Swapping - Fixed Output

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const { decimalsToken0, decimalsToken1 } = await getTokenDecimals(
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  client,
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  testnetPair,
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);
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// We define the amount of tokens that we would like to get out (in token1 units)
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const amountOut = 1000n * 10n ** BigInt(decimalsToken0);
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console.log("Desired amount Out ", amountOut);

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Desired amount Out  1000000000000000000000n

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/**
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 * Quote how much token1 is required to guarantee the specificed token0 amount as an output.
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 * Returns `[amountInMax, amountOut]`
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 */
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async function quoteAmountsIn(
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  pair: `0x${string}`,
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  amountOut: bigint,
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  path: `0x${string}`[],
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) {
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  return await client.readContract({
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    address: pair,
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    abi: stableSwapAbi,
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    functionName: 'getAmountsIn',
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    args: [amountOut, path],
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  });
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}

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const [amountInMax, amountOut] = await quoteAmountsIn(
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  PAIR_CTK_AUSD,
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  amountOut,
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  [TOKEN0_CTK, TOKEN1_AUSD],
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);
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console.log('Quoted amountInMax (raw AUSD):', amountInMax)

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Quoted amountInMax (raw AUSD): 1000200000

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/**
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 * Give `pair` permission to spend `amount` of `tokenToApprove`.
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 * Returns the transaction hash of the on-chain approval.
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 */
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async function approveAllowance(
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  tokenToApprove: `0x${string}`,
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  pair: `0x${string}`,
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  amount: bigint,
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) {
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  // 1) Dry-run to catch reverts & obtain gas estimate
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  const { request } = await client.simulateContract({
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    address: tokenToApprove,
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    abi: ausdImplementationAbi, // standard ERC-20 ABI
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    functionName: "approve",
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    args: [pair, amount],
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  });
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  // 2) Send the real transaction
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  return await client.writeContract(request);
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}

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console.log(
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  `Approving contract ${TESTNET_PAIR_AUSD_CTK} to spend ${amountInMax} units of token ${inputTokenAddress}...`,
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);
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const approveAllowanceTxHash = await approveAllowance(
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  inputTokenAddress,
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  TESTNET_PAIR_AUSD_CTK,
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  amountInMax,
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);
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console.log("Approve transaction hash:", approveAllowanceTxHash);

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Approving pair to spend 1000200000 units of AUSD...
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Approve transaction hash: 0x1d166bbc9ce4e0ba3000a42aa22360c14cb8a8ba8007d137915a3922e304e0f4

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console.log("Executing swapTokensForExactTokens...");
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const { request: swapRequest } = await client.simulateContract({
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  address: TESTNET_PAIR_AUSD_CTK,
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  abi: stableSwapAbi,
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  functionName: "swapTokensForExactTokens",
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  args: [amountOut, amountInMax, swapPath, callerAddress, BigInt(deadline)],
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});
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const swapRequestTxHash = await client.writeContract(swapRequest);
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console.log("Swap transaction hash:", swapRequestTxHash);

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Executing swapTokensForExactTokens...
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Swap transaction hash: 0x5d27ab73a4759720aedd71b32075366a427c8ce21220cd9910b6352715550c3a