import {join} from 'path';
import {task, watch} from 'gulp';
import {buildConfig, sequenceTask} from 'material2-build-tools';

// There are no type definitions available for these imports.
const runSequence = require('run-sequence');

// Default Karma options.
const defaultOptions = {
  configFile: join(buildConfig.projectDir, 'test/karma.conf.js'),
  autoWatch: false,
  singleRun: false
};

/** Builds everything that is necessary for karma. */
task(':test:build', sequenceTask(
  'clean',
  'cdk:build-no-bundles',
  'material:build-no-bundles',
  'cdk-experimental:build-no-bundles',
  'material-experimental:build-no-bundles',
  'youtube-player:build-no-bundles',
  'material-moment-adapter:build-no-bundles',
  'google-maps:build-no-bundles',
));

/**
 * Runs the unit tests. Does not watch for changes.
 * This task should be used when running tests on the CI server.
 */
task('test:single-run', [':test:build'], (done: () => void) => {
  // Load karma not outside. Karma pollutes Promise with a different implementation.
  const karma = require('karma');

  new karma.Server({...defaultOptions, singleRun: true}, (exitCode: number) => {
    // Immediately exit the process if Karma reported errors, because due to
    // potential still running tunnel-browsers gulp won't exit properly.
    exitCode === 0 ? done() : process.exit(exitCode);
  }).start();
});

/**
 * [Watch task] Runs the unit tests, rebuilding and re-testing when sources change.
 * Does not inline resources.
 *
 * This task should be used when running unit tests locally.
 */
task('test', [':test:build'], karmaWatchTask());

/**
 * Runs a Karma server which will run the unit tests against any browser that connects to it.
 * This is identical to `gulp test`, however it won't launch and manage Chrome automatically,
 * which makes it convenient debugging unit tests against multiple different browsers.
 */
task('test:static', [':test:build'], karmaWatchTask({browsers: []}));

/**
 * Returns a Gulp task that spawns a Karma server and reloads whenever the files change.
 * Note that this doesn't use Karma's built-in file watching. Due to the way our build
 * process is set up, Karma ends up firing its change detection for every file that is
 * written to disk, which causes it to run tests multiple time and makes it hard to follow
 * the console output. This approach runs the Karma server and then depends on the Gulp API
 * to tell Karma when to run the tests.
 * @param overrides Karma options to use on top of the defaults.
 */
function karmaWatchTask(options?: any) {
  return () => {
    const patternRoot = join(buildConfig.packagesDir, '**/*');
    // Note: Karma shouldn't be required from the outside, because it
    // pollutes the global Promise with a custom implementation.
    const karma = require('karma');

    // Configure the Karma server and override the autoWatch and singleRun just in case.
    const server = new karma.Server({...defaultOptions, ...options});

    // Refreshes Karma's file list and schedules a test run.
    // Tests will only run if TypeScript compilation was successful.
    const runTests = (error?: Error) => {
      if (!error) {
        server.refreshFiles().then(() => server._injector.get('executor').schedule());
      }
    };

    // Boot up the test server and run the tests whenever a new browser connects.
    server.start();
    server.on('browser_register', () => runTests());

    // Whenever a file change has been recognized, rebuild and re-run the tests.
    watch(patternRoot + '.+(ts|scss|html)', () => runSequence(':test:build', runTests));
  };
}