair: flashloan invalid requested amount", err: SwapError.ErrorCode.INVALID_PARAMETERS ) executorCap.check(): SwapError.ErrorEncode( msg: "SwapPair: flashloan executor resource not properly setup", err: SwapError.ErrorCode.FLASHLOAN_EXECUTOR_SETUP ) self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } post { self.lock == false: SwapError.ErrorEncode(msg: "SwapPair: Reentrant", err: SwapError.ErrorCode.REENTRANT) } self.lock = true self._update(reserve0Last: self.token0Vault.balance, reserve1Last: self.token1Vault.balance) var tokenOut: @FungibleToken.Vault? <- nil if (requestedTokenVaultType == self.token0VaultType) { tokenOut <-! self.token0Vault.withdraw(amount: requestedAmount) } else { tokenOut <-! self.token1Vault.withdraw(amount: requestedAmount) } // Send loans and invoke custom executor let executorRef = executorCap.borrow()! let tokenIn <- executorRef.executeAndRepay(loanedToken: <- tokenOut!, params: params) assert(tokenIn.isInstance(requestedTokenVaultType), message: SwapError.ErrorEncode( msg: "SwapPair: flashloan repaid incompatible token", err: SwapError.ErrorCode.INVALID_PARAMETERS ) ) assert(tokenIn.balance >= requestedAmount * (1.0 + UFix64(SwapFactory.getFlashloanRateBps()) / 10000.0), message: SwapError.ErrorEncode( msg: "SwapPair: flashloan insufficient repayment", err: SwapError.ErrorCode.INVALID_PARAMETERS ) ) if (requestedTokenVaultType == self.token0VaultType) { self.token0Vault.deposit(from: <- tokenIn) } else { self.token1Vault.deposit(from: <- tokenIn) } emit Flashloan(executor: executorRef.owner!.address, executorType: executorRef.getType(), originator: self.account.address, requestedTokenKey: requestedTokenVaultType == self.token0VaultType ? self.token0Key : self.token1Key, amount: requestedAmount) self.lock = false } /// Update cumulative price on the first call per block access(self) fun _update(reserve0Last: UFix64, reserve1Last: UFix64) { let blockTimestamp = getCurrentBlock().timestamp let timeElapsed = blockTimestamp - self.blockTimestampLast if (timeElapsed > 0.0 && reserve0Last != 0.0 && reserve1Last != 0.0) { let timeElapsedScaled = SwapConfig.UFix64ToScaledUInt256(timeElapsed) let stableswap_p = self.getStableCurveP() let price0 = self.isStableSwap() ? SwapConfig.quoteStable(amountA: 1.0, reserveA: reserve0Last, reserveB: reserve1Last, p: stableswap_p) : SwapConfig.quote(amountA: 1.0, reserveA: reserve0Last, reserveB: reserve1Last) var price1 = 0.0 if (price0 == 0.0) { price1 = self.isStableSwap() ? SwapConfig.quoteStable(amountA: 1.0, reserveA: reserve1Last, reserveB: reserve0Last, p: 1.0 / stableswap_p) : SwapConfig.quote(amountA: 1.0, reserveA: reserve1Last, reserveB: reserve0Last) } else { price1 = 1.0 / price0 } self.price0CumulativeLastScaled = SwapConfig.overflowAddUInt256( self.price0CumulativeLastScaled, SwapConfig.UFix64ToScaledUInt256(price0) * timeElapsedScaled / SwapConfig.scaleFactor ) self.price1CumulativeLastScaled = SwapConfig.overflowAddUInt256( self.price1CumulativeLastScaled, SwapConfig.UFix64ToScaledUInt256(price1) * timeElapsedScaled / SwapConfig.scaleFactor ) } self.blockTimestampLast = blockTimestamp } /// If feeTo is set, mint 1/6th (the default cut) of the growth in sqrt(k) which is only generated by trading behavior. /// Instead of collecting protocol fees at the time of each trade, accumulated fees are collected only /// when liquidity is deposited or withdrawn. /// access(self) fun _mintFee(reserve0: UFix64, reserve1: UFix64): Bool { let rootKLast = self.rootKLast if SwapFactory.feeTo == nil { if rootKLast > 0.0 { self.rootKLast = 0.0 } return false } if rootKLast > 0.0 { let rootK = self._rootK(balance0: reserve0, balance1: reserve1) if rootK > rootKLast { let numerator = self.totalSupply * (rootK - rootKLast) let denominator = (1.0 / SwapFactory.getProtocolFeeCut() - 1.0) * rootK + rootKLast let liquidity = numerator / denominator if liquidity > 0.0 { let lpTokenVault <-self.mintLpToken(amount: liquidity) let lpTokenCollectionCap = getAccount(SwapFactory.feeTo!).getCapability<&{SwapInterfaces.LpTokenCollectionPublic}>(SwapConfig.LpTokenCollectionPublicPath) assert(lpTokenCollectionCap.check(), message: SwapError.ErrorEncode( msg: "SwapPair: Cannot borrow reference to LpTokenCollection resource in feeTo account", err: SwapError.ErrorCode.LOST_PUBLIC_CAPABILITY ) ) lpTokenCollectionCap.borrow()!.deposit(pairAddr: self.account.address, lpTokenVault: <-lpTokenVault) } } } return true } pub fun _rootK(balance0: UFix64, balance1: UFix64): UFix64 { let e18: UInt256 = SwapConfig.scaleFactor let balance0Scaled = SwapConfig.UFix64ToScaledUInt256(balance0) let balance1Scaled = SwapConfig.UFix64ToScaledUInt256(balance1) if self.isStableSwap() { let _p_scaled: UInt256 = SwapConfig.UFix64ToScaledUInt256(self.getStableCurveP()) let _k_scaled: UInt256 = SwapConfig.k_stable_p(balance0Scaled, balance1Scaled, _p_scaled) return SwapConfig.ScaledUInt256ToUFix64(SwapConfig.sqrt(SwapConfig.sqrt(_k_scaled / 2))) } else { return SwapConfig.ScaledUInt256ToUFix64(SwapConfig.sqrt(balance0Scaled * balance1Scaled / e18)) } } pub fun isStableSwap(): Bool { return (self._reservedFields["isStableSwap"] as! Bool?) ?? false } pub fun getSwapFeeBps(): UInt64 { return SwapFactory.getSwapFeeRateBps(stableMode: self.isStableSwap()) } pub fun getStableCurveP(): UFix64 { return 1.0 } /// Public interfaces /// pub resource PairPublic: SwapInterfaces.PairPublic { pub fun swap(vaultIn: @FungibleToken.Vault, exactAmountOut: UFix64?): @FungibleToken.Vault { return <- SwapPair.swap(vaultIn: <-vaultIn, exactAmountOut: exactAmountOut) } pub fun flashloan(executorCap: Capability<&{SwapInterfaces.FlashLoanExecutor}>, requestedTokenVaultType: Type, requestedAmount: UFix64, params: {String: AnyStruct}) { SwapPair.flashloan(executorCap: executorCap, requestedTokenVaultType: requestedTokenVaultType, requestedAmount: requestedAmount, params: params) } pub fun removeLiquidity(lpTokenVault: @FungibleToken.Vault) : @[FungibleToken.Vault] { return <- SwapPair.removeLiquidity(lpTokenVault: <- lpTokenVault) } pub fun addLiquidity(tokenAVault: @FungibleToken.Vault, tokenBVault: @FungibleToken.Vault): @FungibleToken.Vault { return <- SwapPair.addLiquidity(tokenAVault: <- tokenAVault, tokenBVault: <- tokenBVault) } pub fun getAmountIn(amountOut: UFix64, tokenOutKey: String): UFix64 { if SwapPair.isStableSwap() { if tokenOutKey == SwapPair.token1Key { return SwapConfig.getAmountInStable(amountOut: amountOut, reserveIn: SwapPair.token0Vault.balance, reserveOut: SwapPair.token1Vault.balance, p: SwapPair.getStableCurveP(), swapFeeRateBps: SwapPair.getSwapFeeBps()) } else { return SwapConfig.getAmountInStable(amountOut: amountOut, reserveIn: SwapPair.token1Vault.balance, reserveOut: SwapPair.token0Vault.balance, p: 1.0/SwapPair.getStableCurveP(), swapFeeRateBps: SwapPair.getSwapFeeBps()) } } else { if tokenOutKey == SwapPair.token1Key { return SwapConfig.getAmountInVolatile(amountOut: amountOut, reserveIn: SwapPair.token0Vault.balance, reserveOut: SwapPair.token1Vault.balance, swapFeeRateBps: SwapPair.getSwapFeeBps()) } else { return SwapConfig.getAmountInVolatile(amountOut: amountOut, reserveIn: SwapPair.token1Vault.balance, reserveOut: SwapPair.token0Vault.balance, swapFeeRateBps: SwapPair.getSwapFeeBps()) } } } pub fun getAmountOut(amountIn: UFix64, tokenInKey: String): UFix64 { if SwapPair.isStableSwap() { if tokenInKey == SwapPair.token0Key { return SwapConfig.getAmountOutStable(amountIn: amountIn, reserveIn: SwapPair.token0Vault.balance, reserveOut: SwapPair.token1Vault.balance, p: SwapPair.getStableCurveP(), swapFeeRateBps: SwapPair.getSwapFeeBps()) } else { return SwapConfig.getAmountOutStable(amountIn: amountIn, reserveIn: SwapPair.token1Vault.balance, reserveOut: SwapPair.token0Vault.balance, p: 1.0/SwapPair.getStableCurveP(), swapFeeRateBps: SwapPair.getSwapFeeBps()) } } else { if tokenInKey == SwapPair.token0Key { return SwapConfig.getAmountOutVolatile(amountIn: amountIn, reserveIn: SwapPair.token0Vault.balance, reserveOut: SwapPair.token1Vault.balance, swapFeeRateBps: SwapPair.getSwapFeeBps()) } else { return SwapConfig.getAmountOutVolatile(amountIn: amountIn, reserveIn: SwapPair.token1Vault.balance, reserveOut: SwapPair.token0Vault.balance, swapFeeRateBps: SwapPair.getSwapFeeBps()) } } } pub fun getPrice0CumulativeLastScaled(): UInt256 { return SwapPair.price0CumulativeLastScaled } pub fun getPrice1CumulativeLastScaled(): UInt256 { return SwapPair.price1CumulativeLastScaled } pub fun getBlockTimestampLast(): UFix64 { return SwapPair.blockTimestampLast } pub fun getPairInfo(): [AnyStruct] { return [ SwapPair.token0Key, // 0 SwapPair.token1Key, SwapPair.token0Vault.balance, SwapPair.token1Vault.balance, SwapPair.account.address, SwapPair.totalSupply, // 5 SwapPair.getSwapFeeBps(), SwapPair.isStableSwap(), SwapPair.getStableCurveP() ] } pub fun getLpTokenVaultType(): Type { return Type<@SwapPair.Vault>() } pub fun isStableSwap(): Bool { return SwapPair.isStableSwap() } pub fun getStableCurveP(): UFix64 { return SwapPair.getStableCurveP() } } init(token0Vault: @FungibleToken.Vault, token1Vault: @FungibleToken.Vault, stableMode: Bool) { self.totalSupply = 0.0 self.token0VaultType = token0Vault.getType() self.token1VaultType = token1Vault.getType() self.token0Vault <- token0Vault self.token1Vault <- token1Vault self.lock = false self.blockTimestampLast = getCurrentBlock().timestamp self.price0CumulativeLastScaled = 0 self.price1CumulativeLastScaled = 0 self.rootKLast = 0.0 self._reservedFields = {} self._reservedFields["isStableSwap"] = stableMode self.token0Key = SwapConfig.SliceTokenTypeIdentifierFromVaultType(vaultTypeIdentifier: self.token0VaultType.identifier) self.token1Key = SwapConfig.SliceTokenTypeIdentifierFromVaultType(vaultTypeIdentifier: self.token1VaultType.identifier) /// Open public interface capability destroy <-self.account.load<@AnyResource>(from: /storage/pair_public) self.account.save(<-create PairPublic(), to: /storage/pair_public) /// Pair interface public path: SwapConfig.PairPublicPath self.account.link<&{SwapInterfaces.PairPublic}>(SwapConfig.PairPublicPath, target: /storage/pair_public) emit TokensInitialized(initialSupply: self.totalSupply) } }

🎉Happy diving into the flow

Contract

🎉Happy diving into the flow