var fs = require('fs');

function getNames(part) {
  var basename = part.split('_')[0]; // e.g. template_crx -> template
  var sources  = fs.readdirSync(`src/${basename}`);

  // Extract variables to be made global from source file list
  // e.g. ImageExpand from src/Images/ImageExpand.coffee
  // but not QR.post or eventPage
  var names = [];
  for (var f of sources) {
    var m = f.match(/^([$A-Z][$\w]*)\.coffee$/);
    if (m) names.push(m[1]);
  }
  return names;
}

function globalize(script, names) {
  var replaced = 0;

  script = script.replace(

    // matches declaration at the start of the function, not including helper function assignments
    /^( *var )(.*)(,\n *|;\n)/m,

    function(declaration, v, n, e) {
      replaced++;
      var n0 = names.sort().join(', ');
      if (n0 !== n) throw new Error(`expected variables (${n0}) found (${n})`);
      return (e[0] === ',') ? v : '';
    }

  );

  if (replaced !== 1) {
    throw new Error(`no declaration found`);
  }

  return script;
}

module.exports = {
  getNames: getNames,
  globalize: globalize
};

if (require.main === module) {
  (function() {
    for (var part of process.argv.slice(2)) {
      var filename = `tmp/${part}.js`;
      var names = getNames(part);
      var script = fs.readFileSync(filename, 'utf8').replace(/\r\n/g, '\n');
      script = globalize(script, names);
      fs.writeFileSync(filename, script);
    }
  })();
}