using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using Muchinfo.PC.Common.Extensions;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading.Tasks;

namespace Muchinfo.MTPClient.Infrastructure.DataPager
{
    public abstract class QueryViewModelBase<T> : ViewModelBase
    {
        #region Fields

        private ObservableCollection<T> _dataGridItemsSource;
        private T _currentDataGridItem;

        private int _pageSize;
        private int _pageIndex;
        private int _itemCount;

        #endregion

        #region Properties

        /// <summary>
        /// DataGrid绑定集合
        /// </summary>
        public ObservableCollection<T> DataGridItemsSource
        {
            get { return _dataGridItemsSource; }
            set
            {
                Set(() => DataGridItemsSource, ref _dataGridItemsSource, value);
            }
        }

        /// <summary>
        /// DataGrid当前选中项
        /// </summary>
        public T CurrentDataGridItem
        {
            get { return _currentDataGridItem; }
            set { Set(() => CurrentDataGridItem, ref _currentDataGridItem, value); }
        }

        /// <summary>
        /// 总记录条数
        /// </summary>
        public int ItemCount
        {
            get { return _itemCount; }
            set { Set(() => ItemCount, ref _itemCount, value); }
        }

        /// <summary>
        /// 每页条数
        /// </summary>
        public int PageSize
        {
            get { return _pageSize; }
            set { Set(() => PageSize, ref _pageSize, value); }
        }

        /// <summary>
        /// 当前页
        /// </summary>
        public int PageIndex
        {
            get { return _pageIndex; }
            set { Set(() => PageIndex, ref _pageIndex, value); }
        }

        /// <summary>
        /// 重置命令
        /// </summary>
        public RelayCommand ResetCommand
        {
            get
            {
                return new RelayCommand(Reset);
            }
        }

        private bool isQuery = false;
        /// <summary>
        /// 查询命令
        /// </summary>
        public RelayCommand SearchCommand
        {
            get
            {
                return new RelayCommand(() =>
                {
                    if (QuerCheck())
                    {
                        //通过PageIndex触发PagerSearchCommand
                        if (PageIndex == 0) PageIndex = -1;
                        PageIndex = 0;
                    }
                }, () => { return !isQuery; });
            }
        }

        /// <summary>
        /// 分页命令
        /// </summary>
        public RelayCommand PagerSearchCommand
        {
            get
            {
                return new RelayCommand(() => Task.Factory.TryStartNew(() =>
                {
                    isQuery = true;

                    if (QuerCheck())
                    {
                        int totalCount;
                        var result = Query(out totalCount);
                        ItemCount = totalCount;
                        DataGridItemsSource = result.ToObservableCollection();
                        if (DataGridItemsSource != null && DataGridItemsSource.Any())
                        {
                            CurrentDataGridItem = DataGridItemsSource[0];
                        }
                    }
                    isQuery = false;
                }, () => { isQuery = false; }));
            }
        }

        #endregion

        #region Constructor

        protected QueryViewModelBase()
        {
            PageSize = 15;
            RegisterMessage();
        }

        #endregion

        #region Methods

        /// <summary>
        /// 查询数据集合
        /// </summary>
        /// <returns>IEnumerable{`0}.</returns>
        protected abstract IEnumerable<T> Query(out int totalCount);

        /// <summary>
        ///  查询检查
        /// </summary>
        /// <returns><c>true</c> if XXXX, <c>false</c> otherwise.</returns>
        protected virtual bool QuerCheck()
        {
            return true;
        }

        /// <summary>
        /// 重置查询条件
        /// </summary>
        protected virtual void Reset() { }

        /// <summary>
        /// 初始化
        /// </summary>
        protected virtual void Initialize()
        {
            Reset();
            SearchCommand.Execute(string.Empty);
        }

        /// <summary>
        /// 注册消息
        /// </summary>
        protected virtual void RegisterMessage() { }

        #endregion
    }
}