"use client";

import { useEffect, useMemo, useRef, useState } from "react";
import { useRouter } from "next/navigation";
import { ChevronRight, Search, X } from "lucide-react";
import Modal from "@/components/Modal";
import { libraryDocReadPath, type UrlStyle } from "@/lib/urlStyle";
import { searchBook, type BookChapterIndex, type BookSnippet } from "@/lib/bookSearch";

/** 阅读页正文章节容器 id（read/page.tsx 的 <article>），高亮作用域 */
const ARTICLE_ID = "j13-book-article";
/** 关键词长度上限（避免超长输入卡顿） */
const MAX_QUERY = 64;
/** CSS Custom Highlight 注册名（对应 globals.css 的 ::highlight(...)） */
const HL_ALL = "j13-find";
const HL_CURRENT = "j13-find-current";

/** 特性检测：CSS Custom Highlight API（Chrome105+/Safari17.2+/FF140+），不支持时只跳转不高亮 */
function highlightsSupported(): boolean {
  return (
    typeof window !== "undefined" &&
    typeof window.Highlight !== "undefined" &&
    typeof CSS !== "undefined" &&
    !!CSS.highlights
  );
}

function clearHighlights(): void {
  if (!highlightsSupported()) return;
  CSS.highlights!.delete(HL_ALL);
  CSS.highlights!.delete(HL_CURRENT);
}

/**
 * 运行时注入高亮样式：构建器的 CSS 压缩器不识别 ::highlight() 会丢规则，
 * 且 highlight 伪元素不继承自定义属性，这里从 :root 读出 --accent/--accent-on
 * 的实际色值拼规则。hex 转带透明度的 rgba；非 hex 值原样使用。
 */
let highlightStyleInjected = false;
function ensureHighlightStyle(): void {
  if (highlightStyleInjected || !highlightsSupported()) return;
  const css = getComputedStyle(document.documentElement);
  const accent = (css.getPropertyValue("--accent") || "").trim();
  const accentOn = (css.getPropertyValue("--accent-on") || "").trim() || "#fff";
  let h = accent;
  if (h.length === 4) h = "#" + h.slice(1).split("").map((c) => c + c).join("");
  const soft =
    /^#[0-9a-f]{6}$/i.test(h)
      ? `rgba(${parseInt(h.slice(1, 3), 16)},${parseInt(h.slice(3, 5), 16)},${parseInt(h.slice(5, 7), 16)},0.24)`
      : accent;
  const style = document.createElement("style");
  style.dataset.j13 = "find-highlight";
  style.textContent =
    `::highlight(${HL_ALL}){background-color:${soft}}` +
    `::highlight(${HL_CURRENT}){background-color:${accent};color:${accentOn}}`;
  document.head.appendChild(style);
  highlightStyleInjected = true;
}

/**
 * 收集正文内命中 Range：按文本节点逐个匹配（大小写不敏感子串），不改 DOM。
 * 用 Range 而非包 <mark>：正文是 server 组件渲染的，直接替换文本节点会让
 * React 在章节切换后的原地复用错位；Range 随章节重建自然失效，无副作用。
 * 跨标签边界的词匹配不到——可接受，绝大多数中文命中落在同一文本节点。
 */
function collectRanges(root: HTMLElement, query: string): Range[] {
  const q = query.trim().toLowerCase();
  if (!q) return [];
  const targets: Text[] = [];
  const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT, {
    acceptNode(node) {
      const el = node.parentElement;
      if (!el || !node.nodeValue) return NodeFilter.FILTER_REJECT;
      const tag = el.tagName;
      if (tag === "SCRIPT" || tag === "STYLE" || tag === "NOSCRIPT") {
        return NodeFilter.FILTER_REJECT;
      }
      return node.nodeValue.toLowerCase().includes(q)
        ? NodeFilter.FILTER_ACCEPT
        : NodeFilter.FILTER_REJECT;
    },
  });
  let n: Node | null;
  while ((n = walker.nextNode())) targets.push(n as Text);

  const ranges: Range[] = [];
  for (const textNode of targets) {
    const tv = textNode.nodeValue ?? "";
    const low = tv.toLowerCase();
    let from = 0;
    for (;;) {
      const idx = low.indexOf(q, from);
      if (idx < 0) break;
      const range = document.createRange();
      range.setStart(textNode, idx);
      range.setEnd(textNode, idx + q.length);
      ranges.push(range);
      from = idx + q.length;
    }
  }
  return ranges;
}

/** 注册高亮（全部命中 + 当前命中两组）；返回文档序命中 Range 列表 */
function paintRanges(query: string, currentOrdinal: number): Range[] {
  const root = document.getElementById(ARTICLE_ID);
  if (!root) return [];
  const ranges = collectRanges(root, query);
  if (!highlightsSupported()) return ranges;
  ensureHighlightStyle();
  clearHighlights();
  if (ranges.length > 0) {
    const all = new Highlight(...ranges);
    const cur = new Highlight();
    const curRange = ranges[Math.min(Math.max(currentOrdinal, 0), ranges.length - 1)];
    if (curRange) cur.add(curRange);
    CSS.highlights!.set(HL_ALL, all);
    CSS.highlights!.set(HL_CURRENT, cur);
  }
  return ranges;
}

/** 滚动到命中 Range（视口垂直居中，留出吸顶头空间） */
function scrollToRange(range: Range, smooth: boolean): void {
  const rect = range.getBoundingClientRect();
  if (rect.width === 0 && rect.height === 0) return;
  const top =
    window.scrollY + rect.top - window.innerHeight / 2 + (rect.height || 16) / 2;
  window.scrollTo({ top: Math.max(0, top), behavior: smooth ? "smooth" : "auto" });
}

/** 重新高亮当前章并定位到指定命中（ordinal 为章内 0 基命中序号） */
function highlightAndScroll(query: string, ordinal: number, smooth: boolean): void {
  const ranges = paintRanges(query, ordinal);
  const target = ranges[Math.min(Math.max(ordinal, 0), ranges.length - 1)];
  if (!target) return;
  // 双层 rAF：等章节切换后的布局与图片占位稳定再定位
  requestAnimationFrame(() =>
    requestAnimationFrame(() => scrollToRange(target, smooth))
  );
}

function SnippetText({ snip }: { snip: BookSnippet }) {
  return (
    <span className="leading-relaxed">
      {snip.before ? <span className="meta">…{snip.before}</span> : null}
      <mark className="j13-find-mark">{snip.match}</mark>
      {snip.after ? <span className="meta">{snip.after}…</span> : null}
    </span>
  );
}

export interface BookSearchProps {
  slug: string;
  urlStyle: UrlStyle;
  /** 当前章序号（1 基） */
  currentNo: number;
  chapters: BookChapterIndex[];
}

export default function BookSearch({ slug, urlStyle, currentNo, chapters }: BookSearchProps) {
  const router = useRouter();
  const [open, setOpen] = useState(false);
  const [query, setQuery] = useState("");
  const inputRef = useRef<HTMLInputElement>(null);
  /**
   * 跨章跳转待执行的高亮。组件跨章导航不重挂载（位置稳定），query 状态保留，
   * 仅在 currentNo 变化、新章 DOM 提交后执行一次，因此无需把关键词写进 URL。
   */
  const pendingRef = useRef<{ q: string; ordinal: number } | null>(null);

  const trimmed = query.trim();
  const results = useMemo(() => searchBook(chapters, trimmed), [chapters, trimmed]);
  const totalHits = useMemo(() => results.reduce((acc, h) => acc + h.count, 0), [results]);

  useEffect(() => {
    const pending = pendingRef.current;
    if (!pending) return;
    pendingRef.current = null;
    highlightAndScroll(pending.q, pending.ordinal, false);
  }, [currentNo]);

  // 关键词清空或离开读页时撤掉正文高亮
  useEffect(() => {
    if (!trimmed) clearHighlights();
  }, [trimmed]);
  useEffect(() => () => clearHighlights(), []);

  const focusHit = (no: number, ordinal: number) => {
    if (no === currentNo) {
      highlightAndScroll(trimmed, ordinal, true);
      setOpen(false);
      return;
    }
    pendingRef.current = { q: trimmed, ordinal };
    setOpen(false);
    router.push(libraryDocReadPath(urlStyle, slug, no));
  };

  const onKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    if (e.key === "Enter" && results[0]) {
      const first = results[0];
      focusHit(first.no, first.snippets[0]?.ordinal ?? 0);
    }
  };

  return (
    <>
      <button
        type="button"
        onClick={() => {
          setOpen(true);
          requestAnimationFrame(() => inputRef.current?.focus());
        }}
        className="inline-flex items-center gap-2 rounded-full pl-3.5 pr-4 py-2 text-[13px] transition-colors hover:bg-[var(--panel-2)] hover:border-[color-mix(in_srgb,var(--accent)_40%,var(--line))] shrink-0 w-36 sm:w-52"
        style={{ color: "var(--ink-3)", border: "1px solid var(--line)", background: "var(--panel)" }}
        aria-label="搜索本书"
      >
        <Search size={14} className="shrink-0" aria-hidden />
        <span className="truncate text-left">搜索本书</span>
      </button>

      <Modal
        open={open}
        onClose={() => setOpen(false)}
        title="搜索本书"
        description={`共 ${chapters.length} 章 · 命中后可直接跳到对应位置`}
        maxWidthClass="max-w-lg"
        panelClassName="p-5 sm:p-6"
      >
        <div className="relative">
          <Search
            size={15}
            className="absolute left-3.5 top-1/2 -translate-y-1/2 pointer-events-none"
            style={{ color: "var(--ink-3)" }}
            aria-hidden
          />
          <input
            ref={inputRef}
            type="text"
            value={query}
            maxLength={MAX_QUERY}
            onChange={(e) => setQuery(e.target.value)}
            onKeyDown={onKeyDown}
            placeholder="搜索章节标题与正文"
            aria-label="搜索章节标题与正文"
            className="j13-search-field w-full rounded-xl pl-10 pr-9 py-2.5 text-[13.5px]"
            style={{ background: "var(--panel)", border: "1px solid var(--line)" }}
          />
          {query ? (
            <button
              type="button"
              onClick={() => setQuery("")}
              aria-label="清除关键词"
              className="absolute right-3 top-1/2 -translate-y-1/2 w-6 h-6 flex items-center justify-center rounded-full hover:bg-[var(--panel-2)] transition-colors"
              style={{ color: "var(--ink-3)" }}
            >
              <X size={13} />
            </button>
          ) : null}
        </div>

        <div className="mt-3 max-h-[56vh] overflow-y-auto j13-rail-scroll -mx-1 px-1">
          {!trimmed ? (
            <p className="meta text-[12.5px] py-8 text-center">
              输入关键词，按章查看命中片段，点击即可跳转
            </p>
          ) : totalHits === 0 ? (
            <p className="meta text-[12.5px] py-8 text-center">全书没有找到「{trimmed}」</p>
          ) : (
            <div className="flex flex-col gap-2">
              <p className="meta text-[11.5px] px-1">
                {results.length} 章命中 · 共 {totalHits} 处
              </p>
              {results.map((hit) => {
                const isCurrent = hit.no === currentNo;
                return (
                  <section
                    key={hit.no}
                    className="rounded-xl overflow-hidden"
                    style={{ border: "1px solid var(--line)" }}
                  >
                    <button
                      type="button"
                      onClick={() => focusHit(hit.no, 0)}
                      className="w-full flex items-center gap-2 px-3 py-2 text-left hover:bg-[var(--panel-2)] transition-colors"
                    >
                      <span
                        className="text-[12.5px] font-bold truncate min-w-0"
                        style={{ color: "var(--ink)" }}
                      >
                        第 {hit.no} 章 · {hit.title}
                      </span>
                      {isCurrent ? (
                        <span
                          className="shrink-0 text-[10px] font-semibold px-1.5 py-0.5 rounded"
                          style={{ color: "var(--accent)", background: "var(--accent-soft)" }}
                        >
                          本章
                        </span>
                      ) : null}
                      <span className="meta text-[11px] ml-auto shrink-0 inline-flex items-center gap-0.5">
                        {hit.count} 处
                        <ChevronRight size={12} aria-hidden />
                      </span>
                    </button>
                    {hit.snippets.map((snip) => (
                      <button
                        key={snip.ordinal}
                        type="button"
                        onClick={() => focusHit(hit.no, snip.ordinal)}
                        className="block w-full text-left px-3 py-1.5 text-[12.5px] border-t border-[var(--line)] hover:bg-[var(--panel-2)] transition-colors"
                        style={{ color: "var(--ink-2)" }}
                      >
                        <SnippetText snip={snip} />
                      </button>
                    ))}
                  </section>
                );
              })}
            </div>
          )}
        </div>
      </Modal>
    </>
  );
}