import React, { useEffect, useState, useRef } from 'react'
import { Users, Server, HardDrive, Activity, AlertTriangle, CheckCircle2, Sun, Moon } from 'lucide-react'
import { AreaChart, Area, XAxis, YAxis, Tooltip, ResponsiveContainer } from 'recharts'
import { api } from '../api/client'
import { useAuth } from '../contexts/AuthContext'
import { useTheme } from '../contexts/ThemeContext'

interface SystemStats {
  cpu: number
  memory: { total: number; used: number; free: number; percent: number }
  disk: { total: number; used: number; free: number; percent: number }
  load: [number, number, number]
  uptime: number
}

interface AccountStats {
  total: number
  active: number
  suspended: number
  terminated: number
}

interface SystemInfo {
  hostname: string
  os: string
}

interface ServiceStatus {
  name: string
  status: 'running' | 'stopped' | 'failed' | 'unknown'
  enabled: boolean
}

interface StatCard {
  label: string
  value: string | number
  sub?: string
  icon: React.ComponentType<{ size?: number | string; className?: string }>
  color: string
}

const formatBytes = (bytes: number) => {
  const gb = bytes / 1024 / 1024 / 1024
  return gb >= 1 ? `${gb.toFixed(1)} GB` : `${(bytes / 1024 / 1024).toFixed(0)} MB`
}

// ─── Server Info Bar ─────────────────────────────────────────────────────────

interface InfoCellProps {
  label: string
  value: React.ReactNode
}

function InfoCell({ label, value }: InfoCellProps) {
  return (
    <div className="flex flex-col min-w-0">
      <span className="text-[#4a5568] text-[10px] font-medium uppercase tracking-wide leading-none mb-0.5">
        {label}
      </span>
      <span className="text-[#94a3b8] text-xs font-medium leading-none truncate">
        {value}
      </span>
    </div>
  )
}

function Divider() {
  return <div className="w-px h-8 bg-[#2a2d3e] flex-shrink-0" />
}

// ─── Component ───────────────────────────────────────────────────────────────

export default function Dashboard() {
  const { user } = useAuth()
  const { theme, toggleTheme } = useTheme()
  const [stats, setStats] = useState<SystemStats | null>(null)
  const [accountStats, setAccountStats] = useState<AccountStats | null>(null)
  const [cpuHistory, setCpuHistory] = useState<{ t: string; cpu: number; mem: number }[]>([])
  const [systemInfo, setSystemInfo] = useState<SystemInfo | null>(null)
  const [version, setVersion] = useState<string | null>(null)
  const [alertCount, setAlertCount] = useState<number | null>(null)
  const wsRef = useRef<WebSocket | null>(null)

  useEffect(() => {
    api.get('/nixserver/accounts/stats').then(r => setAccountStats(r.data.data)).catch(() => {})
    api.get('/nixserver/system/stats').then(r => setStats(r.data.data)).catch(() => {})
    api.get('/nixserver/system/info').then(r => setSystemInfo(r.data.data)).catch(() => {})
    api.get('/nixserver/system/version').then(r => setVersion(r.data.data?.currentVersion ?? null)).catch(() => {})
    api.get('/nixserver/services').then(r => {
      const services: ServiceStatus[] = r.data.data ?? []
      setAlertCount(services.filter(s => s.status !== 'running').length)
    }).catch(() => { setAlertCount(0) })

    // WebSocket live stats
    const token = localStorage.getItem('access_token')
    if (token) {
      const ws = new WebSocket(`ws://${window.location.hostname}:2087/ws/stats?token=${token}`)
      wsRef.current = ws
      ws.onmessage = e => {
        const msg = JSON.parse(e.data)
        if (msg.type === 'stats') {
          setStats(msg.data)
          setCpuHistory(prev => [
            ...prev.slice(-29),
            { t: new Date().toLocaleTimeString(), cpu: msg.data.cpu, mem: msg.data.memory.percent },
          ])
        }
      }
    }

    return () => wsRef.current?.close()
  }, [])

  const cards: StatCard[] = [
    {
      label: 'Total Accounts',
      value: accountStats?.total ?? '—',
      sub: `${accountStats?.active ?? 0} active`,
      icon: Users,
      color: 'text-indigo-400',
    },
    {
      label: 'CPU Usage',
      value: stats ? `${stats.cpu}%` : '—',
      sub: `Load: ${stats?.load[0].toFixed(2) ?? '—'}`,
      icon: Activity,
      color: 'text-emerald-400',
    },
    {
      label: 'Memory',
      value: stats ? `${stats.memory.percent}%` : '—',
      sub: stats ? `${formatBytes(stats.memory.used)} / ${formatBytes(stats.memory.total)}` : '—',
      icon: Server,
      color: 'text-blue-400',
    },
    {
      label: 'Disk',
      value: stats ? `${stats.disk.percent}%` : '—',
      sub: stats ? `${formatBytes(stats.disk.used)} / ${formatBytes(stats.disk.total)}` : '—',
      icon: HardDrive,
      color: 'text-amber-400',
    },
  ]

  const loadStr = stats
    ? `${stats.load[0].toFixed(2)}\u00a0\u00a0${stats.load[1].toFixed(2)}\u00a0\u00a0${stats.load[2].toFixed(2)}`
    : '…'

  const monitoringNode =
    alertCount === null ? (
      <span className="text-[#4a5568]">…</span>
    ) : alertCount === 0 ? (
      <span className="flex items-center gap-1 text-emerald-400">
        <CheckCircle2 size={11} />
        All Clear
      </span>
    ) : (
      <span className="flex items-center gap-1 text-amber-400">
        <AlertTriangle size={11} />
        {alertCount} Alert{alertCount !== 1 ? 's' : ''}
      </span>
    )

  return (
    <div className="space-y-6">

      {/* ── cPanel-style server info bar ─────────────────────────────────── */}
      <div className="bg-[#1a1d27] border border-[#2a2d3e] rounded-xl px-5 py-3.5 flex flex-wrap items-center gap-x-5 gap-y-3">
        <InfoCell label="Username"          value={user?.username ?? '…'} />
        <Divider />
        <InfoCell label="Hostname"          value={systemInfo?.hostname ?? '…'} />
        <Divider />
        <InfoCell label="OS"                value={systemInfo?.os ?? '…'} />
        <Divider />
        <InfoCell label="NixPanel Version"  value={version ? `v${version}` : '…'} />
        <Divider />
        <InfoCell label="Load Averages"     value={loadStr} />
        <Divider />
        <InfoCell label="Server Monitoring" value={monitoringNode} />

        {/* ── Day / Night toggle — far right ── */}
        <div className="ml-auto flex items-center gap-2 flex-shrink-0">
          <Moon
            size={13}
            className={theme === 'dark' ? 'text-indigo-400' : 'text-[#94a3b8]'}
          />
          <button
            onClick={toggleTheme}
            title={theme === 'dark' ? 'Switch to day mode' : 'Switch to night mode'}
            className={`relative flex items-center w-10 h-5 rounded-full transition-colors cursor-pointer flex-shrink-0 ${
              theme === 'light' ? 'bg-amber-400' : 'bg-[#2a2d3e]'
            }`}
          >
            <span
              className={`absolute h-4 w-4 rounded-full bg-white shadow-sm transition-transform ${
                theme === 'light' ? 'translate-x-5' : 'translate-x-0.5'
              }`}
            />
          </button>
          <Sun
            size={13}
            className={theme === 'light' ? 'text-amber-500' : 'text-[#4a5568]'}
          />
        </div>
      </div>

      {/* ── Stat cards ───────────────────────────────────────────────────── */}
      <div className="grid grid-cols-1 sm:grid-cols-2 xl:grid-cols-4 gap-4">
        {cards.map(card => (
          <div key={card.label} className="bg-[#1a1d27] border border-[#2a2d3e] rounded-xl p-4">
            <div className="flex items-center justify-between mb-3">
              <span className="text-[#64748b] text-xs font-medium">{card.label}</span>
              <card.icon size={16} className={card.color} />
            </div>
            <p className="text-white text-2xl font-bold">{card.value}</p>
            {card.sub && <p className="text-[#64748b] text-xs mt-1">{card.sub}</p>}
          </div>
        ))}
      </div>

      {/* ── CPU / Memory chart ───────────────────────────────────────────── */}
      <div className="bg-[#1a1d27] border border-[#2a2d3e] rounded-xl p-4">
        <h2 className="text-white text-sm font-medium mb-4">CPU & Memory — Live</h2>
        {cpuHistory.length > 0 ? (
          <ResponsiveContainer width="100%" height={160}>
            <AreaChart data={cpuHistory}>
              <defs>
                <linearGradient id="cpu" x1="0" y1="0" x2="0" y2="1">
                  <stop offset="5%" stopColor="#6366f1" stopOpacity={0.3} />
                  <stop offset="95%" stopColor="#6366f1" stopOpacity={0} />
                </linearGradient>
                <linearGradient id="mem" x1="0" y1="0" x2="0" y2="1">
                  <stop offset="5%" stopColor="#10b981" stopOpacity={0.3} />
                  <stop offset="95%" stopColor="#10b981" stopOpacity={0} />
                </linearGradient>
              </defs>
              <XAxis dataKey="t" tick={{ fill: '#64748b', fontSize: 10 }} tickLine={false} axisLine={false} />
              <YAxis domain={[0, 100]} tick={{ fill: '#64748b', fontSize: 10 }} tickLine={false} axisLine={false} />
              <Tooltip
                contentStyle={{
                  background: theme === 'light' ? '#ffffff' : '#1e2130',
                  border: `1px solid ${theme === 'light' ? '#e2e8f0' : '#2a2d3e'}`,
                  borderRadius: 8,
                  fontSize: 12,
                  color: theme === 'light' ? '#0f172a' : '#e2e8f0',
                }}
                labelStyle={{ color: theme === 'light' ? '#64748b' : '#94a3b8' }}
              />
              <Area type="monotone" dataKey="cpu" stroke="#6366f1" fill="url(#cpu)" strokeWidth={2} name="CPU %" />
              <Area type="monotone" dataKey="mem" stroke="#10b981" fill="url(#mem)" strokeWidth={2} name="Mem %" />
            </AreaChart>
          </ResponsiveContainer>
        ) : (
          <div className="h-40 flex items-center justify-center text-[#64748b] text-sm">
            Connecting to live stats...
          </div>
        )}
      </div>

      {/* ── Account status breakdown ─────────────────────────────────────── */}
      {accountStats && (
        <div className="bg-[#1a1d27] border border-[#2a2d3e] rounded-xl p-4">
          <h2 className="text-white text-sm font-medium mb-4">Account Status</h2>
          <div className="grid grid-cols-3 gap-4">
            {[
              { label: 'Active',     value: accountStats.active,     color: 'text-emerald-400' },
              { label: 'Suspended',  value: accountStats.suspended,  color: 'text-amber-400'   },
              { label: 'Terminated', value: accountStats.terminated, color: 'text-red-400'     },
            ].map(s => (
              <div key={s.label} className="text-center">
                <p className={`text-2xl font-bold ${s.color}`}>{s.value}</p>
                <p className="text-[#64748b] text-xs mt-0.5">{s.label}</p>
              </div>
            ))}
          </div>
        </div>
      )}
    </div>
  )
}