const { Server } = require('karma');
const merge = require('deepmerge');
const { join } = require('path');

module.exports = (neutrino, tap) => {
  const tests = join(neutrino.options.tests, '**/*_test.js');
  const sources = join(neutrino.options.source, '**/*.js*');
  const defaults = {
    plugins: [
      require.resolve('karma-webpack'),
      require.resolve('karma-chrome-launcher'),
      require.resolve('karma-coverage'),
      require.resolve('karma-mocha'),
      require.resolve('karma-mocha-reporter')
    ],
    basePath: neutrino.options.root,
    browsers: [process.env.CI ? 'ChromeCI' : 'Chrome'],
    customLaunchers: {
      ChromeCI: {
        base: 'Chrome',
        flags: ['--no-sandbox']
      }
    },
    frameworks: ['mocha'],
    files: [tests],
    preprocessors: {
      [tests]: ['webpack'],
      [sources]: ['webpack']
    },
    webpackMiddleware: { noInfo: true },
    reporters: ['mocha', 'coverage'],
    coverageReporter: {
      dir: '.coverage',
      reporters: [
        { type: 'html', subdir: 'report-html' },
        { type: 'lcov', subdir: 'report-lcov' }
      ]
    }
  };

  Object.assign(neutrino.options, {
    karma: merge(defaults, neutrino.options.karma || {})
  });

  neutrino.on('test', ({ files, watch }) => {
    const base = typeof tap === 'function' ?
      tap(neutrino.options.karma) :
      neutrino.options.karma;
    const karma = merge(base, {
      singleRun: !watch,
      autoWatch: watch,
      webpack: neutrino.config.toConfig()
    });

    delete karma.webpack.plugins;

    if (files && files.length) {
      karma.files = files;
    }

    return new Promise(resolve => new Server(karma, resolve).start());
  });
};