"use client"

import { Search } from "lucide-react"
import {
  useEffect,
  useId,
  useMemo,
  useRef,
  useState,
  useSyncExternalStore,
  type FormEvent,
  type KeyboardEvent,
} from "react"

import { LocalSearchResults } from "@/features/home/components/local-search-results"
import { SearchProviderMenu } from "@/features/home/components/search-provider-menu"
import { searchLocalLinks } from "@/features/home/lib/local-search"
import {
  parseStoredProvider,
  SEARCH_PROVIDER_STORAGE_KEY,
} from "@/features/home/lib/provider-preference"
import { buildSearchUrl } from "@/features/home/lib/search-providers"
import type { Category, NavLink } from "@/types/navigation"
import type { SearchProvider } from "@/types/search"

type SearchBoxProps = {
  links: NavLink[]
  categories: Category[]
  defaultProvider: SearchProvider
  enabledProviders: SearchProvider[]
  onExternalNavigate?: (url: string) => void
}

function subscribeHydration() {
  return () => undefined
}

function getClientHydrationSnapshot() {
  return true
}

function getServerHydrationSnapshot() {
  return false
}

function readStoredProvider(
  defaultProvider: SearchProvider,
  enabledProviders: SearchProvider[],
): SearchProvider {
  try {
    const storedProvider = parseStoredProvider(
      window.localStorage.getItem(SEARCH_PROVIDER_STORAGE_KEY),
      defaultProvider,
    )
    return enabledProviders.includes(storedProvider)
      ? storedProvider
      : defaultProvider
  } catch {
    return defaultProvider
  }
}

export function SearchBox({
  links,
  categories,
  defaultProvider,
  enabledProviders,
  onExternalNavigate,
}: SearchBoxProps) {
  const inputRef = useRef<HTMLInputElement>(null)
  const optionRefs = useRef<Array<HTMLAnchorElement | null>>([])
  const listboxId = useId()
  const [query, setQuery] = useState("")
  const [selectedProvider, setSelectedProvider] =
    useState<SearchProvider | null>(null)
  const [activeIndex, setActiveIndex] = useState(0)
  const hydrated = useSyncExternalStore(
    subscribeHydration,
    getClientHydrationSnapshot,
    getServerHydrationSnapshot,
  )

  // Server 与 hydration 首帧保持默认 Provider；hydration 后再容错读取浏览器偏好。
  const restoredProvider = hydrated
    ? readStoredProvider(defaultProvider, enabledProviders)
    : defaultProvider
  const provider = selectedProvider ?? restoredProvider

  const results = useMemo(
    () =>
      provider === "local" ? searchLocalLinks(query, links, categories, 8) : [],
    [categories, links, provider, query],
  )
  const panelOpen = provider === "local" && query.trim().length > 0
  const resolvedActiveIndex =
    results.length > 0 ? Math.min(activeIndex, results.length - 1) : 0
  const activeOptionId =
    panelOpen && results.length > 0
      ? `${listboxId}-option-${resolvedActiveIndex}`
      : undefined
  const shortcutHint =
    hydrated && navigator.userAgent.includes("Mac") ? "⌘K" : "Ctrl K"

  useEffect(() => {
    inputRef.current?.focus()

    const focusSearch = (event: globalThis.KeyboardEvent) => {
      if ((event.ctrlKey || event.metaKey) && event.key.toLowerCase() === "k") {
        event.preventDefault()
        inputRef.current?.focus()
      }
    }

    window.addEventListener("keydown", focusSearch)
    return () => window.removeEventListener("keydown", focusSearch)
  }, [])

  const changeProvider = (nextProvider: SearchProvider) => {
    setSelectedProvider(nextProvider)
    setActiveIndex(0)
    try {
      window.localStorage.setItem(SEARCH_PROVIDER_STORAGE_KEY, nextProvider)
    } catch {
      // Provider 已保留在当前组件状态，存储受限时不影响本次交互。
    }
  }

  const openActiveLocalResult = () => {
    if (results.length === 0) return
    // 复用真实 anchor 的导航语义，键盘 Enter 不另造 click-only 跳转路径。
    optionRefs.current[resolvedActiveIndex]?.click()
  }

  const submitSearch = (event: FormEvent<HTMLFormElement>) => {
    event.preventDefault()

    // Local 只打开站内结果；外部 Provider 只构建搜索 URL，两条路径严格分离。
    if (provider === "local") {
      openActiveLocalResult()
      return
    }

    const url = buildSearchUrl(provider, query)
    if (!url) return
    if (onExternalNavigate) onExternalNavigate(url)
    else window.location.assign(url)
  }

  const handleInputKeyDown = (event: KeyboardEvent<HTMLInputElement>) => {
    if (event.key === "Escape") {
      event.preventDefault()
      setQuery("")
      setActiveIndex(0)
      return
    }

    if (provider !== "local") return

    if (event.key === "Enter") {
      event.preventDefault()
      openActiveLocalResult()
      return
    }

    if (results.length === 0) return
    if (event.key === "ArrowDown") {
      event.preventDefault()
      setActiveIndex((index) => (index + 1) % results.length)
    } else if (event.key === "ArrowUp") {
      event.preventDefault()
      setActiveIndex((index) => (index - 1 + results.length) % results.length)
    }
  }

  return (
    <div className="search-box">
      <form className="search-box__form" role="search" onSubmit={submitSearch}>
        <SearchProviderMenu
          provider={provider}
          enabledProviders={enabledProviders}
          onProviderChange={changeProvider}
        />
        <Search className="search-box__icon" aria-hidden="true" />
        <input
          ref={inputRef}
          className="search-box__input"
          role="combobox"
          aria-label="搜索网站、书签或关键词"
          aria-autocomplete="list"
          aria-expanded={panelOpen}
          aria-controls={panelOpen ? listboxId : undefined}
          aria-activedescendant={activeOptionId}
          placeholder="搜索网站、书签或关键词..."
          value={query}
          onChange={(event) => {
            setQuery(event.target.value)
            setActiveIndex(0)
          }}
          onKeyDown={handleInputKeyDown}
        />
        <kbd className="search-box__shortcut" aria-hidden="true">
          {shortcutHint}
        </kbd>
      </form>

      {panelOpen ? (
        <LocalSearchResults
          listboxId={listboxId}
          results={results}
          activeIndex={resolvedActiveIndex}
          optionRefs={optionRefs}
          onActiveIndexChange={setActiveIndex}
        />
      ) : null}
    </div>
  )
}