Preface

In the cryptocurrency market, trading opportunities are fleeting, especially high-yield arbitrage windows, which often only last for a very short time. If you rely solely on manual trading, it is often difficult to keep up with the market. Therefore, pending order trading has become an important means to improve trading efficiency.

Based on the ideas of Xiaocao's article, this article reconstructs Curve.fi's trading pool pending order strategy on the FMZ platform and introduces how to achieve the same effect through the FMZ platform. At the same time, the private key protection scheme will be discussed in detail to ensure that security and convenience are taken into account during programmatic trading.

The strategy is written in JavaScript and uses the web3 eth exchange object of the FMZ platform.

Security Design

Based on the security design in the article How to Implement Pending Orders in Decentralized Exchanges — Taking Curve as An Example, we use a similar AES encryption method. We use a password and count to encrypt data.

  • Password: hashed with sha256.
  • Count: use the timestamp as a random count to participate in encryption.
  1. Encrypt the private key offline, use the "password" and "count" to encrypt the private key, and get an encrypted secret key.
  2. Configure the encrypted key, password, count, etc. to the FMZ platform, and use the strategy interface parameter "Encrypted String" control. The content entered in the control will be encrypted, and the configuration information recorded on the platform is not the plain text content in the control.
  3. When the strategy is running, the docker can decrypt the information and load the secret key (after loading the secret key, all related variables will be reset).
// Encryption/decryption methodfunctioncryptoKey(type, data, passWord, count) {
    // Loading the encryption libraryeval(HttpQuery("https://cdnjs.cloudflare.com/ajax/libs/aes-js/3.1.2/index.min.js"))

    // sha256 passwordvar hash = Encode("sha256", "string", "hex", passWord).substring(0, 32)

    if (type == "encrypt") {
        var key = aesjs.utils.utf8.toBytes(hash.substring(0, 32))
        var counter = new aesjs.Counter(count)
        var textBytes = aesjs.utils.utf8.toBytes(data)
        var aesCtr = new aesjs.ModeOfOperation.ctr(key, counter)
        var encryptedBytes = aesCtr.encrypt(textBytes)
        var encryptedHex = aesjs.utils.hex.fromBytes(encryptedBytes)
        return encryptedHex
    } elseif (type == "decrypt") {
        var key = aesjs.utils.utf8.toBytes(hash.substring(0, 32))
        var counter = new aesjs.Counter(count)
        var aesCtrDecrypt = new aesjs.ModeOfOperation.ctr(key, counter)
        const decryptedBytes = aesCtrDecrypt.decrypt(aesjs.utils.hex.toBytes(data))
        const decryptedText = aesjs.utils.utf8.fromBytes(decryptedBytes)        
        return decryptedText
    } else {
        throw"function cryptoKey(), param 'type' not support"
    }
}

Configure web3 Exchange Object

https://www.fmz.com/m/platforms/add

There are many Ethereum nodes available online, the commonly used ones are:

You can apply to create your own address, and then configure it for use. I will not go into details here. You can fill in the key information at will. We plan to load it dynamically, so there is no point in configuring it here.

    exchange.IO("key", cryptoKey(descCryptoType[cryptoType], keyData, password, count))
    walletAddress = exchange.IO("address")
    Log("Load secret key, wallet address:", walletAddress)

Use the exchange.IO("key", ...) function encapsulated by the platform to load and update the private key after decryption.

Register ABI

After solving the security problem, the next step is to do some operations on Ethereum smart contracts. According to Curve.fi DEX mentioned by Xiaocao, we can easily find this dApp online:

https://curve.fi/dex/ethereum/pools/factory-stable-ng-102/deposit

On the sDAI/sUSDe exchange pool page, you can find the address of the exchange pool contract and observe the contract. The methods we may use are:

  • coins: Get the contract address of the token participating in the transaction in the pool
  • get_dy: Calculate the current exchange quantity in the pool.
  • exchange: Execute exchange.

To call these methods, you need to register the ABI of the pool contract first. I did not filter the methods used, but copied and pasted the complete ABI directly and then registered it:

// sDAI/sUSDe pool contract address and ABIvar poolAddress = "0x167478921b907422F8E88B43C4Af2B8BEa278d3A"// contract ABIvar poolABI = `[{"name":"Transfer","inputs":[{"name":"sender","type":"address","indexed":true},{"name":"receiver","type":"address","indexed":true},{"name":"value","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"Approval","inputs":[{"name":"owner","type":"address","indexed":true},{"name":"spender","type":"address","indexed":true},{"name":"value","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"TokenExchange","inputs":[{"name":"buyer","type":"address","indexed":true},{"name":"sold_id","type":"int128","indexed":false},{"name":"tokens_sold","type":"uint256","indexed":false},{"name":"bought_id","type":"int128","indexed":false},{"name":"tokens_bought","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"TokenExchangeUnderlying","inputs":[{"name":"buyer","type":"address","indexed":true},{"name":"sold_id","type":"int128","indexed":false},{"name":"tokens_sold","type":"uint256","indexed":false},{"name":"bought_id","type":"int128","indexed":false},{"name":"tokens_bought","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"AddLiquidity","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"invariant","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidity","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidityOne","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_id","type":"int128","indexed":false},{"name":"token_amount","type":"uint256","indexed":false},{"name":"coin_amount","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidityImbalance","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"invariant","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RampA","inputs":[{"name":"old_A","type":"uint256","indexed":false},{"name":"new_A","type":"uint256","indexed":false},{"name":"initial_time","type":"uint256","indexed":false},{"name":"future_time","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"StopRampA","inputs":[{"name":"A","type":"uint256","indexed":false},{"name":"t","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"ApplyNewFee","inputs":[{"name":"fee","type":"uint256","indexed":false},{"name":"offpeg_fee_multiplier","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"SetNewMATime","inputs":[{"name":"ma_exp_time","type":"uint256","indexed":false},{"name":"D_ma_time","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"stateMutability":"nonpayable","type":"constructor","inputs":[{"name":"_name","type":"string"},{"name":"_symbol","type":"string"},{"name":"_A","type":"uint256"},{"name":"_fee","type":"uint256"},{"name":"_offpeg_fee_multiplier","type":"uint256"},{"name":"_ma_exp_time","type":"uint256"},{"name":"_coins","type":"address[]"},{"name":"_rate_multipliers","type":"uint256[]"},{"name":"_asset_types","type":"uint8[]"},{"name":"_method_ids","type":"bytes4[]"},{"name":"_oracles","type":"address[]"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"exchange","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange_received","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange_received","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"add_liquidity","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_min_mint_amount","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"add_liquidity","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_min_mint_amount","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"},{"name":"_min_received","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"},{"name":"_min_received","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_imbalance","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_max_burn_amount","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_imbalance","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_max_burn_amount","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"},{"name":"_receiver","type":"address"},{"name":"_claim_admin_fees","type":"bool"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"withdraw_admin_fees","inputs":[],"outputs":[]},{"stateMutability":"view","type":"function","name":"last_price","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ema_price","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_p","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"price_oracle","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"D_oracle","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"transfer","inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"transferFrom","inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"approve","inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"permit","inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"},{"name":"_deadline","type":"uint256"},{"name":"_v","type":"uint8"},{"name":"_r","type":"bytes32"},{"name":"_s","type":"bytes32"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"view","type":"function","name":"DOMAIN_SEPARATOR","inputs":[],"outputs":[{"name":"","type":"bytes32"}]},{"stateMutability":"view","type":"function","name":"get_dx","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_dy","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"dx","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"calc_withdraw_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"totalSupply","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_virtual_price","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"calc_token_amount","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_is_deposit","type":"bool"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"A_precise","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"balances","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_balances","inputs":[],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"view","type":"function","name":"stored_rates","inputs":[],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"view","type":"function","name":"dynamic_fee","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"ramp_A","inputs":[{"name":"_future_A","type":"uint256"},{"name":"_future_time","type":"uint256"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"stop_ramp_A","inputs":[],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"set_new_fee","inputs":[{"name":"_new_fee","type":"uint256"},{"name":"_new_offpeg_fee_multiplier","type":"uint256"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"set_ma_exp_time","inputs":[{"name":"_ma_exp_time","type":"uint256"},{"name":"_D_ma_time","type":"uint256"}],"outputs":[]},{"stateMutability":"view","type":"function","name":"N_COINS","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"coins","inputs":[{"name":"arg0","type":"uint256"}],"outputs":[{"name":"","type":"address"}]},{"stateMutability":"view","type":"function","name":"fee","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"offpeg_fee_multiplier","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"admin_fee","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"initial_A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"future_A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"initial_A_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"future_A_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"admin_balances","inputs":[{"name":"arg0","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ma_exp_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"D_ma_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ma_last_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"name","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"symbol","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"decimals","inputs":[],"outputs":[{"name":"","type":"uint8"}]},{"stateMutability":"view","type":"function","name":"version","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"balanceOf","inputs":[{"name":"arg0","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"allowance","inputs":[{"name":"arg0","type":"address"},{"name":"arg1","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"nonces","inputs":[{"name":"arg0","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"salt","inputs":[],"outputs":[{"name":"","type":"bytes32"}]}]`// register ABI
    exchange.IO("abi", poolAddress, poolABI)

Read Wallet Balance and Token Balance

Reading wallet token balance, token precision, token name, etc. are all methods of ERC20 contracts and are registered by default.

var token0Name = exchange.IO("api", token0Address, "symbol")
    var token1Name = exchange.IO("api", token1Address, "symbol")
    var token0Decimals = exchange.IO("api", token0Address, "decimals")
    var token1Decimals = exchange.IO("api", token1Address, "decimals")
var sDAI_Balance = exchange.IO("api", sDAI["address"], "balanceOf", walletAddress)
    var sUSDe_Balance = exchange.IO("api", sUSDe["address"], "balanceOf", walletAddress)

Monitor Exchange Pools

functiongetBuyProfit(poolAddress, sDAI, sUSDe, amountIn, entryPriceForDAI) {    
    var data = exchange.IO("api", poolAddress, "get_dy", sDAI["idx"], sUSDe["idx"], toInnerAmount(amountIn, sDAI["decimals"]))
    Log("get_dy:", data)
    var amountOut = toAmount(data, sUSDe["decimals"])
    if (!amountOut) {
        returnnull
    }
    
    var profit = amountOut - entryPriceForDAI * amountIn  
    return {"profit": profit, "amountOut": amountOut, "sDAI_sUSDe_price": amountOut / amountIn}
}

The trigger conditions are designed as follows:

if (profit > 1000 && sDAI_Balance > amountIn) {
        Log("The exchange conditions are met and the sDAI -> sUSDe exchange trading begins...")
        /* The redemption operation code is only for teaching demonstration. Please use this function with caution and test it first. 
        executeTrade(poolAddress, sDAI, sUSDe, amountIn, 0.999*amountOut)
        */
    }

The exchange operation can only be performed when the current exchange amount satisfies the profit greater than 1000 and there are enough sDAI tokens in the wallet.

Exchange Operation

functionexecuteTrade(poolAddress, tokenIn, tokenOut, amountIn, minOutAmount) {
    // exchange : i , j , _dx , _min_dyvar swapTx = exchange.IO("api", poolAddress, "exchange", tokenIn["idx"], tokenOut["idx"], toInnerAmount(amountIn, tokenIn["decimals"]), toInnerAmount(minOutAmount, tokenOut["decimals"]))
    if (swapTx) {
        while (true) {
            Sleep(1000 * 3)
            let info = e.IO("api", "eth", "eth_getTransactionReceipt", swapTx)
            if (info && info.gasUsed) {
                returntrue
            }
            Log('Transaction not yet mined', swapTx)
        }
    }

    returnfalse 
}

Complete Strategy Code

functiontoAmount(s, decimals) {
    returnNumber((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

functiontoInnerAmount(n, decimals) {
    return (BigDecimal(n) * BigDecimal(Math.pow(10, decimals))).toFixed(0)
}

functiongetBuyProfit(poolAddress, sDAI, sUSDe, amountIn, entryPriceForDAI) {    
    var data = exchange.IO("api", poolAddress, "get_dy", sDAI["idx"], sUSDe["idx"], toInnerAmount(amountIn, sDAI["decimals"]))
    var amountOut = toAmount(data, sUSDe["decimals"])
    if (!amountOut) {
        returnnull
    }
    
    var profit = amountOut - entryPriceForDAI * amountIn  
    return {"profit": profit, "amountOut": amountOut, "sDAI_sUSDe_price": amountOut / amountIn}
}

functionexecuteTrade(poolAddress, tokenIn, tokenOut, amountIn, minOutAmount) {
    // exchange : i , j , _dx , _min_dyvar swapTx = exchange.IO("api", poolAddress, "exchange", tokenIn["idx"], tokenOut["idx"], toInnerAmount(amountIn, tokenIn["decimals"]), toInnerAmount(minOutAmount, tokenOut["decimals"]))
    if (swapTx) {
        while (true) {
            Sleep(1000 * 3)
            let info = e.IO("api", "eth", "eth_getTransactionReceipt", swapTx)
            if (info && info.gasUsed) {
                returntrue
            }
            Log('Transaction not yet mined', swapTx)
        }
    }

    returnfalse 
}

// Encryption/decryption methodfunctioncryptoKey(type, data, passWord, count) {
    // Loading the encryption libraryeval(HttpQuery("https://cdnjs.cloudflare.com/ajax/libs/aes-js/3.1.2/index.min.js"))

    // sha256 passwordvar hash = Encode("sha256", "string", "hex", passWord).substring(0, 32)

    if (type == "encrypt") {
        var key = aesjs.utils.utf8.toBytes(hash.substring(0, 32))
        var counter = new aesjs.Counter(count)
        var textBytes = aesjs.utils.utf8.toBytes(data)
        var aesCtr = new aesjs.ModeOfOperation.ctr(key, counter)
        var encryptedBytes = aesCtr.encrypt(textBytes)
        var encryptedHex = aesjs.utils.hex.fromBytes(encryptedBytes)
        return encryptedHex
    } elseif (type == "decrypt") {
        var key = aesjs.utils.utf8.toBytes(hash.substring(0, 32))
        var counter = new aesjs.Counter(count)
        var aesCtrDecrypt = new aesjs.ModeOfOperation.ctr(key, counter)
        const decryptedBytes = aesCtrDecrypt.decrypt(aesjs.utils.hex.toBytes(data))
        const decryptedText = aesjs.utils.utf8.fromBytes(decryptedBytes)        
        return decryptedText
    } else {
        throw"function cryptoKey(), param 'type' not support"
    }
}

// Encryption/decryption optionsconst descCryptoType = ["encrypt", "decrypt"]

functionmain() {
    LogReset(1)

    var count = _G("count")
    if (!count) {
        count = newDate().getTime()
        _G("count", count)
    }

    var walletAddress = nullif (cryptoType == 1) {
        exchange.IO("key", cryptoKey(descCryptoType[cryptoType], keyData, password, count))
        walletAddress = exchange.IO("address")
        Log("Load secret key, wallet address:", walletAddress)
    } else {
        Log("Encrypted key:", cryptoKey(descCryptoType[cryptoType], keyData, password, count))
        return 
    }
    
    Log("Wallet ETH balance:", toAmount(exchange.IO("api", "eth", "eth_getBalance", walletAddress, "latest"), 18))
    
    // sDAI/sUSDe pool contract address and ABIvar poolAddress = "0x167478921b907422F8E88B43C4Af2B8BEa278d3A"// contract ABIvar poolABI = `[{"name":"Transfer","inputs":[{"name":"sender","type":"address","indexed":true},{"name":"receiver","type":"address","indexed":true},{"name":"value","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"Approval","inputs":[{"name":"owner","type":"address","indexed":true},{"name":"spender","type":"address","indexed":true},{"name":"value","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"TokenExchange","inputs":[{"name":"buyer","type":"address","indexed":true},{"name":"sold_id","type":"int128","indexed":false},{"name":"tokens_sold","type":"uint256","indexed":false},{"name":"bought_id","type":"int128","indexed":false},{"name":"tokens_bought","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"TokenExchangeUnderlying","inputs":[{"name":"buyer","type":"address","indexed":true},{"name":"sold_id","type":"int128","indexed":false},{"name":"tokens_sold","type":"uint256","indexed":false},{"name":"bought_id","type":"int128","indexed":false},{"name":"tokens_bought","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"AddLiquidity","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"invariant","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidity","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidityOne","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_id","type":"int128","indexed":false},{"name":"token_amount","type":"uint256","indexed":false},{"name":"coin_amount","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RemoveLiquidityImbalance","inputs":[{"name":"provider","type":"address","indexed":true},{"name":"token_amounts","type":"uint256[]","indexed":false},{"name":"fees","type":"uint256[]","indexed":false},{"name":"invariant","type":"uint256","indexed":false},{"name":"token_supply","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"RampA","inputs":[{"name":"old_A","type":"uint256","indexed":false},{"name":"new_A","type":"uint256","indexed":false},{"name":"initial_time","type":"uint256","indexed":false},{"name":"future_time","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"StopRampA","inputs":[{"name":"A","type":"uint256","indexed":false},{"name":"t","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"ApplyNewFee","inputs":[{"name":"fee","type":"uint256","indexed":false},{"name":"offpeg_fee_multiplier","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"name":"SetNewMATime","inputs":[{"name":"ma_exp_time","type":"uint256","indexed":false},{"name":"D_ma_time","type":"uint256","indexed":false}],"anonymous":false,"type":"event"},{"stateMutability":"nonpayable","type":"constructor","inputs":[{"name":"_name","type":"string"},{"name":"_symbol","type":"string"},{"name":"_A","type":"uint256"},{"name":"_fee","type":"uint256"},{"name":"_offpeg_fee_multiplier","type":"uint256"},{"name":"_ma_exp_time","type":"uint256"},{"name":"_coins","type":"address[]"},{"name":"_rate_multipliers","type":"uint256[]"},{"name":"_asset_types","type":"uint8[]"},{"name":"_method_ids","type":"bytes4[]"},{"name":"_oracles","type":"address[]"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"exchange","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange_received","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"exchange_received","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"_dx","type":"uint256"},{"name":"_min_dy","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"add_liquidity","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_min_mint_amount","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"add_liquidity","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_min_mint_amount","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"},{"name":"_min_received","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"},{"name":"_min_received","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_imbalance","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_max_burn_amount","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity_imbalance","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_max_burn_amount","type":"uint256"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"},{"name":"_receiver","type":"address"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"remove_liquidity","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"_min_amounts","type":"uint256[]"},{"name":"_receiver","type":"address"},{"name":"_claim_admin_fees","type":"bool"}],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"nonpayable","type":"function","name":"withdraw_admin_fees","inputs":[],"outputs":[]},{"stateMutability":"view","type":"function","name":"last_price","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ema_price","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_p","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"price_oracle","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"D_oracle","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"transfer","inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"transferFrom","inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"approve","inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"nonpayable","type":"function","name":"permit","inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"},{"name":"_deadline","type":"uint256"},{"name":"_v","type":"uint8"},{"name":"_r","type":"bytes32"},{"name":"_s","type":"bytes32"}],"outputs":[{"name":"","type":"bool"}]},{"stateMutability":"view","type":"function","name":"DOMAIN_SEPARATOR","inputs":[],"outputs":[{"name":"","type":"bytes32"}]},{"stateMutability":"view","type":"function","name":"get_dx","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"dy","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_dy","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"},{"name":"dx","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"calc_withdraw_one_coin","inputs":[{"name":"_burn_amount","type":"uint256"},{"name":"i","type":"int128"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"totalSupply","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_virtual_price","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"calc_token_amount","inputs":[{"name":"_amounts","type":"uint256[]"},{"name":"_is_deposit","type":"bool"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"A_precise","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"balances","inputs":[{"name":"i","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"get_balances","inputs":[],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"view","type":"function","name":"stored_rates","inputs":[],"outputs":[{"name":"","type":"uint256[]"}]},{"stateMutability":"view","type":"function","name":"dynamic_fee","inputs":[{"name":"i","type":"int128"},{"name":"j","type":"int128"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"nonpayable","type":"function","name":"ramp_A","inputs":[{"name":"_future_A","type":"uint256"},{"name":"_future_time","type":"uint256"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"stop_ramp_A","inputs":[],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"set_new_fee","inputs":[{"name":"_new_fee","type":"uint256"},{"name":"_new_offpeg_fee_multiplier","type":"uint256"}],"outputs":[]},{"stateMutability":"nonpayable","type":"function","name":"set_ma_exp_time","inputs":[{"name":"_ma_exp_time","type":"uint256"},{"name":"_D_ma_time","type":"uint256"}],"outputs":[]},{"stateMutability":"view","type":"function","name":"N_COINS","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"coins","inputs":[{"name":"arg0","type":"uint256"}],"outputs":[{"name":"","type":"address"}]},{"stateMutability":"view","type":"function","name":"fee","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"offpeg_fee_multiplier","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"admin_fee","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"initial_A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"future_A","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"initial_A_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"future_A_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"admin_balances","inputs":[{"name":"arg0","type":"uint256"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ma_exp_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"D_ma_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"ma_last_time","inputs":[],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"name","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"symbol","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"decimals","inputs":[],"outputs":[{"name":"","type":"uint8"}]},{"stateMutability":"view","type":"function","name":"version","inputs":[],"outputs":[{"name":"","type":"string"}]},{"stateMutability":"view","type":"function","name":"balanceOf","inputs":[{"name":"arg0","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"allowance","inputs":[{"name":"arg0","type":"address"},{"name":"arg1","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"nonces","inputs":[{"name":"arg0","type":"address"}],"outputs":[{"name":"","type":"uint256"}]},{"stateMutability":"view","type":"function","name":"salt","inputs":[],"outputs":[{"name":"","type":"bytes32"}]}]`// Register ABI
    exchange.IO("abi", poolAddress, poolABI)

    // Get the token address and name in the poolvar token0Address = exchange.IO("api", poolAddress, "coins", 0)
    var token1Address = exchange.IO("api", poolAddress, "coins", 1)    
    var token0Name = exchange.IO("api", token0Address, "symbol")
    var token1Name = exchange.IO("api", token1Address, "symbol")
    var token0Decimals = exchange.IO("api", token0Address, "decimals")
    var token1Decimals = exchange.IO("api", token1Address, "decimals")

    var sDAI = {}
    var sUSDe = {}
    if (token0Name == "sDAI") {
        sDAI["name"] = token0Name
        sDAI["address"] = token0Address
        sDAI["idx"] = 0
        sDAI["decimals"] = token0Decimals ? token0Decimals : 18
    } else {
        throw"pool error"
    }
    if (token1Name == "sUSDe") {
        sUSDe["name"] = token1Name
        sUSDe["address"] = token1Address
        sUSDe["idx"] = 1
        sUSDe["decimals"] = token1Decimals ? token1Decimals : 18
    } else {
        throw"pool error"
    }

    // Assume DAI purchase cost price: 0.9929var entryPriceForDAI = 0.9929while (true) {
        var sDAI_Balance = exchange.IO("api", sDAI["address"], "balanceOf", walletAddress)
        var sUSDe_Balance = exchange.IO("api", sUSDe["address"], "balanceOf", walletAddress)
        if (!sDAI_Balance || !sUSDe_Balance) {
            Sleep(1000 * 5)
            continue 
        }
        
        var tbl = {"type": "table", "title": "data", "cols": ["tokenName", "address", "idx", "decimals", "balance"], "rows": []}
        tbl["rows"].push([sDAI["name"], sDAI["address"], sDAI["idx"], sDAI["decimals"], toAmount(sDAI_Balance, sDAI["decimals"])])
        tbl["rows"].push([sUSDe["name"], sUSDe["address"], sUSDe["idx"], sUSDe["decimals"], toAmount(sUSDe_Balance, sUSDe["decimals"])])

        // Monitor the exchange price, calculate real-time profit and other information based on the DAI purchase cost pricevar amountIn = 100000var ret = getBuyProfit(poolAddress, sDAI, sUSDe, amountIn, entryPriceForDAI)
        if (!ret) {
            Sleep(1000 * 5)
            continue 
        }

        var profit = ret["profit"] 
        var amountOut = ret["amountOut"]
        var sDAI_sUSDe_price = ret["sDAI_sUSDe_price"]
        if (profit > 1000 && sDAI_Balance > amountIn) {
            Log("The exchange conditions are met and the sDAI -> sUSDe exchange trading begins...")

            /* The exchange operation code is only for teaching demonstration. Please use this function with caution and test it first.
            executeTrade(poolAddress, sDAI, sUSDe, amountIn, 0.999*amountOut)
            */
        }

        LogStatus(_D(), ", amountIn:", amountIn, ", amountOut:", amountOut, ", sDAI_sUSDe_price:", sDAI_sUSDe_price, ", profit:", profit, "\n`" + JSON.stringify(tbl) + "`")
        Sleep(1000 * 60)
    }
}

END

According to the design idea of ​​the original strategy, the goal should be to capture extreme market conditions similar to those shown in the figure.

Thank you for your reading and support.

From: FMZ Platform Web3 Ethereum Practice - Pending Order Exchange Based on Smart Contract

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