import { nextTick, ref } from 'vue'

const initialMessages = [
  {
    id: 1,
    role: 'agent',
    text: '我已读取当前报销、发票、行程和制度命中情况。当前建议：优先处理即将超时与高风险单据。'
  },
  {
    id: 2,
    role: 'user',
    text: '请列出今天最需要关注的风险。'
  },
  {
    id: 3,
    role: 'agent',
    text: '主要风险包括：3 笔单据将在 30 分钟内超时，市场部存在 2 笔高风险差旅报销，另有 1 笔报销缺少酒店入住清单。'
  }
]

export const prompts = ['生成审批意见', '列出补件清单', '解释风险原因', '生成运营简报']

export function useChat(activeView) {
  const messages = ref([...initialMessages])
  const draft = ref('')
  const uploadedFiles = ref([])
  const messageList = ref(null)
  const activeCase = ref(null)

  function agentReply(text) {
    const c = activeCase.value
    if (text.includes('超时') || text.includes('SLA')) {
      return '当前最紧急的是 3 笔即将超时单据，建议先按剩余处理时长排序，并把缺附件单据转给申请人补齐。'
    }
    if (text.includes('高风险') || text.includes('风险')) {
      return '高风险主要集中在市场部差旅报销，风险点包括住宿超标、重复发票疑似命中、行程说明缺失。建议人工复核后再通过。'
    }
    if (text.includes('部门')) {
      return '从待处理金额看，销售部与研发中心占比最高；从异常占比看，市场部更需要优先关注。'
    }
    if (text.includes('简报')) {
      return '运营简报：今日待审批 12 单，高风险 4 单，平均审批 5.6h，SLA 达成率 96%。建议优先处理差旅报销和即将超时单据。'
    }
    if (text.includes('补件') || text.includes('附件')) {
      return '建议补件清单：酒店入住水单、完整行程单、发票原件或验真结果、直属经理确认记录。'
    }
    if (text.includes('审批意见')) {
      return c
        ? `${c.id} 建议审批意见：费用归属与预算中心基本匹配，请补充必要说明后通过。`
        : '建议审批意见：当前单据存在待确认项，请先完成风险核查和附件补齐后再审批。'
    }
    return '收到。我可以继续帮你拆解异常原因、比较部门趋势、生成审批意见，或整理一份今日报销运营简报。'
  }

  function scrollToBottom() {
    nextTick(() => messageList.value?.scrollTo({ top: messageList.value.scrollHeight, behavior: 'smooth' }))
  }

  function sendMessage() {
    const text = draft.value.trim()
    if (!text) return false
    messages.value.push({ id: Date.now(), role: 'user', text })
    draft.value = ''
    setTimeout(() => {
      messages.value.push({ id: Date.now() + 1, role: 'agent', text: agentReply(text) })
      scrollToBottom()
    }, 260)
    return true
  }

  function handleUpload(event) {
    uploadedFiles.value = Array.from(event.target.files ?? []).map((file) => ({
      name: file.name,
      size: file.size
    }))
    if (uploadedFiles.value.length) {
      const names = uploadedFiles.value.map((file) => file.name).join('、')
      messages.value.push({
        id: Date.now(),
        role: 'agent',
        text: `已接收 ${uploadedFiles.value.length} 个附件：${names}。我会优先核对发票验真、费用标准、预算归属和必要审批材料。`
      })
      scrollToBottom()
    }
  }

  function openChat(request) {
    activeCase.value = request
    activeView.value = 'chat'
    nextTick(() => messageList.value?.scrollTo({ top: messageList.value.scrollHeight }))
  }

  function openNewChat() {
    activeCase.value = null
    activeView.value = 'chat'
  }

  return {
    messages, draft, uploadedFiles, messageList, activeCase, prompts,
    sendMessage, handleUpload, openChat, openNewChat, scrollToBottom
  }
}