using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;

namespace LehrerApp.Desktop.Services;

/// <summary>Schließt nicht nachgereichte Hausaufgaben 14 Kalendertage nach der Unterrichtsstunde.
/// Nur noch offene Nachreichungen werden geändert; andere Stati und archivierte Gruppen bleiben
/// unangetastet.</summary>
public sealed class HomeworkOverdueService(
    IGroupRepository groups, IParticipationSessionRepository sessions,
    IParticipationRepository participation)
{
    public const int GracePeriodDays = 14;

    public int Advance(DateOnly today)
    {
        var cutoff = today.AddDays(-GracePeriodDays);
        var activeGroupIds = groups.GetAll().Where(g => g.IsActive).Select(g => g.Id).ToHashSet();
        var changed = 0;
        foreach (var session in sessions.GetAll()
                     .Where(s => s.Date <= cutoff && activeGroupIds.Contains(s.GroupId)))
        foreach (var entry in participation.GetBySession(session.Id))
        {
            if (entry.Homework != HomeworkStatus.MissingOpen &&
                !(entry.Homework is null && entry.HomeworkMissing)) continue;
            entry.Homework = HomeworkStatus.MissingOverdue;
            entry.HomeworkMissing = true;
            participation.Save(entry);
            changed++;
        }
        return changed;
    }
}