/// <summary>
/// Every 30s queries mail server for new email.
/// When there are new emails available it first download all mail headers and publishes them to the stream.
/// Afterwards start downloading all mail content for just downloaded mail headers.
/// </summary>
/// <param name="cancel"></param>
/// <returns></returns>
private async Task RunCheckForNewMailAsyncLoop(CancellationToken cancel)
{
// Create mail client.
IMailClient client = (new TrivialMailDllFactory()).Build(_serverType);
try
{
// Publish Connecting state.
_controllerStateStream.OnNext(ControllerState.Connecting);
client.Connect(_serverEncryption, _host);
// Publish LoggingIn state.
_controllerStateStream.OnNext(ControllerState.LoggingIn);
client.Login(_user, _password);
// Publish Connected state.
_controllerStateStream.OnNext(ControllerState.Connected);
// Main loop
while (!cancel.IsCancellationRequested)
{
// If disconnect or not encrypted (when should be) then reconnect.
if (client.IsConnected && (_serverEncryption == MailServerEncryption.Unencrypted || client.IsEncrypted))
{
// MailHeaderList contains new headers which will be published to subscribers.
List <MailHeaderEntity> mailHeaderEntities = new List <MailHeaderEntity>();
using (IMailStorage <MailHeaderEntity> storage = _mailHeaderStorageFactory())
{
// 1. Get from mail server all uids (emails).
// ToDo: for Imap this could be improved.
List <string> newUids = client.GetAllUids().ToList();
// 2. Distinct list of uids which are not yet stored in the database.
// Let's reverse and start checking with the most recent email (the latest uid).
newUids.Reverse();
List <string> uidList = new List <string>();
foreach (var uid in newUids)
{
if (!storage.Exists(x => x.Uid == uid))
{
uidList.Add(uid);
}
else
{
break;
}
// Note: if any first exists, break the loop other emails are probably downloaded.
}
if (uidList.Count > 0)
{
// 3. Download mail headers.
foreach (var uid in uidList)
{
// Download message header.
var header = client.GetHeadersByUid(uid);
// Note: MailDll documentation states that header can be null.
if (header == null)
{
throw new ArgumentNullException(nameof(header), $"Downloaded an empty email header ({uid}).");
}
var email = new MailBuilder().CreateFromEml(header);
var emailFrom = email?.From.FirstOrDefault();
var mailHeaderEntity = new MailHeaderEntity()
{
Uid = uid,
Date = email?.Date ?? DateTime.MinValue,
Subject = email?.Subject,
MailFromEntity = new MailFromEntity()
{
Address = emailFrom?.Address,
Name = emailFrom?.Name,
LocalPart = emailFrom?.LocalPart,
DomainPart = emailFrom?.DomainPart
}
};
mailHeaderEntities.Add(mailHeaderEntity);
}
// 4. Insert all new mail headers into the storage.
storage.Insert(mailHeaderEntities);
}
}
// For all new email headers publish them to the subscribers and download the content.
// Note: This whole block is taken out from above using() to release storage handle asap.
if (mailHeaderEntities.Count > 0)
{
// 5. Publish all new mail headers to the stream.
mailHeaderEntities.ForEach(mailHeaderEntity => { _mailHeaderStream.OnNext(new MailHeader(mailHeaderEntity)); });
// 6. Start downloading content loop
// It's not done in above foreach loop to not to keep storage open for too long
// when running over slow internet connection.
RunDownloadContentAsyncLoop(cancel, mailHeaderEntities.Select(x => x.Uid).ToList());
}
}
else
{
break;
}
// Check for new email again in 30s
await Observable.Return(0).Delay(TimeSpan.FromSeconds(30), Scheduler.CurrentThread).ToTask(cancel);
}
}
catch (Exception e)
{
Logger.Error(e, $"RunCheckForNewMailAsyncLoop");
}
finally
{
client?.Close();
if (!cancel.IsCancellationRequested)
{
// Publish Disconnected state.
_controllerStateStream.OnNext(ControllerState.Disconnected);
}
}
}