// Mandatory chain-specific SDKs
import { makePaymentTxnWithSuggestedParams } from "algosdk";
import { encode } from "algo-msgpack-with-bigint";

async function signTransaction(plainTransaction: any) {

  // A. Complete transaction with missing info
    // 1. Compute transaction fees
      // a. Fetch transaction params
      const paramsResponse = await fetch(`<NODE_ROOT_URL>/transactions/params`, { method: "GET" });
      const paramsData = paramsResponse.json();
   
      const { fee, minFee} = {
        fee: paramsData["fee"],
        minFee: paramsData["min-fee"],
      };
   
      // b. Compute fees
      let suggestedFees = 0;
      if (fee) {
        const encoded = await buildEncodedTransaction(plainTransaction); // (encapsulated into function for brievity here)
        suggestedFees = fee * (Buffer.from(encoded, "hex").length + 71);
      }
      const fees = BigInt(Math.max(suggestedFees, minFee));

    // 2. Compute transaction amount

      // a. Fetch account data
      const dataResponse = await fetch(`<NODE_ROOT_URL>/accounts/${plainTransaction.sender}`, { method: "GET" });
      const accountData = dataResponse.json();

      const { balance, assets } = {
        balance: BigInt(accountData.amount),
        assets: accountData.assets,
      };

      // b. Compute max spendable
      const base = 100000;
      const currentAssets = assets.length;
      const newAsset = plainTransaction.mode === "optIn" ? 1 : 0;
      const minBalance = base * (1 + currentAssets + newAsset);
      const maxSpendable = balance - BigInt(minBalance);


      // c. Compute amount
      const amount = plainTransaction.useMaxAmount
        ? maxSpendable - fees
        : plainTransaction.amount;
   
      const completedTransaction = { ...plainTransaction, amount, fees };

  // B. Build raw transaction to sign

    // 1. Build raw transaction payload
    const { senders, recipients, mode, memo } = completedTransaction;
   
    const note = memo ? new TextEncoder().encode(memo) : undefined;

    const algoTxn = makePaymentTxnWithSuggestedParams(
      senders[0],
      recipients[0],
      amount,
      undefined,
      note,
      paramsData
    );

    algoTxn.firstRound = paramsData.lastRound;
    algoTxn.lastRound = paramsData.lastRound + 1000;

    const transactionPayload = Object.fromEntries(
      Object.entries(algoTxn.get_obj_for_encoding()).sort()
    );

    // 2. Encode raw transaction in chain-specific format
    const msgPackEncoded = encode(transactionPayload);

    const rawTransaction = Buffer.from(msgPackEncoded).toString("hex");

  // C. Sign raw transaction here

}