using System.Net;
using System.Text.Json;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using XFEToolBox.Client.Model;
using XFEToolBox.Client.Models;
using XFEToolBox.Client.Profiles.CacheProfiles;
using XFEToolBox.Client.Utilities;
using XFEToolBox.Client.Utilities.Server;
using XFEToolBox.Client.ViewModel.Pages;
using XFEToolBox.Core.Downloads;

namespace XFEToolBox.Client.Views.Pages;

public partial class DownloadPage : Page
{
    private static readonly SemaphoreSlim IconLoadGate = new(4);
    private static readonly JsonSerializerOptions CacheJsonOptions = new(JsonSerializerDefaults.Web);
    private readonly List<SoftwareCardViewModel> _software = [];
    private SoftwareCatalogRowViewModel[] _softwareRows = [];
    private int _visibleCategoryCount;
    private SoftwareCatalogResponse _cachedCatalog = new();
    private bool _updatingCategories;
    private bool _cacheLoaded;
    private bool _hasCachedCatalog;
    private int _refreshGeneration;

    public static DownloadPage Current { get; private set; } = new();

    public DownloadPage()
    {
        Current = this;
        InitializeComponent();
        CategoryFilter.Items.Add("全部分类");
        CategoryFilter.SelectedIndex = 0;
    }

    private async void Page_Loaded(object sender, RoutedEventArgs e) => await RefreshAsync(refreshFullCatalog: true);
    private async void RefreshButton_Click(object sender, RoutedEventArgs e) => await RefreshAsync(refreshFullCatalog: true);
    private async void SearchButton_Click(object sender, RoutedEventArgs e) => await RefreshAsync(updateCategories: false);

    private async void SearchTextBox_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter) await RefreshAsync(updateCategories: false);
    }

    private async void CategoryFilter_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (!_updatingCategories && IsLoaded) await RefreshAsync(updateCategories: false);
    }

    private async Task RefreshAsync(bool updateCategories = true, bool refreshFullCatalog = false)
    {
        EnsureCacheLoaded();
        var query = SearchTextBox.Text.Trim();
        var category = GetSelectedCategory();
        if (_hasCachedCatalog)
        {
            if (updateCategories) UpdateCategories(_cachedCatalog.Categories, category);
            category = GetSelectedCategory();
            ApplySoftware(FilterCachedSoftware(query, category));
            StatusText.Text = _software.Count == 0
                ? "缓存中没有符合条件的软件，正在后台刷新…"
                : "已显示本地缓存，正在后台刷新…";
        }
        else
        {
            StatusText.Text = "正在连接工具服务器…";
        }

        var refreshGeneration = ++_refreshGeneration;
        SearchButton.IsEnabled = RefreshButton.IsEnabled = false;
        CategoryFilter.IsEnabled = false;

        try
        {
            var requestQuery = refreshFullCatalog ? string.Empty : query;
            var requestCategory = refreshFullCatalog ? string.Empty : category;
            var response = await ClientSession.Requester.Request<SoftwareCatalogResponse>(
                "softwareCatalog", requestQuery, requestCategory);
            if (refreshGeneration != _refreshGeneration) return;
            if (response.StatusCode != HttpStatusCode.OK || response.Result is null)
            {
                ShowRefreshFailure(string.IsNullOrWhiteSpace(response.Message) ? "服务器没有返回软件下载目录。" : response.Message);
                return;
            }

            if (updateCategories)
            {
                UpdateCategories(response.Result.Categories, category);
                category = GetSelectedCategory();
            }
            IReadOnlyList<SoftwareCatalogItem> software = response.Result.Items;
            if (refreshFullCatalog || string.IsNullOrWhiteSpace(query) && string.IsNullOrWhiteSpace(category))
            {
                _cachedCatalog = response.Result;
                _hasCachedCatalog = true;
                TrySaveCatalogCache(response.Result);
                software = FilterCachedSoftware(query, category);
            }

            ApplySoftware(software);
            StatusText.Text = _software.Count == 0 ? "没有符合条件的软件。" : "点击卡片查看详情与获取方式。";
        }
        catch (Exception exception)
        {
            if (refreshGeneration == _refreshGeneration)
                ShowRefreshFailure($"连接失败：{exception.Message}");
        }
        finally
        {
            if (refreshGeneration == _refreshGeneration)
            {
                SearchButton.IsEnabled = RefreshButton.IsEnabled = true;
                CategoryFilter.IsEnabled = true;
            }
        }
    }

    private void EnsureCacheLoaded()
    {
        if (_cacheLoaded) return;
        _cacheLoaded = true;
        try
        {
            var json = AppCacheProfile.SoftwareCatalogJson;
            if (string.IsNullOrWhiteSpace(json)) return;
            _cachedCatalog = JsonSerializer.Deserialize<SoftwareCatalogResponse>(json, CacheJsonOptions) ?? new SoftwareCatalogResponse();
            _cachedCatalog.Items ??= [];
            _cachedCatalog.Categories ??= [];
            _hasCachedCatalog = true;
        }
        catch
        {
            _cachedCatalog = new SoftwareCatalogResponse();
            _hasCachedCatalog = false;
        }
    }

    private SoftwareCatalogItem[] FilterCachedSoftware(string query, string category) =>
        _cachedCatalog.Items.Where(item =>
                (string.IsNullOrWhiteSpace(category) || string.Equals(item.Category, category, StringComparison.CurrentCultureIgnoreCase))
                && (string.IsNullOrWhiteSpace(query)
                    || Contains(item.Name, query)
                    || Contains(item.Summary, query)
                    || Contains(item.Description, query)
                    || Contains(item.Publisher, query)
                    || Contains(item.Category, query)
                    || item.Tags?.Any(tag => Contains(tag, query)) == true))
            .ToArray();

    private void ApplySoftware(IReadOnlyList<SoftwareCatalogItem> software)
    {
        var existingById = _software
            .GroupBy(card => card.Id, StringComparer.OrdinalIgnoreCase)
            .ToDictionary(group => group.Key, group => group.First(), StringComparer.OrdinalIgnoreCase);
        var desiredCards = software.Select(item =>
        {
            if (existingById.TryGetValue(item.Id, out var existing)
                && SoftwareItemsEquivalent(existing.Software, item)) return existing;
            return new SoftwareCardViewModel(item, GetBundledIcon(item.Id));
        }).ToArray();

        _software.Clear();
        _software.AddRange(desiredCards);
        RebuildCatalogRows();
        EmptyState.Visibility = _software.Count == 0 ? Visibility.Visible : Visibility.Collapsed;
        EmptyTitle.Text = "暂时没有找到软件";
        EmptyHint.Text = "可以换个关键词或分类，或稍后刷新再试";
        SoftwareCountText.Text = FormatSoftwareCount();
    }

    private void RebuildCatalogRows()
    {
        var categoryOrder = CategoryFilter.Items.Cast<object>()
            .Skip(1)
            .Select((item, index) => (Name: item?.ToString() ?? string.Empty, Index: index))
            .Where(item => !string.IsNullOrWhiteSpace(item.Name))
            .GroupBy(item => item.Name, StringComparer.CurrentCultureIgnoreCase)
            .ToDictionary(group => group.Key, group => group.Min(item => item.Index), StringComparer.CurrentCultureIgnoreCase);

        var groups = _software
            .GroupBy(card => NormalizeCategory(card.Category), StringComparer.CurrentCultureIgnoreCase)
            .Select(group => (Name: group.Key, Items: (IReadOnlyList<SoftwareCardViewModel>)group.ToArray()))
            .OrderBy(group => categoryOrder.TryGetValue(group.Name, out var index) ? index : int.MaxValue)
            .ThenBy(group => group.Name, StringComparer.CurrentCultureIgnoreCase)
            .ToArray();

        var rows = new List<SoftwareCatalogRowViewModel>(_software.Count / 2 + groups.Length * 2);
        foreach (var group in groups)
        {
            rows.Add(SoftwareCatalogRowViewModel.Header(
                new SoftwareCategoryGroupViewModel(group.Name, group.Items.Count)));
            for (var index = 0; index < group.Items.Count; index += 2)
                rows.Add(SoftwareCatalogRowViewModel.Cards(
                    group.Items[index],
                    index + 1 < group.Items.Count ? group.Items[index + 1] : null));
        }

        _visibleCategoryCount = groups.Length;
        _softwareRows = rows.ToArray();
        SoftwareCards.ItemsSource = _softwareRows;
    }

    private string FormatSoftwareCount() => _software.Count == 0
        ? "0 个软件"
        : $"{_software.Count} 个软件 · {_visibleCategoryCount} 个分类";

    private static string NormalizeCategory(string? category) =>
        string.IsNullOrWhiteSpace(category) ? "其他软件" : category.Trim();

    private void ShowRefreshFailure(string message)
    {
        if (_hasCachedCatalog)
        {
            EmptyState.Visibility = _software.Count == 0 ? Visibility.Visible : Visibility.Collapsed;
            SoftwareCountText.Text = FormatSoftwareCount();
            StatusText.Text = $"后台刷新失败，当前显示本地缓存：{message}";
            return;
        }

        ShowEmptyResult(message, connectionError: true);
    }

    private static void TrySaveCatalogCache(SoftwareCatalogResponse catalog)
    {
        try
        {
            AppCacheProfile.SoftwareCatalogJson = JsonSerializer.Serialize(catalog, CacheJsonOptions);
        }
        catch
        {
            // 缓存写入失败不应影响已成功获取的在线目录。
        }
    }

    private static bool Contains(string? value, string query) =>
        value?.Contains(query, StringComparison.CurrentCultureIgnoreCase) == true;

    private static bool SoftwareItemsEquivalent(SoftwareCatalogItem left, SoftwareCatalogItem right) =>
        JsonSerializer.Serialize(left, CacheJsonOptions) == JsonSerializer.Serialize(right, CacheJsonOptions);

    private void UpdateCategories(IEnumerable<string> categories, string selectedCategory)
    {
        _updatingCategories = true;
        CategoryFilter.Items.Clear();
        CategoryFilter.Items.Add("全部分类");
        foreach (var category in categories) CategoryFilter.Items.Add(category);
        CategoryFilter.SelectedItem = CategoryFilter.Items.Cast<object>()
            .FirstOrDefault(item => string.Equals(item.ToString(), selectedCategory, StringComparison.CurrentCultureIgnoreCase));
        if (CategoryFilter.SelectedIndex < 0) CategoryFilter.SelectedIndex = 0;
        _updatingCategories = false;
    }

    private string GetSelectedCategory() =>
        CategoryFilter.SelectedIndex > 0 ? CategoryFilter.SelectedItem?.ToString() ?? string.Empty : string.Empty;

    private void ShowEmptyResult(string message, bool connectionError)
    {
        _software.Clear();
        _softwareRows = [];
        _visibleCategoryCount = 0;
        SoftwareCards.ItemsSource = _softwareRows;
        EmptyState.Visibility = Visibility.Visible;
        EmptyTitle.Text = connectionError ? "无法读取软件下载目录" : "暂时没有找到软件";
        EmptyHint.Text = connectionError ? "请检查网络连接与服务状态，然后点击刷新" : "可以换个关键词或分类再试";
        SoftwareCountText.Text = string.Empty;
        StatusText.Text = message;
    }

    private void SoftwareCard_Click(object sender, RoutedEventArgs e)
    {
        if (sender is not Button { CommandParameter: SoftwareCardViewModel card }) return;
        ShowSoftwareDetails(card);
    }

    private void TogglePinnedSoftwareMenuItem_Click(object sender, RoutedEventArgs e)
    {
        e.Handled = true;
        if (sender is not MenuItem { CommandParameter: SoftwareCardViewModel card }) return;
        var wasPinned = PinnedItemService.IsPinned(LauncherItemKind.Software, card.Id);
        var success = wasPinned
            ? PinnedItemService.Unpin(LauncherItemKind.Software, card.Id)
            : PinnedItemService.TryPin(LauncherItemKind.Software, card.Id);
        StatusText.Text = !success
            ? $"最多只能固定 {PinnedItemService.MaximumPinnedItems} 项。"
            : wasPinned ? $"已取消固定 {card.Name}。" : $"已将 {card.Name} 固定到主页。";
    }

    private async void SoftwareCard_Loaded(object sender, RoutedEventArgs e)
    {
        if (sender is Button { DataContext: SoftwareCardViewModel card } && card.TryBeginIconLoad())
            await LoadConfiguredIconAsync(card);
    }

    /// <summary>
    /// 供主页最近使用卡片调用。目录缓存不存在时会从当前服务器重新解析软件信息。
    /// </summary>
    public async Task<bool> OpenSoftwareByIdAsync(string softwareId)
    {
        if (string.IsNullOrWhiteSpace(softwareId)) return false;
        EnsureCacheLoaded();

        var card = _software.FirstOrDefault(item => string.Equals(item.Id, softwareId, StringComparison.OrdinalIgnoreCase));
        var software = card?.Software ?? _cachedCatalog.Items.FirstOrDefault(item =>
            string.Equals(item.Id, softwareId, StringComparison.OrdinalIgnoreCase));
        if (software is null)
        {
            try
            {
                StatusText.Text = "正在更新软件下载目录…";
                var response = await ClientSession.Requester.Request<SoftwareCatalogResponse>(
                    "softwareCatalog", string.Empty, string.Empty);
                if (response.StatusCode == HttpStatusCode.OK && response.Result is not null)
                {
                    _cachedCatalog = response.Result;
                    _cachedCatalog.Items ??= [];
                    _cachedCatalog.Categories ??= [];
                    _hasCachedCatalog = true;
                    TrySaveCatalogCache(_cachedCatalog);
                    software = _cachedCatalog.Items.FirstOrDefault(item =>
                        string.Equals(item.Id, softwareId, StringComparison.OrdinalIgnoreCase));
                }
                else
                {
                    StatusText.Text = string.IsNullOrWhiteSpace(response.Message)
                        ? "无法更新软件下载目录。"
                        : response.Message;
                }
            }
            catch (Exception exception)
            {
                StatusText.Text = $"更新软件下载目录失败：{exception.Message}";
            }
        }

        if (software is null)
        {
            StatusText.Text = "该软件已下架或当前服务器不再提供。";
            return false;
        }

        if (card is null)
        {
            card = new SoftwareCardViewModel(software, GetBundledIcon(software.Id));
            if (card.TryBeginIconLoad()) await LoadConfiguredIconAsync(card);
        }

        ShowSoftwareDetails(card);
        return true;
    }

    private static void ShowSoftwareDetails(SoftwareCardViewModel card)
    {
        RecentUsageIconCache.Remember(RecentUsageKind.Software, card.Id, card.IconSource);
        RecentUsageService.RecordSoftware(card.Software);
        PopupHelper.ShowDialog(new DownloadInfoPage(card.Software, card.IconSource), new PopupWindowOptions
        {
            Title = card.Name,
            Subtitle = $"{card.Publisher} · {card.Category}",
            Width = 610,
            Height = 590,
            ContentMargin = new Thickness(0)
        });
    }

    private static async Task LoadConfiguredIconAsync(SoftwareCardViewModel card)
    {
        if (string.IsNullOrWhiteSpace(card.Software.IconUrl)) return;
        await IconLoadGate.WaitAsync();
        try
        {
            var icon = await WebImageSourceLoader.LoadAsync(card.Software.IconUrl);
            if (icon is not null) card.IconSource = icon;
        }
        catch
        {
            // 无法读取服务端配置的图标时保留内置或默认图标。
        }
        finally
        {
            IconLoadGate.Release();
        }
    }

    private static ImageSource GetBundledIcon(string id)
    {
        var resource = id.ToLowerInvariant() switch
        {
            "steam" => "/Resources/Image/DownloadImage/steam_logo.png",
            "watt-toolkit" or "steampp" => "/Resources/Image/DownloadImage/steampp.png",
            "visual-studio" => "/Resources/Image/DownloadImage/visual_studio.png",
            "cheat-engine" => "/Resources/Image/DownloadImage/cheat_engine.png",
            _ => "/Resources/Image/download.png"
        };
        var image = new BitmapImage(new Uri($"pack://application:,,,{resource}", UriKind.Absolute));
        image.Freeze();
        return image;
    }

}