107 lines
5.3 KiB
C#
107 lines
5.3 KiB
C#
using System.Net.Http.Json;
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using LehrerApp.Data;
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using LehrerApp.Sync.Crypto;
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using LehrerApp.Sync.Models;
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namespace LehrerApp.Sync;
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/// <summary>
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/// Device-Pairing via verschlüsseltem Snapshot + Einmal-Code.
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///
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/// Sender: CreateAndUploadAsync() → zeigt Code dem Nutzer
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/// Empfänger: RestoreFromCodeAsync(code) → entschlüsselt Schlüssel + DB
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/// </summary>
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public class SnapshotService(
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HttpClient http, LiteDbContext db, byte[] syncKey,
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DeviceType deviceType, string dbPath, string keyPath)
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{
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public event Action<SnapshotProgress>? ProgressChanged;
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public async Task<SnapshotUploadResponse> CreateAndUploadAsync(CancellationToken ct = default)
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{
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Report(SnapshotStep.Checkpointing, "Datenbank wird gesichert…");
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db.Checkpoint();
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Report(SnapshotStep.Reading, "Datenbank wird gelesen…");
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var dbBytes = await File.ReadAllBytesAsync(dbPath, ct);
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Report(SnapshotStep.Encrypting, "Verschlüsselung läuft…");
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var encPayload = Convert.ToBase64String(SyncCrypto.Encrypt(dbBytes, syncKey));
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// Schritt 1: Upload ohne Key → Code erhalten
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Report(SnapshotStep.Uploading, "Code wird angefordert…");
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using var request1 = SyncProtocol.CreateRequest(HttpMethod.Post, "/api/snapshot/upload");
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request1.Content = JsonContent.Create(
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new SnapshotUploadRequest { EncryptedPayload = encPayload, DeviceType = deviceType });
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using var r1 = await http.SendAsync(request1, ct);
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await SyncProtocol.EnsureCompatibleSuccessAsync(r1);
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var init = await r1.Content.ReadFromJsonAsync<SnapshotUploadResponse>(ct)
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?? throw new InvalidOperationException("Leere Server-Antwort.");
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// Schritt 2: Key mit Code verschlüsseln + erneut hochladen
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Report(SnapshotStep.Uploading, "Schlüssel wird verschlüsselt…");
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var encKey = SyncCrypto.EncryptKeyWithCode(syncKey, init.Code);
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using var request2 = SyncProtocol.CreateRequest(HttpMethod.Post, "/api/snapshot/upload");
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request2.Content = JsonContent.Create(
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new SnapshotUploadRequest { EncryptedPayload = encPayload,
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EncryptedSyncKey = encKey, DeviceType = deviceType,
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Code = init.Code });
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using var r2 = await http.SendAsync(request2, ct);
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await SyncProtocol.EnsureCompatibleSuccessAsync(r2);
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var result = await r2.Content.ReadFromJsonAsync<SnapshotUploadResponse>(ct)
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?? throw new InvalidOperationException("Leere Server-Antwort.");
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Report(SnapshotStep.Done, $"Bereit – Code: {result.Code}");
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return result;
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}
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public async Task<byte[]> RestoreFromCodeAsync(string code, string targetDbPath,
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CancellationToken ct = default)
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{
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var sanitized = code.Trim().ToUpperInvariant();
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Report(SnapshotStep.Downloading, "Snapshot wird geladen…");
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using var request = SyncProtocol.CreateRequest(HttpMethod.Get, $"/api/snapshot/{sanitized}");
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using var resp = await http.SendAsync(request, ct);
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if (resp.StatusCode == System.Net.HttpStatusCode.NotFound)
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throw new SnapshotNotFoundException($"Code '{sanitized}' nicht gefunden oder abgelaufen.");
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await SyncProtocol.EnsureCompatibleSuccessAsync(resp);
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var dl = await resp.Content.ReadFromJsonAsync<SnapshotDownloadResponse>(ct)
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?? throw new InvalidOperationException("Leere Server-Antwort.");
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Report(SnapshotStep.Decrypting, "Schlüssel wird entschlüsselt…");
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byte[] restoredKey;
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try { restoredKey = SyncCrypto.DecryptKeyWithCode(dl.EncryptedSyncKey, sanitized); }
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catch (System.Security.Cryptography.CryptographicException)
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{ throw new InvalidOperationException("Schlüssel-Entschlüsselung fehlgeschlagen – Code korrekt?"); }
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SyncCrypto.SaveKey(restoredKey, keyPath);
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Report(SnapshotStep.Decrypting, "Datenbank wird entschlüsselt…");
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var dbBytes = SyncCrypto.Decrypt(Convert.FromBase64String(dl.EncryptedPayload), restoredKey);
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Report(SnapshotStep.Writing, "Datenbank wird geschrieben…");
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Directory.CreateDirectory(Path.GetDirectoryName(targetDbPath)!);
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if (File.Exists(targetDbPath))
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File.Move(targetDbPath, $"{targetDbPath}.backup-{DateTime.Now:yyyyMMdd-HHmmss}");
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await File.WriteAllBytesAsync(targetDbPath, dbBytes, ct);
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Report(SnapshotStep.Done, "Abgeschlossen – bitte App neu starten.");
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return restoredKey;
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}
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private void Report(SnapshotStep step, string msg) =>
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ProgressChanged?.Invoke(new(step, msg));
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}
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public record SnapshotProgress(SnapshotStep Step, string Message)
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{
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public int Percent => Step switch
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{
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SnapshotStep.Checkpointing => 10, SnapshotStep.Reading => 20,
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SnapshotStep.Encrypting => 35, SnapshotStep.Uploading => 60,
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SnapshotStep.Downloading => 35, SnapshotStep.Decrypting => 65,
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SnapshotStep.Writing => 85, SnapshotStep.Done => 100,
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_ => 0,
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};
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public bool IsComplete => Step == SnapshotStep.Done;
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}
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public enum SnapshotStep { Idle, Checkpointing, Reading, Encrypting,
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Uploading, Downloading, Decrypting, Writing, Done }
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public class SnapshotNotFoundException(string msg) : Exception(msg);
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