namespace HSchool.People;

public readonly record struct StaffOpening(string RoomId, string Position);

public readonly record struct PupilSeat(string ClassId, string RoomId, int Year, string Letter);

/// <summary>
/// How many pupils and staff a map asks for. Homeroom rooms with pupil slots become roster
/// classes; every <see cref="RoomDef.Positions"/> entry is a staff opening.
/// </summary>
public sealed class SchoolDemand
{
    internal SchoolDemand(
        IReadOnlyList<SchoolClass> classes,
        IReadOnlyList<PupilSeat> seats,
        IReadOnlyList<StaffOpening> staff)
    {
        Classes = classes;
        Seats = seats;
        Staff = staff;
    }

    public IReadOnlyList<SchoolClass> Classes { get; }

    public IReadOnlyList<PupilSeat> Seats { get; }

    public IReadOnlyList<StaffOpening> Staff { get; }

    public static SchoolDemand From(DefCatalog catalog, MapLayout map)
    {
        var classrooms = new List<(RoomNode Room, int Slots)>();
        var staff = new List<StaffOpening>();

        foreach (var room in map.Rooms)
        {
            var slots = RoomOccupancy.PupilSlots(catalog, room);
            if (catalog.Rooms.TryGetValue(room.Def, out var def))
            {
                foreach (var position in def.Positions)
                {
                    staff.Add(new StaffOpening(room.Id, position));
                }

                if (slots > 0 && def.Homeroom)
                {
                    classrooms.Add((room, slots));
                }
            }
        }

        const string letters = "АБВГДЕЖЗИКЛМНОПРСТУФХЦЧШЩЭЮЯ";
        var classes = new SchoolClass[classrooms.Count];
        var seats = new List<PupilSeat>();
        for (var i = 0; i < classrooms.Count; i++)
        {
            var (room, capacity) = classrooms[i];
            var year = (i % 11) + 1;
            var letterIndex = i / 11;
            var letter = letterIndex < letters.Length ? letters[letterIndex].ToString() : "?";
            var classId = $"class-{room.Id}";
            classes[i] = new SchoolClass(classId, year, letter, room.Id, capacity, []);
            for (var seat = 0; seat < capacity; seat++)
            {
                seats.Add(new PupilSeat(classId, room.Id, year, letter));
            }
        }

        return new SchoolDemand(classes, seats, staff);
    }
}