ChatBot/ChatBot/Models/ChatSession.cs

using ChatBot.Models.Dto;

namespace ChatBot.Models
{
    /// <summary>
    /// Represents a chat session with message history and AI parameters
    /// </summary>
    public class ChatSession
    {
        private readonly object _lock = new object();
        private readonly List<ChatMessage> _messageHistory = new List<ChatMessage>();

        /// <summary>
        /// Unique identifier for the chat session
        /// </summary>
        public string SessionId { get; set; } = Guid.NewGuid().ToString();

        /// <summary>
        /// Telegram chat ID (can be private chat or group chat)
        /// </summary>
        public long ChatId { get; set; }

        /// <summary>
        /// Chat type (private, group, supergroup, channel)
        /// </summary>
        public string ChatType { get; set; } = "private";

        /// <summary>
        /// Chat title (for groups)
        /// </summary>
        public string ChatTitle { get; set; } = string.Empty;

        /// <summary>
        /// AI model to use for this session
        /// </summary>
        public string Model { get; set; } = string.Empty;

        /// <summary>
        /// When the session was created
        /// </summary>
        public DateTime CreatedAt { get; set; } = DateTime.UtcNow;

        /// <summary>
        /// When the session was last updated
        /// </summary>
        public DateTime LastUpdatedAt { get; set; } = DateTime.UtcNow;

        /// <summary>
        /// Maximum number of messages to keep in history
        /// </summary>
        public int MaxHistoryLength { get; set; } = 20;

        /// <summary>
        /// Add a message to the history and manage history length (thread-safe)
        /// </summary>
        public void AddMessage(ChatMessage message)
        {
            lock (_lock)
            {
                _messageHistory.Add(message);
                LastUpdatedAt = DateTime.UtcNow;

                // Trim history if it exceeds max length
                if (_messageHistory.Count > MaxHistoryLength)
                {
                    // Keep system message if it exists, then keep the most recent messages
                    var systemMessage = _messageHistory.FirstOrDefault(m => m.Role == "system");
                    var recentMessages = _messageHistory
                        .Where(m => m.Role != "system")
                        .TakeLast(MaxHistoryLength - (systemMessage != null ? 1 : 0))
                        .ToList();

                    _messageHistory.Clear();
                    if (systemMessage != null)
                    {
                        _messageHistory.Add(systemMessage);
                    }
                    _messageHistory.AddRange(recentMessages);
                }
            }
        }

        /// <summary>
        /// Add a user message with username information
        /// </summary>
        public void AddUserMessage(string content, string username)
        {
            var message = new ChatMessage
            {
                Role = "user",
                Content = ChatType == "private" ? content : $"{username}: {content}",
            };
            AddMessage(message);
        }

        /// <summary>
        /// Add an assistant message
        /// </summary>
        public void AddAssistantMessage(string content)
        {
            var message = new ChatMessage { Role = "assistant", Content = content };
            AddMessage(message);
        }

        /// <summary>
        /// Get all messages (thread-safe)
        /// </summary>
        public List<ChatMessage> GetAllMessages()
        {
            lock (_lock)
            {
                return new List<ChatMessage>(_messageHistory);
            }
        }

        /// <summary>
        /// Get the count of messages in history (thread-safe)
        /// </summary>
        public int GetMessageCount()
        {
            lock (_lock)
            {
                return _messageHistory.Count;
            }
        }

        /// <summary>
        /// Clear message history (thread-safe)
        /// </summary>
        public void ClearHistory()
        {
            lock (_lock)
            {
                _messageHistory.Clear();
                LastUpdatedAt = DateTime.UtcNow;
            }
        }
    }
}