using LehrerApp.Core.Models;
using LiteDB;
using Xunit;

namespace LehrerApp.Data.Tests;

public sealed class LiteDbContextTests
{
    [Fact]
    public void MigratesLegacyEnrollmentAndSubjectTextWithoutLosingData()
    {
        using var temp = new TempDatabase();
        var groupId = Guid.NewGuid();
        var studentId = Guid.NewGuid();
        var membershipId = Guid.NewGuid();
        var examId = Guid.NewGuid();
        var gradeId = Guid.NewGuid();
        var entryId = Guid.NewGuid();
        var addedOn = new DateOnly(2026, 6, 23);

        using (var legacy = new LiteDatabase(temp.Path))
        {
            legacy.GetCollection<Subject>("subjects").Insert(new Subject { Name = "mathematik" });
            legacy.GetCollection<BsonDocument>("groups").Insert(new BsonDocument
            {
                ["_id"] = groupId,
                [nameof(LearningGroup.Name)] = "Mathe G",
                ["Subject"] = "Mathematik",
                [nameof(LearningGroup.SchoolYear)] = "2025/26",
            });
            legacy.GetCollection<BsonDocument>("enrollments").Insert(new BsonDocument
            {
                ["_id"] = membershipId,
                [nameof(GroupMembership.StudentId)] = studentId,
                [nameof(GroupMembership.GroupId)] = groupId,
                ["SchoolYear"] = "2025/26",
                ["EnrolledAt"] = BsonMapper.Global.Serialize(addedOn),
            });
            legacy.GetCollection<BsonDocument>("exams").Insert(new BsonDocument
            {
                ["_id"] = examId,
                [nameof(Exam.GroupId)] = groupId,
                ["Subject"] = "Mathematik",
            });
            legacy.GetCollection<BsonDocument>("grades").Insert(new BsonDocument
            {
                ["_id"] = gradeId,
                [nameof(Grade.StudentId)] = studentId,
                [nameof(Grade.GroupId)] = groupId,
                ["SchoolYear"] = "2025/26",
            });
            legacy.GetCollection<BsonDocument>("participation").Insert(new BsonDocument
            {
                ["_id"] = entryId,
                [nameof(ParticipationEntry.SessionId)] = Guid.NewGuid(),
                [nameof(ParticipationEntry.StudentId)] = studentId,
                ["GroupId"] = groupId,
                ["Date"] = BsonMapper.Global.Serialize(addedOn),
            });
        }

        using (var context = new LiteDbContext(temp.Path))
        {
            var group = context.Groups.FindById(groupId);
            var membership = context.Memberships.FindById(membershipId);
            Assert.NotNull(group);
            Assert.NotNull(group.SubjectId);
            Assert.Equal("mathematik", context.Subjects.FindById(group.SubjectId.Value)?.Name);
            Assert.Equal(1, context.Subjects.Count());
            Assert.NotNull(membership);
            Assert.Equal(addedOn, membership.AddedOn);
        }

        using var migrated = new LiteDatabase(temp.Path);
        Assert.DoesNotContain("enrollments", migrated.GetCollectionNames());
        Assert.Contains("group_memberships", migrated.GetCollectionNames());
        var rawGroup = migrated.GetCollection<BsonDocument>("groups").FindById(groupId);
        var rawMembership = migrated.GetCollection<BsonDocument>("group_memberships").FindById(membershipId);
        var rawExam = migrated.GetCollection<BsonDocument>("exams").FindById(examId);
        var rawGrade = migrated.GetCollection<BsonDocument>("grades").FindById(gradeId);
        var rawEntry = migrated.GetCollection<BsonDocument>("participation").FindById(entryId);
        Assert.False(rawGroup.ContainsKey("Subject"));
        Assert.False(rawMembership.ContainsKey("SchoolYear"));
        Assert.False(rawMembership.ContainsKey("EnrolledAt"));
        Assert.True(rawMembership.ContainsKey(nameof(GroupMembership.AddedOn)));
        Assert.False(rawExam.ContainsKey("Subject"));
        Assert.False(rawGrade.ContainsKey("SchoolYear"));
        Assert.False(rawEntry.ContainsKey("GroupId"));
        Assert.False(rawEntry.ContainsKey("Date"));
    }

    [Fact]
    public void RejectsASecondMembershipForTheSameStudentAndGroup()
    {
        using var temp = new TempDatabase();
        using var context = new LiteDbContext(temp.Path);
        var studentId = Guid.NewGuid();
        var groupId = Guid.NewGuid();
        context.Memberships.Insert(new GroupMembership { StudentId = studentId, GroupId = groupId });

        Assert.Throws<LiteException>(() => context.Memberships.Insert(
            new GroupMembership { StudentId = studentId, GroupId = groupId }));
    }

    [Fact]
    public void RejectsASecondExamResultForTheSameStudentAndExam()
    {
        using var temp = new TempDatabase();
        using var context = new LiteDbContext(temp.Path);
        var studentId = Guid.NewGuid();
        var examId = Guid.NewGuid();
        context.ExamResults.Insert(new ExamResult { StudentId = studentId, ExamId = examId });

        Assert.Throws<LiteException>(() => context.ExamResults.Insert(
            new ExamResult { StudentId = studentId, ExamId = examId }));
    }

    [Fact]
    public void NeueDatenbank_HatDieAktuelleSchemaVersionNachDemErstenOeffnen()
    {
        using var temp = new TempDatabase();
        using var context = new LiteDbContext(temp.Path);

        Assert.Equal(4, context.SchemaVersion);
    }

    [Fact]
    public void SchemaVersion_WirdUeberEinenNeustartHinwegBeibehalten()
    {
        using var temp = new TempDatabase();
        using (var first = new LiteDbContext(temp.Path)) { }

        using var second = new LiteDbContext(temp.Path);

        Assert.Equal(4, second.SchemaVersion);
    }

    [Fact]
    public void MigrateLessonPhases_FasstAltePhaseMethodenUndMaterialienVerlustfreiZusammen()
    {
        using var temp = new TempDatabase();
        var lessonWithDataId = Guid.NewGuid();
        var lessonEmptyId = Guid.NewGuid();

        using (var legacy = new LiteDatabase(temp.Path))
        {
            legacy.GetCollection<BsonDocument>("lessons").Insert(new BsonDocument
            {
                ["_id"] = lessonWithDataId,
                [nameof(Lesson.UnitId)] = Guid.NewGuid(),
                [nameof(Lesson.GroupId)] = Guid.NewGuid(),
                ["Phase"] = "Einstieg",
                ["Methods"] = new BsonArray { "Gespräch", "Tafelbild" },
                ["Materials"] = new BsonArray { "Arbeitsblatt" },
            });
            // Alte Stunde ganz ohne Phase/Methoden/Materialien — soll leere Phases-Liste bekommen,
            // nicht eine leere synthetisierte Zeile.
            legacy.GetCollection<BsonDocument>("lessons").Insert(new BsonDocument
            {
                ["_id"] = lessonEmptyId,
                [nameof(Lesson.UnitId)] = Guid.NewGuid(),
                [nameof(Lesson.GroupId)] = Guid.NewGuid(),
            });
        }

        using (var context = new LiteDbContext(temp.Path))
        {
            var withData = context.Lessons.FindById(lessonWithDataId);
            Assert.NotNull(withData);
            Assert.Single(withData.Phases);
            Assert.Equal("Einstieg", withData.Phases[0].Name);
            Assert.Equal("Gespräch; Tafelbild", withData.Phases[0].Activity);
            Assert.Equal("Arbeitsblatt", withData.Phases[0].Material);
            Assert.Equal(0, withData.Phases[0].DurationMinutes);

            var empty = context.Lessons.FindById(lessonEmptyId);
            Assert.NotNull(empty);
            Assert.Empty(empty.Phases);
        }

        using var migrated = new LiteDatabase(temp.Path);
        var raw = migrated.GetCollection<BsonDocument>("lessons").FindById(lessonWithDataId);
        Assert.False(raw.ContainsKey("Phase"));
        Assert.False(raw.ContainsKey("Methods"));
        Assert.False(raw.ContainsKey("Materials"));
    }

    [Fact]
    public void MigrateLessonShorthand_FasstVonUndNachInEinFreitextfeldZusammen()
    {
        using var temp = new TempDatabase();
        var lessonId = Guid.NewGuid();

        using (var legacy = new LiteDatabase(temp.Path))
        {
            legacy.GetCollection<BsonDocument>("lessons").Insert(new BsonDocument
            {
                ["_id"] = lessonId,
                [nameof(Lesson.UnitId)] = Guid.NewGuid(),
                [nameof(Lesson.GroupId)] = Guid.NewGuid(),
                [nameof(Lesson.Phases)] = new BsonArray
                {
                    new BsonDocument { ["ShorthandFrom"] = "Tb", ["ShorthandTo"] = "SH" },
                    new BsonDocument { ["ShorthandFrom"] = "Plenum" }, // nur "Von" gesetzt, kein Pfeil
                    new BsonDocument { },                             // weder Von noch Nach
                },
            });
        }

        using (var context = new LiteDbContext(temp.Path))
        {
            var lesson = context.Lessons.FindById(lessonId);
            Assert.NotNull(lesson);
            Assert.Equal(3, lesson.Phases.Count);
            Assert.Equal("Tb->SH", lesson.Phases[0].Shorthand);
            Assert.Equal("Plenum", lesson.Phases[1].Shorthand);
            Assert.Equal("", lesson.Phases[2].Shorthand);
        }

        using var migratedShorthand = new LiteDatabase(temp.Path);
        var rawLesson = migratedShorthand.GetCollection<BsonDocument>("lessons").FindById(lessonId);
        var rawPhases = rawLesson["Phases"].AsArray;
        Assert.False(rawPhases[0].AsDocument.ContainsKey("ShorthandFrom"));
        Assert.False(rawPhases[0].AsDocument.ContainsKey("ShorthandTo"));
    }

    [Fact]
    public void MigrateLessonAlternativePaths_ErzeugtKatalogEintraegeUndVerweistDarauf()
    {
        using var temp = new TempDatabase();
        var lesson1Id = Guid.NewGuid();
        var lesson2Id = Guid.NewGuid();

        using (var legacy = new LiteDatabase(temp.Path))
        {
            legacy.GetCollection<BsonDocument>("lessons").Insert(new BsonDocument
            {
                ["_id"] = lesson1Id,
                [nameof(Lesson.UnitId)] = Guid.NewGuid(),
                [nameof(Lesson.GroupId)] = Guid.NewGuid(),
                [nameof(Lesson.Phases)] = new BsonArray
                {
                    new BsonDocument { ["AlternativePath"] = "Kurzversion" },
                    new BsonDocument { ["AlternativePath"] = "" }, // Hauptweg, kein Katalogeintrag
                    new BsonDocument { },                          // gar kein Feld, unangetastet
                },
            });
            legacy.GetCollection<BsonDocument>("lessons").Insert(new BsonDocument
            {
                ["_id"] = lesson2Id,
                [nameof(Lesson.UnitId)] = Guid.NewGuid(),
                [nameof(Lesson.GroupId)] = Guid.NewGuid(),
                [nameof(Lesson.Phases)] = new BsonArray
                {
                    new BsonDocument { ["AlternativePath"] = "Kurzversion" }, // gleicher Name -> gleicher Katalogeintrag
                },
            });
        }

        using (var context = new LiteDbContext(temp.Path))
        {
            var catalog = context.AlternativeLessonPaths.FindAll().ToList();
            var entry = Assert.Single(catalog);
            Assert.Equal("Kurzversion", entry.Name);

            var lesson1 = context.Lessons.FindById(lesson1Id)!;
            Assert.Equal(entry.Id, lesson1.Phases[0].AlternativePathId);
            Assert.Null(lesson1.Phases[1].AlternativePathId);
            Assert.Null(lesson1.Phases[2].AlternativePathId);

            var lesson2 = context.Lessons.FindById(lesson2Id)!;
            Assert.Equal(entry.Id, lesson2.Phases[0].AlternativePathId); // wiederverwendeter Katalogeintrag
        }

        using var migrated = new LiteDatabase(temp.Path);
        var rawLesson1 = migrated.GetCollection<BsonDocument>("lessons").FindById(lesson1Id);
        var rawPhases = rawLesson1["Phases"].AsArray;
        Assert.False(rawPhases[0].AsDocument.ContainsKey("AlternativePath"));
    }

    private sealed class TempDatabase : IDisposable
    {
        private readonly string _directory = System.IO.Path.Combine(
            System.IO.Path.GetTempPath(), $"lehrerapp-tests-{Guid.NewGuid():N}");
        public string Path { get; }

        public TempDatabase()
        {
            Directory.CreateDirectory(_directory);
            Path = System.IO.Path.Combine(_directory, "test.db");
        }

        public void Dispose()
        {
            if (Directory.Exists(_directory)) Directory.Delete(_directory, recursive: true);
        }
    }
}