index.js

const zcLib = require("bitcoinjs-lib-zcash");
const TransactionBuilder = zcLib.TransactionBuilder;
const ECPair = zcLib.ECPair;

const _fetch = typeof fetch === "function" ? fetch : require("node-fetch");

const request = require('request');

const kotoNet = {
    "messagePrefix": "\u0015Koto Signed Message:\n",
    "bip32": {
        "public": 76067358,
        "private": 76066276
    },
    "pubKeyHash": 6198,
    "scriptHash": 6203,
    "wif": 128
};

function jsonFetch(addr) {
    return _fetch(addr).then(e => e.json());
}

function postProm(uri, json) {
    return new Promise((resolve, reject) => {
        request.post({ uri, json, headers: {} }, (error, response, body) => {
            if (error) {
                reject(error);
            } else {
                resolve({ response, body });
            }
        });
    });
}

const result = opts => {
    opts = opts || {};

    // you can change here if it's down
    const insight = opts.insight ? opt.insight : "https://insight.kotocoin.info/api";

    const toAddress = opts.toAddress;
    const feeInSat = opts.feeInSat ? parseInt(opts.feeInSat) : 10;
    const fromWif = opts.fromSecret ? ECPair.fromWIF(opts.fromSecret, kotoNet) : null;
    // below statement does that thing:
    // If fromAddress was given, use it
    // Otherwise, derive address from fromWif
    const fromAddress = opts.fromAddress ? opts.fromAddress : (fromWif ? fromWif.getAddress() : null);

    // 80 KOTO
    const minimumTarget = opts.minimumTarget ? parseInt(opts.minimumTarget) : 8e9;

    if (!fromAddress) {
        return Promise.reject("\"fromAddress\" or \"fromSecret\" must be specified");
    } else if (!toAddress) {
        return Promise.reject("\"toAddress\" must be specified");
    }

    return jsonFetch(insight + "/addr/" + fromAddress + "/utxo")
        .then(utxo => {
            if (utxo.length <= 0) {
                return Promise.reject("No UTXO: cancelling");
            }
            if (utxo.length > 300) {
                utxo = utxo.slice(0, 300);
            }
            // it's time to build transaction
            let txb = new TransactionBuilder(kotoNet);
            let totalBalanceSat = 0;
            utxo.forEach(tx => {
                const vin = txb.addInput(tx.txid, tx.vout);
                txb.inputs[vin].value = tx.satoshis;
                totalBalanceSat += tx.satoshis;
            });
            const balanceWoFee = totalBalanceSat - feeInSat;
            if (balanceWoFee < minimumTarget) {
                return Promise.reject("Balance is less than target: expected " + minimumTarget + " but " + balanceWoFee);
            }
            txb.addOutput(toAddress, balanceWoFee);

            if (fromWif) {
                // we have private key
                for (let i = 0; i < txb.inputs.length; i++)
                    txb.sign(i, fromWif);
                // broadcast tx
                return postProm(insight + "/tx/send", {
                    rawtx: txb.build().toHex()
                }).then(x => x.body.txid || x.body);
            } else {
                // no private key: display non-signed rawtx
                return Promise.resolve(txb.buildIncomplete().toHex());
            }
        });
};

result.kotoNet = kotoNet;
result.fetchUsed = _fetch;

module.exports = result;