cinny/src/app/features/common-settings/general/RoomShareInvite.tsx

import React, { useCallback, useRef, useState } from 'react';
import { Box, Button, color, config, Icon, Icons, Text } from 'folds';
import { QRCodeSVG, QRCodeCanvas } from 'qrcode.react';
import { SequenceCard } from '../../../components/sequence-card';
import { SequenceCardStyle } from '../../room-settings/styles.css';
import { SettingTile } from '../../../components/setting-tile';
import { CutoutCard } from '../../../components/cutout-card';
import { useRoom } from '../../../hooks/useRoom';
import { getViaServers } from '../../../plugins/via-servers';
import { useSaveFile } from '../../../hooks/useSaveFile';
import { useLotusShareBase } from '../../../hooks/useLotusLinkBase';
import { getLotusRoomPermalink, getLotusSpacePermalink } from '../../../plugins/lotus-permalink';

// Filesystem-safe basename from an arbitrary room name. Denylist only the
// path-hostile / control characters so Unicode names (CJK, Cyrillic, emoji, …)
// survive instead of being stripped to the 'room' fallback. Collapse whitespace,
// trim separator runs, and cap length to stay under filesystem name limits.
// eslint-disable-next-line no-control-regex
const UNSAFE_FILENAME = /[/\\:*?"<>|-]+/g;
function sanitizeFilename(name: string): string {
  const cleaned = name
    .replace(UNSAFE_FILENAME, '')
    .replace(/\s+/g, '-')
    .replace(/^[-.]+|[-.]+$/g, '')
    .slice(0, 80)
    .replace(/[-.]+$/g, '');
  return cleaned || 'room';
}

export function RoomShareInvite() {
  const room = useRoom();
  const saveFile = useSaveFile();
  const [copied, setCopied] = useState(false);
  const [qrError, setQrError] = useState(false);
  // Offscreen high-resolution canvas used only to export the QR as a PNG; the
  // visible code stays an SVG so it renders crisply at any size/theme.
  const qrCanvasRef = useRef<HTMLCanvasElement>(null);

  // Use the shared via-server resolver (creator's/highest-power server plus the
  // top-populated member servers) instead of only the local homeserver, so the
  // link keeps resolving even if the sharer's own server later goes offline.
  // [Gitea #285] matrix.to can't open Lotus Chat (its Cinny adapter is
  // app.cinny.in), so share a link straight into this deployment.
  const lotusBase = useLotusShareBase();
  const inviteUrl = room.isSpaceRoom()
    ? getLotusSpacePermalink(lotusBase, room.roomId, getViaServers(room))
    : getLotusRoomPermalink(lotusBase, room.roomId, undefined, getViaServers(room));

  const handleCopy = useCallback(() => {
    navigator.clipboard.writeText(inviteUrl).then(() => {
      setCopied(true);
      setTimeout(() => setCopied(false), 2000);
    });
  }, [inviteUrl]);

  const handleDownloadQr = useCallback(() => {
    const canvas = qrCanvasRef.current;
    if (!canvas) return;
    setQrError(false);
    canvas.toBlob((blob) => {
      if (blob) {
        saveFile(blob, `${sanitizeFilename(room.name)}-invite-qr.png`);
      } else {
        // PNG encoding failed — surface it so the user isn't left re-clicking a
        // button that silently did nothing.
        setQrError(true);
        setTimeout(() => setQrError(false), 4000);
      }
    }, 'image/png');
  }, [saveFile, room.name]);

  return (
    <SequenceCard
      className={SequenceCardStyle}
      variant="SurfaceVariant"
      direction="Column"
      gap="400"
    >
      <SettingTile
        title="Share Room"
        description="Share this invite link so others can join the room."
      />
      <CutoutCard variant="Surface" style={{ padding: config.space.S300 }}>
        <Box direction="Column" gap="300">
          <Box gap="200" alignItems="Center">
            <Box grow="Yes">
              <Text
                size="T200"
                style={{
                  wordBreak: 'break-all',
                  userSelect: 'all',
                }}
              >
                {inviteUrl}
              </Text>
            </Box>
            <Box shrink="No">
              <Button
                size="300"
                variant={copied ? 'Success' : 'Secondary'}
                fill={copied ? 'Solid' : 'Soft'}
                radii="300"
                onClick={handleCopy}
                before={<Icon size="100" src={copied ? Icons.Check : Icons.Link} />}
              >
                <Text size="B300">{copied ? 'Copied!' : 'Copy Link'}</Text>
              </Button>
            </Box>
          </Box>
          <Box direction="Column" alignItems="Center" gap="300">
            {/* Generated locally (qrcode.react) — no third-party service, works
                offline + under strict CSP. White padded quiet-zone so the
                default black-on-white code scans on any theme. */}
            <Box
              style={{
                padding: config.space.S200,
                background: '#ffffff',
                borderRadius: config.radii.R300,
                lineHeight: 0,
              }}
            >
              <QRCodeSVG value={inviteUrl} size={160} level="M" title="Room invite QR code" />
            </Box>
            <Button
              size="300"
              variant="Secondary"
              fill="Soft"
              radii="300"
              onClick={handleDownloadQr}
              before={<Icon size="100" src={Icons.Download} />}
            >
              <Text size="B300">Download QR</Text>
            </Button>
            {qrError && (
              <Text size="T200" style={{ color: color.Critical.Main }}>
                Could not generate the QR image. Try again.
              </Text>
            )}
          </Box>
        </Box>
      </CutoutCard>
      {/* Offscreen, high-res (spec 4-module quiet zone) source for PNG export. */}
      <QRCodeCanvas
        ref={qrCanvasRef}
        value={inviteUrl}
        size={1024}
        level="M"
        marginSize={4}
        style={{ display: 'none' }}
      />
    </SequenceCard>
  );
}