using System;
using System.Collections.Generic;
using System.Linq;
using _2021_backend.Data;
using _2021_backend.Models;
using System.IO;
using System.Threading.Tasks;

namespace _2021_backend.Utils
{
    public class Arranger
    {
        static BackendContext Context;
        static List<Student> students;
        static List<Session> sessions;
        public static bool Arrange(BackendContext context)
        {
            Context = context;
            students = context.Students.Where(it => it.Status != status.不通过 && it.Status != status.已确认时间 && it.Timelist.Count != 0 && it.InterviewTime == Guid.Empty && it.Status != status.需调整时间).OrderBy(it => it.Timelist.Count).ToList();
            sessions = context.Sessions.OrderBy(it => it.Day).ThenByDescending(it => it.Capacity - it.Students.Count).ThenBy(it => it.BeginTime).ThenBy(it => it.Place).ToList();
            students.Sort((Student a, Student b) =>
            {
                var capa = 0;
                var capb = 0;
                foreach (var tm in a.Timelist)
                {
                    var t = sessions.Find(x => x.Guid == tm);
                    capa += t.Capacity - t.Students.Count;
                }
                foreach (var tm in b.Timelist)
                {
                    var t = sessions.Find(x => x.Guid == tm);
                    capb += t.Capacity - t.Students.Count;
                }
                return capa - capb;
            });

#if DEBUG
            var str = "";
            foreach(var st in students)
            {
                var cap = 0;
                var tmstr = "";
                foreach (var tm in st.Timelist)
                {
                    var t = sessions.Find(x => x.Guid == tm);
                    cap += t.Capacity - t.Students.Count;
                    tmstr += t.Day.ToString("dd") + "-" + t.BeginTime.ToString("HH:mm-") + t.Place + "   ";
                }
                str += st.Name + "\t" + st.Timelist.Count.ToString() + "\t" + cap.ToString() + "\t"+ tmstr+  "\n";
            }
            File.WriteAllText("./students.txt", str);
#endif
            var res = DFS(0);
            context.SaveChanges();
            return res;
        }
        static bool DFS(int m)
        {
            if (m >= students.Count) return true;
            var lst = students[m].Timelist;
            var stu = students[m];
            
            if (stu.Timelist.Contains(stu.InterviewTime) || stu.Timelist.Count() == 0 || stu.InterviewTime != Guid.Empty || stu.Status != status.已选时间)
            {

                return m >= students.Count - 1 ? true : DFS(m + 1);
            }
            else
            {
                var tm = Context.Sessions.Find(stu.InterviewTime);
                if (tm != null)
                {
                    tm.Students.RemoveAll(it => it == stu.Guid);
                }
                stu.InterviewTime = Guid.Empty;
            }
            bool depth = false;
            foreach (var i in lst)
            {
                var tm = sessions.Find(s => s.Guid == i);
                if (tm.Students.Count < tm.Capacity && tm.Day.CompareTo(DateTime.Now.AddHours(-14)) > 0)
                {
                    status prev = students[m].Status;
                    Guid prevs = students[m].InterviewTime;
                    students[m].Status = status.已选时间;
                    students[m].InterviewTime = tm.Guid;
                    tm.Students.Add(students[m].Guid);
                    if (m == students.Count - 1)
                    {
                        return true;
                    }
                    else
                    {
                        depth = true;
                        if (!DFS(m + 1))
                        {
                            students[m].Status = prev;
                            students[m].InterviewTime = prevs;
                            tm.Students.Remove(students[m].Guid);
                            continue;
                        }
                        else return true;
                    }
                }
            }
            if (!depth) Console.WriteLine("Unable to find an arrangement. Stack trace:");
            Console.WriteLine(stu.Name + " " + stu.Stuid);
            return false;
        }
    }
}