OKX DEX API Essentials: Pertukaran Tunggal dan Cross-Chain pada Avalanche C-Chain

/**
 * Generates headers required for OKX DEX quote API calls
 * Headers include timestamp, signature, and API credentials
 * 
 * @param {Object} quoteParams - Parameters for the quote request
 * @returns {Object} Headers object with required authentication
 */
function getQuoteHeaders(quoteParams) {
    const date = new Date();
    const timestamp = date.toISOString();

    // Create signature string following OKX API requirements
    const stringToSign =
        timestamp +
        "GET" +
        "/api/v5/dex/aggregator/quote?" +
        new URLSearchParams(quoteParams).toString();

    // Return headers with HMAC signature
    return {
        "Content-Type": "application/json",
        "OK-ACCESS-KEY": apiKey,
        "OK-ACCESS-SIGN": cryptoJS.enc.Base64.stringify(
            cryptoJS.HmacSHA256(stringToSign, secretKey)
        ),
        "OK-ACCESS-TIMESTAMP": timestamp,
        "OK-ACCESS-PASSPHRASE": apiPassphrase,
    };
}

/**
 * Fetches a quote from the OKX DEX Aggregator
 * Used to get current prices and optimal swap routes
 * 
 * @param {Object} quoteParams - Parameters including tokens, amount, and chain
 * @returns {Promise<Object>} Quote data including price and route information
 */
async function getQuote(quoteParams) {
    const apiRequestUrl = `${apiBaseUrl}/quote?${new URLSearchParams(quoteParams)}`;
    const response = await fetch(apiRequestUrl, {
        method: "GET",
        headers: getQuoteHeaders(quoteParams),
    });

    if (!response.ok) {
        throw new Error("Network response was not ok");
    }

    return response.json();
}

/**
* Generates headers required for OKX DEX approve transaction API calls
* Headers include timestamp, signature, and API credentials
* 
* @param {Object} params - Parameters for the approve transaction
* @returns {Promise<Object>} Headers object with required authentication
*/
function getApproveTransactionHeaders(params) {
   const date = new Date();
   const timestamp = date.toISOString();
   const stringToSign =
       timestamp +
       "GET" +
       "/api/v5/dex/aggregator/approve-transaction?" +
       new URLSearchParams(params).toString();

   // Check if required environment variables are present
   if (!projectId || !apiKey || !secretKey || !apiPassphrase) {
       throw new Error(
           "Missing required environment variables for API authentication"
       );
   }

   return {
       "Content-Type": "application/json",
       "OK-PROJECT-ID": projectId,
       "OK-ACCESS-KEY": apiKey,
       "OK-ACCESS-SIGN": cryptoJS.enc.Base64.stringify(
           cryptoJS.HmacSHA256(stringToSign, secretKey)
       ),
       "OK-ACCESS-TIMESTAMP": timestamp,
       "OK-ACCESS-PASSPHRASE": apiPassphrase,
   };
}

// ABI for ERC20 token allowance function
// This minimal ABI only includes the allowance function needed for checking token approvals
// Full ERC20 ABI not needed since we're only checking allowances
const tokenABI = [
    {
        constant: true,
        inputs: [
            {
                name: "_owner",
                type: "address",
            },
            {
                name: "_spender",
                type: "address",
            },
        ],
        name: "allowance",
        outputs: [
            {
                name: "",
                type: "uint256",
            },
        ],
        payable: false,
        stateMutability: "view",
        type: "function",
    },
];

/**
 * Checks the current allowance for a token
 * Used to determine if approval is needed before swap
 * 
 * @param {string} ownerAddress - Address of token owner
 * @param {string} spenderAddress - Address of spender (DEX contract)
 * @param {string} tokenAddress - Address of token contract
 * @returns {Promise<number>} Current allowance amount
 */
async function getAllowance(ownerAddress, spenderAddress, tokenAddress) {
    const tokenContract = new web3.eth.Contract(tokenABI, tokenAddress);
    try {
        const allowance = await tokenContract.methods
            .allowance(ownerAddress, spenderAddress)
            .call();
        return parseFloat(allowance);
    } catch (error) {
        console.error("Failed to query allowance:", error);
        throw error;
    }
}


/**
 * Gets approval transaction data from the API
 * 
 * @param {string} chainId - Network chain ID
 * @param {string} tokenContractAddress - Token to approve
 * @param {string} approveAmount - Amount to approve
 * @returns {Promise<Object>} Approval transaction data
 */
async function approveTransaction(chainId, tokenContractAddress, approveAmount) {
    if (!chainId || !tokenContractAddress || !approveAmount) {
        throw new Error("Missing required parameters for approval");
    }

    const params = { chainId, tokenContractAddress, approveAmount };
    const apiRequestUrl = getAggregatorRequestUrl("/approve-transaction", params);
    const headersParams = getApproveTransactionHeaders(params);

    try {
        const response = await fetch(apiRequestUrl, {
            method: "GET",
            headers: headersParams,
        });

        if (!response.ok) {
            const errorData = await response.json().catch(() => null);
            throw new Error(
                `API request failed: ${response.status} ${response.statusText}${
                    errorData ? ` - ${JSON.stringify(errorData)}` : ""
                }`
            );
        }

        const data = await response.json();

        // Validate the response data
        if (!data || !data.data || !Array.isArray(data.data) || data.data.length === 0) {
            throw new Error("Invalid response format from approval API");
        }

        return data;
    } catch (error) {
        console.error("Approval request failed:", error);
        throw error;
    }
}

/**
 * Handles the approval transaction if needed
 * Checks current allowance and submits approval transaction if necessary
 * 
 * @param {string} approveAmount - Amount to approve for spending
 * @returns {Promise<Object|null>} Transaction receipt or null if approval not needed
 */
async function sendApproveTx(approveAmount) {
    // Skip approval for native tokens (ETH/AVAX)
    if (fromTokenAddress.toLowerCase() === baseTokenAddress.toLowerCase()) {
        return null;
    }

    const allowanceAmount = await getAllowance(
        user,
        spenderAddress,
        fromTokenAddress
    );

    // Only approve if current allowance is insufficient
    if (BigInt(allowanceAmount) < BigInt(approveAmount)) {
        const approvalResult = await approveTransaction(
            chainId,
            fromTokenAddress,
            approveAmount
        );

        // Prepare approval transaction with safety margins for gas
        const txObject = {
            nonce: await web3.eth.getTransactionCount(user),
            to: fromTokenAddress,
            gasLimit: BigInt(approvalResult.data[0].gasLimit) * BigInt(2),
            gasPrice: (BigInt(await web3.eth.getGasPrice()) * BigInt(3)) / BigInt(2),
            data: approvalResult.data[0].data,
            value: "0",
        };

        return sendSignedTransaction(txObject);
    }

    return null;
}

/**
 * Helper function to get headers for swap API calls
 * @param {Object} swapParams - Swap parameters
 * @returns {Object} Headers with authentication
 */
function getSwapHeaders(swapParams) {
    const date = new Date();
    const timestamp = date.toISOString();
    const stringToSign = 
        timestamp + 
        "GET" + 
        "/api/v5/dex/aggregator/swap?" + 
        new URLSearchParams(swapParams).toString();

    return {
        "Content-Type": "application/json",
        "OK-ACCESS-KEY": apiKey,
        "OK-ACCESS-SIGN": cryptoJS.enc.Base64.stringify(
            cryptoJS.HmacSHA256(stringToSign, secretKey)
        ),
        "OK-ACCESS-TIMESTAMP": timestamp,
        "OK-ACCESS-PASSPHRASE": apiPassphrase,
    };
}

/**
 * Helper function to get swap data from API
 * @param {Object} swapParams - Swap parameters
 * @returns {Promise<Object>} Swap transaction data
 */
async function getSwapData(swapParams) {
    const apiRequestUrl = getAggregatorRequestUrl("/swap", swapParams);
    const response = await fetch(apiRequestUrl, {
        method: "GET",
        headers: getSwapHeaders(swapParams),
    });

    if (!response.ok) {
        throw new Error("Network response was not ok");
    }

    return response.json();
}

/**
 * Executes a single-chain token swap
 * Handles the main swap transaction after approval
 * 
 * @param {Object} swapParams - Parameters for the swap
 * @returns {Promise<Object>} Transaction receipt
 */
async function sendSwapTx(swapParams) {
    // Get swap transaction data from API
    const { data: swapData } = await getSwapData(swapParams);

    // Validate swap data
    if (!swapData || swapData.length === 0 || !swapData[0].tx) {
        throw new Error("Invalid swap data received");
    }

    const swapDataTxInfo = swapData[0].tx;
    const nonce = await web3.eth.getTransactionCount(user, "latest");

    // Prepare transaction with adjusted gas parameters for safety
    const signTransactionParams = {
        data: swapDataTxInfo.data,
        gasPrice: BigInt(swapDataTxInfo.gasPrice) * BigInt(ratio),
        to: swapDataTxInfo.to,
        value: swapDataTxInfo.value,
        gas: BigInt(swapDataTxInfo.gas) * BigInt(ratio),
        nonce,
    };

    return sendSignedTransaction(signTransactionParams);
}