using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Core.Services;
using Xunit;

namespace LehrerApp.Tests;

public sealed class GroupRolloverServiceTests
{
    [Fact]
    public void RollOver_KopiertStammdatenUndErzeugtNeueGanzjaehrigeMitgliedschaften()
    {
        var source = new LearningGroup
        {
            Name = "8a", SchoolYear = "2025/26", GradeLevel = 8,
            Type = GroupType.Class, SubjectId = Guid.NewGuid(), GradingSystem = GradingSystem.Grades1To6,
            HoursPerWeek = 4, IsOwnClass = true, IsDifferentiated = true,
        };
        var oldMembership = new GroupMembership
        {
            StudentId = Guid.NewGuid(), GroupId = source.Id, Period = MembershipPeriod.H2Only,
            JoinedAt = new DateOnly(2026, 2, 1), LeftAt = new DateOnly(2026, 7, 31), Niveau = Niveau.E,
        };
        var groups = new MemoryGroups([source]);
        var memberships = new MemoryMemberships([oldMembership]);
        var schemes = new MemorySchemes();
        schemes.Save(new GradingScheme
        {
            GroupId = source.Id, ExamsPercent = 40, ParticipationPercent = 50, OtherPercent = 10,
        });
        var service = new GroupRolloverService(groups, memberships, schemes, new SchoolYearService());

        var target = service.RollOver(source, new GroupRolloverRequest(
            "9a", "2026/27", 9, [oldMembership.Id], true, true));

        Assert.Equal("9a", target.Name);
        Assert.Equal(source.SubjectId, target.SubjectId);
        Assert.Equal(source.HoursPerWeek, target.HoursPerWeek);
        Assert.True(target.IsOwnClass);
        Assert.True(target.IsDifferentiated);
        Assert.False(source.IsActive);

        var copied = Assert.Single(memberships.GetByGroup(target.Id));
        Assert.NotEqual(oldMembership.Id, copied.Id);
        Assert.Equal(MembershipPeriod.FullYear, copied.Period);
        Assert.Equal(new DateOnly(2026, 8, 1), copied.JoinedAt);
        Assert.Null(copied.LeftAt);
        Assert.Equal(Niveau.E, copied.Niveau);

        var scheme = schemes.GetByGroup(target.Id);
        Assert.NotNull(scheme);
        Assert.Equal(40, scheme.ExamsPercent);
        Assert.NotEqual(schemes.GetByGroup(source.Id)!.Id, scheme.Id);
    }

    [Fact]
    public void RollOver_GleichnamigeGruppeImZieljahr_WirdAbgelehnt()
    {
        var subjectId = Guid.NewGuid();
        var source = new LearningGroup
        {
            Name = "8a", SchoolYear = "2025/26", GradeLevel = 8,
            Type = GroupType.Class, SubjectId = subjectId,
        };
        var existing = new LearningGroup
        {
            Name = "9a", SchoolYear = "2026/27", GradeLevel = 9,
            Type = GroupType.Class, SubjectId = subjectId,
        };
        var membership = new GroupMembership { StudentId = Guid.NewGuid(), GroupId = source.Id };
        var service = new GroupRolloverService(
            new MemoryGroups([source, existing]), new MemoryMemberships([membership]),
            new MemorySchemes(), new SchoolYearService());

        var error = Assert.Throws<InvalidOperationException>(() => service.RollOver(source,
            new GroupRolloverRequest("9a", "2026/27", 9, [membership.Id], false, false)));

        Assert.Contains("bereits", error.Message);
    }

    private sealed class MemoryGroups(List<LearningGroup> items) : IGroupRepository
    {
        public LearningGroup? GetById(Guid id) => items.FirstOrDefault(g => g.Id == id);
        public List<LearningGroup> GetAll(bool includeInactive = false) =>
            items.Where(g => includeInactive || g.IsActive).ToList();
        public List<LearningGroup> GetBySchoolYear(string schoolYear, bool includeInactive = false) =>
            items.Where(g => g.SchoolYear == schoolYear && (includeInactive || g.IsActive)).ToList();
        public void Save(LearningGroup group) { items.RemoveAll(g => g.Id == group.Id); items.Add(group); }
        public void Delete(Guid id) => items.RemoveAll(g => g.Id == id);
    }

    private sealed class MemoryMemberships(List<GroupMembership> items) : IGroupMembershipRepository
    {
        public List<GroupMembership> GetByStudent(Guid studentId) => items.Where(m => m.StudentId == studentId).ToList();
        public List<GroupMembership> GetByGroup(Guid groupId) => items.Where(m => m.GroupId == groupId).ToList();
        public GroupMembership? GetByStudentAndGroup(Guid studentId, Guid groupId) =>
            items.FirstOrDefault(m => m.StudentId == studentId && m.GroupId == groupId);
        public void Save(GroupMembership membership) { items.RemoveAll(m => m.Id == membership.Id); items.Add(membership); }
        public void Delete(Guid id) => items.RemoveAll(m => m.Id == id);
    }

    private sealed class MemorySchemes : IGradingSchemeRepository
    {
        private readonly List<GradingScheme> _items = [];
        public GradingScheme? GetByGroup(Guid groupId) => _items.FirstOrDefault(s => s.GroupId == groupId);
        public GradingScheme? GetDefaultForType(GroupType type) => _items.FirstOrDefault(s => s.GroupType == type);
        public void Save(GradingScheme scheme) { _items.RemoveAll(s => s.Id == scheme.Id); _items.Add(scheme); }
        public void Delete(Guid id) => _items.RemoveAll(s => s.Id == id);
    }
}