import { memo, useCallback, useEffect, useRef, useState } from 'react'
import { useTranslation } from 'react-i18next'
import '@/i18n/domains'
import { Activity, Database, Gauge, Loader2, RefreshCw } from 'lucide-react'
import { Button } from '@/components/ui/button'
import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
import { PageContainer } from '@/components/PageContainer'
import { EmptyState } from '@/components/EmptyState'
import { ErrorState } from '@/components/ErrorState'
import { LoadingSpinner } from '@/components/LoadingSpinner'
import { StatCard } from '@/components/StatCard'
import { http } from '@/api/http'
import { getUser } from '@/lib/auth-storage'

interface PathCount { path: string; count: number }
interface Summary {
  http: { total: number; byStatus: Record<string, number>; inFlight: number; topPaths: PathCount[] }
  db: { sizeBytes: number; saves: number; saveFailures: number; records: Record<string, number> }
  alerts: { evaluations: Record<string, number> }
  loki: { queries: Record<string, number> }
  runtime: { goroutines: number; goVersion: string; version: string }
}

const fmtBytes = (n: number) => {
  if (n >= 1 << 30) return `${(n / (1 << 30)).toFixed(2)} GB`
  if (n >= 1 << 20) return `${(n / (1 << 20)).toFixed(1)} MB`
  if (n >= 1 << 10) return `${(n / (1 << 10)).toFixed(1)} KB`
  return `${n} B`
}

/** 平台自监控(admin):聚合 /metrics 为可读快照 — 请求/DB/告警引擎/运行时 */
const MonitorPage = memo(function MonitorPage() {
  const { t } = useTranslation('monitor')
  const isAdmin = getUser()?.role === 'admin'
  const [data, setData] = useState<Summary | null>(null)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState('')
  const versionRef = useRef(0)

  const load = useCallback(() => {
    const v = ++versionRef.current
    setLoading(true)
    setError('')
    http.get<Summary>('/system/metrics-summary')
      .then(result => { if (v === versionRef.current) setData(result) })
      .catch(err => { if (v === versionRef.current) setError(err instanceof Error ? err.message : t('loadFailed')) })
      .finally(() => { if (v === versionRef.current) setLoading(false) })
  }, [t])

  useEffect(() => {
    if (isAdmin) load()
  }, [isAdmin, load])

  if (!isAdmin) {
    return (
      <PageContainer title={t('title')}>
        <EmptyState icon={Activity} title={t('adminOnly.title')} description={t('adminOnly.desc')} />
      </PageContainer>
    )
  }

  const statusEntries = data ? Object.entries(data.http.byStatus).sort(([a], [b]) => a.localeCompare(b)) : []
  const err5xx = statusEntries.filter(([code]) => code.startsWith('5')).reduce((acc, [, v]) => acc + v, 0)

  return (
    <PageContainer
      title={t('title')}
      description={t('subtitle')}
      action={
        <Button variant="outline" onClick={load} disabled={loading}>
          {loading ? <Loader2 className="mr-1 size-4 animate-spin" /> : <RefreshCw className="mr-1 size-4" />}
          {t('refresh')}
        </Button>
      }
    >
      {error ? (
        <ErrorState message={error} onRetry={load} />
      ) : loading && !data ? (
        <LoadingSpinner className="h-64" />
      ) : !data ? null : (
        <>
          <div className="grid gap-4 sm:grid-cols-2 xl:grid-cols-4">
            <StatCard label={t('stats.requests')} value={data.http.total.toLocaleString()} icon={Activity} iconColor="text-info" iconBg="bg-info/10" />
            <StatCard label={t('stats.errors5xx')} value={err5xx.toLocaleString()} icon={Gauge} iconColor={err5xx > 0 ? 'text-destructive' : 'text-muted-foreground'} iconBg={err5xx > 0 ? 'bg-destructive/10' : 'bg-muted'} />
            <StatCard label={t('stats.dbSize')} value={fmtBytes(data.db.sizeBytes)} icon={Database} iconColor="text-primary" iconBg="bg-primary/10" />
            <StatCard label={t('stats.goroutines')} value={data.runtime.goroutines} icon={Gauge} iconColor="text-warning" iconBg="bg-warning/10" />
          </div>

          <div className="grid gap-4 lg:grid-cols-3">
            <Card className="lg:col-span-2">
              <CardHeader className="pb-3">
                <CardTitle className="text-base">{t('topPaths.title')}</CardTitle>
                <p className="text-xs text-muted-foreground">{t('topPaths.subtitle')}</p>
              </CardHeader>
              <CardContent className="pt-0">
                {data.http.topPaths.length === 0 ? (
                  <p className="py-8 text-center text-sm text-muted-foreground">{t('empty')}</p>
                ) : (
                  <table className="w-full text-left text-xs">
                    <thead className="text-muted-foreground">
                      <tr><th className="border-b px-3 py-2 font-medium">{t('topPaths.path')}</th><th className="border-b px-3 py-2 font-medium text-right">{t('topPaths.count')}</th></tr>
                    </thead>
                    <tbody className="divide-y">
                      {data.http.topPaths.map(item => (
                        <tr key={item.path} className="hover:bg-muted/40">
                          <td className="px-3 py-2 font-mono">{item.path}</td>
                          <td className="px-3 py-2 text-right tabular-nums">{item.count.toLocaleString()}</td>
                        </tr>
                      ))}
                    </tbody>
                  </table>
                )}
              </CardContent>
            </Card>

            <Card>
              <CardHeader className="pb-3">
                <CardTitle className="text-base">{t('breakdown.title')}</CardTitle>
                <p className="text-xs text-muted-foreground">{t('breakdown.subtitle')}</p>
              </CardHeader>
              <CardContent className="space-y-4 pt-0 text-xs">
                <div>
                  <p className="mb-1 font-medium">{t('breakdown.byStatus')}</p>
                  {statusEntries.length === 0 ? <p className="text-muted-foreground">{t('empty')}</p> : statusEntries.map(([code, count]) => (
                    <div key={code} className="flex items-center justify-between py-0.5">
                      <span className={`font-mono ${code.startsWith('5') ? 'text-destructive' : code.startsWith('4') ? 'text-warning' : 'text-success'}`}>{code}</span>
                      <span className="tabular-nums text-muted-foreground">{count.toLocaleString()}</span>
                    </div>
                  ))}
                </div>
                <div>
                  <p className="mb-1 font-medium">{t('breakdown.alerts')}</p>
                  {Object.entries(data.alerts.evaluations).map(([result, count]) => (
                    <div key={result} className="flex items-center justify-between py-0.5">
                      <span className="text-muted-foreground">{t(`result.${result}`, result)}</span>
                      <span className="tabular-nums">{count.toLocaleString()}</span>
                    </div>
                  ))}
                </div>
                <div>
                  <p className="mb-1 font-medium">{t('breakdown.loki')}</p>
                  {Object.entries(data.loki.queries).map(([result, count]) => (
                    <div key={result} className="flex items-center justify-between py-0.5">
                      <span className="text-muted-foreground">{t(`result.${result}`, result)}</span>
                      <span className="tabular-nums">{count.toLocaleString()}</span>
                    </div>
                  ))}
                </div>
                <div>
                  <p className="mb-1 font-medium">{t('breakdown.db')}</p>
                  <div className="flex items-center justify-between py-0.5"><span className="text-muted-foreground">{t('breakdown.dbSaves')}</span><span className="tabular-nums">{data.db.saves.toLocaleString()}</span></div>
                  <div className="flex items-center justify-between py-0.5"><span className={data.db.saveFailures > 0 ? 'text-destructive' : 'text-muted-foreground'}>{t('breakdown.dbFailures')}</span><span className="tabular-nums">{data.db.saveFailures.toLocaleString()}</span></div>
                </div>
                <p className="border-t pt-3 text-muted-foreground">{t('buildInfo', { version: data.runtime.version || '-', go: data.runtime.goVersion || '-' })}</p>
              </CardContent>
            </Card>
          </div>
        </>
      )}
    </PageContainer>
  )
})

export default MonitorPage