/// <summary>
/// Gets a bitcoin block. In case the requested block is not available in the repository it is returned
/// immediately to the caller; otherwise it obtains the block from the source provider and stores it in
/// the repository to satisfy future requests.
/// </summary>
/// <param name="hash">The block's hash that identifies the requested block.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>The requested bitcoin block.</returns>
public async Task <Block> GetBlockAsync(uint256 hash, CancellationToken cancellationToken)
{
Block?block = await BlockRepository.TryGetAsync(hash, cancellationToken).ConfigureAwait(false);
if (block is null)
{
block = await BlockSourceProvider.GetBlockAsync(hash, cancellationToken).ConfigureAwait(false);
await BlockRepository.SaveAsync(block, cancellationToken).ConfigureAwait(false);
}
return(block);
}