transaction.js

const crypto = require("crypto"), SHA256 = message => crypto.createHash("sha256").update(message).digest("hex");
const EC = require("./node_modules/elliptic/lib/elliptic").ec, ec = new EC("secp256k1");
const MINT_PRIVATE_ADDRESS = "0700a1ad28a20e5b2a517c00242d3e25a88d84bf54dce9e1733e6096e6d6495e";
const MINT_KEY_PAIR = ec.keyFromPrivate(MINT_PRIVATE_ADDRESS, "hex");
const MINT_PUBLIC_ADDRESS = MINT_KEY_PAIR.getPublic("hex");

class Transaction{
    constructor(from, to, amount, gas = 0, args = []) {
        this.from = from;
        this.to = to;
        this.amount = amount;
        this.gas = gas;
        this.args = args;
    }
    
    sign(keyPair) {
        if (keyPair.getPublic("hex") === this.from) {
            this.signature = keyPair.sign(SHA256(this.from + this.to + this.amount + this.gas + JSON.stringify(this.args)), "base64").toDER("hex");

        }
    }
    static isValid(tx, chain) {
        return (
            tx.from &&
            tx.to &&
            tx.amount >= 0 &&
            (chain.getBalance(tx.from) >= tx.amount + tx.gas || tx.from ===MINT_PUBLIC_ADDRESS) &&
            ec.keyFromPublic(tx.from, "hex").verify(SHA256(tx.from + tx.to + tx.amount + tx.gas + JSON.stringify(tx.args)), tx.signature)
        )
    }
}
module.exports = Transaction;