evidencija-rezija/web-app/app/[locale]/share/attachment/[id]/route.tsx

import { fetchBillById } from '@/app/lib/actions/billActions';
import { notFound } from 'next/navigation';
import { extractShareId, validateShareChecksum } from '@evidencija-rezija/shared-code';
import { getDbClient } from '@/app/lib/dbClient';
import { BillingLocation } from '@evidencija-rezija/shared-code';

export async function GET(request: Request, { params: { id } }: { params: { id: string } }) {
    // Parse shareId-billID format
    // shareId = 40 chars (locationId 24 + checksum 16)
    const shareId = id.substring(0, 40);
    const billID = id.substring(41); // Skip the '-' separator

    if (!shareId || !billID) {
        notFound();
    }

    // Validate shareId and extract locationId
    const extracted = extractShareId(shareId);
    if (!extracted) {
        notFound();
    }

    const { locationId: locationID, checksum } = extracted;

    // Validate checksum
    if (!validateShareChecksum(locationID, checksum)) {
        notFound();
    }

    // Check TTL before fetching bill
    const dbClient = await getDbClient();
    const location = await dbClient.collection<BillingLocation>("lokacije")
        .findOne({ _id: locationID }, { projection: { shareTTL: 1 } });

    if (!location) {
        notFound();
    }

    // Check if sharing is active and not expired
    if (!location.shareTTL || new Date() > location.shareTTL) {
        notFound();
    }

    const [_, bill] = await fetchBillById(locationID, billID, true) ?? [];

    if (!bill?.attachment) {
        notFound();
    }

    // convert fileContentsBase64 from Base64 string to binary string
    const fileContentsBuffer = Buffer.from(bill.attachment.fileContentsBase64, 'base64');

    // convert fileContentsBuffer to format that can be sent to the client
    const fileContents = new Uint8Array(fileContentsBuffer);
    
    return new Response(fileContents, {
        status: 200,
        headers: {
            'Content-Type': "application/octet-stream",
            'Content-Disposition': `attachment; filename="${bill.attachment.fileName}"`,
            'Last-Modified': `${bill.attachment.fileLastModified}`
        }
    });
}