Implement parameter count

Author: tvandinther

Libsql.Client.Tests/StatementTests.cs

@@ -92,6 +92,24 @@ public async Task Statement_CanBind_NNNIndex()
         Assert.Equal(expected, text.Value);
     }
 
+    [Theory]
+    [InlineData("SELECT 1", 0)]
+    [InlineData("SELECT ?", 1)]
+    [InlineData("SELECT ?, ?", 2)]
+    [InlineData("SELECT ?, ?, ?", 3)]
+    [InlineData("SELECT ?10, ?11, ?33", 33)]
+    [InlineData("SELECT ?10, ?33, ?11", 33)]
+    [InlineData("SELECT ?, ?, ?2", 2)]
+    [InlineData("SELECT ?, ?, ?2, ?, ?", 4)]
+    public async Task Statement_CanGetParameterCount(string query, int expected)
+    {
+        using var statement = await _db.Prepare(query);
+
+        var parameterCount = statement.ParameterCount;
+
+        Assert.Equal(expected, parameterCount);
+    }
+
     [Fact]
     public async Task Statement_BoundValuesCount_IsCorrect()
     {

Libsql.Client/IStatement.cs

@@ -13,6 +13,15 @@ public interface IStatement : IDisposable
         /// </summary>
         int BoundValuesCount { get; }
 
+        /// <summary>
+        /// Gets the number of parameters in the prepared statement.
+        /// </summary>
+        /// <remarks>
+        /// If <c>?NNN</c> syntax is used, the Parameter count is the maximum value of 
+        /// <c>NNN</c> used plus any unannotated positional parameters to the right.
+        /// </remarks>
+        int ParameterCount { get; }
+
         /// <summary>
         /// Binds a value to the prepared statement.
         /// </summary>

Libsql.Client/StatementWrapper.cs

@@ -8,6 +8,9 @@ namespace Libsql.Client
     internal class StatementWrapper : IStatement
     {
         int IStatement.BoundValuesCount => _bindIndex - 1;
+
+        public int ParameterCount => GetParameterCount();
+
         private int _bindIndex = 1;
         public readonly libsql_stmt_t Stmt;
         private readonly libsql_connection_t _connection;
@@ -120,6 +123,17 @@ private unsafe void Bind(int index)
             _bindIndex++;
         }
 
+        private unsafe int GetParameterCount()
+        {
+            var error = new Error();
+            int count;
+            var exitCode = Bindings.libsql_stmt_parameter_count(Stmt, &count,&error.Ptr);
+
+            error.ThrowIfNonZero(exitCode, $"Failed to get parameter count");
+
+            return count;
+        }
+
         public void Bind(Integer integer, int index)
         {
             BindInt(integer.Value, index);