tinklu-paslaugos/Lab4/ChatRoom/ChatRoomLogic.cs

using NLog;

namespace ChatRoom;

/// <summary>
/// Chat room service logic
/// </summary>
public class ChatRoomLogic
{
    /// <summary>
    /// Background thread of deleting approved or rejected messages
    /// </summary>
    private Thread thread;
    /// <summary>
    /// Chat Room state
    /// </summary>
    private ChatRoomState state = new ChatRoomState();
    /// <summary>
    /// Logger
    /// </summary>
    private Logger log = LogManager.GetCurrentClassLogger();

    /// <summary>
    /// Chat room logic constructor
    /// </summary>
    public ChatRoomLogic()
    {
        thread = new Thread(BackgroundTask);
        thread.Start();
    }

    /// <summary>
    /// Generate the next incrementing ID
    /// </summary>
    /// <returns>Unique ID</returns>
    int NextId()
    {
        int id = state.lastUniqueId;
        state.lastUniqueId++;
        return id;
    }

    /// <summary>
    /// Register a client
    /// </summary>
    /// <param name="name">Client name</param>
    /// <returns>Client ID</returns>
    public int RegisterClient(string name)
    {
        lock (state.accessLock)
        {
            int clientId = NextId();
            state.clients.Add(new Client
            {
                id = clientId,
                name = name
            });
            log.Info($"Registered with client '{name}' with id {clientId}");
            return clientId;
        }
    }

    /// <summary>
    /// Find a client by ID, can return NULL if not found
    /// </summary>
    /// <param name="clientId">Client ID</param>
    /// <returns>Optional client object</returns>
    Client? FindClientById(int clientId)
    {
        foreach (var client in state.clients)
        {
            if (client.id == clientId)
            {
                return client;
            }
        }
        return null;
    }

    /// <summary>
    /// Find message by ID, can return NULL if not found
    /// </summary>
    /// <param name="messageId">Message ID</param>
    /// <returns>Optional message object</returns>
    Message? FindMessageById(int messageId)
    {
        foreach (var message in state.messages)
        {
            if (message.id == messageId)
            {
                return message;
            }
        }
        return null;
    }

    /// <summary>
    /// Check if client is still blocked, will clear `blockedUntil` if client became unblocked
    /// </summary>
    /// <param name="client">Client object</param>
    /// <returns>Is client blocked?</returns>
    bool GetAndUpdateBlockedState(Client client)
    {
        if (client.blockedUntil != null && DateTime.UtcNow >= client.blockedUntil)
        {
            client.blockedUntil = null;
        }

        return client.blockedUntil != null;
    }

    /// <summary>
    /// Send a message
    /// </summary>
    /// <param name="clientId">Client ID</param>
    /// <param name="contents">Message contents</param>
    /// <param name="needsToBeCensored">Does this message need to be censored?</param>
    /// <returns>Was sending the message successful, can fail if client is blocked</returns>
    public bool SendMessage(int clientId, string contents, bool needsToBeCensored)
    {
        lock (state.accessLock)
        {
            var client = FindClientById(clientId);
            if (client == null)
            {
                return false;
            }

            if (GetAndUpdateBlockedState(client))
            {
                return false;
            }

            var message = new Message
            {
                id = NextId(),
                clientId = clientId,
                contents = contents,
                needsToBeCensored = needsToBeCensored,
                status = MessageStatus.WaitingForModerator,
                sentAt = DateTime.UtcNow
            };
            state.messages.Add(message);
            log.Info($"Client '{client.name}' ({client.id}) sent message '{contents}' ({message.id}). Needs to censored: {needsToBeCensored}");
        }

        return true;
    }

    /// <summary>
    /// Get next message which isin't approved or rejected
    /// </summary>
    /// <returns>Optional message object</returns>
    public ChatRoomContract.Message? GetNewMessage()
    {
        lock (state.accessLock)
        {
            foreach (var message in state.messages)
            {
                if (message.status != MessageStatus.WaitingForModerator) continue;

                log.Info($"Message '{message.id}' given to moderator");
                message.status = MessageStatus.GivenToModerator;
                return new ChatRoomContract.Message
                {
                    id = message.id,
                    contents = message.contents,
                    needsToBeCensored = message.needsToBeCensored
                };
            }
        }

        return null;
    }

    /// <summary>
    /// Approve a message
    /// </summary>
    /// <param name="messageId">Message ID</param>
    public void ApproveMessage(int messageId)
    {
        lock (state.accessLock)
        {
            var message = FindMessageById(messageId);
            if (message == null)
            {
                return;
            }

            if (message.status != MessageStatus.GivenToModerator)
            {
                return;
            }

            message.status = MessageStatus.Approved;
            log.Info($"Message {message.id} was approved");
        }
    }

    /// <summary>
    /// Reject a message
    /// </summary>
    /// <param name="messageId">Message ID</param>
    public void RejectMessage(int messageId)
    {
        lock (state.accessLock)
        {
            var message = FindMessageById(messageId);
            if (message == null)
            {
                return;
            }

            if (message.status != MessageStatus.GivenToModerator)
            {
                return;
            }

            message.status = MessageStatus.Rejected;
            log.Info($"Message {message.id} was rejected");

            var client = FindClientById(message.clientId);
            if (client != null && !GetAndUpdateBlockedState(client))
            {
                client.strikes++;

                var rnd = new Random();
                if (client.strikes > rnd.Next(0, 10))
                {
                    log.Info($"Client '{client.name}' ({client.id}) was blocked for {client.strikes}s");
                    client.blockedUntil = DateTime.UtcNow.AddSeconds(client.strikes);
                    client.strikes = 0;
                }
            }
        }
    }

    /// <summary>
    /// Get number of strikes a client has
    /// </summary>
    /// <param name="clientId">Client ID</param>
    /// <returns>Number of strikes</returns>
    public int GetStrikes(int clientId)
    {
        lock (state.accessLock)
        {
            var client = FindClientById(clientId);
            if (client == null)
            {
                return 0;
            }

            return client.strikes;
        }
    }

    /// <summary>
    /// Get timestamp until when the client is blocked
    /// </summary>
    /// <param name="clientId">Client ID</param>
    /// <returns>Optional datetime object</returns>
    public DateTime? GetBlockedUntil(int clientId)
    {
        lock (state.accessLock)
        {
            var client = FindClientById(clientId);
            if (client == null)
            {
                return null;
            }

            return client.blockedUntil;
        }
    }

    /// <summary>
    /// Main loop for background thread. Used for deleting approved or rejected messages.
    /// </summary>
    public void BackgroundTask()
    {
        while (true)
        {
            lock (state.accessLock)
            {
                var now = DateTime.UtcNow;
                int count = state.messages.RemoveAll(msg =>
                    (now - msg.sentAt).TotalSeconds > 5 &&
                    (msg.status == MessageStatus.Approved || msg.status == MessageStatus.Rejected)
                );
                log.Info($"Running periodic cleanup, removed {count} messages");
            }

            Thread.Sleep(10 * 1000);
        }
    }
}