using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using LittleShop.Data;
using LittleShop.Models;
using LittleShop.DTOs;
using LittleShop.Enums;

namespace LittleShop.Services;

public interface IMessageDeliveryService
{
    Task<bool> QueueRecoveryMessageAsync(long telegramUserId, string message);
}

public interface IBotContactService
{
    Task<BotContact> RecordContactAsync(Guid botId, TelegramUserDto user);
    Task<IEnumerable<BotContact>> GetBotContactsAsync(Guid botId, bool activeOnly = true);
    Task<IEnumerable<BotContact>> GetOrphanedContactsAsync(Guid failedBotId);
    Task<bool> MigrateContactsAsync(Guid fromBotId, Guid toBotId);
    Task<BotContactRecoveryDto> PrepareContactRecoveryAsync(Guid failedBotId);
    Task<bool> NotifyContactOfBotChangeAsync(long telegramUserId, string newBotUsername);
    Task<ContactBackupDto> CreateContactBackupAsync(Guid botId);
    Task<bool> RestoreContactsFromBackupAsync(Guid toBotId, ContactBackupDto backup);
}

public class BotContactService : IBotContactService
{
    private readonly LittleShopContext _context;
    private readonly ILogger<BotContactService> _logger;
    private readonly IMessageDeliveryService _messageService;

    public BotContactService(
        LittleShopContext context,
        ILogger<BotContactService> logger,
        IMessageDeliveryService messageService)
    {
        _context = context;
        _logger = logger;
        _messageService = messageService;
    }

    public async Task<BotContact> RecordContactAsync(Guid botId, TelegramUserDto user)
    {
        var existingContact = await _context.BotContacts
            .FirstOrDefaultAsync(c => c.BotId == botId && c.TelegramUserId == user.Id);

        if (existingContact != null)
        {
            // Update existing contact
            existingContact.TelegramUsername = user.Username ?? string.Empty;
            existingContact.DisplayName = $"{user.FirstName} {user.LastName}".Trim();
            existingContact.FirstName = user.FirstName ?? string.Empty;
            existingContact.LastName = user.LastName ?? string.Empty;
            existingContact.LastContactDate = DateTime.UtcNow;
            existingContact.TotalInteractions++;
            existingContact.UpdatedAt = DateTime.UtcNow;

            _context.BotContacts.Update(existingContact);
        }
        else
        {
            // Create new contact record
            existingContact = new BotContact
            {
                Id = Guid.NewGuid(),
                BotId = botId,
                TelegramUserId = user.Id,
                TelegramUsername = user.Username ?? string.Empty,
                DisplayName = $"{user.FirstName} {user.LastName}".Trim(),
                FirstName = user.FirstName ?? string.Empty,
                LastName = user.LastName ?? string.Empty,
                FirstContactDate = DateTime.UtcNow,
                LastContactDate = DateTime.UtcNow,
                TotalInteractions = 1,
                LastKnownLanguage = user.LanguageCode ?? "en",
                Status = ContactStatus.Active,
                CreatedAt = DateTime.UtcNow,
                UpdatedAt = DateTime.UtcNow,
                IsActive = true
            };

            await _context.BotContacts.AddAsync(existingContact);
        }

        await _context.SaveChangesAsync();
        _logger.LogInformation("Recorded contact {UserId} for bot {BotId}", user.Id, botId);

        return existingContact;
    }

    public async Task<IEnumerable<BotContact>> GetBotContactsAsync(Guid botId, bool activeOnly = true)
    {
        var query = _context.BotContacts.Where(c => c.BotId == botId);

        if (activeOnly)
            query = query.Where(c => c.IsActive && c.Status == ContactStatus.Active);

        return await query
            .OrderByDescending(c => c.LastContactDate)
            .ToListAsync();
    }

    public async Task<IEnumerable<BotContact>> GetOrphanedContactsAsync(Guid failedBotId)
    {
        // Get contacts from failed bot that haven't been recovered yet
        return await _context.BotContacts
            .Where(c => c.BotId == failedBotId &&
                       c.Status == ContactStatus.Active &&
                       !c.IsRecovered)
            .OrderByDescending(c => c.TotalInteractions) // Prioritize most active users
            .ToListAsync();
    }

    public async Task<bool> MigrateContactsAsync(Guid fromBotId, Guid toBotId)
    {
        try
        {
            var contactsToMigrate = await GetOrphanedContactsAsync(fromBotId);
            var toBot = await _context.Bots.FindAsync(toBotId);

            if (toBot == null)
            {
                _logger.LogError("Target bot {BotId} not found", toBotId);
                return false;
            }

            foreach (var contact in contactsToMigrate)
            {
                // Create new contact record for new bot
                var newContact = new BotContact
                {
                    Id = Guid.NewGuid(),
                    BotId = toBotId,
                    TelegramUserId = contact.TelegramUserId,
                    TelegramUsername = contact.TelegramUsername,
                    DisplayName = contact.DisplayName,
                    FirstName = contact.FirstName,
                    LastName = contact.LastName,
                    FirstContactDate = DateTime.UtcNow,
                    LastContactDate = DateTime.UtcNow,
                    TotalInteractions = 0, // Reset for new bot
                    LastKnownLanguage = contact.LastKnownLanguage,
                    Status = ContactStatus.Recovered,
                    CustomerId = contact.CustomerId,
                    IsRecovered = true,
                    RecoveredFromBotId = fromBotId,
                    RecoveredAt = DateTime.UtcNow,
                    CreatedAt = DateTime.UtcNow,
                    UpdatedAt = DateTime.UtcNow,
                    IsActive = true,
                    Preferences = contact.Preferences,
                    Notes = $"Migrated from bot {fromBotId} on {DateTime.UtcNow:yyyy-MM-dd}"
                };

                await _context.BotContacts.AddAsync(newContact);

                // Mark original contact as migrated
                contact.Status = ContactStatus.Migrated;
                contact.IsRecovered = true;
                contact.UpdatedAt = DateTime.UtcNow;
                _context.BotContacts.Update(contact);

                _logger.LogInformation("Migrated contact {UserId} from bot {FromBot} to {ToBot}",
                    contact.TelegramUserId, fromBotId, toBotId);
            }

            await _context.SaveChangesAsync();
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to migrate contacts from {FromBot} to {ToBot}", fromBotId, toBotId);
            return false;
        }
    }

    public async Task<BotContactRecoveryDto> PrepareContactRecoveryAsync(Guid failedBotId)
    {
        var orphanedContacts = await GetOrphanedContactsAsync(failedBotId);
        var failedBot = await _context.Bots.FindAsync(failedBotId);
        var availableBots = await _context.Bots
            .Where(b => b.Id != failedBotId && b.Status == BotStatus.Active)
            .ToListAsync();

        return new BotContactRecoveryDto
        {
            FailedBotId = failedBotId,
            FailedBotName = failedBot?.Name ?? "Unknown",
            OrphanedContactCount = orphanedContacts.Count(),
            HighValueContacts = orphanedContacts
                .Where(c => c.TotalInteractions > 10 || c.CustomerId != null)
                .Count(),
            AvailableRecoveryBots = availableBots.Select(b => new BotInfoDto
            {
                Id = b.Id,
                Name = b.Name,
                Status = b.Status.ToString(),
                CurrentContactCount = _context.BotContacts.Count(c => c.BotId == b.Id && c.IsActive)
            }).ToList(),
            ContactDetails = orphanedContacts.Select(c => new ContactSummaryDto
            {
                TelegramUserId = c.TelegramUserId,
                Username = c.TelegramUsername,
                DisplayName = c.DisplayName,
                TotalInteractions = c.TotalInteractions,
                LastContactDate = c.LastContactDate,
                IsCustomer = c.CustomerId != null
            }).ToList()
        };
    }

    public async Task<bool> NotifyContactOfBotChangeAsync(long telegramUserId, string newBotUsername)
    {
        try
        {
            // This would integrate with the message delivery service
            var message = $"Hello! Your previous bot is temporarily unavailable. " +
                         $"Please continue your conversation with our new bot: @{newBotUsername} " +
                         $"All your order history and preferences have been preserved.";

            // Queue message for delivery when user contacts new bot
            await _messageService.QueueRecoveryMessageAsync(telegramUserId, message);

            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to notify user {UserId} of bot change", telegramUserId);
            return false;
        }
    }

    public async Task<ContactBackupDto> CreateContactBackupAsync(Guid botId)
    {
        var contacts = await GetBotContactsAsync(botId, activeOnly: false);
        var bot = await _context.Bots.FindAsync(botId);

        return new ContactBackupDto
        {
            BackupId = Guid.NewGuid(),
            BotId = botId,
            BotName = bot?.Name ?? "Unknown",
            BackupDate = DateTime.UtcNow,
            ContactCount = contacts.Count(),
            Contacts = contacts.Select(c => new ContactExportDto
            {
                TelegramUserId = c.TelegramUserId,
                TelegramUsername = c.TelegramUsername,
                DisplayName = c.DisplayName,
                FirstName = c.FirstName,
                LastName = c.LastName,
                FirstContactDate = c.FirstContactDate,
                LastContactDate = c.LastContactDate,
                TotalInteractions = c.TotalInteractions,
                LastKnownLanguage = c.LastKnownLanguage,
                Status = c.Status.ToString(),
                CustomerId = c.CustomerId,
                Preferences = c.Preferences,
                Notes = c.Notes
            }).ToList()
        };
    }

    public async Task<bool> RestoreContactsFromBackupAsync(Guid toBotId, ContactBackupDto backup)
    {
        try
        {
            foreach (var contactData in backup.Contacts)
            {
                // Check if contact already exists for this bot
                var existingContact = await _context.BotContacts
                    .FirstOrDefaultAsync(c => c.BotId == toBotId &&
                                             c.TelegramUserId == contactData.TelegramUserId);

                if (existingContact == null)
                {
                    var newContact = new BotContact
                    {
                        Id = Guid.NewGuid(),
                        BotId = toBotId,
                        TelegramUserId = contactData.TelegramUserId,
                        TelegramUsername = contactData.TelegramUsername,
                        DisplayName = contactData.DisplayName,
                        FirstName = contactData.FirstName,
                        LastName = contactData.LastName,
                        FirstContactDate = contactData.FirstContactDate,
                        LastContactDate = contactData.LastContactDate,
                        TotalInteractions = contactData.TotalInteractions,
                        LastKnownLanguage = contactData.LastKnownLanguage,
                        Status = Enum.Parse<ContactStatus>(contactData.Status),
                        CustomerId = contactData.CustomerId,
                        IsRecovered = true,
                        RecoveredFromBotId = backup.BotId,
                        RecoveredAt = DateTime.UtcNow,
                        CreatedAt = DateTime.UtcNow,
                        UpdatedAt = DateTime.UtcNow,
                        IsActive = true,
                        Preferences = contactData.Preferences,
                        Notes = $"Restored from backup {backup.BackupId} on {DateTime.UtcNow:yyyy-MM-dd}"
                    };

                    await _context.BotContacts.AddAsync(newContact);
                }
            }

            await _context.SaveChangesAsync();
            _logger.LogInformation("Restored {Count} contacts from backup to bot {BotId}",
                backup.Contacts.Count, toBotId);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to restore contacts from backup");
            return false;
        }
    }
}

// DTOs for contact management
public class TelegramUserDto
{
    public long Id { get; set; }
    public string? Username { get; set; }
    public string? FirstName { get; set; }
    public string? LastName { get; set; }
    public string? LanguageCode { get; set; }
}

public class BotContactRecoveryDto
{
    public Guid FailedBotId { get; set; }
    public string FailedBotName { get; set; } = string.Empty;
    public int OrphanedContactCount { get; set; }
    public int HighValueContacts { get; set; }
    public List<BotInfoDto> AvailableRecoveryBots { get; set; } = new();
    public List<ContactSummaryDto> ContactDetails { get; set; } = new();
}

public class BotInfoDto
{
    public Guid Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string Status { get; set; } = string.Empty;
    public int CurrentContactCount { get; set; }
}

public class ContactSummaryDto
{
    public long TelegramUserId { get; set; }
    public string Username { get; set; } = string.Empty;
    public string DisplayName { get; set; } = string.Empty;
    public int TotalInteractions { get; set; }
    public DateTime LastContactDate { get; set; }
    public bool IsCustomer { get; set; }
}

public class ContactBackupDto
{
    public Guid BackupId { get; set; }
    public Guid BotId { get; set; }
    public string BotName { get; set; } = string.Empty;
    public DateTime BackupDate { get; set; }
    public int ContactCount { get; set; }
    public List<ContactExportDto> Contacts { get; set; } = new();
}

public class ContactExportDto
{
    public long TelegramUserId { get; set; }
    public string TelegramUsername { get; set; } = string.Empty;
    public string DisplayName { get; set; } = string.Empty;
    public string FirstName { get; set; } = string.Empty;
    public string LastName { get; set; } = string.Empty;
    public DateTime FirstContactDate { get; set; }
    public DateTime LastContactDate { get; set; }
    public int TotalInteractions { get; set; }
    public string LastKnownLanguage { get; set; } = string.Empty;
    public string Status { get; set; } = string.Empty;
    public Guid? CustomerId { get; set; }
    public string? Preferences { get; set; }
    public string? Notes { get; set; }
}