process.js

const fs = require('fs');
const os = require('os');

const RRESLT = /^\{(\d+) elems\.\} \[(.*?) ms; (.*?) err\.\] (.*)/m;




// *-FILE
// ------

function readFile(pth) {
  var d = fs.readFileSync(pth, 'utf8');
  return d.replace(/\r?\n/g, '\n');
}

function writeFile(pth, d) {
  d = d.replace(/\r?\n/g, os.EOL);
  fs.writeFileSync(pth, d);
}




// *-CSV
// -----

function writeCsv(pth, rows) {
  var cols = Object.keys(rows[0]);
  var a = cols.join()+'\n';
  for (var r of rows)
    a += [...Object.values(r)].map(v => `"${v}"`).join()+'\n';
  writeFile(pth, a);
}




// *-LOG
// -----

function readLogLine(ln, data, state) {
  if (!data.has(state)) data.set(state, []);
  if (RRESLT.test(ln)) {
    var [, elements, time, error, technique] = RRESLT.exec(ln);
    data.get(state).push({
      elements: parseFloat(elements),
      time: parseFloat(time),
      error: parseFloat(error),
      technique
    });
  }
  return state;
}

function readLog(pth) {
  var text = readFile(pth);
  var lines = text.split('\n');
  var data = new Map();
  var state = null;
  for (var ln of lines)
    state = readLogLine(ln, data, state);
  return data;
}




// PROCESS-*
// ---------

function processCsv(data) {
  var a = [];
  for (var rows of data.values())
    a.push(...rows);
  return a;
}




// MAIN
// ----

function main(cmd, log, out) {
  var data = readLog(log);
  switch (cmd) {
    case 'csv':
      var rows = processCsv(data);
      writeCsv(out, rows);
      break;
    default:
      console.error(`error: "${cmd}"?`);
      break;
  }
}
main(...process.argv.slice(2));