arm-web/src/widgets/DocumentReview/SourcePreview.tsx

import { Button, Empty, Spin } from 'antd';
import { useEffect, useState } from 'react';
import { ApiError } from '../../api/client';
import { fetchFileContent } from '../../services/api/files';
import { saveBlob } from '../../utils/download';
import PdfPages from './PdfPages';

type Loaded = { kind: 'pdf'; data: ArrayBuffer } | { kind: 'image'; url: string } | { kind: 'other'; blob: Blob; filename: string };

export function SourcePreview({ fileId }: { fileId: string }) {
	const [loaded, setLoaded] = useState<Loaded | null>(null);
	const [error, setError] = useState<string | null>(null);

	useEffect(() => {
		let cancelled = false;
		let objectUrl: string | null = null;
		setLoaded(null);
		setError(null);
		fetchFileContent(fileId)
			.then(async ({ blob, filename }) => {
				if (cancelled) {
					return;
				}
				if (blob.type === 'application/pdf') {
					const data = await blob.arrayBuffer();
					if (!cancelled) {
						setLoaded({ kind: 'pdf', data });
					}
				} else if (blob.type.startsWith('image/')) {
					objectUrl = URL.createObjectURL(blob);
					setLoaded({ kind: 'image', url: objectUrl });
				} else {
					setLoaded({ kind: 'other', blob, filename: filename ?? 'исходный_файл' });
				}
			})
			.catch((e: unknown) => {
				if (!cancelled) {
					setError(e instanceof ApiError ? e.message : 'Не удалось получить исходный файл');
				}
			});
		return () => {
			cancelled = true;
			if (objectUrl) {
				URL.revokeObjectURL(objectUrl);
			}
		};
	}, [fileId]);

	if (error) {
		return <Empty description={error} />;
	}
	if (!loaded) {
		return <Spin style={{ margin: 48 }} />;
	}
	if (loaded.kind === 'pdf') {
		return <PdfPages data={loaded.data} />;
	}
	if (loaded.kind === 'image') {
		return <img src={loaded.url} alt='Исходный документ' style={{ width: '100%' }} />;
	}
	return (
		<Empty description='Превью недоступно для этого формата'>
			<Button onClick={() => saveBlob(loaded.blob, loaded.filename)}>Скачать исходник</Button>
		</Empty>
	);
}