cinny/src/app/hooks/useDecryptedMediaUrl.ts

import { useEffect, useRef, useState } from 'react';
import { MatrixClient } from 'matrix-js-sdk';
import { IEncryptedFile } from '../../types/matrix/common';
import { decryptFile, downloadEncryptedMedia, mxcUrlToHttp } from '../utils/matrix';

type DecryptState = { status: 'loading' } | { status: 'ok'; url: string } | { status: 'error' };

export function useDecryptedMediaUrl(
  mx: MatrixClient,
  mxcUrl: string | undefined,
  encInfo: IEncryptedFile | undefined,
  useAuthentication: boolean,
  mimeType?: string,
  enabled = true,
): DecryptState {
  const [state, setState] = useState<DecryptState>({ status: 'loading' });
  const prevBlobUrl = useRef<string | null>(null);

  useEffect(() => {
    if (!enabled) return undefined;
    if (!mxcUrl) {
      setState({ status: 'error' });
      return;
    }
    let cancelled = false;
    setState({ status: 'loading' });

    const run = async () => {
      const httpUrl = mxcUrlToHttp(mx, mxcUrl, useAuthentication);
      if (!httpUrl) throw new Error('bad url');
      if (encInfo) {
        const blob = await downloadEncryptedMedia(httpUrl, (buf) =>
          decryptFile(buf, mimeType ?? 'application/octet-stream', encInfo),
        );
        const blobUrl = URL.createObjectURL(blob);
        if (cancelled) {
          URL.revokeObjectURL(blobUrl);
          return;
        }
        if (prevBlobUrl.current) URL.revokeObjectURL(prevBlobUrl.current);
        prevBlobUrl.current = blobUrl;
        setState({ status: 'ok', url: blobUrl });
      } else {
        setState({ status: 'ok', url: httpUrl });
      }
    };

    run().catch(() => {
      if (!cancelled) setState({ status: 'error' });
    });

    return () => {
      cancelled = true;
    };
  }, [mx, mxcUrl, encInfo, useAuthentication, mimeType, enabled]);

  useEffect(
    () => () => {
      if (prevBlobUrl.current) URL.revokeObjectURL(prevBlobUrl.current);
    },
    [],
  );

  return state;
}