fix: Npsql invalid case error

Added built-in support for the `ag_catalog.agtype` PostgreSQL type to Npgsql using a custom converter. This fixes #3 .

README.md

@@ -12,6 +12,7 @@ Here's a simple example to get you started:
 
 ```csharp
 using ApacheAGE;
+using ApacheAGE.Types;
 
 var connectionString = "Host=server;Port=5432;Username=user;Password=pass;Database=sample1";
 
@@ -21,8 +22,8 @@ await using var client = clientBuilder.Build();
 await client.OpenConnectionAsync();
 
 // Create a graph and add vertices.
-await client.CreateGraphAsync("graph1")
-await client.ExecuteCypherAsync("graph1", "CREATE (:Person {age: 23}), (:Person {age:78})");
+await client.CreateGraphAsync("graph1");
+await client.ExecuteCypherAsync("graph1", "CREATE (:Person {age: 23}), (:Person {age: 78})");
 await using var reader = await client.ExecuteQueryAsync(
 @"SELECT * FROM cypher('graph1', $$
     MATCH (n:Person)
@@ -32,9 +33,8 @@ $$) AS (persons agtype);");
 // Read the result row by row.
 while(await reader.ReadAsync())
 {
-    var agtypeResult = reader.GetValue(0);
+    var agtypeResult = reader.GetValue<Agtype>(0);
     Vertex person = agtypeResult.GetVertex();
-
-    // Do something with vertex.
+    Console.WriteLine(person);
 }
 ```

src/ApacheAGE/AGEClientEventId.cs

@@ -1,6 +1,6 @@
 namespace ApacheAGE
 {
-    public static class AgeClientEventId
+    internal static class AgeClientEventId
     {
         #region Connection
         public const int CONNECTION_OPENED      = 1000;
@@ -26,7 +26,9 @@ public static class AgeClientEventId
 
         #region Commands
         public const int GRAPH_CREATED                  = 3001;
-        public const int GRAPH_DROPPED                  = 3003;
+        public const int GRAPH_DROPPED                  = 3002;
+        public const int GRAPH_EXISTS                   = 3003;
+        public const int GRAPH_DOES_NOT_EXIST           = 3004;
 
         public const int CYPHER_EXECUTED    = 3101;
         public const int QUERY_EXECUTED     = 3102;
@@ -37,7 +39,6 @@ public static class AgeClientEventId
         public const int QUERY_EXECUTION_ERROR      = 3903;
         #endregion
 
-        #region Command
-        #endregion
+        public const int UNKNOWN_ERROR              = 9900;
     }
 }

src/ApacheAGE/AgeClient.cs

@@ -21,8 +21,11 @@ public class AgeClient: IAgeClient, IDisposable, IAsyncDisposable
 
         internal AgeClient(string connectionString, AgeConfiguration configuration)
         {
-            _dataSource = new NpgsqlDataSourceBuilder(connectionString)
-                .Build();
+            var builder = new NpgsqlDataSourceBuilder(connectionString);
+
+            builder.UseAge();
+
+            _dataSource = builder.Build();
             _configuration = configuration;
         }
 
@@ -73,6 +76,9 @@ public async Task CreateGraphAsync(
         {
             CheckForExistingConnection();
 
+            if (await GraphExistsAsync(graphName, cancellationToken))
+                return;
+
             await using var command = new NpgsqlCommand(
                 "SELECT * FROM create_graph($1);",
                 _connection)
@@ -257,6 +263,49 @@ public async Task<AgeDataReader> ExecuteQueryAsync(
             }
         }
 
+        public async Task<bool> GraphExistsAsync(
+            string graphName,
+            CancellationToken cancellationToken = default)
+        {
+            CheckForExistingConnection();
+
+            await using var command = new NpgsqlCommand(
+                "SELECT * FROM ag_catalog.ag_graph WHERE name = $1;",
+                _connection)
+            {
+                Parameters =
+                    {
+                        new() { Value = graphName },
+                    }
+            };
+
+            try
+            {
+                object? result = await command.ExecuteScalarAsync(cancellationToken)
+                    .ConfigureAwait(false);
+
+                if (result is null)
+                {
+                    LogMessages.GraphExists(
+                        _configuration!.Logger.CommandLogger,
+                        graphName);
+
+                    return false;
+                }
+
+                LogMessages.GraphDoesNotExist(
+                        _configuration!.Logger.CommandLogger,
+                        graphName);
+
+                return true;
+            }
+            catch (Exception e)
+            {
+                LogMessages.UnknownError(_configuration!.Logger.CommandLogger, e);
+                throw new AgeException($"An error occurred.", e);
+            }
+        }
+
         #endregion
 
         #region Dispose

src/ApacheAGE/AgeDataReader.cs

@@ -1,7 +1,5 @@
 using System;
-using System.Data;
 using System.Threading.Tasks;
-using ApacheAGE.Data;
 using Npgsql;
 
 namespace ApacheAGE
@@ -14,11 +12,6 @@ public class AgeDataReader: IAgeDataReader, IDisposable, IAsyncDisposable
         private readonly NpgsqlDataReader _reader;
         private bool _isDisposed = false;
 
-        public int FieldCount => _reader.FieldCount;
-        public bool IsOnRow => _reader.IsOnRow;
-        public bool HasRows => _reader.HasRows;
-        public bool IsClosed => _reader.IsClosed;
-
         /// <summary>
         /// Initialises a new instance of <see cref="AgeDataReader"/>.
         /// </summary>
@@ -29,29 +22,28 @@ internal AgeDataReader(NpgsqlDataReader reader)
             _reader = reader;
         }
 
+        public int FieldCount => _reader.FieldCount;
+        public bool IsOnRow => _reader.IsOnRow;
+        public bool HasRows => _reader.HasRows;
+        public bool IsClosed => _reader.IsClosed;
+
         public void Close() => _reader.Close();
 
         public void CloseAsync() => _reader.CloseAsync();
 
-        public Task<bool> ReadAsync() => _reader.ReadAsync();
+        public bool Read() => _reader.Read();
 
-        public AgeRowSet GetValues()
-        {
-            object[] values = new object[FieldCount];
+        public Task<bool> ReadAsync() => _reader.ReadAsync();
 
-            _ = _reader.GetValues(values);
+        public int GetValues(object[] values) => _reader.GetValues(values);
 
-            return new(values);
-        }
+        public T? GetValue<T>(int ordinal) => _reader.GetFieldValueAsync<T?>(ordinal).GetAwaiter().GetResult();
 
-        public AgType GetValue(int ordinal)
+        public async Task<T?> GetValueAsync<T>(int ordinal)
         {
-            var value = _reader.GetValue(ordinal);
-
-            if (value is DBNull)
-                value = null;
-
-            return new(value);
+            var value = await _reader.GetFieldValueAsync<T?>(ordinal)
+                .ConfigureAwait(false);
+            return value;
         }
 
         public string GetName(int ordinal) => _reader.GetName(ordinal);

src/ApacheAGE/ApacheAGE.csproj

@@ -18,6 +18,7 @@
     <PackageLicenseFile>LICENSE.txt</PackageLicenseFile>
     <IncludeSymbols>False</IncludeSymbols>
     <PackageRequireLicenseAcceptance>True</PackageRequireLicenseAcceptance>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
 
   </PropertyGroup>
 
@@ -33,7 +34,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Npgsql" Version="8.0.0" />
+    <PackageReference Include="Npgsql" Version="8.0.3" />
   </ItemGroup>
 
 </Project>

src/ApacheAGE/Converters/AgtypeConverter.cs

@@ -0,0 +1,42 @@
+using System.Buffers;
+using System.Text;
+using ApacheAGE.Types;
+using Npgsql.Internal;
+
+namespace ApacheAGE.Converters
+{
+#pragma warning disable NPG9001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
+    internal class AgtypeConverter: PgBufferedConverter<Agtype>
+    {
+        public override bool CanConvert(DataFormat format, out BufferRequirements bufferRequirements)
+        {
+            bufferRequirements = BufferRequirements.None;
+            return format is DataFormat.Text;
+        }
+
+        /// <summary>
+        /// Read agtype from its binary representation.
+        /// </summary>
+        /// <param name="reader"></param>
+        /// <returns></returns>
+        protected override Agtype ReadCore(PgReader reader)
+        {
+            ReadOnlySequence<byte> textBytes = reader.ReadBytes(reader.CurrentRemaining);
+            string text = Encoding.UTF8.GetString(textBytes);
+
+            return new(text);
+        }
+
+        /// <summary>
+        /// Write agtype to its binary representation.
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="value"></param>
+        protected override void WriteCore(PgWriter writer, Agtype value)
+        {
+            byte[] bytes = Encoding.UTF8.GetBytes(value.GetString());
+            writer.WriteBytes(bytes);
+        }
+    }
+#pragma warning restore NPG9001 // Type is for evaluation purposes only and is subject to change or removal in future updates. Suppress this diagnostic to proceed.
+}