import React, { useEffect, useRef, useState } from 'react'
import { useLocation, useNavigate } from 'react-router-dom'
import axios from 'axios'
import { BotIcon, CloudDbIcon, PlusCircleIcon, SearchIcon, TrashIcon } from './Icons'
import { useAuth, roleLabel } from '../auth'
import { useBranding } from '../branding'
import TimeZoneClock from './TimeZoneClock'
import FxCalculator from './FxCalculator'
import { HOME_PATH, PAGE_LABELS } from '../navigation'

const TABS_STORAGE_KEY = 'happy.openTabs'
/* 工作台恒定占第一位，后面最多再挂 4 个页面 */
const MAX_TAB_PAGES = 4
const MAX_TABS = MAX_TAB_PAGES + 1

/* 从本地缓存读取上次打开的页面（只保留仍然存在的路由，工作台恒定在首位） */
function readStoredTabs() {
  try {
    const raw = JSON.parse(localStorage.getItem(TABS_STORAGE_KEY) || '[]')
    const list = Array.isArray(raw) ? raw.filter(path => PAGE_LABELS[path] && path !== HOME_PATH) : []
    return [HOME_PATH, ...list.slice(0, MAX_TAB_PAGES)]
  } catch { return [HOME_PATH] }
}

function GlobalHeader({ onOpenAssistant, onNavigate }) {
  const { user } = useAuth()
  const [now, setNow] = useState(new Date())
  const [searchOpen, setSearchOpen] = useState(false)
  const [query, setQuery] = useState('')
  const [results, setResults] = useState([])
  const [searching, setSearching] = useState(false)
  const [openTabs, setOpenTabs] = useState(readStoredTabs)
  const searchRef = useRef(null)
  const tabsRef = useRef(null)
  const navigate = useNavigate()
  const location = useLocation()

  useEffect(() => {
    const timer = window.setInterval(() => setNow(new Date()), 1000)
    return () => window.clearInterval(timer)
  }, [])

  /* 访问过的页面自动登记成标签：工作台恒在首位，其余按最近使用排序，新页插在第二位 */
  useEffect(() => {
    const path = location.pathname
    if (!PAGE_LABELS[path]) return
    setOpenTabs(current => {
      if (current[0] === path) return current
      if (current[1] === path) return current
      const rest = current.filter(item => item !== path && item !== HOME_PATH)
      return [HOME_PATH, path, ...rest].slice(0, MAX_TABS)
    })
  }, [location.pathname])

  useEffect(() => {
    try { localStorage.setItem(TABS_STORAGE_KEY, JSON.stringify(openTabs)) } catch { /* 存储不可用时仅本次会话有效 */ }
    const active = tabsRef.current?.querySelector('.page-tab.active')
    active?.scrollIntoView({ block: 'nearest', inline: 'nearest' })
  }, [openTabs, location.pathname])

  /* 关闭标签：关掉的若是当前页，就退到剩下的最近一个，没有则回工作台 */
  const closeTab = (event, path) => {
    event.stopPropagation()
    const next = openTabs.filter(item => item !== path)
    const result = next.length ? next : [HOME_PATH]
    setOpenTabs(result)
    if (path === location.pathname) {
      /* 退到「最近使用过的另一个页面」，全关光了才回工作台 */
      navigate(result.find(item => item !== HOME_PATH) || HOME_PATH)
    }
  }

  /* 清空快捷标签：工作台常驻不动，其余一次性摘掉；当前页若被清掉就回工作台 */
  const clearTabs = () => {
    setOpenTabs([HOME_PATH])
    if (location.pathname !== HOME_PATH && PAGE_LABELS[location.pathname]) navigate(HOME_PATH)
  }

  useEffect(() => {
    const keyword = query.trim()
    if (!keyword) { setResults([]); setSearching(false); return }
    const timer = window.setTimeout(async () => {
      setSearching(true)
      try {
        const response = await axios.get('/api/search', { params: { q: keyword } })
        setResults(response.data.results || [])
      } catch { setResults([]) } finally { setSearching(false) }
    }, 180)
    return () => window.clearTimeout(timer)
  }, [query])

  useEffect(() => {
    const onKeyDown = event => {
      if ((event.ctrlKey || event.metaKey) && event.key.toLowerCase() === 'k') {
        event.preventDefault()
        setSearchOpen(true)
        window.setTimeout(() => searchRef.current?.focus(), 0)
      }
      if (event.key === 'Escape') { setSearchOpen(false); searchRef.current?.blur() }
    }
    window.addEventListener('keydown', onKeyDown)
    return () => window.removeEventListener('keydown', onKeyDown)
  }, [])

  /* 页内所有跳转都走外壳的 guardedNavigate：个人资料有未保存改动时会先弹确认 */
  const go = React.useCallback(path => {
    if (onNavigate) onNavigate(path)
    else navigate(path)
  }, [onNavigate, navigate])

  const selectResult = result => { go(result.path); setQuery(''); setSearchOpen(false) }

  const displayName = user?.display_name || user?.username || '未登录'
  const brand = useBranding()
  const positionText = user?.position || roleLabel(user?.role)
  const avatarText = (displayName || '?').slice(0, 1).toUpperCase()

  return (
    <header className="global-header">
      <div className="global-header-brand"><span className="brand-mark" title={brand.name}><CloudDbIcon size={36} /><span className="header-status-dot" /></span><div><strong>{brand.name}</strong><span>{brand.subtitle}</span></div></div>
      <div className={`global-search ${searchOpen ? 'is-open' : ''}`}>
        <SearchIcon size={17} />
        <input type="text" ref={searchRef} aria-label="搜索 everything" value={query} onFocus={() => setSearchOpen(true)} onChange={event => setQuery(event.target.value)} placeholder="搜索 everything" autoComplete="off" />
        <kbd>⌘ K</kbd>
        {searchOpen && query.trim() && <div className="global-search-results" role="listbox" aria-label="全局搜索结果">
          {searching ? <div className="global-search-status">正在检索系统业务数据…</div> : results.length ? results.map(result => <button key={`${result.type}-${result.id}`} role="option" onMouseDown={event => event.preventDefault()} onClick={() => selectResult(result)}><span className={`search-result-mark ${result.type}`}>{result.typeLabel}</span><span><strong>{result.title}</strong><small>{result.detail}</small></span></button>) : <div className="global-search-status">未找到匹配的数据</div>}
          <div className="global-search-footnote">已检索客户、供应商、产品、订单、商机、待办和活动记录</div>
        </div>}
      </div>
      {/* 已打开页面：搜索框后的快速跳转标签，工作台常驻且不可关闭 */}
      <nav className="page-tabs" ref={tabsRef} aria-label="已打开页面">
        {openTabs.map(path => {
          const label = PAGE_LABELS[path] || path
          const isHome = path === HOME_PATH
          const active = location.pathname === path
          return (
            <div key={path} className={`page-tab${active ? ' active' : ''}`}>
              <button type="button" className="page-tab-label" title={label} aria-current={active ? 'page' : undefined} onClick={() => go(path)}>{label}</button>
              {!isHome && <button type="button" className="page-tab-close" aria-label={`关闭${label}`} title={`关闭${label}`} onClick={event => closeTab(event, path)}>×</button>}
            </div>
          )
        })}
      </nav>
      {openTabs.length > 1 && (
        <button
          type="button"
          className="page-tabs-clear"
          onClick={clearTabs}
          aria-label="清空快捷标签"
          title="清空快捷标签（工作台保留）"
        >
          <TrashIcon size={14} />
        </button>
      )}
      <div className="global-header-actions"><TimeZoneClock now={now} /><FxCalculator /><button className="quick-create-btn" title="快速新建"><PlusCircleIcon size={19} /><span>快速新建</span></button><button className="ai-entry-btn" onClick={onOpenAssistant} title="打开小皮"><BotIcon size={19} /><span>小皮</span><i>β</i></button><button type="button" className="header-user" onClick={() => go('/profile')} title={`${displayName} · ${positionText} · 个人资料`} aria-label="个人资料"><span className="header-avatar">{user?.avatar ? <img src={user.avatar} alt="" /> : avatarText}</span><span className="header-user-text"><b>{displayName}</b><small>{positionText}</small></span></button><button className="mobile-search-btn" onClick={() => { setSearchOpen(v => !v); window.setTimeout(() => searchRef.current?.focus(), 0) }} title="搜索"><SearchIcon size={18} /></button></div>
    </header>
  )
}

export default GlobalHeader