private void DeleteAllExpiredSessionsAndMessages()
{
CryptoChatEntities context = new CryptoChatEntities();
DateTime minAllowedLastActivityTime =
DateTime.Now.AddSeconds(-Settings.Default.HttpSessionTimeoutSeconds);
// Delete any expired chat sessions in the DB
string deleteChatSessionsSQL =
"DELETE FROM ChatSessions " +
"FROM Users u JOIN ChatSessions s " +
" ON (u.UserId = s.FromUserId or u.UserId = s.ToUserId) " +
"WHERE LastActivity < {0}";
context.ExecuteStoreCommand(deleteChatSessionsSQL,
new object[] { minAllowedLastActivityTime });
// Delete any expired messages in the DB
string deleteMessagesSQL =
"DELETE FROM Messages " +
"FROM Users u JOIN Messages m ON (u.UserId = m.ToUserId) " +
"WHERE LastActivity < {0}";
context.ExecuteStoreCommand(deleteMessagesSQL,
new object[] { minAllowedLastActivityTime });
// Send notifications about all users whose sessions were expired
var usersWithExpiredSession =
from u in context.Users
where u.LastActivity < minAllowedLastActivityTime &&
u.SessionKey != null
select u;
foreach (var user in usersWithExpiredSession)
{
user.SessionKey = null;
MobileCryptoChatService.SendMessageToAllOnlineUsers(user,
MessageType.MSG_USER_OFFLINE, "User lost connection with the server.");
}
context.SaveChanges();
}
public MessageResponse GetNextMessage(string sessionID)
{
MessageResponse messageToReturn = null;
ExecuteAndHandleExceptions(() =>
{
User user = CheckUserSession(sessionID);
CryptoChatEntities context = new CryptoChatEntities();
Message nextMsg =
(from m in context.Messages.Include("FromUser")
where m.ToUserId == user.UserId
orderby m.MsgDate
select m).FirstOrDefault();
if (nextMsg != null)
{
// A message is found --> return it as a result and delete it from DB
messageToReturn = new MessageResponse()
{
MsgType = nextMsg.MsgType,
MsgText = nextMsg.MsgText,
Msisdn = nextMsg.FromUser.MSISDN
};
context.DeleteObject(nextMsg);
context.SaveChanges();
}
else
{
// No messages are waiting --> return MSG_NO_MESSAGES
messageToReturn = new MessageResponse()
{
MsgType = MessageType.MSG_NO_MESSAGES.ToString()
};
}
});
return messageToReturn;
}
private LoginResponse LoginUser(string msisdn, string authCode)
{
LoginResponse loginResult = null;
ExecuteAndHandleExceptions(() =>
{
CheckMSISDN(msisdn);
CheckAuthCode(authCode);
// Check whether the MSISDN and authCode are correct
CryptoChatEntities context = new CryptoChatEntities();
var user =
(from u in context.Users
where u.MSISDN == msisdn && u.AuthCodeSHA1 == authCode
select u).FirstOrDefault();
if (user == null)
{
throw new ErrorResponseException(HttpStatusCode.Forbidden,
"ERR_INV_LOGIN", "Invalid MSISDN or password.");
}
// User found in the database -> perform login
user.SessionKey = GenerateNewSessionKey(user.UserId);
user.LastActivity = DateTime.Now;
context.SaveChanges();
// Delete all messages waiting at the server for the just logged user
DeleteWaitingMessagesAndSessions(user);
// Send the "user online" notification to all online users
SendMessageToAllOnlineUsers(user,
MessageType.MSG_USER_ONLINE, "User logged in the system.");
loginResult = new LoginResponse() { SessionID = user.SessionKey };
});
return loginResult;
}
private void SendMessage(User senderUser, User recipientUser,
MessageType messageType, string msgText)
{
Message msg = new Message();
msg.FromUserId = senderUser.UserId;
msg.ToUserId = recipientUser.UserId;
msg.MsgType = messageType.ToString();
msg.MsgDate = DateTime.Now;
msg.MsgText = msgText;
CryptoChatEntities context = new CryptoChatEntities();
context.Messages.AddObject(msg);
context.SaveChanges();
}
private User CheckUserSession(string sessionID)
{
CryptoChatEntities context = new CryptoChatEntities();
DateTime minAllowedLastActivityTime =
DateTime.Now.AddSeconds(-Settings.Default.HttpSessionTimeoutSeconds);
var dbUser =
(from u in context.Users
where u.SessionKey == sessionID &&
u.LastActivity >= minAllowedLastActivityTime
select u).FirstOrDefault();
if (dbUser == null)
{
// The session is either too old or does not exist
throw new ErrorResponseException(HttpStatusCode.Forbidden,
"ERR_SESSIONID", "Invalid sessionID.");
}
// The user session is valid -> update the last activity time
dbUser.LastActivity = DateTime.Now;
context.SaveChanges();
return dbUser;
}
internal static void SendMessageToAllOnlineUsers(
User senderUser, MessageType msgType, string msgText)
{
DateTime minAllowedLastActivityTime =
DateTime.Now.AddSeconds(-Settings.Default.HttpSessionTimeoutSeconds);
CryptoChatEntities context = new CryptoChatEntities();
var allUserIds =
from u in context.Users
where u.LastActivity >= minAllowedLastActivityTime
select u.UserId;
foreach (var recipientUserId in allUserIds)
{
if (senderUser.UserId != recipientUserId)
{
Message msg = new Message();
msg.FromUserId = senderUser.UserId;
msg.ToUserId = recipientUserId;
msg.MsgType = msgType.ToString();
msg.MsgText = msgText;
msg.MsgDate = DateTime.Now;
context.Messages.AddObject(msg);
}
}
context.SaveChanges();
}
public StatusResponse StartChat(string sessionID, string recipientMSISDN)
{
ExecuteAndHandleExceptions(() =>
{
User senderUser = CheckUserSession(sessionID);
CheckMSISDN(recipientMSISDN);
User recipientUser = CheckIfUserIsOnline(recipientMSISDN);
CryptoChatEntities context = new CryptoChatEntities();
// Find the existing chat session between the users
var existingChatSession =
(from s in context.ChatSessions
where s.FromUserId == senderUser.UserId && s.ToUserId == recipientUser.UserId
select s).FirstOrDefault();
if (existingChatSession == null ||
existingChatSession.ChatState != ChatSessionState.RESPONSE_SENT.ToString())
{
throw new ErrorResponseException(HttpStatusCode.NotFound,
"ERR_INVALID_STATE", "No accepted response exists from " +
recipientUser.MSISDN + " to " + senderUser.MSISDN + ".");
}
// Change the state of the chat session to "response sent"
existingChatSession.ChatState = ChatSessionState.ACTIVE.ToString();
context.SaveChanges();
// Send a notification to the recipient user (through a message)
SendMessage(senderUser, recipientUser, MessageType.MSG_START_CHAT, "Chat started");
});
return new StatusResponse();
}
public LoginResponse RegisterNewUser(string msisdn, string authCode)
{
CheckMSISDN(msisdn);
CheckAuthCode(authCode);
LoginResponse loginResult = null;
ExecuteAndHandleExceptions(() =>
{
// Register the user in the DB
CryptoChatEntities context = new CryptoChatEntities();
User user = new User();
user.MSISDN = msisdn.ToLowerInvariant();
user.AuthCodeSHA1 = authCode;
context.Users.AddObject(user);
context.SaveChanges();
// Login the user into the system after the registration
loginResult = LoginUser(msisdn, authCode);
// Send the "user online" notification to all online users
SendMessageToAllOnlineUsers(user,
MessageType.MSG_USER_ONLINE, "New user registered in the system.");
});
return loginResult;
}
public StatusResponse InviteUser(string sessionID,
string recipientMSISDN, string challenge)
{
ExecuteAndHandleExceptions(() =>
{
User senderUser = CheckUserSession(sessionID);
CheckMSISDN(recipientMSISDN);
User recipientUser = CheckIfUserIsOnline(recipientMSISDN);
CheckChallengeCode(challenge);
if (senderUser.UserId == recipientUser.UserId)
{
throw new ErrorResponseException(HttpStatusCode.NotFound,
"ERR_AUTO_CHAT", "Users cannot send chat invitations to themselves.");
}
DeleteChatSession(senderUser, recipientUser);
CryptoChatEntities context = new CryptoChatEntities();
// Create a new chat session between the users
ChatSession newChatSession = new ChatSession();
newChatSession.FromUserId = senderUser.UserId;
newChatSession.ToUserId = recipientUser.UserId;
newChatSession.ChatState = ChatSessionState.CHALLENGE_SENT.ToString();
context.ChatSessions.AddObject(newChatSession);
context.SaveChanges();
// Send the challenge to the recipient user (through a message)
SendMessage(senderUser, recipientUser, MessageType.MSG_CHALLENGE, challenge);
});
return new StatusResponse();
}