'use client';

import { useState } from 'react';
import dynamic from 'next/dynamic';
import { ExternalLink, ZoomIn } from 'lucide-react';
import { useQuery } from '@tanstack/react-query';

import {
  Dialog,
  DialogContent,
  DialogDescription,
  DialogHeader,
  DialogTitle,
} from '@/components/ui/dialog';
import { apiFetch } from '@/lib/api/client';

// yet-another-react-lightbox is ~50kb, lazy-load it.
const Lightbox = dynamic(() => import('yet-another-react-lightbox'), { ssr: false });
import 'yet-another-react-lightbox/styles.css';

// pdfjs-dist is ~150kb gzip — lazy-load so routes that never preview
// PDFs don't ship it. ssr:false because the worker setup needs window.
const PdfViewer = dynamic(() => import('./pdf-viewer').then((m) => ({ default: m.PdfViewer })), {
  ssr: false,
  loading: () => (
    <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
      Loading PDF viewer…
    </div>
  ),
});

interface FilePreviewDialogProps {
  open: boolean;
  onOpenChange: (open: boolean) => void;
  fileId?: string;
  fileName?: string;
  mimeType?: string;
}

export function FilePreviewDialog({
  open,
  onOpenChange,
  fileId,
  fileName,
  mimeType,
}: FilePreviewDialogProps) {
  const [lightboxOpen, setLightboxOpen] = useState(false);

  // useQuery replaces the prior useEffect(fetch+setState) pattern. The
  // request is gated on the dialog being open and a fileId being set.
  const previewQuery = useQuery<{ data: { url: string } }>({
    queryKey: ['file-preview', fileId],
    queryFn: () => apiFetch(`/api/v1/files/${fileId}/preview`),
    enabled: open && !!fileId,
  });
  const previewUrl = previewQuery.data?.data.url ?? null;
  const loading = previewQuery.isLoading;
  const error = previewQuery.error ? 'Failed to load preview' : null;

  const isImage = mimeType?.startsWith('image/');
  const isPdf = mimeType === 'application/pdf';

  return (
    <Dialog open={open} onOpenChange={onOpenChange}>
      <DialogContent className="max-w-4xl w-full h-[80vh] flex flex-col">
        <DialogHeader>
          <DialogTitle className="flex items-center gap-2 truncate">
            <span className="truncate">{fileName ?? 'Preview'}</span>
            {previewUrl && (
              <a
                href={previewUrl}
                target="_blank"
                rel="noopener noreferrer"
                className="shrink-0 text-muted-foreground hover:text-foreground"
              >
                <ExternalLink className="h-4 w-4" />
              </a>
            )}
          </DialogTitle>
          {/* A6: screen-reader description; visually hidden because the
           *  title + preview surface tells sighted users what the dialog
           *  contains. Skips the Radix "missing aria-describedby" warning. */}
          <DialogDescription className="sr-only">
            Inline preview of {fileName ?? 'the selected file'}.
          </DialogDescription>
        </DialogHeader>

        <div className="flex-1 overflow-hidden rounded-lg border bg-muted/20">
          {loading && (
            <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
              Loading preview...
            </div>
          )}

          {error && (
            <div className="flex h-full items-center justify-center text-sm text-destructive">
              {error}
            </div>
          )}

          {!loading && !error && previewUrl && isImage && (
            <button
              type="button"
              onClick={() => setLightboxOpen(true)}
              className="flex h-full w-full items-center justify-center p-4 group"
              aria-label="Open in lightbox"
            >
              {/* eslint-disable-next-line @next/next/no-img-element */}
              <img
                src={previewUrl}
                alt={fileName ?? 'Preview'}
                className="max-h-full max-w-full object-contain rounded transition-transform group-hover:scale-[1.02]"
              />
              <ZoomIn className="absolute right-6 bottom-6 h-6 w-6 rounded-full bg-background/80 p-1 text-foreground opacity-0 transition-opacity group-hover:opacity-100" />
            </button>
          )}

          {!loading && !error && previewUrl && isPdf && (
            <PdfViewer url={previewUrl} fileName={fileName} />
          )}
        </div>
      </DialogContent>

      {/* Lightbox renders OUTSIDE the parent Dialog so the dialog's own
       *  bounds don't clip the fullscreen overlay. yet-another-react-
       *  lightbox handles zoom/pan/keyboard nav out of the box. */}
      {previewUrl && isImage && (
        <Lightbox
          open={lightboxOpen}
          close={() => setLightboxOpen(false)}
          slides={[{ src: previewUrl, alt: fileName ?? 'Preview' }]}
          controller={{ closeOnBackdropClick: true }}
          carousel={{ finite: true }}
        />
      )}
    </Dialog>
  );
}