estimateBitcoinFee.js


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const config = require("./config");

const l = require("pino")();
const SATS = 100000000;

module.exports = (app, bc, db, emit) => async (req, res) => {
  let { user } = req;
  let { address, amount, confTarget, feeRate, mode } = req.body;
  let tx, fee;

  try {
    amount = parseInt(amount);

    tx = await bc.createRawTransaction([], {
      [address]: (amount / SATS).toFixed(8)
    });

    let params = {
      subtractFeeFromOutputs: amount === user.balance ? [0] : []
    } 

    if (feeRate) params["feeRate"] = (parseInt(feeRate) / SATS * 1000).toFixed(8);
    if (confTarget) params["conf_target"] = parseInt(confTarget);
    if (mode) params["estimate_mode"] = mode;

    tx = await bc.fundRawTransaction(tx, params);
    res.send({ tx });
  } catch (e) {
    l.error(e);
    return res.status(500).send(e.message);
  }
};