using Core.Entities;

namespace Core.Calculation;

/// <summary>
/// Helper methods for calculating overlaps in team scheduling solutions.
/// </summary>
public static class OverlapCalculationHelper
{
    /// <summary>
    /// Creates teams with excluded students and absent students filtered out for overlap calculation.
    /// </summary>
    /// <param name="teams">The teams to filter</param>
    /// <param name="timeSlotIndex">The time slot index for exclusion lookups</param>
    /// <param name="excludedStudents">Dictionary of excluded students: key is (teamId, timeSlotIndex, studentId), value is true if excluded</param>
    /// <param name="absentStudentIds">Set of absent student IDs to exclude from overlap calculations</param>
    /// <returns>Teams with excluded and absent students removed</returns>
    public static Team[] GetTeamsWithoutExcludedStudents(
        Team[] teams,
        int timeSlotIndex,
        Dictionary<(int teamId, int timeSlotIndex, int studentId), bool> excludedStudents,
        HashSet<int> absentStudentIds)
    {
        return teams.Select(team =>
        {
            // Find excluded students for this team in this time slot
            // Also exclude absent students from overlap calculations
            var includedStudents = team.Students
                .Where(s => !IsStudentExcluded(team.Id, timeSlotIndex, s.Id, excludedStudents) && 
                           !absentStudentIds.Contains(s.Id))
                .ToList();

            // If no students are excluded, return original team
            if (includedStudents.Count == team.Students.Count)
                return team;

            // Create a temporary team with excluded and absent students removed
            return new Team
            {
                Id = team.Id,
                Event = team.Event,
                Students = includedStudents,
                Captain = team.Captain,
                Identifier = team.Identifier
            };
        }).ToArray();
    }

    private static bool IsStudentExcluded(
        int teamId,
        int timeSlotIndex,
        int studentId,
        Dictionary<(int teamId, int timeSlotIndex, int studentId), bool> excludedStudents)
    {
        var key = (teamId, timeSlotIndex, studentId);
        return excludedStudents.TryGetValue(key, out var isExcluded) && isExcluded;
    }
}