const fs = require('fs');
const readline = require('readline');
const minimist = require('./minimist.js');

const opts = minimist(process.argv.slice(2));
const args = opts._;

if (args.length !== 1) {
  console.error('Invalid number of arguments received.');
  process.exit(1);
}

const spacesString = buildSpaces(opts.n || 2);
const inputFile = getInputFile(args[0]);
const outputFile = getOutputFile(inputFile);

const fileReader = readline.createInterface({
  input: fs.createReadStream(inputFile.path, {encoding: 'utf8'}),
});
const outputFD = fs.openSync(outputFile.path, 'w');

let totalTabChars = 0;
let start = null;

fileReader.on('line', line => {
  let matches = line.match(/\t/g);

  if (matches) {
    totalTabChars += matches.length;
  }

  fs.writeSync(outputFD, line.replace(/\t/g, spacesString) + '\n', 'utf8');
});

fileReader.on('close', () => {
  let end = Date.now();
  fs.closeSync(outputFD);

  console.log('\nFile processing done.');
  console.log(`Time elapsed  : ${end-start}ms`);
  console.log(`Tabs replaced : ${totalTabChars}`);
});

start = Date.now();

/********** functions **********/

function buildSpaces(numSpaces) {
  let str = '';

  for (let i = 0; i < numSpaces; i++) {
    str += ' ';
  }

  return str;
}

function getInputFile(arg) {
  const path = require('path');
  const file = {};

  file.dir = path.join(process.cwd(), path.dirname(arg));
  file.ext = path.extname(arg);
  file.basename = path.basename(arg, file.ext);
  file.name = path.basename(arg);
  file.path = path.join(file.dir, file.name);

  return file;
}

function getOutputFile(inputFile) {
  const path = require('path');
  const file = {};

  file.dir = inputFile.dir;
  file.ext = inputFile.ext;
  file.basename = inputFile.basename + '-spaces';
  file.name = file.basename + inputFile.ext;
  file.path = path.join(file.dir, file.name);

  return file;
}