/**
 * 浏览器端 stream 桩模块
 *
 * webpack5 不再内置 node polyfill，sax 等依赖在模块加载阶段就会 require('stream')：
 *   var Stream
 *   try { Stream = require('stream').Stream } catch (ex) { Stream = function () {} }
 *   SAXStream.prototype = Object.create(Stream.prototype, {...})
 *
 * 若把 stream 置空（fallback: { stream: false }），require('stream') 不会抛错，
 * 取到的 .Stream 是 undefined，上面这行就会抛
 * “Cannot read properties of undefined (reading 'prototype')”，导致整个应用启动失败。
 * 这里提供一个最小可用的 Stream 实现，保证模块加载期不报错。
 */
function Stream() {}

Stream.prototype.on = function () {
  return this;
};
Stream.prototype.once = function () {
  return this;
};
Stream.prototype.emit = function () {
  return false;
};
Stream.prototype.removeListener = function () {
  return this;
};
Stream.prototype.pipe = function () {
  return this;
};
Stream.prototype.write = function () {
  return true;
};
Stream.prototype.end = function () {
  return this;
};

exports.Stream = Stream;
exports.Readable = Stream;
exports.Writable = Stream;
exports.Duplex = Stream;
exports.Transform = Stream;
exports.PassThrough = Stream;