var common = require('./common');
var fs = require('fs');

//@
//@ ### grep([options ,] regex_filter, file [, file ...])
//@ ### grep([options ,] regex_filter, file_array)
//@ Available options:
//@
//@ + `-v`: Inverse the sense of the regex and print the lines not matching the criteria.
//@
//@ Examples:
//@
//@ ```javascript
//@ grep('-v', 'GLOBAL_VARIABLE', '*.js');
//@ grep('GLOBAL_VARIABLE', '*.js');
//@ ```
//@
//@ Reads input string from given files and returns a string containing all lines of the
//@ file that match the given `regex_filter`. Wildcard `*` accepted.
function _grep(options, regex, files) {
  options = common.parseOptions(options, {
    'v': 'inverse'
  });

  if (!files)
    common.error('no paths given');

  if (typeof files === 'string')
    files = [].slice.call(arguments, 2);
  // if it's array leave it as it is

  files = common.expand(files);

  var grep = '';
  files.forEach(function(file) {
    if (!fs.existsSync(file)) {
      common.error('no such file or directory: ' + file, true);
      return;
    }

    var contents = fs.readFileSync(file, 'utf8'),
        lines = contents.split(/\r*\n/);
    lines.forEach(function(line) {
      var matched = line.match(regex);
      if ((options.inverse && !matched) || (!options.inverse && matched))
        grep += line + '\n';
    });
  });

  return common.ShellString(grep);
}
module.exports = _grep;