"use client";

import { useEffect, useRef, useState } from "react";

/**
 * Modal preview for image and PDF attachments.
 *
 * Uses the native <dialog> element for focus trap, Esc-to-close, and
 * inert-background semantics — saves ~100 lines of bespoke a11y wiring
 * that we'd otherwise have to maintain.
 *
 * For an `image/*` mime, renders an <img>. For `application/pdf`, an
 * <iframe>. Anything else should not reach this component — FileLink is
 * responsible for branching office/other types to plain download links.
 */
export function AttachmentLightbox({
  open,
  onClose,
  previewSrc,
  downloadHref,
  filename,
  mime,
}: {
  open: boolean;
  onClose: () => void;
  /** URL the <img>/<iframe> loads from. Should serve with Content-Disposition: inline. */
  previewSrc: string;
  /** Anchor target for the Download button. Serves with Content-Disposition: attachment. */
  downloadHref: string;
  filename: string;
  /** Resolved mime; used to pick between <img> and <iframe>. */
  mime: string;
}) {
  const ref = useRef<HTMLDialogElement | null>(null);

  // When embedded in the CiviCRM tab, the iframe is auto-expanded to its full
  // content height (no nested scrollbar), so a modal <dialog> — which centers
  // in *its* viewport — lands in the vertical middle of the whole document and
  // is off-screen unless the parent page happens to be scrolled there. The
  // iframe can't read the parent's scroll position (cross-origin), so the
  // extension's tab template broadcasts the iframe's currently-visible slice
  // as `webform-mw-viewport` messages. We pin the dialog to that slice and
  // size it to fill the visible height. Standalone (non-embedded) keeps the
  // native viewport centering.
  const [framed, setFramed] = useState(false);
  const vpRef = useRef<{ top: number; height: number } | null>(null);
  const [vp, setVp] = useState<{ top: number; height: number } | null>(null);

  useEffect(() => {
    setFramed(window.parent !== window);
  }, []);

  useEffect(() => {
    const onMsg = (e: MessageEvent) => {
      if (e.source !== window.parent) return;
      const d = e.data as { type?: string; top?: number; height?: number } | null;
      if (!d || d.type !== "webform-mw-viewport") return;
      const next = { top: Number(d.top) || 0, height: Number(d.height) || 0 };
      vpRef.current = next;
      // Only reflect into render state while open — many FileLinks mount a
      // (closed) lightbox each, and we don't want every one re-rendering on
      // each scroll frame.
      if (open) setVp(next);
    };
    window.addEventListener("message", onMsg);
    return () => window.removeEventListener("message", onMsg);
  }, [open]);

  // Seed from the latest known viewport the moment we open.
  useEffect(() => {
    if (open) setVp(vpRef.current);
  }, [open]);

  // Drive the native <dialog>'s open state from our prop.
  useEffect(() => {
    const dlg = ref.current;
    if (!dlg) return;
    if (open && !dlg.open) {
      dlg.showModal();
    } else if (!open && dlg.open) {
      dlg.close();
    }
  }, [open]);

  // Native <dialog> fires a 'close' event on Esc and on form-method=dialog
  // submit. Mirror that back into React state so the parent stays in sync.
  useEffect(() => {
    const dlg = ref.current;
    if (!dlg) return;
    const handle = () => onClose();
    dlg.addEventListener("close", handle);
    return () => dlg.removeEventListener("close", handle);
  }, [onClose]);

  // Close when the user clicks the backdrop (everything outside the inner
  // panel). The dialog itself receives the click event when the backdrop
  // is hit because the panel uses pointer-events the same way.
  const onDialogClick = (e: React.MouseEvent<HTMLDialogElement>) => {
    if (e.target === ref.current) onClose();
  };

  const isImage = mime.startsWith("image/");
  const isPdf = mime === "application/pdf";

  // Vertical placement + height.
  //   - framed + known viewport: pin to the visible slice and fill it.
  //   - framed but no viewport yet (e.g. an older extension that doesn't
  //     broadcast): fall back to a safe fixed box so we never balloon to the
  //     full multi-thousand-pixel iframe height.
  //   - standalone: native viewport centering, tall enough for documents.
  const margin = 16;
  const dialogStyle: React.CSSProperties | undefined =
    framed && vp
      ? { top: Math.max(8, vp.top + margin), bottom: "auto", marginTop: 0, marginBottom: 0 }
      : undefined;
  const panelHeight = framed
    ? vp
      ? Math.max(360, vp.height - margin * 2)
      : 640
    : undefined;

  return (
    <dialog
      ref={ref}
      onClick={onDialogClick}
      aria-label={`Preview: ${filename}`}
      style={dialogStyle}
      className="m-auto w-[min(92vw,900px)] rounded-md bg-transparent p-0 shadow-2xl backdrop:bg-ink/70"
    >
      <div
        style={panelHeight !== undefined ? { height: panelHeight } : undefined}
        className={`flex flex-col overflow-hidden rounded-md ${framed ? "" : "h-[85vh] max-h-[860px]"}`}
      >
        <header className="flex items-center justify-between gap-4 bg-paper px-4 py-2.5 sm:px-5">
          <p className="min-w-0 truncate font-display text-sm text-ink">
            {filename}
          </p>
          <div className="flex flex-shrink-0 items-center gap-3">
            <a
              href={downloadHref}
              className="text-xs font-medium text-leaf-700 underline decoration-rule underline-offset-4 hover:decoration-ink hover:text-leaf-800"
              target="_blank"
              rel="noopener noreferrer"
            >
              Download
            </a>
            <button
              type="button"
              onClick={onClose}
              className="rounded px-2 py-1 text-xs font-medium text-ink-soft hover:bg-rule-soft/40 focus:outline-none focus-visible:ring-2 focus-visible:ring-leaf-700"
              aria-label="Close preview"
            >
              Close
            </button>
          </div>
        </header>
        <div className="flex flex-1 items-center justify-center overflow-hidden bg-ink/90 p-3">
          {isImage ? (
            // eslint-disable-next-line @next/next/no-img-element
            <img
              src={previewSrc}
              alt={filename}
              className="max-h-full max-w-full object-contain"
            />
          ) : isPdf ? (
            <iframe
              src={previewSrc}
              title={filename}
              className="h-full w-full border-0 bg-paper"
            />
          ) : (
            // Defensive: FileLink shouldn't open the lightbox for non-previewable
            // types, but if it does, surface a clear message instead of an empty box.
            <p className="px-6 text-paper">
              Preview not available. Use Download above to open the file.
            </p>
          )}
        </div>
      </div>
    </dialog>
  );
}