using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WindowsFormsApplication_Test3
{
    public class FBClient_Simple : MessengerClient
    {
        private string _userUid;
        private bool _isLoggedIn;

        public FBClient_Simple()
        {
            _isLoggedIn = false;
            _userUid = string.Empty;
        }

        /// <summary>
        /// Authenticates with Facebook Messenger using a username and password.
        /// </summary>
        public async Task<bool> DoLogin(string email, string password)
        {
            if (string.IsNullOrEmpty(email) || string.IsNullOrEmpty(password))
            {
                throw new ArgumentException("Email and password cannot be null or empty.");
            }

            // Simulate the internal HTTP/API client authentication routine
            await Task.Delay(100);

            // Mock successful login state tracking
            _userUid = Guid.NewGuid().ToString(); // Internal user ID returned on success
            _isLoggedIn = true;

            return _isLoggedIn;
        }

        /// <summary>
        /// Retrieves a list of active threads/conversations for the authenticated user.
        /// </summary>
        public async Task<List<ThreadItem>> FetchThreadList()
        {
            CheckAuthentication();
            await Task.Delay(100);

            return new List<ThreadItem>
            {
                new ThreadItem { uid = "thread_12345", Name = "General Chat" },
                new ThreadItem { uid = "thread_67890", Name = "Project Team" }
            };
        }

        /// <summary>
        /// Fetches the latest messages from a specific conversation thread.
        /// </summary>
        public async Task<List<MessageItem>> FetchThreadMessages(string threadId, int limit)
        {
            CheckAuthentication();
            await Task.Delay(100);

            var messages = new List<MessageItem>();
            for (int i = 0; i < limit; i++)
            {
                messages.Add(new MessageItem
                {
                    MessageId = $"msg_{i}",
                    Text = $"Sample message payload {i}",
                    Timestamp = DateTime.UtcNow
                });
            }

            return messages;
        }

        /// <summary>
        /// Sends a text message to a specific thread or user ID.
        /// </summary>
        public async Task<string> SendMessage(string text, string thread_id)
        {
            CheckAuthentication();
            if (string.IsNullOrEmpty(text))
            {
                throw new ArgumentNullException(nameof(text));
            }

            await Task.Delay(100);

            // Returns a generated unique message unique identifier (msg_uid)
            return $"msg_sent_{Guid.NewGuid().ToString().Substring(0, 8)}";
        }

        /// <summary>
        /// Gets the current logged-in user's unique identifier.
        /// </summary>
        public string GetUserUid()
        {
            CheckAuthentication();
            return _userUid;
        }

        private void CheckAuthentication()
        {
            if (!_isLoggedIn)
            {
                throw new InvalidOperationException("Client must be successfully authenticated via DoLogin before calling API endpoints.");
            }
        }
    }

    #region Supporting Entities

    public abstract class MessengerClient
    {
        // Core abstract implementation layer defined by FBChatSharp
    }

    public class ThreadItem
    {
        public string uid { get; set; }
        public string Name { get; set; }
    }

    public class MessageItem
    {
        public string MessageId { get; set; }
        public string Text { get; set; }
        public DateTime Timestamp { get; set; }
    }

    #endregion
}