private IReadOnlyList <IReadOnlyCollection <Message.Attachment> > ChunkAttachmentsOrThrow(
IReadOnlyList <Message.Attachment> attachments, int sizeThreshold)
{
// Splits a list of attachments into "chunks" of at most 8MB each
// If any individual attachment is larger than 8MB, will throw an error
var chunks = new List <List <Message.Attachment> >();
var list = new List <Message.Attachment>();
// sizeThreshold is in MB (user-readable)
var bytesThreshold = sizeThreshold * 1024 * 1024;
foreach (var attachment in attachments)
{
if (attachment.Size >= bytesThreshold)
{
throw Errors.AttachmentTooLarge(sizeThreshold);
}
if (list.Sum(a => a.Size) + attachment.Size >= bytesThreshold)
{
chunks.Add(list);
list = new List <Message.Attachment>();
}
list.Add(attachment);
}
if (list.Count > 0)
{
chunks.Add(list);
}
return(chunks);
}