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

import { useQuery } from '@tanstack/react-query';

import { Icon } from '@/app/Icon';
import { createGroupQRCode, createMyQRCode, createUserQRCode, type GroupQRCode, type MyQRCode } from '@/lib/api/qrcodes';
import { avatarBgClass, avatarLetter } from '@/lib/avatar';
import { useEscapeKey } from '@/lib/hooks';

interface QRCodeModalProps {
  /** Omit both to show the CURRENT user's own code; pass a friend's user_id/account to show theirs
   *  (README's "二维码名片" row on a friend's profile). */
  identifier?: string;
  /** 03-group.dc.html #1a's `qr_code_2` icon on the group-info card (admin/owner-visible group-join
   *  code) -- mutually exclusive with `identifier`, a group is never also a user. */
  groupTopic?: string;
  onClose: () => void;
}

/**
 * README §5.4/§8.2's "我的二维码"/"二维码名片", plus the group-join code (03-group.dc.html #1a). The
 * QR image encodes `qr_payload` (`im://qr?token=...&purpose=add_friend|join_group`), never a raw
 * user/group id -- confirmed live for the personal-code path that this is a real, working backend
 * feature (`POST /me/qrcodes` / `POST /users/{id}/qrcodes`), not a documented-but-unbuilt one; the
 * group-code path (`POST /groups/{topic}/qrcodes`) is the same documented shape (docs/IM-前后端对接
 * 文档.md:1590,1737) but not yet live-verified against a real deployment. Re-mints a fresh token on
 * every mount (POST semantics, not cached) since each one is short-lived (~24h) and single-purpose.
 */
export function QRCodeModal({ identifier, groupTopic, onClose }: QRCodeModalProps) {
  useEscapeKey(onClose);
  const canvasRef = useRef<HTMLCanvasElement>(null);
  const [drawError, setDrawError] = useState('');
  const query = useQuery<MyQRCode | GroupQRCode>({
    queryKey: ['qrcode', groupTopic ? `group:${groupTopic}` : identifier || 'me'],
    queryFn: (): Promise<MyQRCode | GroupQRCode> => (groupTopic ? createGroupQRCode(groupTopic) : identifier ? createUserQRCode(identifier) : createMyQRCode()),
  });

  const draw = () => {
    if (!query.data || !canvasRef.current) return;
    const canvas = canvasRef.current;
    setDrawError('');
    // Dynamically imported (like agora-rtc-sdk-ng in agora-client.ts) so a QR-generating library
    // isn't in every visitor's main bundle when most sessions never open this modal.
    import('qrcode')
      .then(({ default: QRCode }) => QRCode.toCanvas(canvas, query.data.qr_payload, { width: 200, margin: 1, color: { dark: '#22262d', light: '#ffffff' } }))
      .catch(() => setDrawError('二维码生成失败'));
  };

  useEffect(draw, [query.data]);

  const retry = () => {
    if (query.isError) query.refetch();
    else draw();
  };

  const profile = query.data && 'display_profile' in query.data ? query.data.display_profile : undefined;
  const group = query.data && 'group_snapshot' in query.data ? query.data.group_snapshot : undefined;
  const title = groupTopic ? '群二维码' : identifier ? '二维码名片' : '我的二维码';
  const fileBaseName = groupTopic ? '群二维码' : identifier ? '二维码名片' : '我的二维码';
  const caption = groupTopic ? '扫一扫上面的二维码，申请加入群聊' : '扫一扫上面的二维码，加我为好友';

  const canvasToBlob = (): Promise<Blob | null> => new Promise((resolve) => canvasRef.current?.toBlob((b) => resolve(b), 'image/png'));

  const saveToAlbum = async () => {
    const blob = await canvasToBlob();
    if (!blob) return;
    const url = URL.createObjectURL(blob);
    const link = document.createElement('a');
    link.href = url;
    link.download = `${fileBaseName}.png`;
    link.click();
    URL.revokeObjectURL(url);
  };

  const shareToFriend = async () => {
    const blob = await canvasToBlob();
    if (!blob) return;
    const file = new File([blob], 'qrcode.png', { type: 'image/png' });
    // Real capability check, not just feature-detecting `navigator.share` itself -- some browsers
    // implement `share()` for URLs/text only and reject a `files` payload at call time, so
    // `canShare({ files })` is the one call that actually answers "can this share an image".
    if (navigator.canShare?.({ files: [file] })) {
      try {
        await navigator.share({ files: [file], title: fileBaseName });
      } catch {
        // AbortError (user cancelled the native share sheet) or any other failure -- either way
        // there's nothing useful to surface, the share sheet's own UI already communicated the outcome.
      }
    } else {
      await saveToAlbum();
    }
  };

  return (
    <div className="fixed inset-0 z-50 flex items-center justify-center bg-[#22262d]/25" onClick={onClose}>
      <div className="flex w-[360px] flex-col rounded-xl bg-white shadow-modal" onClick={(e) => e.stopPropagation()}>
        <header className="flex h-13 flex-none items-center justify-between border-b border-border-list-item px-5">
          <strong className="text-[15px] font-semibold text-text-heading">{title}</strong>
          <button type="button" onClick={onClose} className="grid h-8 w-8 place-items-center text-text-tertiary-4">
            <Icon name="close" />
          </button>
        </header>
        <div className="flex flex-col items-center gap-3 px-6 py-7">
          {profile ? (
            <>
              <span className={`grid h-14 w-14 flex-none place-items-center rounded-xl text-xl font-medium text-white ${avatarBgClass(profile.user_id)}`}>
                {avatarLetter(profile.display_name)}
              </span>
              <strong className="text-base font-semibold text-text-heading">{profile.display_name}</strong>
              {profile.public_account ? <span className="text-xs text-text-tertiary-2">ID：{profile.public_account}</span> : null}
            </>
          ) : group ? (
            <>
              <span className={`grid h-14 w-14 flex-none place-items-center rounded-xl text-xl font-medium text-white ${avatarBgClass(group.topic)}`}>
                {avatarLetter(group.name)}
              </span>
              <strong className="text-base font-semibold text-text-heading">{group.name}</strong>
              <span className="text-xs text-text-tertiary-2">{group.member_count} 人</span>
            </>
          ) : null}
          <div className="mt-2 grid h-[220px] w-[220px] place-items-center rounded-lg border border-border-panel">
            {query.isLoading ? (
              <span className="text-sm text-text-tertiary-4">生成中…</span>
            ) : query.isError || drawError ? (
              <div className="flex flex-col items-center gap-2 px-4 text-center">
                <Icon name="error_outline" className="text-2xl text-danger-text" />
                <span className="text-xs text-text-tertiary-4">{drawError || '二维码生成失败，请重试'}</span>
                <button type="button" onClick={retry} className="text-xs text-accent">
                  重试
                </button>
              </div>
            ) : (
              <canvas ref={canvasRef} />
            )}
          </div>
          <span className="text-xs text-text-tertiary-3">{caption}</span>
          {/* No mock anywhere in this design handoff draws these two buttons (grepped every
              screens/*.dc.html) -- added on the strength of a near-universal QR-display convention
              (save/share), not a documented spec. Reuses the `share` icon the add-friend chip
              (04-contacts.dc.html:101) already uses for the same verb elsewhere in this app. */}
          {query.data && !drawError ? (
            <div className="mt-1 flex gap-2">
              <button
                type="button"
                onClick={saveToAlbum}
                className="flex h-8.5 items-center gap-1.5 rounded-md border border-[#d5d9df] px-3.5 text-[13px] text-text-secondary"
              >
                <Icon name="download" className="text-[16px]" />
                保存到相册
              </button>
              <button
                type="button"
                onClick={shareToFriend}
                className="flex h-8.5 items-center gap-1.5 rounded-md border border-[#d5d9df] px-3.5 text-[13px] text-text-secondary"
              >
                <Icon name="share" className="text-[16px]" />
                分享好友
              </button>
            </div>
          ) : null}
        </div>
      </div>
    </div>
  );
}