import React, { useEffect, useRef, useState } from "react";
import { useParams } from "react-router-dom";
import { Box, Button } from "@mui/material";

import { api } from "../api";
import { useI18n } from "../i18n/I18nProvider";
import { PageHeader } from "../layout/PageLayout";
import ViewStateNotice from "../components/ViewStateNotice";

const A4_WIDTH_PX = (210 / 25.4) * 96;
const A4_HEIGHT_PX = (297 / 25.4) * 96;

type PublicCvRead = {
  slug?: string;
  html?: string;
  name?: string;
  error?: "missing" | "transient";
  loading: boolean;
  height: number;
};

// Anonymous read-only public CV at /cv/:slug. Renders the server-produced HTML in a sandboxed
// iframe. noindex is enforced server-side (X-Robots-Tag) and reinforced with a meta tag here.
export default function PublicCvPage() {
  const { slug } = useParams();
  const { t } = useI18n();
  const pdfUrl = `${api.defaults.baseURL}/public-cv/${encodeURIComponent(slug ?? "")}/pdf`;
  const [read, setRead] = useState<PublicCvRead>({ slug, loading: true, height: A4_HEIGHT_PX });
  const [retry, setRetry] = useState(0);
  const pending = useRef(false);
  const headingRef = useRef<HTMLHeadingElement>(null);
  const previousTitle = useRef("");
  const ownedTitle = useRef<string | null>(null);
  const [frameScale, setFrameScale] = useState(1);
  // Hide the old document on the first render of a new route, before its effect runs.
  const current = read.slug === slug ? read : null;
  const loading = !current || current.loading;
  const frameHeight = current?.height ?? A4_HEIGHT_PX;
  const title = t("publicCvTitle");
  const unavailable = current?.error === "missing";
  const errorTitle = t(unavailable ? "publicCvUnavailableTitle" : "publicCvLoadFailedTitle");

  useEffect(() => {
    const originalTitle = document.title;
    previousTitle.current = originalTitle;
    const meta = document.createElement("meta");
    meta.name = "robots";
    meta.content = "noindex, nofollow";
    document.head.appendChild(meta);
    return () => {
      meta.remove();
      if (document.title === ownedTitle.current) document.title = originalTitle;
    };
  }, []);

  useEffect(() => {
    let alive = true;
    pending.current = true;
    setRead({ slug, loading: true, height: A4_HEIGHT_PX });
    api.get<{ html: string; name: string }>(`/public-cv/${encodeURIComponent(slug ?? "")}`)
      .then((r) => { if (alive) setRead({ slug, html: r.data.html, name: r.data.name, loading: false, height: A4_HEIGHT_PX }); })
      .catch((err) => {
        if (!alive) return;
        // 404 = unknown slug or the owner made it private again. Anything else is a transient error.
        setRead({ slug, error: err?.response?.status === 404 ? "missing" : "transient", loading: false, height: A4_HEIGHT_PX });
      })
      .finally(() => { if (alive) pending.current = false; });
    return () => { alive = false; };
  }, [slug, retry]);

  useEffect(() => {
    const nextTitle = current?.name ? `${current.name} — CV` : previousTitle.current;
    document.title = nextTitle;
    ownedTitle.current = nextTitle;
  }, [current?.name]);

  useEffect(() => {
    const updateScale = () => setFrameScale(Math.min(1, Math.max(0.1, (window.innerWidth - 32) / A4_WIDTH_PX)));
    updateScale();
    window.addEventListener("resize", updateScale);
    return () => window.removeEventListener("resize", updateScale);
  }, []);

  return (
    <Box component="main" sx={{ minHeight: "100vh", bgcolor: "background.default", color: "text.primary", py: 3, px: "16px", display: "flex", flexDirection: "column", alignItems: "center", gap: 2, minWidth: 0 }}>
      <Box sx={{ width: "100%", maxWidth: A4_WIDTH_PX, minWidth: 0 }}>
        <PageHeader title={title} titleRef={headingRef} description={t("publicCvDescription")}
          actions={current?.html !== undefined ? <Button component="a" variant="contained" href={pdfUrl} download>{t("publicCvDownloadPdf")}</Button> : undefined} />
        <ViewStateNotice compact loading={loading} title={errorTitle}
          error={current?.error ? { kind: "unavailable", message: errorTitle, retryable: !unavailable } : null}
          description={t(unavailable ? "publicCvUnavailableBody" : "publicCvLoadFailedBody")}
          onRetry={() => {
            if (pending.current || loading) return;
            pending.current = true;
            headingRef.current?.focus();
            setRead({ slug, loading: true, height: A4_HEIGHT_PX });
            setRetry((value) => value + 1);
          }} />
      </Box>
      {current?.html !== undefined && <div
        data-testid="public-cv-frame-container"
        style={{ width: A4_WIDTH_PX * frameScale, height: frameHeight * frameScale, maxWidth: "100%", overflow: "hidden", boxShadow: "0 8px 30px rgba(0,0,0,0.18)" }}
      >
        <iframe
          title={title}
          srcDoc={current.html}
          sandbox="allow-same-origin"
          onLoad={(event) => {
            const documentHeight = event.currentTarget.contentDocument?.documentElement.scrollHeight ?? A4_HEIGHT_PX;
            setRead((previous) => previous.slug === slug && previous.html === current.html && !previous.loading
              ? { ...previous, height: Math.max(A4_HEIGHT_PX, documentHeight) } : previous);
          }}
          style={{ width: A4_WIDTH_PX, height: frameHeight, transform: `scale(${frameScale})`, transformOrigin: "top left", border: "none", background: "#fff", display: "block" }}
        />
      </div>}
    </Box>
  );
}