'use strict';
const fs = require('fs');
const readChunk = require('read-chunk');
const istextorbinary = require('istextorbinary');
const dateFormat = require('dateformat');
const prettyBytes = require('pretty-bytes');
const Table = require('cli-table');

exports.isBinary = (existingFilePath, newFileContents) => {
  const existingHeader = readChunk.sync(existingFilePath, 0, 512);
  return istextorbinary.isBinarySync(undefined, existingHeader) ||
    (newFileContents && istextorbinary.isBinarySync(undefined, newFileContents));
};

exports.diff = (existingFilePath, newFileContents) => {
  const existingStat = fs.statSync(existingFilePath);
  const table = new Table({
    head: ['', 'Existing', 'Replacement', 'Diff']
  });

  let sizeDiff;

  if (!newFileContents) {
    newFileContents = Buffer.from([]);
  }

  if (existingStat.size > newFileContents.length) {
    sizeDiff = '-';
  } else {
    sizeDiff = '+';
  }

  sizeDiff += prettyBytes(Math.abs(existingStat.size - newFileContents.length));

  table.push([
    'Size',
    prettyBytes(existingStat.size),
    prettyBytes(newFileContents.length),
    sizeDiff
  ], [
    'Last modified',
    dateFormat(existingStat.mtime),
    '',
    ''
  ]);

  return table.toString();
};