import { EventEmitter } from 'events';
import type { ServerResponse, IncomingMessage, Server } from 'http';
import { Readable } from 'stream';
import type { Logger } from '../../../src/logging/Logger';
import { getLoggerFor } from '../../../src/logging/LogUtil';
import { HandlerServerConfigurator } from '../../../src/server/HandlerServerConfigurator';
import type { HttpHandler } from '../../../src/server/HttpHandler';
import { flushPromises } from '../../util/Util';

jest.mock('../../../src/logging/LogUtil', (): any => {
  const logger: Logger =
    { error: jest.fn(), info: jest.fn() } as any;
  return { getLoggerFor: (): Logger => logger };
});

describe('A HandlerServerConfigurator', (): void => {
  const logger: jest.Mocked<Logger> = getLoggerFor('mock') as any;
  let request: jest.Mocked<IncomingMessage>;
  let response: jest.Mocked<ServerResponse>;
  let server: Server;
  let handler: jest.Mocked<HttpHandler>;
  let listener: HandlerServerConfigurator;

  beforeEach(async(): Promise<void> => {
    // Clearing the logger mock
    jest.clearAllMocks();
    request = Readable.from('') as any;
    request.method = 'GET';
    request.url = '/';

    response = {
      headersSent: false,
      end: jest.fn(),
      setHeader: jest.fn(),
      writeHead: jest.fn(),
    } as any;
    response.end.mockImplementation((): any => {
      response.headersSent = true;
    });
    response.writeHead.mockReturnValue(response);

    server = new EventEmitter() as any;

    handler = {
      handleSafe: jest.fn((): void => {
        response.headersSent = true;
      }),
    } as any;

    listener = new HandlerServerConfigurator(handler);
    await listener.handle(server);
  });

  it('sends incoming requests to the handler.', async(): Promise<void> => {
    server.emit('request', request, response);
    await flushPromises();

    expect(handler.handleSafe).toHaveBeenCalledTimes(1);
    expect(handler.handleSafe).toHaveBeenLastCalledWith({ request, response });

    expect(response.setHeader).toHaveBeenCalledTimes(0);
    expect(response.writeHead).toHaveBeenCalledTimes(0);
    expect(response.end).toHaveBeenCalledTimes(0);
  });

  it('returns a 404 when the handler does not do anything.', async(): Promise<void> => {
    handler.handleSafe.mockImplementation(jest.fn());
    server.emit('request', request, response);
    await flushPromises();

    expect(response.setHeader).toHaveBeenCalledTimes(0);
    expect(response.writeHead).toHaveBeenCalledTimes(1);
    expect(response.writeHead).toHaveBeenLastCalledWith(404);
    expect(response.end).toHaveBeenCalledTimes(1);
    expect(response.end).toHaveBeenLastCalledWith();
  });

  it('writes an error to the HTTP response without the stack trace.', async(): Promise<void> => {
    handler.handleSafe.mockRejectedValueOnce(new Error('dummyError'));
    server.emit('request', request, response);
    await flushPromises();

    expect(response.setHeader).toHaveBeenCalledTimes(1);
    expect(response.setHeader).toHaveBeenLastCalledWith('Content-Type', 'text/plain; charset=utf-8');
    expect(response.writeHead).toHaveBeenCalledTimes(1);
    expect(response.writeHead).toHaveBeenLastCalledWith(500);
    expect(response.end).toHaveBeenCalledTimes(1);
    expect(response.end).toHaveBeenLastCalledWith('Error: dummyError\n');
  });

  it('does not write an error if the response had been started.', async(): Promise<void> => {
    response.headersSent = true;
    handler.handleSafe.mockRejectedValueOnce(new Error('dummyError'));
    server.emit('request', request, response);
    await flushPromises();

    expect(response.setHeader).toHaveBeenCalledTimes(0);
    expect(response.writeHead).toHaveBeenCalledTimes(0);
    expect(response.end).toHaveBeenCalledTimes(1);
    expect(response.end).toHaveBeenLastCalledWith();
  });

  it('throws unknown errors if its handler throw non-Error objects.', async(): Promise<void> => {
    handler.handleSafe.mockRejectedValueOnce('apple');
    server.emit('request', request, response);
    await flushPromises();

    expect(response.setHeader).toHaveBeenCalledTimes(1);
    expect(response.setHeader).toHaveBeenLastCalledWith('Content-Type', 'text/plain; charset=utf-8');
    expect(response.writeHead).toHaveBeenCalledTimes(1);
    expect(response.writeHead).toHaveBeenLastCalledWith(500);
    expect(response.end).toHaveBeenCalledTimes(1);
    expect(response.end).toHaveBeenLastCalledWith('Unknown error: apple.\n');
  });

  it('can handle errors on the HttpResponse.', async(): Promise<void> => {
    handler.handleSafe.mockImplementationOnce(async(input): Promise<void> => {
      input.request.emit('error', new Error('bad request'));
    });
    server.emit('request', request, response);
    await flushPromises();

    expect(logger.error).toHaveBeenCalledTimes(1);
    expect(logger.error).toHaveBeenLastCalledWith('Request error: bad request');
  });

  it('prints the stack trace if that option is enabled.', async(): Promise<void> => {
    server.removeAllListeners();
    listener = new HandlerServerConfigurator(handler, true);
    await listener.handle(server);
    const error = new Error('dummyError');
    handler.handleSafe.mockRejectedValueOnce(error);
    server.emit('request', request, response);
    await flushPromises();

    expect(response.setHeader).toHaveBeenCalledTimes(1);
    expect(response.setHeader).toHaveBeenLastCalledWith('Content-Type', 'text/plain; charset=utf-8');
    expect(response.writeHead).toHaveBeenCalledTimes(1);
    expect(response.writeHead).toHaveBeenLastCalledWith(500);
    expect(response.end).toHaveBeenCalledTimes(1);
    expect(response.end).toHaveBeenLastCalledWith(`${error.stack}\n`);
  });
});