import { inject, onBeforeUnmount, provide, ref, watch, type InjectionKey, type Ref } from 'vue'
import type { AgentClient } from '@agent-server/client'

/** 组件只需要带鉴权地下载文件：AgentClient 与 BotClient 都满足 */
export type FileClient = Pick<AgentClient, 'fileBlob'>

const CLIENT_KEY: InjectionKey<FileClient> = Symbol('agent-client')

export function provideClient(client: FileClient) {
  provide(CLIENT_KEY, client)
}

export function useClient(): FileClient {
  const c = inject(CLIENT_KEY)
  if (!c) throw new Error('chat-ui: 缺少 AgentClient（请在外层使用 <AgentChat> 或 provideClient）')
  return c
}

/** 带鉴权地加载文件为 object URL（Agent Key 模式下 <img src> 无法携带请求头） */
export function useFileObjectUrl(fileId: Ref<string | null>): Ref<string | null> {
  const client = useClient()
  const url = ref<string | null>(null)
  let current: string | null = null
  const release = () => {
    if (current) URL.revokeObjectURL(current)
    current = null
  }
  watch(fileId, async id => {
    release()
    url.value = null
    if (!id) return
    try {
      current = URL.createObjectURL(await client.fileBlob(id))
      url.value = current
    } catch {
      url.value = null
    }
  }, { immediate: true })
  onBeforeUnmount(release)
  return url
}

export async function downloadFile(client: FileClient, fileId: string, name: string) {
  const blob = await client.fileBlob(fileId)
  const href = URL.createObjectURL(blob)
  const a = document.createElement('a')
  a.href = href
  a.download = name
  a.click()
  setTimeout(() => URL.revokeObjectURL(href), 10_000)
}