var common = require('./common');
  var fs = require('fs');
  
  common.register('tail', _tail, {
    canReceivePipe: true,
    cmdOptions: {
      'n': 'numLines',
    },
  });
  
  //@
  //@ ### tail([{'-n': \<num\>},] file [, file ...])
  //@ ### tail([{'-n': \<num\>},] file_array)
  //@ Available options:
  //@
  //@ + `-n <num>`: Show the last `<num>` lines of the files
  //@
  //@ Examples:
  //@
  //@ ```javascript
  //@ var str = tail({'-n': 1}, 'file*.txt');
  //@ var str = tail('file1', 'file2');
  //@ var str = tail(['file1', 'file2']); // same as above
  //@ ```
  //@
  //@ Read the end of a file.
  function _tail(options, files) {
    var tail = [];
    var pipe = common.readFromPipe();
  
    if (!files && !pipe) common.error('no paths given');
  
    var idx = 1;
    if (options.numLines === true) {
      idx = 2;
      options.numLines = Number(arguments[1]);
    } else if (options.numLines === false) {
      options.numLines = 10;
    }
    options.numLines = -1 * Math.abs(options.numLines);
    files = [].slice.call(arguments, idx);
  
    if (pipe) {
      files.unshift('-');
    }
  
    var shouldAppendNewline = false;
    files.forEach(function (file) {
      if (!fs.existsSync(file) && file !== '-') {
        common.error('no such file or directory: ' + file, { continue: true });
        return;
      }
  
      var contents = file === '-' ? pipe : fs.readFileSync(file, 'utf8');
  
      var lines = contents.split('
  ');
      if (lines[lines.length - 1] === '') {
        lines.pop();
        shouldAppendNewline = true;
      } else {
        shouldAppendNewline = false;
      }
  
      tail = tail.concat(lines.slice(options.numLines));
    });
  
    if (shouldAppendNewline) {
      tail.push(''); // to add a trailing newline once we join
    }
    return tail.join('
  ');
  }
  module.exports = _tail;