const connex = new Connex({
  node: "https://testnet.veblocks.net/",
  network: "test"
});
const transferABI = {
  constant: false,
  inputs: [
    {
      name: "_to",
      type: "address"
    },
    {
      name: "_amount",
      type: "uint256"
    }
  ],
  name: "transfer",
  outputs: [
    {
      name: "success",
      type: "bool"
    }
  ],
  payable: false,
  stateMutability: "nonpayable",
  type: "function"
};

const paramsABI = {
  constant: true,
  inputs: [
    {
      name: "_key",
      type: "bytes32"
    }
  ],
  name: "get",
  outputs: [
    {
      name: "",
      type: "uint256"
    }
  ],
  payable: false,
  stateMutability: "view",
  type: "function"
};

async function getBaseGasPrice() {
  const baseGasPriceMethod = connex.thor
    // params contract address
    .account("0x0000000000000000000000000000506172616d73")
    .method(paramsABI);
  const outputs = await baseGasPriceMethod.call(
    //0x000000…696365 is the key of baseGasPrice https://docs.vechain.org/others/miscellaneous.html#key-of-governance-params
    "0x000000000000000000000000000000000000626173652d6761732d7072696365"
  );

  return outputs.decoded[0];
}

//get vm gas used
async function vmGasUsed(clauses) {
  const exp = connex.thor.explain(clauses);
  const outputs = await exp
    // Set maximum gas
    .gas(20000000)
    // Set caller
    .caller("0x8a259d8684E88e063EaA2213a7a390A725065c65")
    .execute();

  return outputs.reduce((sum, out) => sum + out.gasUsed, 0);
}

async function estimateTxFee() {
  //Create clauses of transferring VET & VTHO
  const transferMethod = connex.thor
    .account("0x0000000000000000000000000000456E65726779")
    .method(transferABI);
  // Alice's address transfer 1 wei vtho
  const vthoClause = transferMethod.asClause(
    "0xd3ae78222beadb038203be21ed5ce7c9b1bff602",
    1
  );
  //Alice address transfer 1 wei vet
  const vetClause = {
    to: "0xd3ae78222beadb038203be21ed5ce7c9b1bff602",
    value: 1,
    data: "0x486170707920636f64696e6720f09f8e89"
  };

  const clauses = [vetClause, vthoClause];

  const intrinsic = intrinsicGas(clauses);
  const baseGasPrice = await getBaseGasPrice();
  const vmUsed = await vmGasUsed(clauses);

  updateUI(intrinsic, baseGasPrice, vmUsed);
}

estimateTxFee();

function updateUI(intrinsic, baseGasPrice, vmUsed) {
  //adding some extra gas to make sure the transaction go through
  const gas = new BigNumber(intrinsic).plus(vmUsed).plus(15000);
  //priority regular = gasPriceCoef 0/255
  const regularCost = calcFee(gas, baseGasPrice, 0).toFixed(2);
  //priority medium = gasPriceCoef 85/255
  const mediumCost = calcFee(gas, baseGasPrice, 85).toFixed(2);
  //priority high = gasPriceCoef 255/255
  const highCost = calcFee(gas, baseGasPrice, 255).toFixed(2);

  document.getElementById("regular").innerText = regularCost + " VTHO";
  document.getElementById("medium").innerText = mediumCost + " VTHO";
  document.getElementById("high").innerText = highCost + " VTHO";

  const vtho = BigNumber(1e18).dividedBy(baseGasPrice);

  document.getElementById("totalGas").innerText = "Total Gas: " + gas + " gas";
  document.getElementById("bgp").innerText =
    "BaseGasePrice:" + baseGasPrice + " (1 VTHO = " + vtho + " gas)";
  document.getElementById("vmUsed").innerText =
    "Vm gasUsed: " + vmUsed + " gas";
  document.getElementById("intrinsic").innerText =
    "IntrinsicGas: " + intrinsic + " gas";
}

function intrinsicGas(clauses) {
  const txGas = 5000;
  const clauseGas = 16000;
  const clauseGasContractCreation = 48000;

  if (clauses.length === 0) {
    return txGas + clauseGas;
  }

  return clauses.reduce((sum, c) => {
    if (c.to) {
      sum += clauseGas;
    } else {
      sum += clauseGasContractCreation;
    }
    sum += dataGas(c.data);
    return sum;
  }, txGas);
}

function dataGas(data) {
  const zgas = 4;
  const nzgas = 68;

  let sum = 0;
  for (let i = 2; i < data.length; i += 2) {
    if (data.substr(i, 2) === "00") {
      sum += zgas;
    } else {
      sum += nzgas;
    }
  }
  return sum;
}

function calcFee(gas, baseGasPrice, gasPriceCoef) {
  return new BigNumber(baseGasPrice)
    .times(gasPriceCoef)
    .idiv(255)
    .plus(baseGasPrice)
    .times(gas)
    .dividedBy(1e18);
}