Plugin System

/**
 * Resolve plugins from configuration
 * @param plugins - Plugin specifications array
 * @param emitter - Event emitter for plugin events
 * @returns Array of resolved plugin modules
 */
function resolve(plugins: string[], emitter: EventEmitter): any[];

/**
 * Create plugin instantiation function
 * @param injector - Dependency injector instance
 * @returns Function for instantiating plugins
 */
function createInstantiatePlugin(injector: any): Function;

// In karma.conf.js
module.exports = function(config) {
  config.set({
    plugins: [
      // NPM package names
      'karma-jasmine',
      'karma-chrome-launcher',
      'karma-coverage',
      
      // Glob patterns
      'karma-*',
      
      // Scoped packages
      '@angular-devkit/build-angular/plugins/karma',
      
      // Inline plugin objects
      {
        'framework:custom': ['factory', function() {
          // Custom framework implementation
        }]
      },
      
      // Relative paths
      './custom-plugins/my-plugin.js'
    ]
  });
};

/**
 * Plugin type definitions and interfaces
 */
interface PluginTypes {
  // Browser launchers - launch and manage browser instances
  'launcher': BrowserLauncher;
  
  // Test result reporters - format and output test results  
  'reporter': Reporter;
  
  // File preprocessors - transform files before serving
  'preprocessor': Preprocessor;
  
  // Testing frameworks - integrate test libraries
  'framework': Framework;
  
  // HTTP middleware - custom request handling
  'middleware': Middleware;
}

/**
 * Browser launcher interface
 */
interface BrowserLauncher {
  /**
   * Start browser instance
   * @param url - Test runner URL
   * @param onExit - Exit callback
   */
  start(url: string, onExit: Function): void;
  
  /**
   * Kill browser process
   * @param done - Completion callback
   */
  kill(done: Function): void;
  
  /**
   * Force kill browser process
   * @returns Promise for completion
   */
  forceKill(): Promise<void>;
  
  /**
   * Mark browser as captured
   */
  markCaptured(): void;
  
  /**
   * Check if browser is captured
   * @returns True if captured
   */
  isCaptured(): boolean;
  
  // Browser state properties
  state: 'BEING_CAPTURED' | 'CAPTURED' | 'BEING_KILLED' | 'FINISHED' | 'RESTARTING';
  id: string;
  name: string;
  displayName: string;
}

/**
 * Base launcher decorator factory
 */
interface BaseLauncherDecorator {
  (launcher: any): void;
}

// Custom Chrome launcher with specific flags
module.exports = function(config) {
  config.set({
    customLaunchers: {
      ChromeHeadlessCustom: {
        base: 'ChromeHeadless',
        flags: [
          '--no-sandbox',
          '--disable-web-security',
          '--disable-features=VizDisplayCompositor',
          '--remote-debugging-port=9222'
        ]
      },
      
      ChromeDebug: {
        base: 'Chrome',
        flags: ['--remote-debugging-port=9333'],
        debug: true
      },
      
      FirefoxHeadlessCustom: {
        base: 'FirefoxHeadless',
        prefs: {
          'network.proxy.type': 1,
          'network.proxy.http': 'localhost',
          'network.proxy.http_port': 9090
        }
      }
    },
    
    browsers: ['ChromeHeadlessCustom', 'FirefoxHeadlessCustom']
  });
};

// Inline custom launcher plugin
const customLauncher = {
  'launcher:CustomBrowser': ['type', function CustomBrowserLauncher() {
    this.start = function(url) {
      // Launch custom browser
    };
    
    this.kill = function(done) {
      // Kill browser process
      done();
    };
  }]
};

module.exports = function(config) {
  config.set({
    plugins: [customLauncher],
    browsers: ['CustomBrowser']
  });
};

/**
 * Reporter interface
 */
interface Reporter {
  /**
   * Test run started
   * @param browsers - Array of browser instances
   */
  onRunStart(browsers: Browser[]): void;
  
  /**
   * Browser started
   * @param browser - Browser instance
   */
  onBrowserStart(browser: Browser): void;
  
  /**
   * Browser completed
   * @param browser - Browser instance
   * @param result - Test results
   */
  onBrowserComplete(browser: Browser, result: BrowserResult): void;
  
  /**
   * Browser error
   * @param browser - Browser instance  
   * @param error - Error object
   */
  onBrowserError(browser: Browser, error: any): void;
  
  /**
   * Browser log message
   * @param browser - Browser instance
   * @param log - Log message
   * @param type - Log type
   */
  onBrowserLog(browser: Browser, log: string, type: string): void;
  
  /**
   * Individual test completed
   * @param browser - Browser instance
   * @param result - Test result
   */
  onSpecComplete(browser: Browser, result: TestResult): void;
  
  /**
   * Test run completed
   * @param browsers - Array of browser instances
   * @param results - Overall results
   */
  onRunComplete(browsers: Browser[], results: TestResults): void;
  
  // Optional methods
  write?(chunk: string): void;
  writeCommonMsg?(msg: string): void;
  onExit?(done: Function): void;
}

/**
 * Base reporter with utility methods
 */
class BaseReporter implements Reporter {
  write(chunk: string): void;
  renderBrowser(browser: Browser): string;
  specSuccess(browser: Browser, result: TestResult): void;
  specFailure(browser: Browser, result: TestResult): void;
  specSkipped(browser: Browser, result: TestResult): void;
}

// Custom JSON reporter
const jsonReporter = function(baseReporterDecorator, config, logger, helper) {
  baseReporterDecorator(this);
  
  const log = logger.create('reporter.json');
  const reporterConfig = config.jsonReporter || {};
  const outputFile = reporterConfig.outputFile || 'test-results.json';
  
  let results = {
    browsers: {},
    summary: {},
    tests: []
  };
  
  this.onRunStart = function(browsers) {
    results.timestamp = new Date().toISOString();
    results.browsers = browsers.map(b => ({
      id: b.id,
      name: b.name,
      fullName: b.fullName
    }));
  };
  
  this.onSpecComplete = function(browser, result) {
    results.tests.push({
      browser: browser.name,
      suite: result.suite,
      description: result.description,
      success: result.success,
      time: result.time,
      log: result.log
    });
  };
  
  this.onRunComplete = function(browsers, summary) {
    results.summary = summary;
    
    helper.mkdirIfNotExists(path.dirname(outputFile), () => {
      fs.writeFileSync(outputFile, JSON.stringify(results, null, 2));
      log.info('Test results written to %s', outputFile);
    });
  };
};

jsonReporter.$inject = ['baseReporterDecorator', 'config', 'logger', 'helper'];

module.exports = {
  'reporter:json': ['type', jsonReporter]
};

/**
 * Preprocessor interface
 */
interface Preprocessor {
  /**
   * Process file content
   * @param content - Original file content
   * @param file - File object with metadata
   * @param done - Completion callback with (error, content)
   */
  (content: string, file: File, done: (error?: any, content?: string) => void): void;
}

/**
 * File object passed to preprocessors
 */
interface File {
  originalPath: string;     // Original file path
  path: string;            // Processed file path  
  contentPath: string;     // Path to content file
  mtime: Date;            // Modification time
  isUrl: boolean;         // Is external URL
  isBinary: boolean;      // Is binary file
}

// Simple string replacement preprocessor
const stringReplace = function(args, config, logger) {
  const log = logger.create('preprocessor.string-replace');
  const options = args.options || {};
  
  return function(content, file, done) {
    log.debug('Processing "%s".', file.originalPath);
    
    let result = content;
    
    // Apply string replacements
    if (options.replacements) {
      options.replacements.forEach(replacement => {
        result = result.replace(replacement.from, replacement.to);
      });
    }
    
    done(null, result);
  };
};

stringReplace.$inject = ['args', 'config', 'logger'];

// ES6 to ES5 transpiler preprocessor
const babelPreprocessor = function(args, config, logger) {
  const babel = require('@babel/core');
  const log = logger.create('preprocessor.babel');
  
  return function(content, file, done) {
    log.debug('Processing "%s".', file.originalPath);
    
    try {
      const result = babel.transform(content, {
        filename: file.originalPath,
        presets: ['@babel/preset-env'],
        sourceMaps: 'inline'
      });
      
      done(null, result.code);
    } catch (error) {
      log.error('Error processing "%s": %s', file.originalPath, error.message);
      done(error);
    }
  };
};

babelPreprocessor.$inject = ['args', 'config', 'logger'];

module.exports = {
  'preprocessor:string-replace': ['factory', stringReplace],
  'preprocessor:babel': ['factory', babelPreprocessor]
};

/**
 * Framework interface
 */
interface Framework {
  /**
   * Initialize framework on client side
   * @param files - File list to modify
   */
  (files: any[]): void;
}

// Custom testing framework
const customFramework = function(files) {
  // Add framework files to the file list
  files.unshift({
    pattern: require.resolve('./custom-framework.js'),
    included: true,
    served: true,
    watched: false
  });
  
  // Add adapter file
  files.unshift({
    pattern: require.resolve('./custom-adapter.js'), 
    included: true,
    served: true,
    watched: false
  });
};

customFramework.$inject = ['config.files'];

module.exports = {
  'framework:custom': ['factory', customFramework]
};

/**
 * Middleware interface  
 */
interface Middleware {
  /**
   * Express-style middleware function
   * @param req - HTTP request
   * @param res - HTTP response  
   * @param next - Next middleware function
   */
  (req: any, res: any, next: Function): void;
}

// API endpoint middleware
const apiMiddleware = function(config) {
  return function(req, res, next) {
    if (req.url.startsWith('/api/')) {
      // Handle API requests
      res.setHeader('Content-Type', 'application/json');
      res.end(JSON.stringify({ message: 'API response' }));
    } else {
      next();
    }
  };
};

apiMiddleware.$inject = ['config'];

// CORS middleware
const corsMiddleware = function() {
  return function(req, res, next) {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
    
    if (req.method === 'OPTIONS') {
      res.end();
    } else {
      next();
    }
  };
};

module.exports = {
  'middleware:api': ['factory', apiMiddleware],
  'middleware:cors': ['factory', corsMiddleware]
};

// Built-in and popular browser launchers
'karma-chrome-launcher'        // Google Chrome
'karma-firefox-launcher'       // Mozilla Firefox  
'karma-safari-launcher'        // Safari
'karma-ie-launcher'           // Internet Explorer
'karma-edge-launcher'         // Microsoft Edge
'karma-phantomjs-launcher'    // PhantomJS (deprecated)
'karma-browserstack-launcher' // BrowserStack
'karma-sauce-launcher'        // Sauce Labs

// Built-in and popular reporters
'karma-progress-reporter'     // Progress dots (built-in)
'karma-dots-reporter'        // Simple dots (built-in)
'karma-junit-reporter'       // JUnit XML
'karma-coverage-reporter'    // Code coverage
'karma-spec-reporter'        // Detailed spec output
'karma-json-reporter'        // JSON output
'karma-teamcity-reporter'    // TeamCity integration

// Popular preprocessors
'karma-babel-preprocessor'    // Babel transpilation
'karma-webpack'              // Webpack bundling
'karma-rollup-preprocessor'  // Rollup bundling
'karma-browserify'           // Browserify bundling
'karma-typescript'           // TypeScript compilation
'karma-coverage'             // Code coverage instrumentation

// Popular testing frameworks
'karma-jasmine'              // Jasmine
'karma-mocha'               // Mocha
'karma-qunit'               // QUnit
'karma-tap'                 // TAP
'karma-jest'                // Jest compatibility