using System.Text.Json;
using ClawdDotNet.Core.Backup;
using ClawdDotNet.Core.Config;
using ClawdDotNet.Core.Instances;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;

namespace ClawdDotNet.Manager.Tests;

/// <summary>
/// The backups in the manager (#530): encrypted with the license key, once a
/// day, cleaned up, uploaded on request.
/// </summary>
public sealed class ManagerBackupsTests : IAsyncDisposable
{
    private const string Lizenz = "CLAWD-TEST-0000-1111-2222";

    private readonly string _root = Path.Combine(
        Path.GetTempPath(), "clawd-tests", "mbak-" + Guid.NewGuid().ToString("N")[..8]);

    private readonly InstanceDirectoryManager _directories;
    private readonly ManagerSettingsStore _settings;
    private readonly FakeUploader _upload = new();
    private readonly FixedClock _clock = new(new DateTimeOffset(2026, 9, 11, 2, 0, 0, TimeSpan.Zero));

    public ManagerBackupsTests()
    {
        Directory.CreateDirectory(_root);
        _directories = new InstanceDirectoryManager(Path.Combine(_root, "Instances"));
        _settings = new ManagerSettingsStore(_root);
        _settings.Settings.LicenseKey = Lizenz;
    }

    public async ValueTask DisposeAsync()
    {
        await Task.CompletedTask;
        ClawdDotNet.Core.Storage.SqliteStorage.ReleasePooledConnections(_root);
        try { Directory.Delete(_root, recursive: true); }
        catch { /* A leftover test folder does not turn a run red. */ }
    }

    private string Instance(string name, bool automatic = true, string timeOfDay = "03:00", int kept = 14)
    {
        var path = _directories.CreateInstance(name);
        var datei = Path.Combine(path, "InstanceSettings.json");

        var config = JsonSerializer.Deserialize<InstanceConfig>(File.ReadAllText(datei))!;
        config.AutoBackupEnabled = automatic;
        config.AutoBackupTime = timeOfDay;
        config.BackupKeepCount = kept;
        File.WriteAllText(datei, JsonSerializer.Serialize(config));

        return path;
    }

    private async Task<ManagerBackups> ServiceAsync(IBackupUploader? upload = null)
    {
        var register = new InstanceRegistry(
            _directories, new FakeLauncher(), new FakeChannel(), NullLoggerFactory.Instance,
            SupervisionOptions.Default);

        await register.RefreshAsync();

        return new ManagerBackups(
            _settings, register, upload ?? _upload, NullLogger.Instance, _clock);
    }

    private static string[] Backups(string path)
    {
        var folder = Path.Combine(path, "Backups");
        return Directory.Exists(folder) ? Directory.GetFiles(folder) : [];
    }

    // ─── Names ───

    /// <summary>
    /// A prefix is not a boundary: the archives of <c>Test_2</c> do not belong to
    /// <c>Test</c> — otherwise the cleanup of one throws away the backups of the other.
    /// </summary>
    [Fact]
    public void Overlapping_instance_names_are_not_confused()
    {
        var ownOnes = BackupNaming.FileNameFor("Test", new DateTime(2026, 9, 11, 3, 0, 0));
        var foreignOnes = BackupNaming.FileNameFor("Test_2", new DateTime(2026, 9, 11, 3, 0, 0));

        BackupNaming.BelongsTo(ownOnes, "Test").ShouldBeTrue();
        BackupNaming.BelongsTo(foreignOnes, "Test").ShouldBeFalse();
        BackupNaming.BelongsTo(foreignOnes, "Test_2").ShouldBeTrue();
    }

    [Theory]
    [InlineData("backup_Alpha_2026-09-11_0300.zip")]        // daily backup of the instance
    [InlineData("backup_Alpha_20260911_030000.zip")]        // first administration view
    [InlineData("backup_Alpha_2026-09-11_030000.clawdbak")] // Manager
    public void Older_spellings_are_recognised(string name)
    {
        BackupNaming.TimestampOf(name, "Alpha").ShouldBe(new DateTime(2026, 9, 11, 3, 0, 0));
    }

    [Theory]
    [InlineData("notizen.txt")]
    [InlineData("backup_Alpha_kaputt.zip")]
    [InlineData("backup_Alpha_2026-09-11_0300.zip.part")]
    public void Foreign_files_belong_to_nobody(string name)
    {
        BackupNaming.BelongsTo(name, "Alpha").ShouldBeFalse();
    }

    // ─── Backing up ───

    [Fact]
    public async Task Without_license_key_no_backup_is_created()
    {
        var path = Instance("Alpha");
        _settings.Settings.LicenseKey = "";

        await using var service = await ServiceAsync();
        var instance = (await RegisterAsync()).Single();

        await Should.ThrowAsync<BackupException>(() =>
            service.CreateAsync(instance, false, true, CancellationToken.None));

        Backups(path).ShouldBeEmpty("Unverschlüsselt wird nichts abgelegt — auch nicht ersatzweise.");
    }

    [Fact]
    public async Task A_backup_is_encrypted_and_uploaded()
    {
        var path = Instance("Alpha");

        await using var service = await ServiceAsync();
        var instance = (await RegisterAsync()).Single();

        var result = await service.CreateAsync(instance, false, true, CancellationToken.None);

        LicenseBackupCipher.IsEncrypted(result.Path).ShouldBeTrue();
        LicenseBackupCipher.MatchesKey(result.Path, Lizenz).ShouldBeTrue();

        result.Uploaded.ShouldBeTrue();
        _upload.Hochgeladen.ShouldBe([result.Path]);
    }

    /// <summary>
    /// A failed upload is a finding, but no reason to declare the backup
    /// failed — it lies locally, after all.
    /// </summary>
    [Fact]
    public async Task A_failed_upload_keeps_the_backup()
    {
        Instance("Alpha");
        _upload.Fehler = new IOException("Server nicht erreichbar");

        await using var service = await ServiceAsync();
        var instance = (await RegisterAsync()).Single();

        var result = await service.CreateAsync(instance, false, true, CancellationToken.None);

        File.Exists(result.Path).ShouldBeTrue();
        result.Uploaded.ShouldBeFalse();
        result.UploadProblem.ShouldBe("Server nicht erreichbar");
    }

    [Fact]
    public async Task Only_the_own_instance_is_cleaned_up()
    {
        var folder = Path.Combine(_root, "ablage");
        Directory.CreateDirectory(folder);

        for (var tag = 1; tag <= 5; tag++)
        {
            var time = new DateTime(2026, 9, tag, 3, 0, 0);
            File.WriteAllText(Path.Combine(folder, BackupNaming.FileNameFor("Test", time)), "");
            File.WriteAllText(Path.Combine(folder, BackupNaming.FileNameFor("Test_2", time)), "");
        }

        await using var service = await ServiceAsync();
        service.Rotate(folder, "Test", keep: 2);

        var names = Directory.GetFiles(folder).Select(Path.GetFileName).ToList();

        names.Count(n => BackupNaming.BelongsTo(n!, "Test")).ShouldBe(2);
        names.Count(n => BackupNaming.BelongsTo(n!, "Test_2")).ShouldBe(5, "Die andere Instanz bleibt unberührt.");
        names.ShouldContain(BackupNaming.FileNameFor("Test", new DateTime(2026, 9, 5, 3, 0, 0)));
    }

    // ─── The daily timer ───

    [Fact]
    public async Task Before_the_time_nothing_happens()
    {
        var path = Instance("Alpha", timeOfDay: "03:00");

        await using var service = await ServiceAsync();
        await service.TickAsync();   // 02:00

        Backups(path).ShouldBeEmpty();
    }

    [Fact]
    public async Task Once_a_day_and_not_more_often()
    {
        var path = Instance("Alpha", timeOfDay: "03:00");

        await using var service = await ServiceAsync();

        _clock.Jetzt = _clock.Jetzt.AddHours(1.5);   // 03:30
        await service.TickAsync();

        _clock.Jetzt = _clock.Jetzt.AddMinutes(30);  // 04:00
        await service.TickAsync();

        Backups(path).Length.ShouldBe(1);
    }

    /// <summary>
    /// Even across a restart of the manager. Counting only in memory would mean: whoever
    /// restarts after the backup time gets a second backup.
    /// </summary>
    [Fact]
    public async Task A_manager_restart_creates_no_second_backup()
    {
        var path = Instance("Alpha", timeOfDay: "03:00");
        _clock.Jetzt = _clock.Jetzt.AddHours(1.5);

        await using (var firstOne = await ServiceAsync())
            await firstOne.TickAsync();

        _clock.Jetzt = _clock.Jetzt.AddHours(1);

        await using (var secondOne = await ServiceAsync())
            await secondOne.TickAsync();

        Backups(path).Length.ShouldBe(1);
    }

    [Fact]
    public async Task Without_switch_no_automatic_backup()
    {
        var path = Instance("Alpha", automatic: false);
        _clock.Jetzt = _clock.Jetzt.AddHours(5);

        await using var service = await ServiceAsync();
        await service.TickAsync();

        Backups(path).ShouldBeEmpty();
    }

    // ─── Helpers ───

    private async Task<IReadOnlyList<ManagedInstance>> RegisterAsync()
    {
        var register = new InstanceRegistry(
            _directories, new FakeLauncher(), new FakeChannel(), NullLoggerFactory.Instance,
            SupervisionOptions.Default);

        await register.RefreshAsync();
        return register.Instances;
    }

    private sealed class FakeUploader : IBackupUploader
    {
        public List<string> Hochgeladen { get; } = [];
        public Exception? Fehler { get; set; }
        public bool IsConfigured => true;

        public Task UploadAsync(string localPath, string instanceName, int keepCount, CancellationToken ct)
        {
            if (Fehler is not null) throw Fehler;
            Hochgeladen.Add(localPath);
            return Task.CompletedTask;
        }

        public Task<string?> TestAsync(CancellationToken ct) => Task.FromResult<string?>(null);
    }

    /// <summary>A clock in UTC, so "local" means the same everywhere in the test.</summary>
    private sealed class FixedClock(DateTimeOffset start) : TimeProvider
    {
        public DateTimeOffset Jetzt { get; set; } = start;
        public override DateTimeOffset GetUtcNow() => Jetzt;
        public override TimeZoneInfo LocalTimeZone => TimeZoneInfo.Utc;
    }
}