LehrerApp/LehrerApp.Tests/BackupServiceTests.cs

using LehrerApp.Core.Services;
using Xunit;

namespace LehrerApp.Tests;

public sealed class BackupServiceTests
{
    [Fact]
    public void CreateBackup_OhneVorhandeneDatenbank_GibtNullZurueck()
    {
        using var temp = new TempAppData();
        var service = new BackupService(temp.Path);

        var result = service.CreateBackup(Path.Combine(temp.Path, "fehlt.db"));

        Assert.Null(result);
    }

    [Fact]
    public void CreateBackup_KopiertDieDatenbankdatei()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        File.WriteAllText(dbPath, "Testinhalt");
        var service = new BackupService(temp.Path);

        var backupPath = service.CreateBackup(dbPath);

        Assert.NotNull(backupPath);
        Assert.True(File.Exists(backupPath));
        Assert.Equal("Testinhalt", File.ReadAllText(backupPath!));
    }

    [Fact]
    public void ListBackups_SortiertNeuesteZuerst()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        File.WriteAllText(dbPath, "v1");
        var service = new BackupService(temp.Path);

        var first = service.CreateBackup(dbPath)!;
        File.SetLastWriteTime(first, DateTime.Now.AddMinutes(-5));
        File.WriteAllText(dbPath, "v2");
        var second = service.CreateBackup(dbPath)!;

        var backups = service.ListBackups();

        Assert.Equal(2, backups.Count);
        Assert.Equal(second, backups[0].Path);
    }

    [Fact]
    public void CreateBackup_BehaeltNurDieLetztenNBackups()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        var service = new BackupService(temp.Path);

        for (var i = 0; i < 5; i++)
        {
            File.WriteAllText(dbPath, $"v{i}");
            var backup = service.CreateBackup(dbPath, keepCount: 3)!;
            File.SetLastWriteTime(backup, DateTime.Now.AddMinutes(-5 + i));
        }

        Assert.Equal(3, service.ListBackups().Count);
    }

    [Fact]
    public void RestoreBackup_KopiertBackupUeberDieZieldatei()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        File.WriteAllText(dbPath, "alt");
        var service = new BackupService(temp.Path);
        var backupPath = service.CreateBackup(dbPath)!;
        File.WriteAllText(dbPath, "neu-kaputt");

        service.RestoreBackup(backupPath, dbPath);

        Assert.Equal("alt", File.ReadAllText(dbPath));
    }

    [Fact]
    public void RestoreBackup_OhneVorhandenesBackup_WirftException()
    {
        using var temp = new TempAppData();
        var service = new BackupService(temp.Path);

        Assert.Throws<FileNotFoundException>(() =>
            service.RestoreBackup(Path.Combine(temp.Path, "backups", "fehlt.db"), Path.Combine(temp.Path, "lehrerapp.db")));
    }

    [Fact]
    public void CreateBackup_MitSecondaryDirectory_SpiegeltDasBackupDorthin()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        File.WriteAllText(dbPath, "Testinhalt");
        var secondaryDir = Path.Combine(temp.Path, "secondary");
        var service = new BackupService(temp.Path) { SecondaryBackupDirectory = secondaryDir };

        var backupPath = service.CreateBackup(dbPath);

        Assert.NotNull(backupPath);
        var mirrored = Path.Combine(secondaryDir, Path.GetFileName(backupPath!));
        Assert.True(File.Exists(mirrored));
        Assert.Equal("Testinhalt", File.ReadAllText(mirrored));
    }

    [Fact]
    public void CreateBackup_SecondaryDirectoryNichtErreichbar_HauptbackupBleibtErhalten()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        File.WriteAllText(dbPath, "Testinhalt");
        // Eine gewöhnliche Datei blockiert den Pfad, sodass darunter kein Verzeichnis angelegt
        // werden kann — simuliert plattformunabhängig ein nicht eingestecktes USB-Ziel bzw. eine
        // nicht erreichbare Netzwerkfreigabe.
        var blockingFile = Path.Combine(temp.Path, "blockiert");
        File.WriteAllText(blockingFile, "x");
        var unreachable = Path.Combine(blockingFile, "secondary");
        var service = new BackupService(temp.Path) { SecondaryBackupDirectory = unreachable };

        var backupPath = service.CreateBackup(dbPath);

        Assert.NotNull(backupPath);
        Assert.True(File.Exists(backupPath));
    }

    [Fact]
    public void CreateBackup_MitSecondaryDirectory_BehaeltNurDieLetztenNAuchDort()
    {
        using var temp = new TempAppData();
        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
        var secondaryDir = Path.Combine(temp.Path, "secondary");
        var service = new BackupService(temp.Path) { SecondaryBackupDirectory = secondaryDir };

        for (var i = 0; i < 5; i++)
        {
            File.WriteAllText(dbPath, $"v{i}");
            var backup = service.CreateBackup(dbPath, keepCount: 3)!;
            var mirrored = Path.Combine(secondaryDir, Path.GetFileName(backup));
            File.SetLastWriteTime(mirrored, DateTime.Now.AddMinutes(-5 + i));
        }

        Assert.Equal(3, Directory.GetFiles(secondaryDir, "lehrerapp-*.db").Length);
    }

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

        public TempAppData() => Directory.CreateDirectory(Path);
        public void Dispose() { if (Directory.Exists(Path)) Directory.Delete(Path, recursive: true); }
    }
}