const path = require('path');
  
  const extension = require('./lib/extension');
  const normalize = require('./lib/normalize');
  const register = require('./lib/register');
  
  exports.prepare = function (extensions, filepath, cwd, nothrow) {
    var option, attempt;
    var attempts = [];
    var err;
    var onlyErrors = false;
    var ext = extension(filepath);
    if (Object.keys(require.extensions).indexOf(ext) !== -1) {
      return true;
    }
    var config = normalize(extensions[ext]);
    if (!config) {
      if (nothrow) {
        return;
      } else {
        throw new Error('No module loader found for "'+ext+'".');
      }
    }
    if (!cwd) {
      cwd = path.dirname(path.resolve(filepath));
    }
    if (!Array.isArray(config)) {
      config = [config];
    }
    for (var i in config) {
      option = config[i];
      attempt = register(cwd, option.module, option.register);
      error = (attempt instanceof Error) ? attempt : null;
      if (error) {
        attempt = null;
      }
      attempts.push({
        moduleName: option.module,
        module: attempt,
        error: error
      });
      if (!error) {
        onlyErrors = false;
        break;
      } else {
        onlyErrors = true;
      }
    }
    if (onlyErrors) {
      err = new Error('Unable to use specified module loaders for "'+ext+'".');
      err.failures = attempts;
      if (nothrow) {
        return err;
      } else {
        throw err;
      }
    }
    return attempts;
  };