Function setupFileDownloadProxyHandler

apps/hash-api/src/storage/index.ts:162–294

(app: Express, cache: Keyv)

 * @param cache - a cache to store presigned URLs so we don't needlessly create URLs for every download
 */
export const setupFileDownloadProxyHandler = (app: Express, cache: Keyv) => {
  app.get("/file/*splat", async (req, res) => {
    const key = (req.params as { splat: string[] }).splat.join("/");
    const urlOnly = req.query.urlOnly;

    // We purposefully return 404 for all error cases.
    if (!key) {
      res.sendStatus(404);
      return;
    }

    const keyParts = key.split("/");
    const [entityId, editionTimestamp, filename] = keyParts.slice(-3);

    if (!entityId || !editionTimestamp || !filename) {
      res.status(400).json({
        error: `File path ${key} is invalid – should be of the form [EntityId]/[EditionTimestamp]/[Filename], with an optional leading [Prefix]/`,
      });
      return;
    }
    if (!isEntityId(entityId)) {
      res.status(400).json({
        error: `File path contains invalid entityId ${entityId} in ${key}`,
      });
      return;
    }

    const actorId = getActorIdFromRequest(req);

    const fileEntity = await getFileEntity(
      req.context,
      { actorId },
      {
        entityId,
        key,
      },
    );

    if (!fileEntity) {
      res.status(404).json({
        error: `Could not find file entity ${entityId} with edition timestamp ${editionTimestamp}, either it does not exist or you do not have permission to access it.`,
      });
      return;
    }

    if (!isFileEntity(fileEntity)) {
      res.status(400).json({
        error: `Found entity ${fileEntity.metadata.recordId.entityId} is not a file entity – has type(s) ${fileEntity.metadata.entityTypeIds.join(", ")}`,
      });
      return;
    }

    const { fileStorageKey } = simplifyProperties(fileEntity.properties);
    if (!fileStorageKey) {
      res.status(400).json({
        error: `File entity ${fileEntity.metadata.recordId.entityId} is missing the necessary properties for file retrieval`,
      });
      return;