"use client";

import Link from "next/link";
import { CSSProperties, useEffect, useMemo, useRef, useState } from "react";
import { getBookEntries } from "@/lib/book-helpers";
import { Book } from "@/types/book";

type ReaderViewProps = {
  book: Book;
  chapterIndex: number;
  initialThemeKey?: string;
  initialFontKey?: string;
  initialWidthKey?: string;
};

const themeOptions = [
  { key: "warm", label: "暖米", page: "#f7f0e4", stage: "#d8d0c4", text: "#2b241e", catalog: "#e6ddd0" },
  { key: "mist", label: "浅灰", page: "#efede7", stage: "#d6d4cf", text: "#2a2723", catalog: "#dfddd7" },
  { key: "sepia", label: "茶褐", page: "#eee0cf", stage: "#d4c3b1", text: "#35281f", catalog: "#dfcdbb" }
] as const;

const fontOptions = [
  { key: "sm", label: "小", size: "1.02rem", lineHeight: 2.05 },
  { key: "md", label: "中", size: "1.18rem", lineHeight: 2.28 },
  { key: "lg", label: "大", size: "1.34rem", lineHeight: 2.55 }
] as const;

const widthOptions = [
  { key: "narrow", label: "窄", width: 760 },
  { key: "medium", label: "中", width: 920 },
  { key: "wide", label: "宽", width: 1080 }
] as const;

export function ReaderView({
  book,
  chapterIndex,
  initialThemeKey,
  initialFontKey,
  initialWidthKey
}: ReaderViewProps) {
  const entries = useMemo(() => getBookEntries(book), [book]);
  const entry = entries[chapterIndex];
  const prevChapterIndex = chapterIndex > 0 ? chapterIndex - 1 : null;
  const nextChapterIndex = chapterIndex < entries.length - 1 ? chapterIndex + 1 : null;

  const initialThemeIndex = Math.max(0, themeOptions.findIndex((item) => item.key === initialThemeKey));
  const initialFontIndex = Math.max(0, fontOptions.findIndex((item) => item.key === initialFontKey));
  const initialWidthIndex = Math.max(0, widthOptions.findIndex((item) => item.key === initialWidthKey));

  const [themeIndex, setThemeIndex] = useState(initialThemeKey ? initialThemeIndex : 0);
  const [fontIndex, setFontIndex] = useState(initialFontKey ? initialFontIndex : 1);
  const [widthIndex, setWidthIndex] = useState(initialWidthKey ? initialWidthIndex : 1);
  const [catalogOpen, setCatalogOpen] = useState(false);
  const [progress, setProgress] = useState(0);
  const stageRef = useRef<HTMLElement | null>(null);

  useEffect(() => {
    const { page: pageColor } = themeOptions[themeIndex];
    document.body.classList.add("reader-body");
    const previousBodyBackground = document.body.style.background;
    const previousHtmlBackground = document.documentElement.style.background;

    document.body.style.background = pageColor;
    document.documentElement.style.background = pageColor;

    // Force iOS Safari to pick up theme-color by removing old tags and inserting a fresh one
    document.querySelectorAll('meta[name="theme-color"]').forEach((m) => m.remove());
    const metaTheme = document.createElement("meta");
    metaTheme.setAttribute("name", "theme-color");
    metaTheme.setAttribute("content", pageColor);
    document.head.appendChild(metaTheme);

    return () => {
      document.body.classList.remove("reader-body");
      document.body.style.background = previousBodyBackground;
      document.documentElement.style.background = previousHtmlBackground;
      metaTheme.setAttribute("content", "#f4efe7");
    };
  }, [themeIndex]);

  useEffect(() => {
    const stage = stageRef.current;
    if (!stage) return;

    stage.scrollTo({ top: 0, behavior: "auto" });
    setCatalogOpen(false);

    const updateProgress = () => {
      const maxScroll = stage.scrollHeight - stage.clientHeight;
      const nextProgress = maxScroll <= 0 ? 0 : (stage.scrollTop / maxScroll) * 100;
      setProgress(nextProgress);
    };

    updateProgress();
    stage.addEventListener("scroll", updateProgress);
    window.addEventListener("resize", updateProgress);

    return () => {
      stage.removeEventListener("scroll", updateProgress);
      window.removeEventListener("resize", updateProgress);
    };
  }, [chapterIndex]);

  useEffect(() => {
    const stage = stageRef.current;
    if (!stage) return;
    const maxScroll = stage.scrollHeight - stage.clientHeight;
    setProgress(maxScroll <= 0 ? 0 : (stage.scrollTop / maxScroll) * 100);
  }, [fontIndex, widthIndex, themeIndex]);

  const currentTheme = themeOptions[themeIndex];
  const currentFont = fontOptions[fontIndex];
  const currentWidth = widthOptions[widthIndex];
  const entryWords = entry.content.join("").length;
  const isLoreEntry = entry.kind === "lore";

  const shellWidthStyle = useMemo(
    () =>
      ({
        width: "var(--reader-shell-width)"
      }) as CSSProperties,
    []
  );

  const cycleFont = () => setFontIndex((value) => (value + 1) % fontOptions.length);
  const cycleTheme = () => setThemeIndex((value) => (value + 1) % themeOptions.length);
  const cycleWidth = () => setWidthIndex((value) => (value + 1) % widthOptions.length);

  const catalogContent = (
    <>
      <div className="reader-catalog__header">
        <h2>目录</h2>
        <button type="button" className="reader-catalog__close" onClick={() => setCatalogOpen(false)}>
          关闭
        </button>
      </div>

      <div className="reader-catalog-groups">
        {book.sections
          .slice()
          .sort((a, b) => a.order - b.order)
          .map((section) => {
            const sectionEntries = entries.filter((item) => item.sectionId === section.id);

            return (
              <section className="reader-catalog__section" key={section.id}>
                <div className="reader-catalog__section-title">
                  <span className={`reader-catalog__kind reader-catalog__kind--${section.kind}`}>
                    {section.kind === "lore" ? "资料" : "正文"}
                  </span>
                  <strong>{section.title}</strong>
                </div>
                <div className="reader-catalog__grid">
                  {sectionEntries.map((item, index) => (
                    <Link
                      key={item.id}
                      href={`/reader/${book.id}?entry=${item.flatIndex}`}
                      className={`reader-catalog__item${item.flatIndex === chapterIndex ? " reader-catalog__item--active" : ""}`}
                      onClick={() => setCatalogOpen(false)}
                    >
                      <span>
                        {section.kind === "lore" ? `资料 ${index + 1}` : `第 ${index + 1} 章`}
                      </span>
                      <strong>{item.title}</strong>
                    </Link>
                  ))}
                </div>
              </section>
            );
          })}
      </div>
    </>
  );

  return (
    <main
      className="reader-stage"
      style={
        {
          background: currentTheme.stage,
          "--reader-page": currentTheme.page,
          "--reader-stage-color": currentTheme.stage,
          "--reader-shell-width": `min(${currentWidth.width}px, calc(100vw - 280px))`
        } as CSSProperties
      }
      ref={stageRef}
    >
      <div className="reader-progress-rail" aria-hidden="true">
        <div className="reader-progress-rail__track">
          <div className="reader-progress-rail__fill" style={{ height: `${progress}%` }} />
        </div>
      </div>

      <div className="reader-mobile-bar reader-mobile-bar--top">
        <Link className="reader-mobile-bar__icon reader-mobile-bar__icon--back" href="/library" aria-label="返回书架">
          返回
        </Link>
        <button className="reader-mobile-bar__icon" type="button" onClick={cycleTheme} aria-label="切换主题">
          主题 {currentTheme.label}
        </button>
        <button className="reader-mobile-bar__icon" type="button" onClick={cycleFont} aria-label="切换字体">
          字体 {currentFont.label}
        </button>
      </div>

      <div className="reader-mobile-bar reader-mobile-bar--bottom">
        <button className="reader-mobile-bar__action" type="button" onClick={() => setCatalogOpen(true)}>
          目录
        </button>

        {prevChapterIndex !== null ? (
          <Link className="reader-mobile-bar__action" href={`/reader/${book.id}?entry=${prevChapterIndex}`}>
            上一章
          </Link>
        ) : (
          <span className="reader-mobile-bar__action reader-mobile-bar__action--disabled">上一章</span>
        )}

        {nextChapterIndex !== null ? (
          <Link className="reader-mobile-bar__action" href={`/reader/${book.id}?entry=${nextChapterIndex}`}>
            下一章
          </Link>
        ) : (
          <span className="reader-mobile-bar__action reader-mobile-bar__action--disabled">下一章</span>
        )}
      </div>

      <div className="reader-desktop-layout">
        <div className="reader-float reader-float--left" aria-label="阅读左侧工具">
          <Link className="reader-float__button" href="/library">
            <strong>返回</strong>
            <span>回到书架</span>
          </Link>
          <button className="reader-float__button" type="button" onClick={() => setCatalogOpen(true)}>
            <strong>目录</strong>
            <span>弹出目录</span>
          </button>
        </div>

        <section className="reader-qq-shell" style={shellWidthStyle}>
          <div className="reader-catalog-mobile-mask" hidden={!catalogOpen} onClick={() => setCatalogOpen(false)} />

          <div
            className={`reader-catalog-mobile-sheet${catalogOpen ? " is-open" : ""}`}
            style={{ background: currentTheme.catalog }}
            aria-hidden={!catalogOpen}
          >
            {catalogContent}
          </div>

          {catalogOpen ? (
            <div className="reader-catalog-inline" style={{ background: currentTheme.catalog }}>
              {catalogContent}
            </div>
          ) : null}

          <div
            className={`reader-qq-paper${catalogOpen ? " reader-qq-paper--desktop-hidden" : ""}`}
            style={{ background: currentTheme.page }}
          >
            <header className={`reader-qq-header${isLoreEntry ? " reader-qq-header--lore" : ""}`}>
              <div className="reader-entry-badges">
                <span className={`reader-entry-badge reader-entry-badge--${entry.kind}`}>
                  {isLoreEntry ? "资料" : "正文"}
                </span>
                <span className="reader-entry-badge reader-entry-badge--section">{entry.sectionTitle}</span>
              </div>
              <h1>{entry.title}</h1>
              <div className="reader-qq-meta">
                <span>书名：{book.title}</span>
                <span>作者：{book.author}</span>
                <span>当前：{entry.sectionTitle}</span>
                <span>本节字数：{entryWords} 字</span>
                <span>总字数：{book.wordCount}</span>
              </div>
            </header>

            <article
              className={`reader-qq-content${isLoreEntry ? " reader-qq-content--lore" : ""}`}
              style={{ color: currentTheme.text }}
            >
              {entry.content.map((paragraph) => (
                <p key={paragraph} style={{ fontSize: currentFont.size, lineHeight: currentFont.lineHeight }}>
                  {paragraph}
                </p>
              ))}
            </article>

            <footer className="reader-qq-footer">
              <button className="reader-qq-footer__ghost" type="button" onClick={() => setCatalogOpen(true)}>
                目录
              </button>

              {prevChapterIndex !== null ? (
                <Link className="reader-qq-footer__button" href={`/reader/${book.id}?entry=${prevChapterIndex}`}>
                  上一章
                </Link>
              ) : (
                <span className="reader-qq-footer__button reader-qq-footer__button--disabled">已是第一节</span>
              )}

              {nextChapterIndex !== null ? (
                <Link className="reader-qq-footer__button" href={`/reader/${book.id}?entry=${nextChapterIndex}`}>
                  下一章
                </Link>
              ) : (
                <span className="reader-qq-footer__button reader-qq-footer__button--disabled">已是最后一节</span>
              )}
            </footer>
          </div>
        </section>

        <div className="reader-float reader-float--right" aria-label="阅读右侧工具">
          <button className="reader-float__button" type="button" onClick={cycleFont}>
            <strong>字号</strong>
            <span>当前{currentFont.label}</span>
          </button>
          <button className="reader-float__button" type="button" onClick={cycleTheme}>
            <strong>主题</strong>
            <span>当前{currentTheme.label}</span>
          </button>
          <button className="reader-float__button" type="button" onClick={cycleWidth}>
            <strong>版心</strong>
            <span>当前{currentWidth.label}</span>
          </button>
        </div>
      </div>
    </main>
  );
}