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import events from './events.ts'
interface Callback {  (...args: any[]): void}
class Module {  private _specifier: string  private _isLocked: boolean = false  private _isAccepted: boolean = false  private _acceptCallbacks: Callback[] = []
  get specifier() {    return this._specifier  }
  constructor(specifier: string) {    this._specifier = specifier  }
  lock(): void {    this._isLocked = true  }
  accept(callback?: Callback): void {    if (this._isLocked) {      return    }    if (!this._isAccepted) {      sendMessage({ specifier: this._specifier, type: 'hotAccept' })      this._isAccepted = true    }    if (callback) {      this._acceptCallbacks.push(callback)    }  }
  async applyUpdate(url: string) {    try {      const module = await import(url + '?t=' + Date.now())      this._acceptCallbacks.forEach(cb => cb(module))    } catch (e) {      location.reload()    }  }}
const modules: Map<string, Module> = new Map()const state: {  socket: WebSocket | null  messageQueue: string[]} = {  socket: null,  messageQueue: []}
function sendMessage(msg: any) {  const json = JSON.stringify(msg)  if (!state.socket || state.socket.readyState !== WebSocket.OPEN) {    state.messageQueue.push(json)  } else {    state.socket.send(json)  }}
export function connect(basePath: string) {  const { location } = window as any  const { protocol, host } = location  const wsUrl = (protocol === 'https:' ? 'wss' : 'ws') + '://' + host + basePath.replace(/\/+$/, '') + '/_hmr'  const ws = new WebSocket(wsUrl)  const contact = (callback: () => void) => {    setTimeout(() => {      const ws = new WebSocket(wsUrl)      ws.addEventListener('open', callback)      ws.addEventListener('close', () => {        contact(callback) // retry      })    }, 500)  }
  ws.addEventListener('open', () => {    state.socket = ws    state.messageQueue.splice(0, state.messageQueue.length).forEach(msg => ws.send(msg))    console.log('[HMR] listening for file changes...')  })
  ws.addEventListener('close', () => {    if (state.socket !== null) {      state.socket = null      console.log('[HMR] closed.')      // re-connect      setTimeout(() => {        connect(basePath)      }, 300)    } else {      // reload the page when re-connected      contact(() => location.reload())    }  })
  ws.addEventListener('message', ({ data }: { data?: string }) => {    if (data) {      try {        const {          type,          specifier,          updateUrl,          routePath,          isIndex,          refreshPage        } = JSON.parse(data)        if (refreshPage === true) {          location.reload()          return        }        switch (type) {          case 'add':            events.emit('add-module', {              specifier,              routePath,              isIndex,            })            break          case 'update':            const mod = modules.get(specifier)            if (mod) {              mod.applyUpdate(updateUrl)            }            break          case 'remove':            if (modules.has(specifier)) {              modules.delete(specifier)              events.emit('remove-module', specifier)            }            break        }        console.log(`[HMR] ${type} module '${specifier}'`)      } catch (err) {        console.warn(err)      }    }  })}
Object.assign(window, {  $createHotContext: (specifier: string) => {    if (modules.has(specifier)) {      const mod = modules.get(specifier)!      mod.lock()      return mod    }
    const mod = new Module(specifier)    modules.set(specifier, mod)    return mod  }})