using System;
using System.Collections.Generic;
using System.Linq;

namespace spplus;

public class CourseCrafter
{
    public class CourseInstance
    {
        public Sport Sport = null!;
        public int Remaining;
        public List<string> Students = new();
    }
    public static List<(int Semester, CourseInstance Instance)> GeneratedCourses 
        = new();

    public static void Craft()
    {
        GeneratedCourses = new();
        int globalCount = 0;
        List<(Sport, List<string>)> initial_sportlist = new();
        List<string>[] students_in_semester = new List<string>[4] { new(), new(), new(), new() };
        foreach (var sp in Settings.Instance.Sports)
        {
            initial_sportlist.Add((sp, new()));
        }

        foreach (Student s in Settings.Instance.Students)
        {
            foreach (var sp in s.SelectedCourseNames)
            {
                foreach (var item in initial_sportlist)
                {
                    if (item.Item1.AlternativeNames.Contains(sp))
                    {
                        item.Item2.Add(s.ID);
                        break;
                    }
                }
            }
        }

        while (!requestExit())
        {
            Console.WriteLine($"Calculating... ({globalCount})");
            foreach (var item in initial_sportlist)
            {
                if (item.Item2.Count >= item.Item1.MinStudents)
                {
                    int semester = getSemesterForSport(item.Item1);
                    if (semester <= 0) goto semeq0;
                    var inst = new CourseInstance();
                    inst.Sport = item.Item1;
                    inst.Students = new List<string>();
                    // int dist = 1;
                    for (int i = item.Item2.Count - 1; i >= 0; i--)
                    {
                        if (inst.Students.Count >= inst.Sport.MaxStudents)
                            break;

                        string stud = item.Item2[i];

                        if (!students_in_semester[semester - 1].Contains(stud))
                        {
                            inst.Students.Add(stud);
                            students_in_semester[semester - 1].Add(stud);
                            item.Item2.RemoveAt(i);
                        }
                    }
                    if (inst.Students.Count < inst.Sport.MinStudents)
                    {
                        // Rückgängig machen
                        foreach (var s in inst.Students)
                        {
                            students_in_semester[semester-1].Remove(s);
                            item.Item2.Add(s);
                        }
                        continue; // Kurs nicht erstellen
                    }
                    GeneratedCourses.Add((semester, inst));
                    
                    MainWindow.Instance.TbResultLog.Text += ($"{semester} -> {inst.Students.Count}\n");
                    MainWindow.Instance.TbResultLog.Text += ($"{students_in_semester[0].Count} - {students_in_semester[1].Count} - {students_in_semester[2].Count} - {students_in_semester[3].Count}\n\n");
                }

                semeq0: ;
            }
            
            
        }
        
        // Kurse auffüllen (mit restl. Leuten)
        foreach (var item in initial_sportlist)
        {
            if (item.Item2.Count > 0)
            {
                foreach (var ci in GeneratedCourses)
                {
                    
                    if (item.Item1.ID == ci.Instance.Sport.ID)
                    {
                        int semester = ci.Semester;
                        List<string> added = new();
                        foreach (string stud in item.Item2)
                        {
                            if (ci.Instance.Students.Count >= ci.Instance.Sport.MaxStudents) break;
                            if (!students_in_semester[semester-1].Contains(stud))
                            {
                                ci.Instance.Students.Add(stud);
                                students_in_semester[semester-1].Add(stud);
                                //ci.Instance.Students.Add(stud);
                                added.Add(stud);
                            }
                        }

                        // Hinzugefügte aus Initialkurs entfernen
                        foreach (string s in added)
                        {
                            item.Item2.Remove(s);    
                        }
                    }
                    MainWindow.Instance.TbResultLog.Text += ($"{ci.Semester} -> {ci.Instance.Students.Count}\n");
                    MainWindow.Instance.TbResultLog.Text += ($"{students_in_semester[0].Count} - {students_in_semester[1].Count} - {students_in_semester[2].Count} - {students_in_semester[3].Count}\n\n");
                }
            }
            
        }
        
        // Kurs umdisponieren (besser verteilen)
        // Kurs umdisponieren (besser verteilen)
        bool changed;
        int maxIterations = 20;
        int iteration = 0;

        do
        {
            changed = false;
            iteration++;

            // nach Sport gruppieren
            var sports = GeneratedCourses
                .GroupBy(c => c.Instance.Sport.ID);

            foreach (var sportGroup in sports)
            {
                var courses = sportGroup.ToList();

                // paarweise vergleichen
                for (int i = 0; i < courses.Count; i++)
                {
                    for (int j = 0; j < courses.Count; j++)
                    {
                        if (i == j) continue;

                        var cA = courses[i];
                        var cB = courses[j];

                        // nur sinnvoll, wenn Unterschied
                        if (cA.Instance.Students.Count <= cB.Instance.Students.Count + 1)
                            continue;

                        // Kandidaten aus A nach B verschieben
                        for (int k = cA.Instance.Students.Count - 1; k >= 0; k--)
                        {
                            string stud = cA.Instance.Students[k];

                            // 1. Zielsemester frei?
                            if (!isStudentFree(cB.Semester, stud))
                                continue;

                            // 2. Zielkurs hat noch Platz?
                            if (cB.Instance.Students.Count >= cB.Instance.Sport.MaxStudents)
                                continue;

                            // 3. Quellkurs darf nicht unter Min fallen
                            if (cA.Instance.Students.Count - 1 < cA.Instance.Sport.MinStudents)
                                continue;

                            // --- MOVE durchführen ---
                            cA.Instance.Students.RemoveAt(k);
                            students_in_semester[cA.Semester - 1].Remove(stud);

                            cB.Instance.Students.Add(stud);
                            students_in_semester[cB.Semester - 1].Add(stud);

                            changed = true;
                            break; // nach jedem Move neu bewerten
                        }
                    }
                }
            }

        } while (changed && iteration < maxIterations);

        int getSemester()
        {
            //int sem = 0;
            if (GeneratedCourses.Count == 0) return 1; // zunächst im ersten Semester beginnen
            int[] semcount = new int[4] {0,0,0,0}; // Anzahl der generierten Kurse im jeweiligen Semester
            foreach (var inst in GeneratedCourses) 
            {
                semcount[inst.Semester - 1]++; // ...füllen
            }

            for (int i = 0; i<semcount.Length; i++) // durchlaufen und prüfen
            {
                if (semcount[i] < Settings.Instance.NumCoursesPerSemester)
                {
                    return i+1; // Semester zurückgeben, wenn genug da sind
                }
            }
            return 0;
        }

        bool isStudentFree(int semester, string studentID)
        {
            foreach (var inst in GeneratedCourses)
            {
                if (semester != inst.Semester) continue;
                foreach (string stud in inst.Instance.Students)
                {
                    if (stud == studentID) return false; // Schüler in genanntem Semester bereits gefunden
                }
            }

            // Schüler nicht gefunden:
            return true;
        }

        
        bool requestExit()
        {
            globalCount++;
            // max Kursanzahl
            if (GeneratedCourses.Count >= Settings.Instance.NumCoursesPerSemester * 4) return true;
            

            int low = 0;
            foreach (var item in initial_sportlist)
            {
                if (item.Item2.Count < item.Item1.MinStudents) low++;
            }

            if (low >= initial_sportlist.Count) return true;

            if (globalCount >= 20) return true;
            return false;
        }

        foreach (var tuple in initial_sportlist)
        {
            MainWindow.Instance.TbResultTextout.Text += $"{tuple.Item1}: {tuple.Item2.Count} remaining\n";
        }
        
        int getSemesterForSport(Sport sp)
        {
            int[] semcount = new int[4];

            foreach (var inst in GeneratedCourses)
                semcount[inst.Semester - 1]++;

            int bestSem = 0;
            int minCourses = int.MaxValue;

            for (int i = 0; i < 4; i++)
            {
                if (sp.Semester[i] == 0) continue;

                if (semcount[i] < Settings.Instance.NumCoursesPerSemester &&
                    semcount[i] < minCourses)
                {
                    minCourses = semcount[i];
                    bestSem = i + 1;
                }
            }

            return bestSem;
        }

        
    }

    public static string GenerateStatistics()
    {
        string sb = $"Generierte Kurse: {GeneratedCourses.Count}\n\n";
        foreach (var genc in GeneratedCourses)
        {
            sb += $"Sem. {genc.Semester}: {genc.Instance.Sport.Name} ({genc.Instance.Students.Count} SuS)\n";
        }
        
        

        return sb;
    }
    
    public static string GenerateStatisticsOld()
    {
        var settings = Settings.Instance;
        var students = settings.Students;

        if (GeneratedCourses == null || GeneratedCourses.Count == 0)
            return "Keine Kurse generiert.";

        int semesterCount = students
            .Where(s => s.Result != null)
            .Select(s => s.Result!.Count)
            .DefaultIfEmpty(0)
            .Max();

        var sb = new System.Text.StringBuilder();

        sb.AppendLine($"Anzahl generierter Kurse: {GeneratedCourses.Count}");
        sb.AppendLine("Übersicht:");

        // ===== Kursübersicht =====
        var grouped = GeneratedCourses
            .GroupBy(g => new { g.Semester, g.Instance.Sport.Name })
            .OrderBy(g => g.Key.Semester)
            .ThenBy(g => g.Key.Name);

        foreach (var group in grouped)
        {
            int counter = 1;

            foreach (var entry in group)
            {
                int semester = group.Key.Semester + 1;
                string sportName = group.Key.Name;
                string number = counter.ToString("D2");
                int count = entry.Instance.Students.Count;

                sb.AppendLine(
                    $"Semester {semester}: {sportName} {number}: {count} Schüler*innen"
                );

                counter++;
            }
        }

        sb.AppendLine();
        sb.AppendLine("Fehlerübersicht:");

        // ===== Fehler pro Semester =====
        for (int sem = 0; sem < semesterCount; sem++)
        {
            int errors = students.Count(st =>
                st.Result != null &&
                st.Result.Count > sem &&
                st.Result[sem] == "Fehler");

            sb.AppendLine($"Semester {sem + 1}: {errors} Fehler");
        }

        return sb.ToString();
    }
}