import { useEffect, useRef, useState } from "react";
import { apiRaw } from "../api/client";
import { btn } from "../components/ui";
import { useProgressSaver, type ReaderProps } from "../lib/useProgress";

// 仅声明用到的最小子集,避免依赖 epubjs 自带类型的完整性
interface EpubLocation {
  start?: { cfi?: string; sectionIndex?: number };
}
interface EpubRendition {
  display(target?: string): Promise<unknown> | unknown;
  next(): unknown;
  prev(): unknown;
  on(ev: "relocated", cb: (loc: EpubLocation) => void): void;
  destroy(): void;
}
interface EpubBookLike {
  ready: Promise<unknown>;
  spine?: unknown[];
  renderTo(el: HTMLElement, opts: Record<string, unknown>): EpubRendition;
  destroy(): void;
}

async function loadEpub(): Promise<(data: Uint8Array) => EpubBookLike> {
  const m = (await import("epubjs")) as { default?: unknown };
  return m.default as (data: Uint8Array) => EpubBookLike;
}

export default function EpubReader({ book, initialLocator }: ReaderProps) {
  const hostRef = useRef<HTMLDivElement>(null);
  const rendRef = useRef<EpubRendition | null>(null);
  const saver = useProgressSaver(book.id);
  const [err, setErr] = useState("");
  const [nonce, setNonce] = useState(0);
  const [ready, setReady] = useState(false);

  useEffect(() => {
    let dead = false;
    let bookObj: EpubBookLike | null = null;
    setErr("");
    setReady(false);
    (async () => {
      const ePub = await loadEpub();
      const buf = await apiRaw(book.file_url ?? "").then((r) => r.arrayBuffer());
      if (dead) return;
      bookObj = ePub(new Uint8Array(buf)); // 字节已在内存,内部 iframe 不再回源,绕开鉴权问题
      await bookObj.ready;
      if (dead || !hostRef.current) return;
      const spineLen = bookObj.spine?.length ?? 1;
      const r = bookObj.renderTo(hostRef.current, { width: "100%", height: "100%", flow: "paginated" });
      rendRef.current = r;
      r.on("relocated", (loc) => {
        const cfi = loc.start?.cfi ?? "";
        const idx = loc.start?.sectionIndex ?? 0;
        const pct = spineLen > 1 ? (idx + 1) / spineLen : 0.5;
        saver.report(cfi ? { cfi } : {}, Math.min(1, pct));
      });
      const cfi = typeof initialLocator?.cfi === "string" ? (initialLocator.cfi as string) : undefined;
      // epubjs 对失效 cfi 以 reject Promise  signalling,而非同步 throw → 走 then/catch 回退
      Promise.resolve(cfi ? r.display(cfi) : r.display())
        .then(() => setReady(true))
        .catch(() => {
          if (!cfi) {
            setErr("EPUB 无法打开");
            return;
          }
          Promise.resolve(r.display())
            .then(() => setReady(true))
            .catch(() => setErr("EPUB 无法打开"));
        });
    })().catch((e) => !dead && setErr(e instanceof Error ? e.message : "EPUB 加载失败"));
    return () => {
      dead = true;
      rendRef.current?.destroy();
      rendRef.current = null;
      bookObj?.destroy();
    };
  }, [book.file_url, nonce]); // eslint-disable-line react-hooks/exhaustive-deps

  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>
    );

  return (
    <div className="grid h-full grid-rows-[1fr_auto]">
      <div className="relative mx-auto min-h-0 w-full max-w-4xl bg-white shadow-2xl ring-1 ring-stone-800">
        <div ref={hostRef} className="absolute inset-0" />
        {!ready && !err && <div className="grid h-full place-items-center bg-stone-950 text-stone-500">EPUB 加载中…</div>}
      </div>
      <div className="flex items-center justify-center gap-3 border-t border-stone-800 px-4 py-2 text-sm">
        <button className={btn} onClick={() => rendRef.current?.prev()}>
          上一页
        </button>
        <button className={btn} onClick={() => rendRef.current?.next()}>
          下一页
        </button>
      </div>
    </div>
  );
}