import { sse } from '@cloudbase/functions-typings'

import { TcbContext } from './types'

/**
 * SSESender - 用于发送 Server-Sent Events
 */
export class SSESender<T> {
  private _status: 'initial' | 'started' | 'ended' = 'initial'
  private _sse: sse.IServerSentEvent | null = null

  get status() {
    return this._status
  }

  constructor(readonly context: TcbContext) {}

  // lazy，用的时候再转成 sse
  get sse() {
    if (!this._sse) {
      const sse = this.context?.sse?.()
      if (!sse) {
        throw new Error('Invalid sse')
      }
      this._sse = sse
      this._status = 'started'
    }

    return this._sse
  }

  send(data: sse.Event<T>) {
    this.sse.send(data)
  }
  end() {
    this.sse.end({
      data: '[DONE]'
    })
    this._status = 'ended'
  }
}