import { ChevronLeft, ChevronRight, ChevronsLeft, ChevronsRight, PanelLeft } from "lucide-react";
import { useEffect, useRef, useState, type KeyboardEvent } from "react";
import * as pdfjs from "pdfjs-dist";
import { apiRaw } from "../api/client";
import { BookmarksTab } from "../components/Bookmarks";
import { ReaderNav } from "../components/reader-nav";
import { ReaderSettings } from "../components/reader-settings";
import { Button } from "@/components/ui/button";
import { useProgressSaver, type ReaderProps } from "../lib/useProgress";

// Vite 原生 worker 语法;pdfjs v5 要求 module worker
pdfjs.GlobalWorkerOptions.workerPort = new Worker(new URL("pdfjs-dist/build/pdf.worker.mjs", import.meta.url), {
  type: "module",
});

type RenderTask = { cancel(): void; promise: Promise<void> };

export default function PdfReader({ book, initialLocator, initialPercent }: ReaderProps) {
  const wrapRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);
  const docRef = useRef<pdfjs.PDFDocumentProxy | null>(null);
  const docTaskRef = useRef<{ destroy(): Promise<void> } | null>(null);
  const taskRef = useRef<RenderTask | null>(null);
  const restored = useRef(false);
  const saver = useProgressSaver(book.id, { locator: initialLocator, percent: initialPercent });
  const [nav, setNav] = useState(false);
  const [num, setNum] = useState(0);
  const [page, setPage] = useState(0); // 0 基
  const [err, setErr] = useState("");
  const [nonce, setNonce] = useState(0); // 仅加载重试
  const [redraw, setRedraw] = useState(0); // 仅 resize 重绘(不重新下载文档)
  // 重新加载(换书/重试)时先清错误:React 官方推荐的「渲染期按下发 key 重置本地 state」,
  // 替代原先 effect 内的同步 setState(级联渲染);首挂载 key 相等,重置为空操作,行为等价
  const loadKey = (book.file_url ?? "") + "#" + nonce;
  const [prevLoadKey, setPrevLoadKey] = useState(loadKey);
  if (prevLoadKey !== loadKey) {
    setPrevLoadKey(loadKey);
    setErr("");
  }

  useEffect(() => {
    let dead = false;
    (async () => {
      const buf = await apiRaw(book.file_url ?? "").then((r) => r.arrayBuffer());
      if (dead) return;
      const task = pdfjs.getDocument({ data: new Uint8Array(buf) });
      docTaskRef.current = task;
      const doc = await task.promise;
      if (dead) {
        await task.destroy();
        return;
      }
      docRef.current = doc;
      setNum(doc.numPages);
      if (!restored.current) {
        restored.current = true;
        const p = Number(initialLocator?.page);
        if (Number.isInteger(p) && p > 0 && p < doc.numPages) setPage(p);
      }
    })().catch((e) => !dead && setErr(e instanceof Error ? e.message : "PDF 加载失败"));
    return () => {
      dead = true;
      taskRef.current?.cancel();
      docTaskRef.current?.destroy();
      docTaskRef.current = null;
      docRef.current = null;
    };
  }, [book.file_url, nonce]); // initialLocator 是查询缓存值,加载一次即稳定

  // 渲染当前页
  useEffect(() => {
    const doc = docRef.current;
    const canvas = canvasRef.current;
    const wrap = wrapRef.current;
    if (!doc || !canvas || !wrap || num === 0) return;
    let cancelled = false;
    (async () => {
      const p = await doc.getPage(page + 1);
      if (cancelled) return;
      const cssW = wrap.clientWidth;
      const dpr = window.devicePixelRatio || 1;
      const base = p.getViewport({ scale: 1 });
      const vp = p.getViewport({ scale: (cssW * dpr) / base.width });
      canvas.width = Math.floor(vp.width);
      canvas.height = Math.floor(vp.height);
      canvas.style.width = "100%";
      const ctx = canvas.getContext("2d");
      if (!ctx) throw new Error("canvas 2d 上下文不可用");
      const t = p.render({ canvas, viewport: vp }) as RenderTask;
      taskRef.current = t;
      await t.promise;
    })().catch((e) => {
      if (!cancelled && (e as { name?: string }).name !== "AbortException")
        setErr(e instanceof Error ? e.message : "渲染失败");
    });
    saver.report({ page }, (page + 1) / num);
    return () => {
      cancelled = true;
      taskRef.current?.cancel();
    };
  }, [page, num, redraw, saver]);

  // 容器尺寸变化 → 重绘
  useEffect(() => {
    const wrap = wrapRef.current;
    if (!wrap) return;
    let t: ReturnType<typeof setTimeout>;
    const ro = new ResizeObserver(() => {
      clearTimeout(t);
      t = setTimeout(() => setRedraw((x) => x + 1), 200);
    });
    ro.observe(wrap);
    return () => {
      clearTimeout(t);
      ro.disconnect();
    };
  }, []);

  function onKey(e: KeyboardEvent) {
    if (e.key === "ArrowRight" || e.key === "PageDown") setPage((p) => Math.min(num - 1, p + 1));
    else if (e.key === "ArrowLeft" || e.key === "PageUp") setPage((p) => Math.max(0, p - 1));
    else return;
    e.preventDefault();
  }

  if (err)
    return (
      <div className="bg-muted grid h-full place-items-center p-8 text-center">
        <div>
          <p className="text-destructive mb-3">{err}</p>
          <Button variant="secondary" onClick={() => setNonce((x) => x + 1)}>
            重试
          </Button>
        </div>
      </div>
    );
  if (num === 0) return <div className="text-muted-foreground grid h-full place-items-center">PDF 加载中…</div>;

  return (
    <div
      tabIndex={0}
      onKeyDown={onKey}
      aria-label="PDF 阅读器,可用左右方向键翻页"
      className="relative grid h-full grid-rows-[1fr_auto] bg-background text-foreground focus:outline-none focus-visible:outline-hidden"
    >
      <div ref={wrapRef} className="bg-muted/50 flex min-h-0 items-start justify-center overflow-y-auto p-4">
        <canvas ref={canvasRef} className="ring-border max-w-3xl rounded-md shadow-2xl ring-1" />
      </div>
      <ReaderSettings
        left={
          <>
            <Button
              variant="ghost"
              size="sm"
              className="gap-0.5"
              disabled={page === 0}
              onClick={() => setPage(0)}
              aria-label="第一页"
            >
              <ChevronsLeft size={14} /> 首页
            </Button>
            <Button
              variant="ghost"
              size="sm"
              className="gap-0.5"
              disabled={page === 0}
              onClick={() => setPage((p) => Math.max(0, p - 1))}
            >
              <ChevronLeft size={14} /> 上一页
            </Button>
            <span className="min-w-16 text-center text-muted-foreground tabular-nums">
              {page + 1}/{num}
            </span>
            <Button
              variant="ghost"
              size="sm"
              className="gap-0.5"
              disabled={page >= num - 1}
              onClick={() => setPage((p) => Math.min(num - 1, p + 1))}
            >
              下一页 <ChevronRight size={14} />
            </Button>
            <Button
              variant="ghost"
              size="sm"
              className="gap-0.5"
              disabled={page >= num - 1}
              onClick={() => setPage(num - 1)}
              aria-label="最后一页"
            >
              <ChevronsRight size={14} /> 末页
            </Button>
            <Button
              variant="ghost"
              size="sm"
              className="gap-1.5"
              aria-expanded={nav}
              aria-controls="reader-nav"
              onClick={() => setNav((v) => !v)}
            >
              <PanelLeft size={14} /> 导航
            </Button>
          </>
        }
      />
      {nav && (
        <ReaderNav
          tab="bm"
          onClose={() => setNav(false)}
          bookmarks={
            <BookmarksTab
              book={book}
              capture={saver.capture}
              seek={(l) => {
                const p = Number(l.page);
                setNav(false);
                if (Number.isInteger(p) && p >= 0 && p < num) setPage(p);
              }}
            />
          }
        />
      )}
    </div>
  );
}