feat(etl): implement TransformingDataReader and DataTransformerBase

Add core transformer infrastructure for the ETL pipeline: - DataTransformerBase: abstract base class with virtual methods for field count, names, types, values, ordinals, and null checking - TransformingDataReader: IDataReader wrapper that delegates to transformer, enabling on-the-fly data transformations
2026-01-03 09:08:17 -05:00
parent c644b578ba
commit 6e7bcadf68
3 changed files with 370 additions and 0 deletions
@@ -0,0 +1,65 @@
+using System.Data;
+using JdeScoping.DataSync.Etl.Contracts;
+
+namespace JdeScoping.DataSync.Etl.Transformers;
+
+/// <summary>
+/// Base class for data transformers that modify data during the ETL process.
+/// Derived classes can override specific methods to customize transformation behavior.
+/// </summary>
+public abstract class DataTransformerBase : IDataTransformer
+{
+    /// <inheritdoc />
+    public abstract string TransformerName { get; }
+
+    /// <inheritdoc />
+    public IDataReader Transform(IDataReader source)
+    {
+        ArgumentNullException.ThrowIfNull(source);
+        OnInitialize(source);
+        return new TransformingDataReader(source, this);
+    }
+
+    /// <summary>
+    /// Called when the transformer is initialized with a source reader.
+    /// Override to perform initialization logic.
+    /// </summary>
+    /// <param name="source">The source data reader.</param>
+    protected virtual void OnInitialize(IDataReader source) { }
+
+    /// <summary>
+    /// Gets the field count from the source reader.
+    /// Override to add or remove fields.
+    /// </summary>
+    public virtual int GetFieldCount(IDataReader source) => source.FieldCount;
+
+    /// <summary>
+    /// Gets the name of a field at the specified ordinal.
+    /// Override to rename fields.
+    /// </summary>
+    public virtual string GetName(int ordinal, IDataReader source) => source.GetName(ordinal);
+
+    /// <summary>
+    /// Gets the type of a field at the specified ordinal.
+    /// Override to change field types.
+    /// </summary>
+    public virtual Type GetFieldType(int ordinal, IDataReader source) => source.GetFieldType(ordinal);
+
+    /// <summary>
+    /// Gets the value of a field at the specified ordinal.
+    /// Override to transform values.
+    /// </summary>
+    public virtual object GetValue(int ordinal, IDataReader source) => source.GetValue(ordinal);
+
+    /// <summary>
+    /// Gets the ordinal of a field by name.
+    /// Override to support renamed fields.
+    /// </summary>
+    public virtual int GetOrdinal(string name, IDataReader source) => source.GetOrdinal(name);
+
+    /// <summary>
+    /// Checks if a field value is DBNull.
+    /// Override to handle null transformations.
+    /// </summary>
+    public virtual bool IsDBNull(int ordinal, IDataReader source) => source.IsDBNull(ordinal);
+}