using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace NeuWPFTest
{
    public class MainViewModel : INotifyPropertyChanged
    {
        private readonly List<string> _fullDataSource; // 模拟的后端数据源

        private IEnumerable<string> _pagedItems;

        public IEnumerable<string> PagedItems
        {
            get => _pagedItems;
            private set
            {
                _pagedItems = value;
                OnPropertyChanged();
            }
        }

        private int _currentPage = 1;

        public int CurrentPage
        {
            get => _currentPage;
            set
            {
                _currentPage = value;
                OnPropertyChanged();
                UpdatePagedItems();
            }
        }

        private int _pageSize = 10;

        public int PageSize
        {
            get => _pageSize;
            set
            {
                _pageSize = value;
                OnPropertyChanged();
                UpdatePagedItems();
            }
        }

        public long TotalItems { get; private set; }

        public MainViewModel()
        {
            _fullDataSource = new List<string>(Enumerable.Range(1, 1052).Select(i => $"条目 {i}"));
            TotalItems = _fullDataSource.Count;
            OnPropertyChanged(nameof(TotalItems));

            UpdatePagedItems(); // 加载第一页
        }

        private void UpdatePagedItems()
        {
            var skip = (CurrentPage - 1) * PageSize;
            PagedItems = _fullDataSource.Skip(skip).Take(PageSize).ToList();
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
        { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); }
    }
}