using System.Net.Http.Headers;
using System.Text.Json;
using System.Text.Json.Serialization;
using Lagerbestand.Data;
using Lagerbestand.Models;
using Microsoft.EntityFrameworkCore;

namespace Lagerbestand.Services;

/// <summary>
/// Result of a Lexware customer sync operation
/// </summary>
public class LexwareSyncResult
{
    public bool Success { get; set; }
    public string Message { get; set; } = string.Empty;
    public int CustomersCreated { get; set; }
    public int CustomersUpdated { get; set; }
    public int CustomersDeactivated { get; set; }
    public int TotalProcessed { get; set; }
}

/// <summary>
/// Lexware API contact response models
/// </summary>
public class LexwareContactsResponse
{
    [JsonPropertyName("content")]
    public List<LexwareContact> Content { get; set; } = new();

    [JsonPropertyName("totalPages")]
    public int TotalPages { get; set; }

    [JsonPropertyName("totalElements")]
    public int TotalElements { get; set; }

    [JsonPropertyName("last")]
    public bool Last { get; set; }

    [JsonPropertyName("number")]
    public int Number { get; set; }
}

public class LexwareContact
{
    [JsonPropertyName("id")]
    public string Id { get; set; } = string.Empty;

    [JsonPropertyName("organizationId")]
    public string? OrganizationId { get; set; }

    [JsonPropertyName("version")]
    public int Version { get; set; }

    [JsonPropertyName("roles")]
    public LexwareRoles? Roles { get; set; }

    [JsonPropertyName("company")]
    public LexwareCompany? Company { get; set; }

    [JsonPropertyName("person")]
    public LexwarePerson? Person { get; set; }

    [JsonPropertyName("addresses")]
    public LexwareAddresses? Addresses { get; set; }

    [JsonPropertyName("emailAddresses")]
    public LexwareEmailAddresses? EmailAddresses { get; set; }

    [JsonPropertyName("phoneNumbers")]
    public LexwarePhoneNumbers? PhoneNumbers { get; set; }

    [JsonPropertyName("note")]
    public string? Note { get; set; }

    [JsonPropertyName("archived")]
    public bool Archived { get; set; }
}

public class LexwareRoles
{
    [JsonPropertyName("customer")]
    public LexwareCustomerRole? Customer { get; set; }
}

public class LexwareCustomerRole
{
    [JsonPropertyName("number")]
    public long? Number { get; set; }
}

public class LexwareCompany
{
    [JsonPropertyName("name")]
    public string? Name { get; set; }
}

public class LexwarePerson
{
    [JsonPropertyName("salutation")]
    public string? Salutation { get; set; }

    [JsonPropertyName("firstName")]
    public string? FirstName { get; set; }

    [JsonPropertyName("lastName")]
    public string? LastName { get; set; }
}

public class LexwareAddresses
{
    [JsonPropertyName("billing")]
    public List<LexwareAddress>? Billing { get; set; }
}

public class LexwareAddress
{
    [JsonPropertyName("street")]
    public string? Street { get; set; }

    [JsonPropertyName("zip")]
    public string? Zip { get; set; }

    [JsonPropertyName("city")]
    public string? City { get; set; }

    [JsonPropertyName("countryCode")]
    public string? CountryCode { get; set; }
}

public class LexwareEmailAddresses
{
    [JsonPropertyName("business")]
    public List<string>? Business { get; set; }

    [JsonPropertyName("private")]
    public List<string>? Private { get; set; }

    [JsonPropertyName("other")]
    public List<string>? Other { get; set; }
}

public class LexwarePhoneNumbers
{
    [JsonPropertyName("business")]
    public List<string>? Business { get; set; }

    [JsonPropertyName("private")]
    public List<string>? Private { get; set; }

    [JsonPropertyName("mobile")]
    public List<string>? Mobile { get; set; }
}

public interface ILexwareSyncService
{
    /// <summary>
    /// Tests the API connection with the given settings
    /// </summary>
    Task<(bool Success, string Message)> TestConnectionAsync(LexwareApiSettings settings);

    /// <summary>
    /// Syncs customers from Lexware API to the local database
    /// </summary>
    Task<LexwareSyncResult> SyncCustomersAsync(CancellationToken cancellationToken = default);
}

public class LexwareSyncService : ILexwareSyncService
{
    private readonly AppDbContext _context;
    private readonly ISiteSettingsService _siteSettingsService;
    private readonly ICustomerService _customerService;
    private readonly ILogger<LexwareSyncService> _logger;
    private readonly IHttpClientFactory _httpClientFactory;

    public LexwareSyncService(
        AppDbContext context,
        ISiteSettingsService siteSettingsService,
        ICustomerService customerService,
        ILogger<LexwareSyncService> logger,
        IHttpClientFactory httpClientFactory)
    {
        _context = context;
        _siteSettingsService = siteSettingsService;
        _customerService = customerService;
        _logger = logger;
        _httpClientFactory = httpClientFactory;
    }

    public async Task<(bool Success, string Message)> TestConnectionAsync(LexwareApiSettings settings)
    {
        if (!settings.IsConfigured)
            return (false, "API URL und API-Key müssen konfiguriert sein.");

        try
        {
            using var client = CreateHttpClient(settings);
            var response = await client.GetAsync("contacts?page=0&size=1");

            if (response.IsSuccessStatusCode)
            {
                var json = await response.Content.ReadAsStringAsync();
                var result = JsonSerializer.Deserialize<LexwareContactsResponse>(json);
                return (true, $"Verbindung erfolgreich! {result?.TotalElements ?? 0} Kontakte gefunden.");
            }

            return response.StatusCode switch
            {
                System.Net.HttpStatusCode.Unauthorized => (false, "Authentifizierung fehlgeschlagen. Bitte API-Key prüfen."),
                System.Net.HttpStatusCode.Forbidden => (false, "Zugriff verweigert. API-Key hat keine ausreichenden Berechtigungen."),
                System.Net.HttpStatusCode.NotFound => (false, "API-Endpunkt nicht gefunden. Bitte URL prüfen."),
                _ => (false, $"API-Fehler: {response.StatusCode} - {await response.Content.ReadAsStringAsync()}")
            };
        }
        catch (HttpRequestException ex)
        {
            return (false, $"Verbindungsfehler: {ex.Message}");
        }
        catch (TaskCanceledException)
        {
            return (false, "Zeitüberschreitung bei der Verbindung.");
        }
        catch (Exception ex)
        {
            return (false, $"Fehler: {ex.Message}");
        }
    }

    public async Task<LexwareSyncResult> SyncCustomersAsync(CancellationToken cancellationToken = default)
    {
        var settings = await _siteSettingsService.GetLexwareApiSettingsAsync();

        if (!settings.IsEnabled || !settings.IsConfigured)
        {
            return new LexwareSyncResult
            {
                Success = false,
                Message = "Lexware API ist nicht konfiguriert oder deaktiviert."
            };
        }

        var result = new LexwareSyncResult();

        try
        {
            _logger.LogInformation("Starting Lexware customer sync...");

            using var client = CreateHttpClient(settings);
            var allContacts = new List<LexwareContact>();

            // Fetch all pages of customers
            var page = 0;
            bool lastPage = false;
            while (!lastPage)
            {
                cancellationToken.ThrowIfCancellationRequested();

                var response = await client.GetAsync($"contacts?page={page}&size=250&customer=true", cancellationToken);
                response.EnsureSuccessStatusCode();

                var json = await response.Content.ReadAsStringAsync(cancellationToken);
                var pageResult = JsonSerializer.Deserialize<LexwareContactsResponse>(json);

                if (pageResult?.Content != null)
                {
                    // Only include contacts with customer role that are not archived
                    allContacts.AddRange(pageResult.Content.Where(c => !c.Archived));
                }

                lastPage = pageResult?.Last ?? true;
                page++;
            }

            _logger.LogInformation("Fetched {Count} customer contacts from Lexware", allContacts.Count);

            // Get all existing customers indexed by CustomerNumber (include inactive for reactivation)
            var existingCustomers = await _context.Customers
                .Include(c => c.Vehicles.Where(v => v.IsActive))
                .ToListAsync(cancellationToken);

            var customersByNumber = existingCustomers
                .Where(c => !string.IsNullOrEmpty(c.CustomerNumber))
                .ToDictionary(c => c.CustomerNumber, c => c);

            foreach (var contact in allContacts)
            {
                result.TotalProcessed++;

                var customerNumber = contact.Roles?.Customer?.Number?.ToString() ?? "";
                if (string.IsNullOrEmpty(customerNumber))
                    continue;

                var firstName = contact.Person?.FirstName?.Trim() ?? "";
                var lastName = contact.Person?.LastName?.Trim() ?? "";

                // Skip contacts without a name
                if (string.IsNullOrEmpty(firstName) && string.IsNullOrEmpty(lastName))
                {
                    // Use company name as last name fallback
                    if (!string.IsNullOrEmpty(contact.Company?.Name))
                    {
                        lastName = contact.Company.Name;
                    }
                    else
                    {
                        continue;
                    }
                }

                var company = contact.Company?.Name?.Trim();
                var phone = GetFirstPhone(contact.PhoneNumbers);
                var email = GetFirstEmail(contact.EmailAddresses);
                var notes = contact.Note?.Trim();

                if (customersByNumber.TryGetValue(customerNumber, out var existing))
                {
                    // Update existing customer
                    bool changed = false;

                    if (existing.FirstName != firstName) { existing.FirstName = firstName; changed = true; }
                    if (existing.LastName != lastName) { existing.LastName = lastName; changed = true; }
                    if (existing.Company != company) { existing.Company = company; changed = true; }
                    if (existing.Phone != phone) { existing.Phone = phone; changed = true; }
                    if (existing.Email != email) { existing.Email = email; changed = true; }
                    if (existing.Notes != notes) { existing.Notes = notes; changed = true; }

                    // Reactivate if previously deactivated
                    if (!existing.IsActive) { existing.IsActive = true; changed = true; }

                    if (changed)
                    {
                        existing.UpdatedAt = DateTime.UtcNow;
                        _context.Customers.Update(existing);
                        result.CustomersUpdated++;
                    }
                }
                else
                {
                    // Create new customer
                    var newCustomer = new Customer
                    {
                        CustomerNumber = customerNumber,
                        FirstName = string.IsNullOrEmpty(firstName) ? "-" : firstName,
                        LastName = string.IsNullOrEmpty(lastName) ? "-" : lastName,
                        Company = company,
                        Phone = phone,
                        Email = email,
                        Notes = notes,
                        IsActive = true,
                        CreatedAt = DateTime.UtcNow
                    };

                    _context.Customers.Add(newCustomer);
                    result.CustomersCreated++;
                }
            }

            await _context.SaveChangesAsync(cancellationToken);

            // Deactivate customers not found in Lexware (Lexware is single source of truth)
            var lexwareCustomerNumbers = allContacts
                .Select(c => c.Roles?.Customer?.Number?.ToString())
                .Where(n => !string.IsNullOrEmpty(n))
                .ToHashSet();

            var customersToDeactivate = await _context.Customers
                .Where(c => c.IsActive && !string.IsNullOrEmpty(c.CustomerNumber) && !lexwareCustomerNumbers.Contains(c.CustomerNumber))
                .ToListAsync(cancellationToken);

            foreach (var customer in customersToDeactivate)
            {
                customer.IsActive = false;
                customer.UpdatedAt = DateTime.UtcNow;
                result.CustomersDeactivated++;
                _logger.LogWarning("Customer {CustomerNumber} ({Name}) deactivated - not found in Lexware",
                    customer.CustomerNumber, customer.FullName);
            }

            if (customersToDeactivate.Count > 0)
                await _context.SaveChangesAsync(cancellationToken);

            // Update sync timestamp
            settings.LastSyncAt = DateTime.UtcNow;
            settings.LastSyncCount = result.TotalProcessed;
            settings.LastSyncResult = $"{result.CustomersCreated} erstellt, {result.CustomersUpdated} aktualisiert, {result.CustomersDeactivated} deaktiviert";
            await _siteSettingsService.SaveLexwareApiSettingsAsync(settings);

            result.Success = true;
            result.Message = $"Synchronisierung erfolgreich: {result.CustomersCreated} erstellt, {result.CustomersUpdated} aktualisiert, {result.CustomersDeactivated} deaktiviert ({result.TotalProcessed} verarbeitet)";

            _logger.LogInformation("Lexware sync completed: {Message}", result.Message);
        }
        catch (HttpRequestException ex)
        {
            result.Success = false;
            result.Message = $"API-Verbindungsfehler: {ex.Message}";
            _logger.LogError(ex, "Lexware sync failed: HTTP error");
        }
        catch (Exception ex)
        {
            result.Success = false;
            result.Message = $"Synchronisierungsfehler: {ex.Message}";
            _logger.LogError(ex, "Lexware sync failed");
        }

        return result;
    }

    private HttpClient CreateHttpClient(LexwareApiSettings settings)
    {
        var client = _httpClientFactory.CreateClient("LexwareApi");
        client.BaseAddress = new Uri(settings.BaseUrl.TrimEnd('/') + "/");
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", settings.ApiKey);
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.Timeout = TimeSpan.FromSeconds(30);
        return client;
    }

    private static string? GetFirstPhone(LexwarePhoneNumbers? phones)
    {
        if (phones == null) return null;

        return phones.Mobile?.FirstOrDefault()
            ?? phones.Business?.FirstOrDefault()
            ?? phones.Private?.FirstOrDefault();
    }

    private static string? GetFirstEmail(LexwareEmailAddresses? emails)
    {
        if (emails == null) return null;

        return emails.Business?.FirstOrDefault()
            ?? emails.Private?.FirstOrDefault()
            ?? emails.Other?.FirstOrDefault();
    }
}

/// <summary>
/// Background service that runs daily Lexware customer sync
/// </summary>
public class LexwareSyncBackgroundService : BackgroundService
{
    private readonly IServiceProvider _serviceProvider;
    private readonly ILogger<LexwareSyncBackgroundService> _logger;

    public LexwareSyncBackgroundService(IServiceProvider serviceProvider, ILogger<LexwareSyncBackgroundService> logger)
    {
        _serviceProvider = serviceProvider;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("Lexware sync background service started");

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                using var scope = _serviceProvider.CreateScope();
                var settingsService = scope.ServiceProvider.GetRequiredService<ISiteSettingsService>();
                var settings = await settingsService.GetLexwareApiSettingsAsync();

                if (settings is { IsEnabled: true, IsConfigured: true, AutoSyncEnabled: true })
                {
                    // Parse target time
                    if (TimeSpan.TryParse(settings.AutoSyncTime, out var targetTime))
                    {
                        var now = DateTime.UtcNow;
                        var nextRun = now.Date.Add(targetTime);

                        // If we've already passed the target time today, schedule for tomorrow
                        if (now > nextRun)
                            nextRun = nextRun.AddDays(1);

                        var delay = nextRun - now;
                        _logger.LogDebug("Lexware auto-sync scheduled for {NextRun} (in {Delay})", nextRun, delay);

                        await Task.Delay(delay, stoppingToken);

                        if (!stoppingToken.IsCancellationRequested)
                        {
                            _logger.LogInformation("Running scheduled Lexware customer sync...");
                            using var syncScope = _serviceProvider.CreateScope();
                            var syncService = syncScope.ServiceProvider.GetRequiredService<ILexwareSyncService>();
                            var result = await syncService.SyncCustomersAsync(stoppingToken);
                            _logger.LogInformation("Scheduled Lexware sync result: {Message}", result.Message);
                        }
                    }
                    else
                    {
                        // Invalid time format, wait and retry
                        await Task.Delay(TimeSpan.FromHours(1), stoppingToken);
                    }
                }
                else
                {
                    // Not configured or disabled, check again in 15 minutes
                    await Task.Delay(TimeSpan.FromMinutes(15), stoppingToken);
                }
            }
            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
            {
                break;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error in Lexware sync background service");
                await Task.Delay(TimeSpan.FromMinutes(5), stoppingToken);
            }
        }

        _logger.LogInformation("Lexware sync background service stopped");
    }
}