/**
 * Admin 后台 - 系统日志页面(报刊风)
 *
 * 查看应用运行日志(内存缓冲,最新在前):
 * - 级别筛选 + 关键字搜索
 * - 自动刷新(10s)可开关
 * - 缓冲上限 2000 条,进程重启后清零
 */

import { useEffect, useState, useCallback, useRef } from 'react'
import { fetchLogs } from '../dal'
import type { LogEntry } from '../types'
import { Card, CardBody, CardHeader, Badge, SectionHeader, Alert, Spinner, SkeletonBlock } from '../components'

const LEVELS = ['', 'INFO', 'WARNING', 'ERROR'] as const

const LEVEL_BADGE: Record<string, { status: 'success' | 'info' | 'warning' | 'error'; text: string }> = {
  DEBUG: { status: 'info', text: 'DEBUG' },
  INFO: { status: 'info', text: 'INFO' },
  WARNING: { status: 'warning', text: 'WARN' },
  ERROR: { status: 'error', text: 'ERROR' },
  CRITICAL: { status: 'error', text: 'FATAL' },
}

function fmtTs(ts: number): string {
  return new Date(ts * 1000).toLocaleString('zh-CN', { hour12: false })
}

export default function LogsPage() {
  const [entries, setEntries] = useState<LogEntry[]>([])
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState('')
  const [level, setLevel] = useState<string>('')
  const [keyword, setKeyword] = useState('')
  const [autoRefresh, setAutoRefresh] = useState(true)
  const timerRef = useRef<ReturnType<typeof setInterval> | null>(null)

  const load = useCallback(async () => {
    try {
      const d = await fetchLogs({ level: level || undefined, keyword: keyword || undefined, limit: 300 })
      setEntries(d.entries)
      setError('')
    } catch (err) {
      setError(err instanceof Error ? err.message.split('\n')[0] : '加载失败')
    } finally {
      setLoading(false)
    }
  }, [level, keyword])

  // 筛选条件变化 → 立即拉取
  useEffect(() => {
    load()
  }, [load])

  const scrollRef = useRef<HTMLDivElement>(null)
  const userScrolledUp = useRef(false)

  // 检测用户是否向上滚动过
  const handleScroll = () => {
    const el = scrollRef.current
    if (!el) return
    const atBottom = el.scrollHeight - el.scrollTop - el.clientHeight < 50
    userScrolledUp.current = !atBottom
  }

  // 加载后自动滚动到底部(仅当用户未向上滚动时)
  useEffect(() => {
    if (autoRefresh && !userScrolledUp.current && scrollRef.current) {
      scrollRef.current.scrollTop = scrollRef.current.scrollHeight
    }
  }, [entries, autoRefresh])

  // 自动刷新
  useEffect(() => {
    if (timerRef.current) clearInterval(timerRef.current)
    if (autoRefresh) {
      timerRef.current = setInterval(load, 10_000)
    }
    return () => {
      if (timerRef.current) clearInterval(timerRef.current)
    }
  }, [autoRefresh, load])

  return (
    <div className="space-y-6">
      <SectionHeader
        title="系统日志"
        description="应用运行日志(登录、配置变更、采集、预测、异常等)。内存缓冲最近 2000 条,重启后清零。"
      />

      {error && <Alert kind="error" title="无法加载日志" message={error} />}

      <Card>
        <CardHeader
          title="日志查看"
          description={entries.length > 0 ? `显示最新 ${entries.length} 条` : undefined}
          action={
            <div className="flex items-center gap-2">
              <label className="flex cursor-pointer items-center gap-1.5 text-2xs text-ink-500">
                <input
                  type="checkbox"
                  checked={autoRefresh}
                  onChange={e => setAutoRefresh(e.target.checked)}
                  className="accent-current"
                />
                10s 自动刷新
              </label>
              <button onClick={load} disabled={loading} className="btn btn-sm">
                {loading ? (<><Spinner /> 加载中</>) : '刷新'}
              </button>
            </div>
          }
        />
        <CardBody className="px-0 sm:px-0">
          {/* 筛选栏 */}
          <div className="flex flex-col gap-2 border-b border-ink-200 px-4 py-3 sm:flex-row sm:items-center sm:justify-between sm:px-5">
            <div className="flex flex-wrap gap-1.5">
              {LEVELS.map(lv => (
                <button
                  key={lv || 'all'}
                  onClick={() => setLevel(lv)}
                  className={`btn btn-sm ${level === lv ? 'btn-solid' : ''}`}
                >
                  {lv || '全部'}
                </button>
              ))}
            </div>
            <input
              value={keyword}
              onChange={e => setKeyword(e.target.value)}
              placeholder="搜索关键字(消息 / logger)…"
              className="field w-full sm:w-64"
            />
          </div>

          {/* 日志列表 */}
          {loading && entries.length === 0 ? (
            <div className="space-y-2 px-4 py-3 sm:px-5">
              {[1, 2, 3, 4, 5].map(i => <SkeletonBlock key={i} className="h-8 w-full" />)}
            </div>
          ) : entries.length === 0 ? (
            <p className="py-10 text-center text-xs text-ink-400">暂无匹配的日志</p>
          ) : (
            <div ref={scrollRef} onScroll={handleScroll} className="max-h-[60vh] overflow-y-auto">
              {entries.map((e, i) => {
                const badge = LEVEL_BADGE[e.level] ?? { status: 'info' as const, text: e.level }
                return (
                  <div
                    key={`${e.ts}-${i}`}
                    className="flex flex-col gap-0.5 border-b border-ink-200 px-4 py-2 last:border-b-0 sm:flex-row sm:items-baseline sm:gap-3 sm:px-5"
                  >
                    <span className="w-40 flex-shrink-0 text-2xs tabular-nums text-ink-400">{fmtTs(e.ts)}</span>
                    <span className="w-14 flex-shrink-0">
                      <Badge status={badge.status}>{badge.text}</Badge>
                    </span>
                    <span className="w-40 flex-shrink-0 truncate font-mono text-2xs text-ink-400" title={e.logger}>
                      {e.logger}
                    </span>
                    <span className="min-w-0 flex-1 break-all font-mono text-2xs leading-relaxed text-ink-800">
                      {e.message}
                    </span>
                  </div>
                )
              })}
            </div>
          )}
        </CardBody>
      </Card>
    </div>
  )
}