namespace Szmedi.RvKits.FamilyTools
{
    public class PageInfo<T>
    {
        private readonly int pageSize;
        public List<T> dataSource;
        public int CurrentIndex { get; set; }

        public int Pagecount { get; set; }

        public PageInfo()
        {
            //当前页码
            CurrentIndex = 1;
        }

        public PageInfo(List<T> dataSource, int pageSize)
            : this()
        {
            this.dataSource = dataSource;
            //每页的数目
            this.pageSize = pageSize;
            //取商
            Pagecount = dataSource.Count / pageSize;
            //如果整除+0，不整除+1
            Pagecount += dataSource.Count % pageSize != 0 ? 1 : 0;
        }

        public List<T> GetPageData(JumpOperation jo)
        {
            switch (jo)
            {
                case JumpOperation.GoHome:
                    CurrentIndex = 1;
                    break;
                case JumpOperation.GoPrePrevious:
                    if (CurrentIndex > 1)
                    {
                        CurrentIndex -= 1;
                    }

                    break;
                case JumpOperation.GoNext:
                    if (CurrentIndex < Pagecount)
                    {
                        CurrentIndex += 1;
                    }

                    break;
                case JumpOperation.GoEnd:
                    CurrentIndex = Pagecount;
                    break;
                case JumpOperation.GoAny:

                    break;
            }

            List<T> listPageData = new();
            try
            {
                int pageCountTo = pageSize;
                //页数等于1并且取余大于0（即只有一页时）
                if (Pagecount == CurrentIndex && dataSource.Count % pageSize > 0)
                {
                    //pageCountTo=当前条目数
                    pageCountTo = dataSource.Count % pageSize;
                }

                if (null != dataSource)
                {
                    for (int i = 0; i < pageCountTo; i++)
                    {
                        //当前页码-1进行循环，比如有32项时，当前第2页，即从Index=20（第一项Index=0）开始循环
                        if (((CurrentIndex - 1) * pageSize) + i < dataSource.Count)
                        {
                            //将该项添加到listPageData
                            listPageData.Add(dataSource[((CurrentIndex - 1) * pageSize) + i]);
                        }
                        else
                        {
                            break;
                        }
                    }
                }

                return listPageData;
            }
            catch
            {
                return listPageData;
            }
        }
    }

    public enum JumpOperation
    {
        GoHome = 0,
        GoPrePrevious = 1,
        GoNext = 2,
        GoEnd = 3,
        GoAny = 4
    }
}