using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace TEAMModelOS.SDK
{
    public static class BatchTask
    {
        public static async Task<T[]> TaskPage<T>(this  List<Task<T>> tasks,int pagesize) {
            if (tasks.IsNotEmpty())
            {
                if (tasks.Count <= pagesize)
                {
                    return await Task.WhenAll(tasks);
                }
                else
                {
                    List<T> ts = new List<T>();
                    int pages = (tasks.Count + pagesize) / pagesize; //256是批量操作最大值，pages = (total + max -1) / max;
                    for (int i = 0; i < pages; i++)
                    {
                        var lists = tasks.Skip((i) * pagesize).Take(pagesize).ToList();
                        ts.AddRange(await Task.WhenAll(lists));
                    }
                    return ts.ToArray();
                }
            }
            else {
                return null;
            }
        }
        public static async Task TaskPage(this List<Task> tasks, int pagesize)
        {
            if (tasks.IsNotEmpty())
            {
                if (tasks.Count <= pagesize)
                {
                      await Task.WhenAll(tasks);
                }
                else
                {
                    int pages = (tasks.Count + pagesize) / pagesize; //256是批量操作最大值，pages = (total + max -1) / max;
                    for (int i = 0; i < pages; i++)
                    {
                        var lists = tasks.Skip((i) * pagesize).Take(pagesize).ToList();
                        await Task.WhenAll(lists);
                    }
                }
            }
        }


        public static   List<IEnumerable<T>> Page<T>(this IEnumerable<T> tasks, int pagesize)
        {
            if (tasks != null  && tasks.Any())
            {
                if (tasks.Count() <= pagesize)
                {
                    return new List<IEnumerable<T>> { tasks };
                }
                else
                {
                    List<IEnumerable<T>> ts = new List<IEnumerable<T>>();
                    int pages = (tasks.Count() + pagesize) / pagesize; //256是批量操作最大值，pages = (total + max -1) / max;
                    for (int i = 0; i < pages; i++)
                    {
                        var lists = tasks.Skip((i) * pagesize).Take(pagesize).ToList();
                        ts.Add(lists);
                    }
                    return ts;
                }
            }
            else
            {
                return new List<IEnumerable<T>> ();
            }
        }
    }
}