/**
 * @file PdfView.tsx
 * @description A PDF drawn by pdf.js onto canvases, page after page — the
 * Artifacts preview's PDF viewer. The browser's own viewer cannot run inside
 * the sandbox the preview keeps (it blocks plugins), and opening a shared PDF
 * on the dashboard's origin would be the risk the sandbox exists for; pdf.js
 * only DRAWS the file (no scripting sandbox loaded, no XFA, no links
 * followed), so nothing in it runs. pdf.js and its worker are loaded the
 * first time a PDF is opened (a separate chunk), never with the dashboard.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import { useEffect, useRef, useState } from "react";
import { useTranslation } from "react-i18next";
import { Loader2 } from "lucide-react";

/** Pages drawn at most: a 500-page export would otherwise hold every canvas. */
const MAX_PAGES = 200;
const MAX_BYTES = 64 * 1024 * 1024;

async function loadPdfJs() {
  // The legacy build: the modern one needs `Promise.try` and friends, which a
  // browser a year old lacks — the PDF would then just fail to open.
  const pdfjs = await import("pdfjs-dist/legacy/build/pdf.mjs");
  if (!pdfjs.GlobalWorkerOptions.workerSrc) {
    pdfjs.GlobalWorkerOptions.workerSrc = new URL(
      "pdfjs-dist/legacy/build/pdf.worker.min.mjs",
      import.meta.url
    ).toString();
  }
  return pdfjs;
}

export function PdfView({ url, title }: { url: string; title: string }) {
  const { t } = useTranslation("artifacts");
  const box = useRef<HTMLDivElement>(null);
  const [state, setState] = useState<"loading" | "ready" | "failed">("loading");
  const [pages, setPages] = useState(0);

  useEffect(() => {
    let live = true;
    let destroy: (() => void) | null = null;
    setState("loading");
    (async () => {
      const res = await fetch(url, { credentials: "same-origin" });
      if (!res.ok) throw new Error(String(res.status));
      const data = new Uint8Array(await res.arrayBuffer());
      if (data.byteLength > MAX_BYTES) throw new Error("too big");
      const pdfjs = await loadPdfJs();
      const task = pdfjs.getDocument({
        data,
        enableXfa: false,
        disableAutoFetch: true,
      });
      destroy = () => void task.destroy();
      const doc = await task.promise;
      if (!live || !box.current) return;
      setPages(doc.numPages);
      const width = Math.max(320, box.current.clientWidth - 32);
      const ratio = window.devicePixelRatio || 1;
      box.current.replaceChildren();
      for (let n = 1; n <= Math.min(doc.numPages, MAX_PAGES); n++) {
        const page = await doc.getPage(n);
        if (!live || !box.current) return;
        const base = page.getViewport({ scale: 1 });
        const viewport = page.getViewport({ scale: (width / base.width) * ratio });
        const canvas = document.createElement("canvas");
        canvas.width = Math.floor(viewport.width);
        canvas.height = Math.floor(viewport.height);
        canvas.style.width = `${Math.floor(viewport.width / ratio)}px`;
        canvas.className = "mx-auto mb-3 block bg-white shadow";
        canvas.setAttribute("aria-label", t("pdf.page", { n }));
        box.current.appendChild(canvas);
        await page.render({ canvas, viewport }).promise;
        if (n === 1 && live) setState("ready");
      }
    })().catch(() => live && setState("failed"));
    return () => {
      live = false;
      destroy?.();
    };
  }, [url, t]);

  return (
    <div className="relative h-full overflow-auto bg-surface-2 p-4" data-testid="pdf-view">
      {state === "loading" && (
        <div className="absolute inset-0 flex items-center justify-center text-fg-muted">
          <Loader2 className="h-5 w-5 animate-spin" aria-label={t("loading")} />
        </div>
      )}
      {state === "failed" && (
        <p className="p-6 text-center text-sm text-fg-secondary">{t("pdf.failed")}</p>
      )}
      <div ref={box} role="document" aria-label={title} />
      {pages > MAX_PAGES && (
        <p className="py-2 text-center text-xs text-fg-muted">
          {t("pdf.more", { shown: MAX_PAGES, total: pages })}
        </p>
      )}
    </div>
  );
}