using Lattice.Themes.Core.Tokens;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Media;

namespace Lattice.Themes;

/// <summary>
/// Менеджер тем для Lattice Framework.
/// </summary>
public sealed class ThemeManager
{
    public static ThemeManager Current { get; } = new();

    private ThemePack? _currentTheme;
    private readonly Dictionary<string, ThemePack> _registeredThemes = new();

    public ThemePack? CurrentTheme => _currentTheme;

    public event EventHandler<ThemeChangedEventArgs>? ThemeChanged;

    private ThemeManager() { }

    /// <summary>
    /// Регистрирует тему в менеджере.
    /// </summary>
    public void RegisterTheme(ThemePack theme)
    {
        if (theme == null)
            throw new ArgumentNullException(nameof(theme));

        _registeredThemes[theme.Name] = theme;
    }

    /// <summary>
    /// Получает зарегистрированную тему по имени.
    /// </summary>
    public ThemePack? GetTheme(string name)
    {
        _registeredThemes.TryGetValue(name, out var theme);
        return theme;
    }

    /// <summary>
    /// Получает список всех зарегистрированных тем.
    /// </summary>
    public IReadOnlyCollection<ThemePack> GetRegisteredThemes()
    {
        return _registeredThemes.Values.ToList();
    }

    /// <summary>
    /// Получение информации о теме.
    /// </summary>
    /// <param name="themeName"></param>
    /// <returns></returns>
    public ThemeInfo GetThemeInfo(string themeName)
    {
        if (!_registeredThemes.TryGetValue(themeName, out var theme))
            return null;

        return new ThemeInfo
        {
            Name = theme.Name,
            Description = theme.Description,
            Version = theme.Version,
            IsDark = theme.IsDark,
            TokenCount = CountTokensInTheme(theme)
        };
    }

    /// <summary>
    /// Применяет тему по имени.
    /// </summary>
    public void ApplyTheme(string themeName)
    {
        if (!_registeredThemes.TryGetValue(themeName, out var theme))
        {
            throw new ArgumentException($"Theme '{themeName}' is not registered.", nameof(themeName));
        }

        ApplyTheme(theme);
    }

    /// <summary>
    /// Применяет указанную тему.
    /// </summary>
    public void ApplyTheme(ThemePack theme)
    {
        if (theme == null)
            throw new ArgumentNullException(nameof(theme));

        if (_currentTheme == theme)
            return;

        var old = _currentTheme;
        _currentTheme = theme;

        try
        {
            ReplaceApplicationResources(theme);
            ThemeChanged?.Invoke(this, new ThemeChangedEventArgs(old!, theme));
        }
        catch (Exception ex)
        {
            // В случае ошибки возвращаемся к старой теме
            _currentTheme = old;
            if (old != null)
            {
                ReplaceApplicationResources(old);
            }
            throw new InvalidOperationException($"Failed to apply theme '{theme.Name}'.", ex);
        }
    }

    /// <summary>
    /// Загружает ресурсы темы в указанный словарь ресурсов.
    /// </summary>
    public void LoadThemeIntoDictionary(ResourceDictionary targetDictionary, ThemePack theme)
    {
        if (targetDictionary == null)
            throw new ArgumentNullException(nameof(targetDictionary));

        if (theme == null)
            throw new ArgumentNullException(nameof(theme));

        // Очищаем старые словари Lattice
        for (int i = targetDictionary.MergedDictionaries.Count - 1; i >= 0; i--)
        {
            if (targetDictionary.MergedDictionaries[i] is ThemeDictionary)
                targetDictionary.MergedDictionaries.RemoveAt(i);
        }

        // Добавляем новые словари темы
        foreach (var uri in theme.GetResourceUris())
        {
            try
            {
                var themeDict = new ThemeDictionary { Source = uri };
                targetDictionary.MergedDictionaries.Add(themeDict);
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException($"Failed to load theme resource from '{uri}'.", ex);
            }
        }
    }

    private int CountTokensInTheme(ThemePack theme)
    {
        try
        {
            var dict = new ResourceDictionary();
            LoadThemeIntoDictionary(dict, theme);
            return dict.Count;
        }
        catch
        {
            return 0;
        }
    }

    private void ReplaceApplicationResources(ThemePack theme)
    {
        var app = Application.Current;
        if (app == null)
            return;

        var root = app.Resources;
        LoadThemeIntoDictionary(root, theme);
        ForceUpdateUI();
    }

    private void ForceUpdateUI()
    {
        foreach (var window in WindowTracker.Windows)
        {
            if (window.Content is FrameworkElement root)
                RefreshElement(root);
        }
    }

    private void RefreshElement(FrameworkElement element)
    {
        var stack = new Stack<FrameworkElement>();
        stack.Push(element);

        while (stack.Count > 0)
        {
            var current = stack.Pop();

            // Пересоздаём Template только у Control
            if (current is Control control)
            {
                var template = control.Template;
                control.Template = null;
                control.Template = template;
            }
            else if (current is ContentPresenter contentPresenter)
            {
                // Обновляем ContentPresenter
                var content = contentPresenter.Content;
                contentPresenter.Content = null;
                contentPresenter.Content = content;
            }

            // Добавляем детей в стек
            int count = VisualTreeHelper.GetChildrenCount(current);
            for (int i = 0; i < count; i++)
            {
                if (VisualTreeHelper.GetChild(current, i) is FrameworkElement child)
                    stack.Push(child);
            }
        }
    }

    /// <summary>
    /// Проверяет, что все необходимые токены определены в текущей теме.
    /// </summary>
    public bool ValidateThemeTokens()
    {
        if (_currentTheme == null)
            return false;

        var app = Application.Current;
        if (app == null)
            return false;

        var requiredTokens = LatticeTokens.GetAllTokens().Values;
        var missingTokens = new List<string>();

        foreach (var token in requiredTokens)
        {
            if (!app.Resources.ContainsKey(token))
            {
                missingTokens.Add(token);
            }
        }

        if (missingTokens.Any())
        {
            System.Diagnostics.Debug.WriteLine($"Missing theme tokens: {string.Join(", ", missingTokens)}");
            return false;
        }

        return true;
    }

    /// <summary>
    /// Получает значение токена из текущей темы.
    /// </summary>
    public object? GetTokenValue(string tokenKey)
    {
        var app = Application.Current;
        if (app == null)
            return null;

        if (app.Resources.TryGetValue(tokenKey, out var value))
        {
            return value;
        }

        return null;
    }

    /// <summary>
    /// Получает значение токена с приведением к указанному типу.
    /// </summary>
    public T? GetTokenValue<T>(string tokenKey)
    {
        object? value = GetTokenValue(tokenKey);

        if (value is T typedValue)
            return typedValue;

        return default;
    }
}

/// <summary>
/// Информация о теме.
/// </summary>
public class ThemeInfo
{
    /// <summary>
    /// Название темы.
    /// </summary>
    public string Name { get; set; }
    public string Description { get; set; }
    public string Version { get; set; }
    public bool IsDark { get; set; }
    public int TokenCount { get; set; }
}