import * as util from 'util';

const timers = require('timers');

type AnyFn = (...args: any[]) => any

// setImmediate and process.nextTick makes use of uv_check and uv_prepare to
// run the callbacks, however since we only run uv loop on requests, the
// callbacks wouldn't be called until something else activated the uv loop,
// which would delay the callbacks for arbitrary long time. So we should
// initiatively activate the uv loop once setImmediate and process.nextTick is
// called.
const wrapWithActivateUvLoop = function <T extends AnyFn> (func: T): T {
  return wrap(func, function (func) {
    return function (this: any, ...args: any[]) {
      process.activateUvLoop();
      return func.apply(this, args);
    };
  }) as T;
};

/**
 * Casts to any below for func are due to Typescript not supporting symbols
 * in index signatures
 *
 * Refs: https://github.com/Microsoft/TypeScript/issues/1863
 */
function wrap <T extends AnyFn> (func: T, wrapper: (fn: AnyFn) => T) {
  const wrapped = wrapper(func);
  if ((func as any)[util.promisify.custom]) {
    (wrapped as any)[util.promisify.custom] = wrapper((func as any)[util.promisify.custom]);
  }
  return wrapped;
}

process.nextTick = wrapWithActivateUvLoop(process.nextTick);

global.setImmediate = timers.setImmediate = wrapWithActivateUvLoop(timers.setImmediate);
global.clearImmediate = timers.clearImmediate;

// setTimeout needs to update the polling timeout of the event loop, when
// called under Chromium's event loop the node's event loop won't get a chance
// to update the timeout, so we have to force the node's event loop to
// recalculate the timeout in browser process.
timers.setTimeout = wrapWithActivateUvLoop(timers.setTimeout);
timers.setInterval = wrapWithActivateUvLoop(timers.setInterval);

// Only override the global setTimeout/setInterval impls in the browser process
if (process.type === 'browser') {
  global.setTimeout = timers.setTimeout;
  global.setInterval = timers.setInterval;
}

if (process.platform === 'win32') {
  // Always returns EOF for stdin stream.
  const { Readable } = require('stream');
  const stdin = new Readable();
  stdin.push(null);
  Object.defineProperty(process, 'stdin', {
    configurable: false,
    enumerable: true,
    get () {
      return stdin;
    }
  });
}