using LehrerApp.Core.Models;
using LehrerApp.Data;
using LehrerApp.Sync.Crypto;
using LehrerApp.Sync.Models;
using Xunit;

namespace LehrerApp.Sync.Tests;

public sealed class EventApplierTests
{
    private static LiteDbContext NewInMemoryContext() => new(new MemoryStream());
    private static readonly byte[] Key = SyncCrypto.GenerateKey();

    [Fact]
    public void Apply_Save_SchreibtEntitaetDirektInDieCollection()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };

        applier.Apply(MakeEvent(nameof(Student), student.Id.ToString(), "Save", student));

        var saved = db.Students.FindById(student.Id);
        Assert.NotNull(saved);
        Assert.Equal("Anna", saved!.FirstName);
    }

    [Fact]
    public void Apply_Delete_EntferntDenDatensatz()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        db.Students.Insert(student);

        applier.Apply(MakeEvent(nameof(Student), student.Id.ToString(), "Delete", null));

        Assert.Null(db.Students.FindById(student.Id));
    }

    [Fact]
    public void Apply_UnbekannterEntityType_TutNichtsUndWirftNicht()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);

        var exception = Record.Exception(() =>
            applier.Apply(MakeEvent("UnbekannterTyp", Guid.NewGuid().ToString(), "Save", new { Foo = "Bar" })));

        Assert.Null(exception);
    }

    [Fact]
    public void Apply_GroupDelete_FuehrtDieselbeKaskadeAusWieDasRepository()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var groupId = Guid.NewGuid();
        db.Groups.Insert(new LearningGroup { Id = groupId, Name = "8a", SchoolYear = "2025/26" });
        var gradeId = Guid.NewGuid();
        db.Grades.Insert(new Grade { Id = gradeId, GroupId = groupId, StudentId = Guid.NewGuid() });

        applier.Apply(MakeEvent(nameof(LearningGroup), groupId.ToString(), "Delete", null));

        Assert.Null(db.Groups.FindById(groupId));
        Assert.Null(db.Grades.FindById(gradeId));
    }

    [Fact]
    public void Apply_VerletztHartenUniqueIndex_WirdUebersprungenOhneAusnahme()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var studentId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        db.Memberships.Insert(new GroupMembership { StudentId = studentId, GroupId = groupId });
        // Zweite Mitgliedschaft für dasselbe Schüler/Gruppe-Paar verletzt den ux_student_group-Index.
        var duplicate = new GroupMembership { Id = Guid.NewGuid(), StudentId = studentId, GroupId = groupId };

        var exception = Record.Exception(() =>
            applier.Apply(MakeEvent(nameof(GroupMembership), duplicate.Id.ToString(), "Save", duplicate)));

        Assert.Null(exception);
        Assert.Single(db.Memberships.FindAll());
    }

    // ── Loop-Prevention: der wichtigste Test in dieser Datei ────────────────────
    // Ein angewendetes Ereignis darf NIE selbst wieder ein ausgehendes Ereignis auslösen,
    // sonst entsteht ein Sync-Ping-Pong zwischen den Geräten (siehe EventApplier-Kommentar).

    [Fact]
    public void Apply_Save_LoestNIEMALSDenOnChangeHookAus()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var onChangeCallCount = 0;
        db.OnChange = (_, _, _, _) => onChangeCallCount++;
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };

        applier.Apply(MakeEvent(nameof(Student), student.Id.ToString(), "Save", student));

        Assert.Equal(0, onChangeCallCount);
    }

    [Fact]
    public void Apply_Delete_LoestNIEMALSDenOnChangeHookAus()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var student = new Student { FirstName = "Anna", LastName = "Beispiel" };
        db.Students.Insert(student);
        var onChangeCallCount = 0;
        db.OnChange = (_, _, _, _) => onChangeCallCount++;

        applier.Apply(MakeEvent(nameof(Student), student.Id.ToString(), "Delete", null));

        Assert.Equal(0, onChangeCallCount);
    }

    [Fact]
    public void Apply_GroupDeleteKaskade_LoestNIEMALSDenOnChangeHookAus()
    {
        using var db = NewInMemoryContext();
        var applier = new EventApplier(db, Key);
        var groupId = Guid.NewGuid();
        db.Groups.Insert(new LearningGroup { Id = groupId, Name = "8a", SchoolYear = "2025/26" });
        db.Grades.Insert(new Grade { GroupId = groupId, StudentId = Guid.NewGuid() });
        db.Exams.Insert(new Exam { GroupId = groupId });
        var onChangeCallCount = 0;
        db.OnChange = (_, _, _, _) => onChangeCallCount++;

        applier.Apply(MakeEvent(nameof(LearningGroup), groupId.ToString(), "Delete", null));

        Assert.Equal(0, onChangeCallCount);
    }

    private static SyncEvent MakeEvent(string entityType, string entityId, string operation, object? payload) => new()
    {
        DeviceId = "companion-1",
        DeviceType = DeviceType.Companion,
        EntityType = entityType,
        EntityId = entityId,
        Operation = operation,
        Payload = payload is null ? "" : SyncCrypto.EncryptObject(payload, Key),
        Timestamp = DateTime.UtcNow,
    };
}