1  using GUNRPG.Application.Sessions;
 2  using LiteDB;
 3  using LiteDB.Migration;
 4  
 5  namespace GUNRPG.Infrastructure.Persistence;
 6  
 7  /// <summary>
 8  /// Manages database schema migrations for LiteDB.
 9  /// Handles versioning and upgrading of combat session snapshots.
10  /// </summary>
11  public static class LiteDbMigrations
12  {
13      /// <summary>
14      /// Current schema version of the combat session snapshot.
15      /// Increment this when making breaking changes to the snapshot structure.
16      /// </summary>
17      public const int CurrentSchemaVersion = 1;
18  
19      /// <summary>
20      /// Applies all necessary migrations to the database.
21      /// Should be called during application startup before any data access.
22      /// </summary>
23      /// <param name="database">The LiteDB database instance</param>
24      public static void ApplyMigrations(LiteDatabase database)
25      {
26          if (database == null)
27              throw new ArgumentNullException(nameof(database));
28              
29          // Currently on version 1 with no migrations needed
30          // When schema changes are needed, add migrations here using LiteDB.Migration
31          
32          // Example migration setup for future use:
33          // var migrations = new MigrationContainer(config =>
34          // {
35          //     config.Collection<CombatSessionSnapshot>("combat_sessions", collectionConfig =>
36          //     {
37          //         collectionConfig
38          //             .StartWithModel<OldCombatSessionSnapshot>()
39          //             .WithMigration(old => new CurrentCombatSessionSnapshot
40          //             {
41          //                 Id = old.Id,
42          //                 // ... map properties
43          //                 NewProperty = "default"
44          //             })
45          //             .UseLatestVersion();
46          //     });
47          // });
48          // migrations.Apply(database);
49          
50          // No migrations to apply yet - we're on the initial schema version
51      }
52  
53      /// <summary>
54      /// Gets the current schema version stored in the database metadata.
55      /// Returns 0 if no version is set (new database).
56      /// </summary>
57      public static int GetDatabaseSchemaVersion(LiteDatabase database)
58      {
59          if (database == null)
60              throw new ArgumentNullException(nameof(database));
61              
62          var metadata = database.GetCollection("_metadata");
63          var versionDoc = metadata.FindById("schema_version");
64          
65          if (versionDoc == null)
66          {
67              return 0;
68          }
69  
70          return versionDoc["version"].AsInt32;
71      }
72  
73      /// <summary>
74      /// Sets the schema version in the database metadata.
75      /// Used to track which migrations have been applied.
76      /// </summary>
77      public static void SetDatabaseSchemaVersion(LiteDatabase database, int version)
78      {
79          if (database == null)
80              throw new ArgumentNullException(nameof(database));
81              
82          var metadata = database.GetCollection("_metadata");
83          var versionDoc = new BsonDocument
84          {
85              ["_id"] = "schema_version",
86              ["version"] = version,
87              ["updated_at"] = DateTimeOffset.UtcNow.ToString("O")
88          };
89          metadata.Upsert(versionDoc);
90      }
91  }