add project

apps/api/src/routes/bsc-swap-proxy.routes.ts

@@ -0,0 +1,192 @@
+import { Request, Response, Router } from 'express';
+import { ethers } from 'ethers';
+
+const router = Router();
+
+const BSC_RPC = 'https://bsc-dataseed.binance.org';
+const BSC_CHAIN_ID = 56;
+const BSC_TIMEOUT_MS = 15_000;
+
+// PancakeSwap V2 Router
+const PANCAKE_ROUTER = '0x10ED43C718714eb63d5aA57B78B54704E256024E';
+const WBNB = '0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c';
+
+// Supported tokens
+const TOKEN_MAP: Record<string, string> = {
+  BNB: WBNB,
+  USDT: '0x55d398326f99059fF775485246999027B3197955',
+  DOGE: '0xbA2aE424d960c26247Dd6c32edC70B295c744C43',
+};
+
+const TOKEN_DECIMALS: Record<string, number> = {
+  BNB: 18,
+  USDT: 18,
+  DOGE: 8,
+};
+
+const ROUTER_ABI = [
+  'function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts)',
+  'function swapExactETHForTokensSupportingFeeOnTransferTokens(uint amountOutMin, address[] calldata path, address to, uint deadline) external payable',
+  'function swapExactTokensForETHSupportingFeeOnTransferTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external',
+];
+
+const ERC20_ABI = [
+  'function approve(address spender, uint256 amount) external returns (bool)',
+  'function allowance(address owner, address spender) external view returns (uint256)',
+];
+
+router.get('/quote', getSwapQuote);
+router.post('/build', buildSwapTx);
+
+export default router;
+
+// ─── GET /quote ───
+
+async function getSwapQuote(req: Request, res: Response) {
+  const from = String(req.query.from || '').toUpperCase();
+  const to = String(req.query.to || '').toUpperCase();
+  const amount = String(req.query.amount || '');
+
+  if (!TOKEN_MAP[from] || !TOKEN_MAP[to]) {
+    res.status(400).json({ success: false, error: 'Invalid from/to. Supported: BNB, USDT, DOGE' });
+    return;
+  }
+  if (from === to) {
+    res.status(400).json({ success: false, error: 'from and to must be different' });
+    return;
+  }
+
+  const amountBigInt = BigInt(amount || '0');
+  if (amountBigInt <= 0n) {
+    res.status(400).json({ success: false, error: 'amount must be positive' });
+    return;
+  }
+
+  try {
+    const provider = new ethers.providers.StaticJsonRpcProvider(BSC_RPC, BSC_CHAIN_ID);
+    const routerContract = new ethers.Contract(PANCAKE_ROUTER, ROUTER_ABI, provider);
+
+    const path = [TOKEN_MAP[from], TOKEN_MAP[to]];
+    const amounts: ethers.BigNumber[] = await withTimeout(
+      routerContract.getAmountsOut(amount, path),
+      BSC_TIMEOUT_MS,
+      'PancakeSwap quote timed out'
+    );
+
+    const amountOut = amounts[amounts.length - 1].toString();
+
+    res.json({
+      success: true,
+      amountIn: amountBigInt.toString(),
+      amountOut,
+      from,
+      to,
+      fromDecimals: TOKEN_DECIMALS[from],
+      toDecimals: TOKEN_DECIMALS[to],
+    });
+  } catch (error) {
+    const msg = error instanceof Error ? error.message : 'Failed to get BSC swap quote';
+    res.status(502).json({ success: false, error: msg });
+  }
+}
+
+// ─── POST /build ───
+
+async function buildSwapTx(req: Request, res: Response) {
+  const { from, to, amount, amountOutMin, userAddress } = req.body;
+
+  if (!from || !to || !amount || !amountOutMin || !userAddress) {
+    res.status(400).json({ success: false, error: 'Missing required fields: from, to, amount, amountOutMin, userAddress' });
+    return;
+  }
+
+  const fromUpper = String(from).toUpperCase();
+  const toUpper = String(to).toUpperCase();
+
+  if (!TOKEN_MAP[fromUpper] || !TOKEN_MAP[toUpper] || fromUpper === toUpper) {
+    res.status(400).json({ success: false, error: 'Invalid from/to pair' });
+    return;
+  }
+
+  if (!ethers.utils.isAddress(userAddress)) {
+    res.status(400).json({ success: false, error: 'Invalid BSC address' });
+    return;
+  }
+
+  try {
+    const provider = new ethers.providers.StaticJsonRpcProvider(BSC_RPC, BSC_CHAIN_ID);
+    const routerContract = new ethers.Contract(PANCAKE_ROUTER, ROUTER_ABI, provider);
+    const deadline = Math.floor(Date.now() / 1000) + 1200; // 20 minutes
+    const path = [TOKEN_MAP[fromUpper], TOKEN_MAP[toUpper]];
+
+    const transactions: Array<{ type: string; to: string; data: string; value: string }> = [];
+
+    if (fromUpper === 'BNB') {
+      // BNB → Token: swapExactETHForTokensSupportingFeeOnTransferTokens
+      const data = routerContract.interface.encodeFunctionData(
+        'swapExactETHForTokensSupportingFeeOnTransferTokens',
+        [amountOutMin, path, userAddress, deadline]
+      );
+
+      transactions.push({
+        type: 'swap',
+        to: PANCAKE_ROUTER,
+        data,
+        value: amount, // BNB amount in wei
+      });
+    } else {
+      // Token → BNB: check allowance, build approve if needed, then swap
+      const tokenAddress = TOKEN_MAP[fromUpper];
+      const tokenContract = new ethers.Contract(tokenAddress, ERC20_ABI, provider);
+      const currentAllowance: ethers.BigNumber = await withTimeout(
+        tokenContract.allowance(userAddress, PANCAKE_ROUTER),
+        BSC_TIMEOUT_MS,
+        'Allowance check timed out'
+      );
+
+      if (currentAllowance.lt(ethers.BigNumber.from(amount))) {
+        // Build approve tx
+        const approveData = tokenContract.interface.encodeFunctionData(
+          'approve',
+          [PANCAKE_ROUTER, ethers.constants.MaxUint256]
+        );
+
+        transactions.push({
+          type: 'approve',
+          to: tokenAddress,
+          data: approveData,
+          value: '0',
+        });
+      }
+
+      // Build swap tx
+      const swapData = routerContract.interface.encodeFunctionData(
+        'swapExactTokensForETHSupportingFeeOnTransferTokens',
+        [amount, amountOutMin, path, userAddress, deadline]
+      );
+
+      transactions.push({
+        type: 'swap',
+        to: PANCAKE_ROUTER,
+        data: swapData,
+        value: '0',
+      });
+    }
+
+    res.json({ success: true, transactions });
+  } catch (error) {
+    const msg = error instanceof Error ? error.message : 'Failed to build BSC swap';
+    res.status(502).json({ success: false, error: msg });
+  }
+}
+
+// ─── Utils ───
+
+function withTimeout<T>(promise: Promise<T>, timeoutMs: number, message: string): Promise<T> {
+  return new Promise<T>((resolve, reject) => {
+    const timeoutId = setTimeout(() => reject(new Error(message)), timeoutMs);
+    promise
+      .then((value) => { clearTimeout(timeoutId); resolve(value); })
+      .catch((error) => { clearTimeout(timeoutId); reject(error); });
+  });
+}