import { useEffect, useRef, useState, type KeyboardEvent } from "react";
import * as pdfjs from "pdfjs-dist";
import { apiRaw } from "../api/client";
import { useBookmarks } from "../components/Bookmarks";
import { btn } from "../components/ui";
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 bm = useBookmarks({
    book,
    capture: saver.capture,
    seek: (l) => {
      const p = Number(l.page);
      if (Number.isInteger(p) && p >= 0 && p < num) setPage(p);
    },
  });
  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)

  useEffect(() => {
    let dead = false;
    setErr("");
    (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="grid h-full place-items-center p-8 text-center">
        <div>
          <p className="mb-3 text-red-400">{err}</p>
          <button className={btn} onClick={() => setNonce((x) => x + 1)}>
            重试
          </button>
        </div>
      </div>
    );
  if (num === 0) return <div className="grid h-full place-items-center text-stone-500">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] focus:outline-none"
    >
      <div ref={wrapRef} className="flex min-h-0 items-start justify-center overflow-y-auto bg-stone-900/70 p-4">
        <canvas ref={canvasRef} className="max-w-3xl rounded-md shadow-2xl ring-1 ring-stone-700/50" />
      </div>
      <div className="flex items-center justify-center gap-2 border-t border-stone-800/80 px-4 py-2 text-sm">
        <button className={btn} disabled={page === 0} onClick={() => setPage(0)} aria-label="第一页">
          首页
        </button>
        <button className={btn} disabled={page === 0} onClick={() => setPage((p) => Math.max(0, p - 1))}>
          ← 上一页
        </button>
        <span className="min-w-16 text-center tabular-nums text-stone-400">
          {page + 1}/{num}
        </span>
        <button className={btn} disabled={page >= num - 1} onClick={() => setPage((p) => Math.min(num - 1, p + 1))}>
          下一页 →
        </button>
        <button className={btn} disabled={page >= num - 1} onClick={() => setPage(num - 1)} aria-label="最后一页">
          末页
        </button>
        {bm.btn}
      </div>
      {bm.panel}
    </div>
  );
}