Implement DuckDB Graph Repository Methods and Unit Tests

- Added LabelMethods, NodeMethods, TagMethods, TenantMethods, UserMethods, VectorIndexMethods, and VectorMethods for DuckDB implementation.
- Each method includes not implemented exceptions for future development.
- Created DuckDBGraphRepositoryTests to validate repository functionality, including constructor tests, method implementations, and exception handling.
- Added project file for tests with necessary dependencies.

Author: miserix13

DuckDBGraphRepository.cs

@@ -1,7 +1,287 @@
-namespace WebNet.LiteGraphExtensions.GraphRepositories
+using System;
+using DuckDB.NET.Data;
+using LiteGraph.GraphRepositories.Interfaces;
+
+namespace WebNet.LiteGraphExtensions.GraphRepositories
 {
-    public class DuckDBGraphRepository
+    /// <summary>
+    /// DuckDB Graph Repository implementation.
+    /// Provides graph storage and retrieval using DuckDB as the backend.
+    /// </summary>
+    public class DuckDBGraphRepository : LiteGraph.GraphRepositories.GraphRepositoryBase
     {
+        #region Public-Members
+
+        /// <summary>
+        /// Admin methods.
+        /// </summary>
+        public override IAdminMethods Admin { get; }
+
+        /// <summary>
+        /// Tenant methods.
+        /// </summary>
+        public override ITenantMethods Tenant { get; }
+
+        /// <summary>
+        /// User methods.
+        /// </summary>
+        public override IUserMethods User { get; }
+
+        /// <summary>
+        /// Credential methods.
+        /// </summary>
+        public override ICredentialMethods Credential { get; }
+
+        /// <summary>
+        /// Label methods.
+        /// </summary>
+        public override ILabelMethods Label { get; }
+
+        /// <summary>
+        /// Tag methods.
+        /// </summary>
+        public override ITagMethods Tag { get; }
+
+        /// <summary>
+        /// Vector methods.
+        /// </summary>
+        public override IVectorMethods Vector { get; }
+
+        /// <summary>
+        /// Graph methods.
+        /// </summary>
+        public override IGraphMethods Graph { get; }
+
+        /// <summary>
+        /// Node methods.
+        /// </summary>
+        public override INodeMethods Node { get; }
+
+        /// <summary>
+        /// Edge methods.
+        /// </summary>
+        public override IEdgeMethods Edge { get; }
+
+        /// <summary>
+        /// Batch methods.
+        /// </summary>
+        public override IBatchMethods Batch { get; }
+
+        /// <summary>
+        /// Vector index methods.
+        /// </summary>
+        public override IVectorIndexMethods VectorIndex { get; }
+
+        #endregion
+
+        #region Private-Members
+
+        private readonly string _connectionString;
+        private readonly DuckDBConnection _connection;
+
+        #endregion
+
+        #region Constructors-and-Factories
+
+        /// <summary>
+        /// Initialize the DuckDB graph repository.
+        /// </summary>
+        /// <param name="connectionString">DuckDB connection string.</param>
+        public DuckDBGraphRepository(string connectionString)
+        {
+            if (string.IsNullOrEmpty(connectionString))
+                throw new ArgumentNullException(nameof(connectionString));
+
+            _connectionString = connectionString;
+            _connection = new DuckDBConnection(connectionString);
+            _connection.Open();
+
+            // Initialize implementation classes
+            Admin = new Implementations.AdminMethods(this);
+            Tenant = new Implementations.TenantMethods(this);
+            User = new Implementations.UserMethods(this);
+            Credential = new Implementations.CredentialMethods(this);
+            Label = new Implementations.LabelMethods(this);
+            Tag = new Implementations.TagMethods(this);
+            Vector = new Implementations.VectorMethods(this);
+            Graph = new Implementations.GraphMethods(this);
+            Node = new Implementations.NodeMethods(this);
+            Edge = new Implementations.EdgeMethods(this);
+            Batch = new Implementations.BatchMethods(this);
+            VectorIndex = new Implementations.VectorIndexMethods(this);
+
+            InitializeRepository();
+        }
+
+        #endregion
+
+        #region Public-Methods
+
+        /// <summary>
+        /// Initialize the repository schema.
+        /// </summary>
+        public override void InitializeRepository()
+        {
+            // Create necessary database tables and schemas for DuckDB
+            using (var command = _connection.CreateCommand())
+            {
+                command.CommandText = @"
+                    -- Create tenants table
+                    CREATE TABLE IF NOT EXISTS tenants (
+                        guid VARCHAR PRIMARY KEY,
+                        name VARCHAR NOT NULL,
+                        created_utc TIMESTAMP NOT NULL,
+                        data JSON
+                    );
+
+                    -- Create graphs table
+                    CREATE TABLE IF NOT EXISTS graphs (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        name VARCHAR NOT NULL,
+                        created_utc TIMESTAMP NOT NULL,
+                        labels VARCHAR[],
+                        tags JSON,
+                        data JSON,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid)
+                    );
+
+                    -- Create nodes table
+                    CREATE TABLE IF NOT EXISTS nodes (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        graph_guid VARCHAR NOT NULL,
+                        name VARCHAR,
+                        created_utc TIMESTAMP NOT NULL,
+                        labels VARCHAR[],
+                        tags JSON,
+                        data JSON,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid),
+                        FOREIGN KEY (graph_guid) REFERENCES graphs(guid)
+                    );
+
+                    -- Create edges table
+                    CREATE TABLE IF NOT EXISTS edges (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        graph_guid VARCHAR NOT NULL,
+                        from_node_guid VARCHAR NOT NULL,
+                        to_node_guid VARCHAR NOT NULL,
+                        name VARCHAR,
+                        created_utc TIMESTAMP NOT NULL,
+                        labels VARCHAR[],
+                        tags JSON,
+                        data JSON,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid),
+                        FOREIGN KEY (graph_guid) REFERENCES graphs(guid),
+                        FOREIGN KEY (from_node_guid) REFERENCES nodes(guid),
+                        FOREIGN KEY (to_node_guid) REFERENCES nodes(guid)
+                    );
+
+                    -- Create labels table
+                    CREATE TABLE IF NOT EXISTS labels (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        graph_guid VARCHAR,
+                        name VARCHAR NOT NULL,
+                        created_utc TIMESTAMP NOT NULL,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid)
+                    );
+
+                    -- Create users table
+                    CREATE TABLE IF NOT EXISTS users (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR,
+                        email VARCHAR NOT NULL,
+                        created_utc TIMESTAMP NOT NULL,
+                        data JSON
+                    );
+
+                    -- Create credentials table
+                    CREATE TABLE IF NOT EXISTS credentials (
+                        guid VARCHAR PRIMARY KEY,
+                        user_guid VARCHAR NOT NULL,
+                        credential_type VARCHAR NOT NULL,
+                        credential_data JSON NOT NULL,
+                        created_utc TIMESTAMP NOT NULL,
+                        FOREIGN KEY (user_guid) REFERENCES users(guid)
+                    );
+
+                    -- Create vectors table
+                    CREATE TABLE IF NOT EXISTS vectors (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        graph_guid VARCHAR NOT NULL,
+                        node_guid VARCHAR NOT NULL,
+                        embedding DOUBLE[],
+                        created_utc TIMESTAMP NOT NULL,
+                        metadata JSON,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid),
+                        FOREIGN KEY (graph_guid) REFERENCES graphs(guid),
+                        FOREIGN KEY (node_guid) REFERENCES nodes(guid)
+                    );
+
+                    -- Create tags table
+                    CREATE TABLE IF NOT EXISTS tags (
+                        guid VARCHAR PRIMARY KEY,
+                        tenant_guid VARCHAR NOT NULL,
+                        graph_guid VARCHAR,
+                        name VARCHAR NOT NULL,
+                        value VARCHAR,
+                        created_utc TIMESTAMP NOT NULL,
+                        FOREIGN KEY (tenant_guid) REFERENCES tenants(guid)
+                    );
+
+                    -- Create indexes
+                    CREATE INDEX IF NOT EXISTS idx_graphs_tenant ON graphs(tenant_guid);
+                    CREATE INDEX IF NOT EXISTS idx_nodes_graph ON nodes(graph_guid);
+                    CREATE INDEX IF NOT EXISTS idx_nodes_tenant ON nodes(tenant_guid);
+                    CREATE INDEX IF NOT EXISTS idx_edges_graph ON edges(graph_guid);
+                    CREATE INDEX IF NOT EXISTS idx_edges_from ON edges(from_node_guid);
+                    CREATE INDEX IF NOT EXISTS idx_edges_to ON edges(to_node_guid);
+                    CREATE INDEX IF NOT EXISTS idx_labels_tenant ON labels(tenant_guid);
+                    CREATE INDEX IF NOT EXISTS idx_vectors_node ON vectors(node_guid);
+                    CREATE INDEX IF NOT EXISTS idx_tags_tenant ON tags(tenant_guid);
+                ";
+
+                command.ExecuteNonQuery();
+            }
+        }
+
+        /// <summary>
+        /// Flush database contents to disk.
+        /// </summary>
+        public override void Flush()
+        {
+            // DuckDB automatically flushes to disk, but we can force a checkpoint
+            using (var command = _connection.CreateCommand())
+            {
+                command.CommandText = "CHECKPOINT;";
+                command.ExecuteNonQuery();
+            }
+        }
+
+        /// <summary>
+        /// Get the DuckDB connection.
+        /// </summary>
+        /// <returns>DuckDB connection.</returns>
+        internal DuckDBConnection GetConnection()
+        {
+            return _connection;
+        }
+
+        /// <summary>
+        /// Dispose the repository.
+        /// </summary>
+        public void Dispose()
+        {
+            _connection?.Dispose();
+        }
+
+        #endregion
+
+        #region Private-Methods
 
+        #endregion
     }
 }

Implementations/DuckDB/AdminMethods.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using LiteGraph.GraphRepositories.Interfaces;
+
+namespace WebNet.LiteGraphExtensions.GraphRepositories.Implementations
+{
+    /// <summary>
+    /// Admin methods for DuckDB.
+    /// </summary>
+    public class AdminMethods : IAdminMethods
+    {
+        private readonly DuckDBGraphRepository _repo;
+
+        public AdminMethods(DuckDBGraphRepository repo)
+        {
+            _repo = repo ?? throw new ArgumentNullException(nameof(repo));
+        }
+
+        public async Task Backup(string outputFilename, CancellationToken token = default)
+        {
+            token.ThrowIfCancellationRequested();
+            
+            using (var command = _repo.GetConnection().CreateCommand())
+            {
+                command.CommandText = $"EXPORT DATABASE '{outputFilename}';";
+                await command.ExecuteNonQueryAsync();
+            }
+        }
+    }
+}

Implementations/DuckDB/BatchMethods.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using LiteGraph;
+using LiteGraph.GraphRepositories.Interfaces;
+
+namespace WebNet.LiteGraphExtensions.GraphRepositories.Implementations
+{
+    /// <summary>
+    /// Batch methods for DuckDB.
+    /// </summary>
+    public class BatchMethods : IBatchMethods
+    {
+        private readonly DuckDBGraphRepository _repo;
+
+        public BatchMethods(DuckDBGraphRepository repo)
+        {
+            _repo = repo ?? throw new ArgumentNullException(nameof(repo));
+        }
+
+        public Task<ExistenceResult> Existence(Guid tenantGuid, Guid graphGuid, ExistenceRequest req, CancellationToken token = default)
+        {
+            throw new NotImplementedException("BatchMethods.Existence not yet implemented for DuckDB");
+        }
+    }
+}