zmsgpull

#!/usr/bin/env node
const {NodeClient} = require('hs-client');
const {Network} = require('hsd');
const {Resource} = require('hsd/lib/dns/resource');
const fs = require('fs');
const constants = require("./lib/constants.js");
const prepend = require('prepend');

const network = Network.get('main');
const nodeOptions = {
  network: network.type,
  port: network.rpcPort,
  apiKey: fs.readFileSync(__dirname+"/keys/node").toString().trim()
};
const nodeClient = new NodeClient(nodeOptions);

// Aliases
async function getBlock(height) { return await nodeClient.getBlock(height) }
async function getBlockTx(txh) { return await nodeClient.getTX(txh) }
async function getNameByHash(hash) { return await nodeClient.execute('getnamebyhash', [ hash ]) }
async function getHeight() { return await nodeClient.execute('getblockcount') }

// Functions
async function getUpdates(block) {
  let rupdates = [];
  for(let x=0;x<block.txs.length;x++) {
    const tx = block.txs[x];
    for(let y=0;y<tx.outputs.length;y++) {
      const output = tx.outputs[y];
      if(output.covenant.action === "UPDATE") {
        let name = await getNameByHash(output.covenant.items[0]);
        if(output.covenant.items[2].length!=0) {
          let records = await Resource.decode(Buffer.from(output.covenant.items[2],'hex')).getJSON(name);
          rupdates.push({ name: name, records: records.records });
        }
      }
    }
  }
  return rupdates;
}
function findZmsg(record) {
  for(let x=0;x<record.length;x++) {
    const rec = record[x];
    if(rec.type=='TXT' && rec.txt) {
      for(let y=0;y<rec.txt.length;y++) {
        const txt = rec.txt[y];
        if(txt.startsWith(constants.MAGIC_ZMSG))
          return txt.substr(constants.MAGIC_ZMSG_LENGTH);
      }
    }
  }
  return null;
}

(async () => {
  let x;
  if(fs.existsSync(__dirname+"/.lastBlock"))
    x = parseInt(fs.readFileSync(__dirname+"/.lastBlock"));
  else
    x = constants.ZMSG_START;
  if(!x)
    x = constants.ZMSG_START;

  const height = await getHeight();

  for(;x<=height;x++) {
    console.log(x);
    let block = await getBlock(x);
    let updates = await getUpdates(block);
    if(updates.length>0) {
      for(let y=0;y<updates.length;y++) {
        let zmsg = findZmsg(updates[y].records);
        if(zmsg) {
          prepend(__dirname+"/.posts",`${x},${updates[y].name},${zmsg}`,(err) => {});
        }
      }
    }
  }
  fs.writeFileSync(__dirname+"/.lastBlock",x.toString());
})();