import { useEffect, useState, useCallback } from 'react'
import { useNavigate } from 'react-router-dom'
import { NavBar, Card, Empty, DotLoading } from 'antd-mobile'
import { api } from '../api/client.js'
import SwipeTabs from '../components/SwipeTabs.jsx'

// 监控页: 两个横向分类
//  - 主机监控: 实时数据来自 komari (服务端实时代理, 不落库), 点击节点看 24h 时序
//  - 服务监控: 暂留空占位
function fmtTime(s) {
  if (!s) return ''
  const d = new Date(s)
  if (isNaN(d.getTime())) return s
  const pad = (n) => String(n).padStart(2, '0')
  return pad(d.getHours()) + ':' + pad(d.getMinutes())
}

function fmtBytes(b) {
  if (!b) return '0 B'
  const units = ['B', 'KB', 'MB', 'GB', 'TB']
  let i = 0
  let v = Number(b)
  while (v >= 1024 && i < units.length - 1) { v /= 1024; i++ }
  return v.toFixed(v >= 100 ? 0 : 1) + ' ' + units[i]
}

function fmtUptime(sec) {
  const s = Number(sec) || 0
  const d = Math.floor(s / 86400)
  const h = Math.floor((s % 86400) / 3600)
  return d > 0 ? d + '天' + h + '小时' : h + '小时'
}

function pct(used, total) {
  return total > 0 ? Math.min(100, (used / total) * 100) : 0
}

export default function MonitorPage() {
  const [active, setActive] = useState('servers')
  const tabs = [
    { key: 'servers', label: '主机监控', render: () => <ServerView /> },
    { key: 'services', label: '服务监控', render: () => <ServiceView /> },
  ]
  return (
    <div className="page-with-navbar">
      <NavBar back={null}>监控</NavBar>
      <div className="monitor-content">
        <SwipeTabs tabs={tabs} active={active} onChange={setActive} />
      </div>
    </div>
  )
}

// 主机监控列表模块级缓存: 切走再进入时先展示上次数据, 拉取成功后再静默更新
let cachedServers = null

// 主机监控: komari 实时节点列表 (30s 轮询, 静默刷新)
function ServerView() {
  const [items, setItems] = useState(cachedServers) // 有缓存直接先展示, 无缓存为 null 进入加载态
  const [err, setErr] = useState('')
  const navigate = useNavigate()

  const load = useCallback((silent) => {
    if (!silent && cachedServers === null) setItems(null) // 仅无缓存时显示加载中
    if (!silent) setErr('')
    api('/servers')
      .then((data) => { cachedServers = data.items || []; setErr(''); setItems(data.items || []) })
      .catch((e) => { if (!silent) { setErr(e.message); if (cachedServers === null) setItems([]) } })
  }, [])

  useEffect(() => {
    load(false)
    const timer = setInterval(() => load(true), 30000)
    return () => clearInterval(timer)
  }, [load])

  return (
    <div className="server-list">
      {items === null && <div className="monitor-loading"><DotLoading /> 加载中...</div>}
      {err && (
        <div className="error-banner">
          {err}
          <span className="retry-link" onClick={() => load(false)}>重试</span>
        </div>
      )}
      {items !== null && !err && items.length === 0 && <Empty description="暂无主机" />}
      {items !== null && items.length > 0 && (
        <>
          <div className="monitor-tip">实时数据 · 每 30 秒自动刷新</div>
          <div className="section-list">
            {items.map((n) => (
              <Card key={n.uuid} className="server-card" onClick={() => navigate('/monitor/server/' + n.uuid)}>
                <div className="server-head">
                  <span className="server-name">
                    <span className={'status-dot ' + (n.status === 'online' ? 'on' : 'off')} />
                    {n.name}
                  </span>
                  <span className="server-update">更新于 {fmtTime(n.recordedAt)}</span>
                </div>
                <div className="server-metrics">
                  <div className="metric">
                    <div className="metric-label">CPU</div>
                    <Meter percent={n.cpuUsage} />
                    <div className="metric-value">{n.cpuUsage.toFixed ? n.cpuUsage.toFixed(1) : n.cpuUsage}%</div>
                  </div>
                  <div className="metric">
                    <div className="metric-label">内存</div>
                    <Meter percent={pct(n.ramUsed, n.memTotal)} />
                    <div className="metric-value">{fmtBytes(n.ramUsed)} / {fmtBytes(n.memTotal)}</div>
                  </div>
                  <div className="metric">
                    <div className="metric-label">磁盘</div>
                    <Meter percent={pct(n.diskUsed, n.diskTotal)} />
                    <div className="metric-value">{fmtBytes(n.diskUsed)} / {fmtBytes(n.diskTotal)}</div>
                  </div>
                </div>
                <div className="server-foot">
                  <span>负载 {n.load1} / {n.load5} / {n.load15}</span>
                  <span>{n.cpuCores} 核</span>
                  <span>进程 {n.process}</span>
                  <span>连接 {n.connections}</span>
                  <span>运行 {fmtUptime(n.uptime)}</span>
                </div>
              </Card>
            ))}
          </div>
        </>
      )}
    </div>
  )
}

// 进度条 (超 80% 变红)
function Meter({ percent }) {
  const p = Math.max(0, Math.min(100, Number(percent) || 0))
  return (
    <div className="meter">
      <div className={'meter-fill' + (p >= 80 ? ' warn' : '')} style={{ width: p + '%' }} />
    </div>
  )
}

// 服务监控: 暂留空
function ServiceView() {
  return (
    <div className="monitor-empty">
      <Empty description="服务监控待接入" />
    </div>
  )
}