using System.Collections.ObjectModel;
using System.Windows;
using Prism.Commands;
using Prism.Events;
using YY.Admin.Core;
using YY.Admin.Core.Entity;
using YY.Admin.Core.Events;
using YY.Admin.Core.Services;
using YY.Admin.Services.Service.Print;
using YY.Admin.Views.Print;

namespace YY.Admin.ViewModels.Print;

public class PrintTemplateListViewModel : BaseViewModel
{
    private readonly IPrintTemplateService _printTemplateService;
    private readonly IEventAggregator _eventAggregator;
    private SubscriptionToken? _changeToken;

    private List<PrintTemplate> _allTemplates = new();

    public ObservableCollection<PrintTemplate> Templates { get; } = new();

    private string _statusMessage = string.Empty;
    public string StatusMessage
    {
        get => _statusMessage;
        set => SetProperty(ref _statusMessage, value);
    }

    private string? _filterCode;
    public string? FilterCode
    {
        get => _filterCode;
        set => SetProperty(ref _filterCode, value);
    }

    private string? _filterName;
    public string? FilterName
    {
        get => _filterName;
        set => SetProperty(ref _filterName, value);
    }

    private string? _filterCategory;
    public string? FilterCategory
    {
        get => _filterCategory;
        set => SetProperty(ref _filterCategory, value);
    }

    public DelegateCommand SearchCommand { get; }
    public DelegateCommand ResetCommand { get; }
    public DelegateCommand<PrintTemplate> PreviewCommand { get; }

    public PrintTemplateListViewModel(
        IPrintTemplateService printTemplateService,
        IEventAggregator eventAggregator,
        IContainerExtension container,
        IRegionManager regionManager) : base(container, regionManager)
    {
        _printTemplateService = printTemplateService;
        _eventAggregator = eventAggregator;

        SearchCommand = new DelegateCommand(ApplyFilter);
        PreviewCommand = new DelegateCommand<PrintTemplate>(ShowPreview);
        ResetCommand = new DelegateCommand(() =>
        {
            FilterCode = null;
            FilterName = null;
            FilterCategory = null;
            ApplyFilter();
        });

        _changeToken = _eventAggregator
            .GetEvent<PrintTemplateChangedEvent>()
            .Subscribe(_ => { RefreshSilentlyAsync().ConfigureAwait(false); }, ThreadOption.UIThread);

        // 先用缓存立即填充，再后台静默刷新
        ShowCached();
        _ = RefreshSilentlyAsync();
    }

    private void ShowCached()
    {
        var cached = _printTemplateService.GetCached();
        if (cached.Count == 0) return;
        _allTemplates = cached.ToList();
        ApplyFilter();
        UpdateStatus();
    }

    private async Task RefreshSilentlyAsync()
    {
        try
        {
            var list = await _printTemplateService.RefreshCacheAsync().ConfigureAwait(false);
            System.Windows.Application.Current.Dispatcher.Invoke(() =>
            {
                _allTemplates = list.ToList();
                ApplyFilter();
                UpdateStatus();
            });
        }
        catch
        {
            // 静默失败：保留当前缓存内容不动，不显示错误
            var cached = _printTemplateService.GetCached();
            if (cached.Count > 0 && _allTemplates.Count == 0)
            {
                System.Windows.Application.Current.Dispatcher.Invoke(() =>
                {
                    _allTemplates = cached.ToList();
                    ApplyFilter();
                    UpdateStatus();
                });
            }
        }
    }

    private void ApplyFilter()
    {
        IEnumerable<PrintTemplate> result = _allTemplates;

        if (!string.IsNullOrWhiteSpace(FilterCode))
            result = result.Where(t => (t.TemplateCode ?? string.Empty)
                .Contains(FilterCode, StringComparison.OrdinalIgnoreCase));

        if (!string.IsNullOrWhiteSpace(FilterName))
            result = result.Where(t => (t.TemplateName ?? string.Empty)
                .Contains(FilterName, StringComparison.OrdinalIgnoreCase));

        if (!string.IsNullOrWhiteSpace(FilterCategory))
            result = result.Where(t => (t.Category ?? string.Empty)
                .Contains(FilterCategory, StringComparison.OrdinalIgnoreCase));

        var filtered = result.ToList();

        // 原地差量更新，避免滚动位置重置和闪烁
        for (int i = Templates.Count - 1; i >= 0; i--)
        {
            if (!filtered.Any(t => t.Id == Templates[i].Id))
                Templates.RemoveAt(i);
        }
        for (int i = 0; i < filtered.Count; i++)
        {
            var item = filtered[i];
            var existingIdx = -1;
            for (int j = 0; j < Templates.Count; j++)
            {
                if (Templates[j].Id == item.Id) { existingIdx = j; break; }
            }
            if (existingIdx < 0)
                Templates.Insert(i, item);
            else
            {
                if (existingIdx != i) Templates.Move(existingIdx, i);
                Templates[i] = item;
            }
        }
    }

    private void UpdateStatus()
    {
        var hasFilter = !string.IsNullOrWhiteSpace(FilterCode)
                     || !string.IsNullOrWhiteSpace(FilterName)
                     || !string.IsNullOrWhiteSpace(FilterCategory);
        StatusMessage = hasFilter
            ? $"筛选结果 {Templates.Count} / {_allTemplates.Count} 个"
            : _allTemplates.Count > 0
                ? $"共 {_allTemplates.Count} 个模板"
                : "暂无模板";
    }

    private void ShowPreview(PrintTemplate template)
    {
        if (template == null) return;
        ShowPreviewAsync(template);
    }

    private async Task ShowPreviewAsync(PrintTemplate template)
    {
        // 列表缓存可能不含 templateJson（大字段），按需通过 queryByCode 单独拉取
        var json = template.TemplateJson;
        if (string.IsNullOrWhiteSpace(json) || json == "{}")
        {
            try
            {
                var full = await _printTemplateService.GetByCodeAsync(template.TemplateCode ?? "");
                json = full?.TemplateJson;
            }
            catch { /* 保持 json 为 null，预览窗口显示"尚未设计" */ }
        }

        var win = new PrintPreviewWindow(template, json)
        {
            Owner = Application.Current.MainWindow
        };
        win.Show();
    }
}