# ETL Pipeline Implementation Plan

> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.

**Goal:** Implement a flexible, configuration-driven ETL pipeline for DataSync that replaces the strongly-typed fetcher + source-generated DataReader pattern.

**Architecture:** Pipeline components (Source → Transformer → Destination) connected via `IDataReader`. Transformers are decorators that wrap readers. Destinations own their connections. Pipeline orchestrates with fail-fast error handling and step-by-step metrics.

**Tech Stack:** .NET 10, Microsoft.Data.SqlClient, xUnit, NSubstitute

---

## Phase 1: Core Interfaces and Result Models

### Task 1: Create Result Models

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Results/DestinationResult.cs`
- Create: `src/JdeScoping.DataSync/Etl/Results/StepResult.cs`
- Create: `src/JdeScoping.DataSync/Etl/Results/PipelineResult.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Results/PipelineResultTests.cs`

**Step 1: Create DestinationResult record**

```csharp
// src/JdeScoping.DataSync/Etl/Results/DestinationResult.cs
namespace JdeScoping.DataSync.Etl.Results;

/// <summary>
/// Result from a destination write operation.
/// </summary>
public record DestinationResult(
    long RowsProcessed,
    int BatchCount,
    TimeSpan Elapsed);
```

**Step 2: Create StepResult record**

```csharp
// src/JdeScoping.DataSync/Etl/Results/StepResult.cs
namespace JdeScoping.DataSync.Etl.Results;

/// <summary>
/// Result from a single pipeline step.
/// </summary>
public record StepResult(
    string StepName,
    string StepType,
    long RowsAffected,
    TimeSpan Elapsed);
```

**Step 3: Create PipelineResult record**

```csharp
// src/JdeScoping.DataSync/Etl/Results/PipelineResult.cs
namespace JdeScoping.DataSync.Etl.Results;

/// <summary>
/// Complete result from pipeline execution.
/// </summary>
public record PipelineResult(
    bool Success,
    long TotalRows,
    TimeSpan Elapsed,
    IReadOnlyList<StepResult> Steps,
    Exception? Error = null)
{
    /// <summary>
    /// Creates a successful result.
    /// </summary>
    public static PipelineResult Succeeded(long totalRows, TimeSpan elapsed, IReadOnlyList<StepResult> steps)
        => new(true, totalRows, elapsed, steps);

    /// <summary>
    /// Creates a failed result.
    /// </summary>
    public static PipelineResult Failed(long totalRows, TimeSpan elapsed, IReadOnlyList<StepResult> steps, Exception error)
        => new(false, totalRows, elapsed, steps, error);
}
```

**Step 4: Write test for PipelineResult factory methods**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Results/PipelineResultTests.cs
namespace JdeScoping.DataSync.Tests.Etl.Results;

using JdeScoping.DataSync.Etl.Results;

public class PipelineResultTests
{
    [Fact]
    public void Succeeded_CreatesSuccessfulResult()
    {
        var steps = new List<StepResult>
        {
            new("Source", "Source", 0, TimeSpan.FromSeconds(1)),
            new("Destination", "Destination", 100, TimeSpan.FromSeconds(5))
        };

        var result = PipelineResult.Succeeded(100, TimeSpan.FromSeconds(6), steps);

        Assert.True(result.Success);
        Assert.Equal(100, result.TotalRows);
        Assert.Null(result.Error);
        Assert.Equal(2, result.Steps.Count);
    }

    [Fact]
    public void Failed_CreatesFailedResult()
    {
        var steps = new List<StepResult>();
        var error = new InvalidOperationException("Test error");

        var result = PipelineResult.Failed(0, TimeSpan.FromSeconds(1), steps, error);

        Assert.False(result.Success);
        Assert.Equal(0, result.TotalRows);
        Assert.Same(error, result.Error);
    }
}
```

**Step 5: Run tests**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~PipelineResultTests" --verbosity normal`
Expected: All tests pass

**Step 6: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Results/ tests/JdeScoping.DataSync.Tests/Etl/Results/
git commit -m "feat(etl): add result models for pipeline execution"
```

---

### Task 2: Create Core Interfaces

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Contracts/IImportSource.cs`
- Create: `src/JdeScoping.DataSync/Etl/Contracts/IDataTransformer.cs`
- Create: `src/JdeScoping.DataSync/Etl/Contracts/IImportDestination.cs`
- Create: `src/JdeScoping.DataSync/Etl/Contracts/IScriptRunner.cs`

**Step 1: Create IImportSource interface**

```csharp
// src/JdeScoping.DataSync/Etl/Contracts/IImportSource.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Contracts;

/// <summary>
/// Source that reads data and returns an IDataReader for streaming.
/// </summary>
public interface IImportSource : IAsyncDisposable
{
    /// <summary>
    /// Opens the source and returns a data reader for streaming rows.
    /// </summary>
    Task<IDataReader> ReadDataAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Name of this source for logging and metrics.
    /// </summary>
    string SourceName { get; }
}
```

**Step 2: Create IDataTransformer interface**

```csharp
// src/JdeScoping.DataSync/Etl/Contracts/IDataTransformer.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Contracts;

/// <summary>
/// Transforms an IDataReader by wrapping it with transformation logic.
/// </summary>
public interface IDataTransformer
{
    /// <summary>
    /// Wraps the source reader with transformation logic.
    /// </summary>
    IDataReader Transform(IDataReader source);

    /// <summary>
    /// Name of this transformer for logging and metrics.
    /// </summary>
    string TransformerName { get; }
}
```

**Step 3: Create IImportDestination interface**

```csharp
// src/JdeScoping.DataSync/Etl/Contracts/IImportDestination.cs
using System.Data;
using JdeScoping.DataSync.Etl.Results;

namespace JdeScoping.DataSync.Etl.Contracts;

/// <summary>
/// Destination that writes data from an IDataReader.
/// </summary>
public interface IImportDestination
{
    /// <summary>
    /// Writes all rows from the reader to the destination.
    /// </summary>
    Task<DestinationResult> WriteAsync(
        IDataReader source,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Name of this destination for logging and metrics.
    /// </summary>
    string DestinationName { get; }
}
```

**Step 4: Create IScriptRunner interface**

```csharp
// src/JdeScoping.DataSync/Etl/Contracts/IScriptRunner.cs
namespace JdeScoping.DataSync.Etl.Contracts;

/// <summary>
/// Runs a SQL script as part of pipeline pre/post processing.
/// </summary>
public interface IScriptRunner
{
    /// <summary>
    /// Executes the script.
    /// </summary>
    Task ExecuteAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Name of this script for logging and metrics.
    /// </summary>
    string ScriptName { get; }
}
```

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Contracts/
git commit -m "feat(etl): add core ETL pipeline interfaces"
```

---

## Phase 2: Script Runner Implementation

### Task 3: Implement SqlScriptRunner

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Scripts/SqlScriptRunner.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Scripts/SqlScriptRunnerTests.cs`

**Step 1: Write failing test for SqlScriptRunner**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Scripts/SqlScriptRunnerTests.cs
using System.Data.Common;
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Scripts;
using Microsoft.Data.SqlClient;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Scripts;

public class SqlScriptRunnerTests
{
    [Fact]
    public void Constructor_SetsScriptName()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var runner = new SqlScriptRunner(factory, "SELECT 1", "TestScript");

        Assert.Equal("TestScript", runner.ScriptName);
    }

    [Fact]
    public void Constructor_WithNullName_DefaultsToSqlScript()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var runner = new SqlScriptRunner(factory, "SELECT 1");

        Assert.Equal("SqlScript", runner.ScriptName);
    }

    [Fact]
    public void Constructor_NullFactory_ThrowsArgumentNullException()
    {
        Assert.Throws<ArgumentNullException>(() =>
            new SqlScriptRunner(null!, "SELECT 1"));
    }

    [Fact]
    public void Constructor_NullSql_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new SqlScriptRunner(factory, null!));
    }

    [Fact]
    public void Constructor_EmptySql_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new SqlScriptRunner(factory, ""));
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~SqlScriptRunnerTests" --verbosity normal`
Expected: FAIL - SqlScriptRunner class does not exist

**Step 3: Implement SqlScriptRunner**

```csharp
// src/JdeScoping.DataSync/Etl/Scripts/SqlScriptRunner.cs
using System.Data;
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Contracts;

namespace JdeScoping.DataSync.Etl.Scripts;

/// <summary>
/// Runs a SQL script against the database.
/// </summary>
public class SqlScriptRunner : IScriptRunner
{
    private readonly IDbConnectionFactory _connectionFactory;
    private readonly string _sql;
    private readonly int _timeoutSeconds;

    public string ScriptName { get; }

    public SqlScriptRunner(
        IDbConnectionFactory connectionFactory,
        string sql,
        string? name = null,
        int timeoutSeconds = 3600)
    {
        ArgumentNullException.ThrowIfNull(connectionFactory);
        ArgumentException.ThrowIfNullOrWhiteSpace(sql);

        _connectionFactory = connectionFactory;
        _sql = sql;
        _timeoutSeconds = timeoutSeconds;
        ScriptName = name ?? "SqlScript";
    }

    public async Task ExecuteAsync(CancellationToken cancellationToken = default)
    {
        await using var connection = await _connectionFactory.CreateLotFinderConnectionAsync(cancellationToken);
        await using var command = connection.CreateCommand();
        command.CommandText = _sql;
        command.CommandTimeout = _timeoutSeconds;
        await command.ExecuteNonQueryAsync(cancellationToken);
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~SqlScriptRunnerTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Scripts/SqlScriptRunner.cs tests/JdeScoping.DataSync.Tests/Etl/Scripts/
git commit -m "feat(etl): implement SqlScriptRunner"
```

---

### Task 4: Implement CommonScripts Factory

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Scripts/CommonScripts.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Scripts/CommonScriptsTests.cs`

**Step 1: Write failing test for CommonScripts**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Scripts/CommonScriptsTests.cs
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Scripts;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Scripts;

public class CommonScriptsTests
{
    private readonly IDbConnectionFactory _factory = Substitute.For<IDbConnectionFactory>();

    [Fact]
    public void DisableIndexes_ReturnsRunnerWithCorrectName()
    {
        var runner = CommonScripts.DisableIndexes(_factory, "WorkOrder");

        Assert.Equal("DisableIndexes:WorkOrder", runner.ScriptName);
    }

    [Fact]
    public void RebuildIndexes_ReturnsRunnerWithCorrectName()
    {
        var runner = CommonScripts.RebuildIndexes(_factory, "WorkOrder");

        Assert.Equal("RebuildIndexes:WorkOrder", runner.ScriptName);
    }

    [Fact]
    public void UpdateStatistics_ReturnsRunnerWithCorrectName()
    {
        var runner = CommonScripts.UpdateStatistics(_factory, "WorkOrder");

        Assert.Equal("UpdateStats:WorkOrder", runner.ScriptName);
    }

    [Fact]
    public void CustomSql_ReturnsRunnerWithProvidedName()
    {
        var runner = CommonScripts.CustomSql(_factory, "SELECT 1", "MyCustomScript");

        Assert.Equal("MyCustomScript", runner.ScriptName);
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~CommonScriptsTests" --verbosity normal`
Expected: FAIL - CommonScripts class does not exist

**Step 3: Implement CommonScripts**

```csharp
// src/JdeScoping.DataSync/Etl/Scripts/CommonScripts.cs
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Contracts;

namespace JdeScoping.DataSync.Etl.Scripts;

/// <summary>
/// Factory methods for common SQL scripts used in ETL pipelines.
/// </summary>
public static class CommonScripts
{
    /// <summary>
    /// Creates a script that disables non-clustered indexes on a table.
    /// </summary>
    public static IScriptRunner DisableIndexes(IDbConnectionFactory factory, string tableName)
    {
        var sql = $@"
DECLARE @sql NVARCHAR(MAX) = '';
SELECT @sql = @sql + 'ALTER INDEX [' + i.name + '] ON [{tableName}] DISABLE;' + CHAR(13)
FROM sys.indexes i
INNER JOIN sys.tables t ON i.object_id = t.object_id
WHERE t.name = '{tableName}'
  AND i.type = 2
  AND i.is_disabled = 0;
IF LEN(@sql) > 0 EXEC sp_executesql @sql;";

        return new SqlScriptRunner(factory, sql, $"DisableIndexes:{tableName}", timeoutSeconds: 300);
    }

    /// <summary>
    /// Creates a script that rebuilds all indexes on a table.
    /// </summary>
    public static IScriptRunner RebuildIndexes(IDbConnectionFactory factory, string tableName)
    {
        var sql = $"ALTER INDEX ALL ON [{tableName}] REBUILD WITH (FILLFACTOR = 95)";
        return new SqlScriptRunner(factory, sql, $"RebuildIndexes:{tableName}", timeoutSeconds: 3600);
    }

    /// <summary>
    /// Creates a script that updates statistics on a table.
    /// </summary>
    public static IScriptRunner UpdateStatistics(IDbConnectionFactory factory, string tableName)
    {
        var sql = $"UPDATE STATISTICS [{tableName}]";
        return new SqlScriptRunner(factory, sql, $"UpdateStats:{tableName}", timeoutSeconds: 600);
    }

    /// <summary>
    /// Creates a script runner for custom SQL.
    /// </summary>
    public static IScriptRunner CustomSql(IDbConnectionFactory factory, string sql, string name)
    {
        return new SqlScriptRunner(factory, sql, name);
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~CommonScriptsTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Scripts/CommonScripts.cs tests/JdeScoping.DataSync.Tests/Etl/Scripts/CommonScriptsTests.cs
git commit -m "feat(etl): add CommonScripts factory for index and statistics scripts"
```

---

## Phase 3: Transformer Infrastructure

### Task 5: Implement TransformingDataReader Base

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Transformers/TransformingDataReader.cs`
- Create: `src/JdeScoping.DataSync/Etl/Transformers/DataTransformerBase.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Transformers/TransformingDataReaderTests.cs`

**Step 1: Write failing test for TransformingDataReader**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Transformers/TransformingDataReaderTests.cs
using System.Data;
using JdeScoping.DataSync.Etl.Transformers;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class TransformingDataReaderTests
{
    [Fact]
    public void Read_DelegatesToSourceReader()
    {
        var source = Substitute.For<IDataReader>();
        source.Read().Returns(true, true, false);

        var transformer = new PassThroughTransformer();
        var reader = transformer.Transform(source);

        Assert.True(reader.Read());
        Assert.True(reader.Read());
        Assert.False(reader.Read());
    }

    [Fact]
    public void FieldCount_DelegatesToTransformer()
    {
        var source = Substitute.For<IDataReader>();
        source.FieldCount.Returns(5);

        var transformer = new PassThroughTransformer();
        var reader = transformer.Transform(source);

        Assert.Equal(5, reader.FieldCount);
    }

    [Fact]
    public void GetName_DelegatesToTransformer()
    {
        var source = Substitute.For<IDataReader>();
        source.GetName(0).Returns("OriginalName");

        var transformer = new PassThroughTransformer();
        var reader = transformer.Transform(source);

        Assert.Equal("OriginalName", reader.GetName(0));
    }

    [Fact]
    public void GetValue_DelegatesToTransformer()
    {
        var source = Substitute.For<IDataReader>();
        source.GetValue(0).Returns("TestValue");

        var transformer = new PassThroughTransformer();
        var reader = transformer.Transform(source);

        Assert.Equal("TestValue", reader.GetValue(0));
    }

    [Fact]
    public void Dispose_DisposesSourceReader()
    {
        var source = Substitute.For<IDataReader>();

        var transformer = new PassThroughTransformer();
        var reader = transformer.Transform(source);
        reader.Dispose();

        source.Received(1).Dispose();
    }

    // Test helper - pass-through transformer
    private class PassThroughTransformer : DataTransformerBase
    {
        public override string TransformerName => "PassThrough";
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~TransformingDataReaderTests" --verbosity normal`
Expected: FAIL - classes do not exist

**Step 3: Implement DataTransformerBase**

```csharp
// src/JdeScoping.DataSync/Etl/Transformers/DataTransformerBase.cs
using System.Data;
using JdeScoping.DataSync.Etl.Contracts;

namespace JdeScoping.DataSync.Etl.Transformers;

/// <summary>
/// Base class for data transformers that wrap an IDataReader.
/// Override virtual methods to customize transformation behavior.
/// </summary>
public abstract class DataTransformerBase : IDataTransformer
{
    public abstract string TransformerName { get; }

    public IDataReader Transform(IDataReader source)
    {
        ArgumentNullException.ThrowIfNull(source);
        OnInitialize(source);
        return new TransformingDataReader(source, this);
    }

    /// <summary>
    /// Called once when transform is initialized. Use to cache ordinals.
    /// </summary>
    protected virtual void OnInitialize(IDataReader source) { }

    /// <summary>
    /// Returns the number of fields after transformation.
    /// </summary>
    public virtual int GetFieldCount(IDataReader source) => source.FieldCount;

    /// <summary>
    /// Returns the field name at the given ordinal after transformation.
    /// </summary>
    public virtual string GetName(int ordinal, IDataReader source) => source.GetName(ordinal);

    /// <summary>
    /// Returns the field type at the given ordinal after transformation.
    /// </summary>
    public virtual Type GetFieldType(int ordinal, IDataReader source) => source.GetFieldType(ordinal);

    /// <summary>
    /// Returns the value at the given ordinal after transformation.
    /// </summary>
    public virtual object GetValue(int ordinal, IDataReader source) => source.GetValue(ordinal);

    /// <summary>
    /// Returns the ordinal for a field name after transformation.
    /// </summary>
    public virtual int GetOrdinal(string name, IDataReader source) => source.GetOrdinal(name);

    /// <summary>
    /// Returns whether the value at the given ordinal is null.
    /// </summary>
    public virtual bool IsDBNull(int ordinal, IDataReader source) => source.IsDBNull(ordinal);
}
```

**Step 4: Implement TransformingDataReader**

```csharp
// src/JdeScoping.DataSync/Etl/Transformers/TransformingDataReader.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Transformers;

/// <summary>
/// IDataReader wrapper that delegates to a transformer for value/schema operations.
/// </summary>
internal sealed class TransformingDataReader : IDataReader
{
    private readonly IDataReader _source;
    private readonly DataTransformerBase _transformer;

    public TransformingDataReader(IDataReader source, DataTransformerBase transformer)
    {
        _source = source ?? throw new ArgumentNullException(nameof(source));
        _transformer = transformer ?? throw new ArgumentNullException(nameof(transformer));
    }

    // Schema properties - delegate to transformer
    public int FieldCount => _transformer.GetFieldCount(_source);
    public string GetName(int i) => _transformer.GetName(i, _source);
    public Type GetFieldType(int i) => _transformer.GetFieldType(i, _source);
    public int GetOrdinal(string name) => _transformer.GetOrdinal(name, _source);

    // Value access - delegate to transformer
    public object GetValue(int i) => _transformer.GetValue(i, _source);
    public bool IsDBNull(int i) => _transformer.IsDBNull(i, _source);
    public object this[int i] => GetValue(i);
    public object this[string name] => GetValue(GetOrdinal(name));

    // Row navigation - delegate to source
    public bool Read() => _source.Read();
    public bool NextResult() => _source.NextResult();
    public int Depth => _source.Depth;
    public bool IsClosed => _source.IsClosed;
    public int RecordsAffected => _source.RecordsAffected;
    public void Close() => _source.Close();
    public void Dispose() => _source.Dispose();

    // Type-specific getters - delegate to transformer via GetValue
    public bool GetBoolean(int i) => (bool)GetValue(i);
    public byte GetByte(int i) => (byte)GetValue(i);
    public char GetChar(int i) => (char)GetValue(i);
    public DateTime GetDateTime(int i) => (DateTime)GetValue(i);
    public decimal GetDecimal(int i) => (decimal)GetValue(i);
    public double GetDouble(int i) => (double)GetValue(i);
    public float GetFloat(int i) => (float)GetValue(i);
    public Guid GetGuid(int i) => (Guid)GetValue(i);
    public short GetInt16(int i) => (short)GetValue(i);
    public int GetInt32(int i) => (int)GetValue(i);
    public long GetInt64(int i) => (long)GetValue(i);
    public string GetString(int i) => (string)GetValue(i);

    public string GetDataTypeName(int i) => _source.GetDataTypeName(i);
    public int GetValues(object[] values)
    {
        var count = Math.Min(values.Length, FieldCount);
        for (int i = 0; i < count; i++)
            values[i] = GetValue(i);
        return count;
    }

    public long GetBytes(int i, long fieldOffset, byte[]? buffer, int bufferoffset, int length)
        => _source.GetBytes(i, fieldOffset, buffer, bufferoffset, length);

    public long GetChars(int i, long fieldoffset, char[]? buffer, int bufferoffset, int length)
        => _source.GetChars(i, fieldoffset, buffer, bufferoffset, length);

    public IDataReader GetData(int i) => _source.GetData(i);

    public DataTable? GetSchemaTable() => _source.GetSchemaTable();
}
```

**Step 5: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~TransformingDataReaderTests" --verbosity normal`
Expected: All tests pass

**Step 6: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Transformers/ tests/JdeScoping.DataSync.Tests/Etl/Transformers/
git commit -m "feat(etl): implement TransformingDataReader and DataTransformerBase"
```

---

### Task 6: Implement ColumnDropTransformer

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Transformers/ColumnDropTransformer.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnDropTransformerTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnDropTransformerTests.cs
using System.Data;
using JdeScoping.DataSync.Etl.Transformers;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class ColumnDropTransformerTests
{
    [Fact]
    public void FieldCount_ExcludesDroppedColumns()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });

        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);

        Assert.Equal(3, reader.FieldCount);
    }

    [Fact]
    public void GetName_SkipsDroppedColumns()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });

        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);

        Assert.Equal("Id", reader.GetName(0));
        Assert.Equal("Name", reader.GetName(1));
        Assert.Equal("Value", reader.GetName(2));
    }

    [Fact]
    public void GetOrdinal_ReturnsRemappedOrdinal()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });

        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);

        Assert.Equal(0, reader.GetOrdinal("Id"));
        Assert.Equal(1, reader.GetOrdinal("Name"));
        Assert.Equal(2, reader.GetOrdinal("Value"));
    }

    [Fact]
    public void GetOrdinal_DroppedColumn_ThrowsIndexOutOfRange()
    {
        var source = CreateMockReader(new[] { "Id", "Name", "DropMe", "Value" });

        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);

        Assert.Throws<IndexOutOfRangeException>(() => reader.GetOrdinal("DropMe"));
    }

    [Fact]
    public void GetValue_ReturnsCorrectValues()
    {
        var source = CreateMockReader(
            new[] { "Id", "Name", "DropMe", "Value" },
            new object[] { 1, "Test", "Dropped", 42 });

        var transformer = new ColumnDropTransformer("DropMe");
        var reader = transformer.Transform(source);
        source.Read().Returns(true);
        reader.Read();

        Assert.Equal(1, reader.GetValue(0));
        Assert.Equal("Test", reader.GetValue(1));
        Assert.Equal(42, reader.GetValue(2));
    }

    [Fact]
    public void MultipleDroppedColumns_AllExcluded()
    {
        var source = CreateMockReader(new[] { "Id", "Drop1", "Name", "Drop2", "Value" });

        var transformer = new ColumnDropTransformer("Drop1", "Drop2");
        var reader = transformer.Transform(source);

        Assert.Equal(3, reader.FieldCount);
        Assert.Equal("Id", reader.GetName(0));
        Assert.Equal("Name", reader.GetName(1));
        Assert.Equal("Value", reader.GetName(2));
    }

    private static IDataReader CreateMockReader(string[] columns, object[]? values = null)
    {
        var reader = Substitute.For<IDataReader>();
        reader.FieldCount.Returns(columns.Length);

        for (int i = 0; i < columns.Length; i++)
        {
            var index = i;
            reader.GetName(index).Returns(columns[index]);
            reader.GetOrdinal(columns[index]).Returns(index);
            if (values != null)
                reader.GetValue(index).Returns(values[index]);
        }

        return reader;
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~ColumnDropTransformerTests" --verbosity normal`
Expected: FAIL - ColumnDropTransformer does not exist

**Step 3: Implement ColumnDropTransformer**

```csharp
// src/JdeScoping.DataSync/Etl/Transformers/ColumnDropTransformer.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Transformers;

/// <summary>
/// Transformer that removes columns from the output.
/// </summary>
public class ColumnDropTransformer : DataTransformerBase
{
    private readonly HashSet<string> _columnsToDrop;
    private int[]? _ordinalMap;  // maps output ordinal -> source ordinal
    private Dictionary<string, int>? _nameToOrdinal;

    public override string TransformerName => $"DropColumns:{string.Join(",", _columnsToDrop)}";

    public ColumnDropTransformer(params string[] columnsToDrop)
    {
        ArgumentNullException.ThrowIfNull(columnsToDrop);
        _columnsToDrop = new HashSet<string>(columnsToDrop, StringComparer.OrdinalIgnoreCase);
    }

    protected override void OnInitialize(IDataReader source)
    {
        var ordinalList = new List<int>();
        _nameToOrdinal = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);

        for (int i = 0; i < source.FieldCount; i++)
        {
            var name = source.GetName(i);
            if (!_columnsToDrop.Contains(name))
            {
                _nameToOrdinal[name] = ordinalList.Count;
                ordinalList.Add(i);
            }
        }

        _ordinalMap = ordinalList.ToArray();
    }

    public override int GetFieldCount(IDataReader source) => _ordinalMap!.Length;

    public override string GetName(int ordinal, IDataReader source)
        => source.GetName(_ordinalMap![ordinal]);

    public override Type GetFieldType(int ordinal, IDataReader source)
        => source.GetFieldType(_ordinalMap![ordinal]);

    public override object GetValue(int ordinal, IDataReader source)
        => source.GetValue(_ordinalMap![ordinal]);

    public override int GetOrdinal(string name, IDataReader source)
    {
        if (_nameToOrdinal!.TryGetValue(name, out var ordinal))
            return ordinal;
        throw new IndexOutOfRangeException($"Column '{name}' not found or was dropped.");
    }

    public override bool IsDBNull(int ordinal, IDataReader source)
        => source.IsDBNull(_ordinalMap![ordinal]);
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~ColumnDropTransformerTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Transformers/ColumnDropTransformer.cs tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnDropTransformerTests.cs
git commit -m "feat(etl): implement ColumnDropTransformer"
```

---

### Task 7: Implement ColumnRenameTransformer

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Transformers/ColumnRenameTransformer.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnRenameTransformerTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnRenameTransformerTests.cs
using System.Data;
using JdeScoping.DataSync.Etl.Transformers;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class ColumnRenameTransformerTests
{
    [Fact]
    public void GetName_ReturnsRenamedColumn()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });

        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);

        Assert.Equal("NewName", reader.GetName(0));
        Assert.Equal("Other", reader.GetName(1));
    }

    [Fact]
    public void GetOrdinal_FindsByNewName()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });

        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);

        Assert.Equal(0, reader.GetOrdinal("NewName"));
    }

    [Fact]
    public void GetOrdinal_OldName_ThrowsIndexOutOfRange()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });

        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);

        Assert.Throws<IndexOutOfRangeException>(() => reader.GetOrdinal("OldName"));
    }

    [Fact]
    public void FieldCount_Unchanged()
    {
        var source = CreateMockReader(new[] { "OldName", "Other" });

        var transformer = new ColumnRenameTransformer(("OldName", "NewName"));
        var reader = transformer.Transform(source);

        Assert.Equal(2, reader.FieldCount);
    }

    [Fact]
    public void MultipleRenames_AllApplied()
    {
        var source = CreateMockReader(new[] { "A", "B", "C" });

        var transformer = new ColumnRenameTransformer(("A", "Alpha"), ("C", "Charlie"));
        var reader = transformer.Transform(source);

        Assert.Equal("Alpha", reader.GetName(0));
        Assert.Equal("B", reader.GetName(1));
        Assert.Equal("Charlie", reader.GetName(2));
    }

    private static IDataReader CreateMockReader(string[] columns)
    {
        var reader = Substitute.For<IDataReader>();
        reader.FieldCount.Returns(columns.Length);

        for (int i = 0; i < columns.Length; i++)
        {
            var index = i;
            reader.GetName(index).Returns(columns[index]);
            reader.GetOrdinal(columns[index]).Returns(index);
        }

        return reader;
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~ColumnRenameTransformerTests" --verbosity normal`
Expected: FAIL - ColumnRenameTransformer does not exist

**Step 3: Implement ColumnRenameTransformer**

```csharp
// src/JdeScoping.DataSync/Etl/Transformers/ColumnRenameTransformer.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Transformers;

/// <summary>
/// Transformer that renames columns in the output.
/// </summary>
public class ColumnRenameTransformer : DataTransformerBase
{
    private readonly Dictionary<string, string> _renames; // old -> new
    private string[]? _outputNames;
    private Dictionary<string, int>? _nameToOrdinal;

    public override string TransformerName => $"RenameColumns:{_renames.Count}";

    public ColumnRenameTransformer(params (string OldName, string NewName)[] renames)
    {
        ArgumentNullException.ThrowIfNull(renames);
        _renames = renames.ToDictionary(
            r => r.OldName,
            r => r.NewName,
            StringComparer.OrdinalIgnoreCase);
    }

    protected override void OnInitialize(IDataReader source)
    {
        _outputNames = new string[source.FieldCount];
        _nameToOrdinal = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);

        for (int i = 0; i < source.FieldCount; i++)
        {
            var originalName = source.GetName(i);
            var outputName = _renames.TryGetValue(originalName, out var newName)
                ? newName
                : originalName;
            _outputNames[i] = outputName;
            _nameToOrdinal[outputName] = i;
        }
    }

    public override string GetName(int ordinal, IDataReader source)
        => _outputNames![ordinal];

    public override int GetOrdinal(string name, IDataReader source)
    {
        if (_nameToOrdinal!.TryGetValue(name, out var ordinal))
            return ordinal;
        throw new IndexOutOfRangeException($"Column '{name}' not found.");
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~ColumnRenameTransformerTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Transformers/ColumnRenameTransformer.cs tests/JdeScoping.DataSync.Tests/Etl/Transformers/ColumnRenameTransformerTests.cs
git commit -m "feat(etl): implement ColumnRenameTransformer"
```

---

### Task 8: Implement JdeDateTransformer

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Transformers/JdeDateTransformer.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Transformers/JdeDateTransformerTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Transformers/JdeDateTransformerTests.cs
using System.Data;
using JdeScoping.DataSync.Etl.Transformers;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Transformers;

public class JdeDateTransformerTests
{
    [Fact]
    public void FieldCount_ReducedByOne()
    {
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, 124001m, 120000m, "Test" });

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);

        Assert.Equal(3, reader.FieldCount);
    }

    [Fact]
    public void GetName_DateColumnRenamed_TimeColumnRemoved()
    {
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, 124001m, 120000m, "Test" });

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);

        Assert.Equal("Id", reader.GetName(0));
        Assert.Equal("UpdatedAt", reader.GetName(1));
        Assert.Equal("Name", reader.GetName(2));
    }

    [Fact]
    public void GetValue_ParsesJulianDateAndTime()
    {
        // Julian date 124001 = Jan 1, 2024 (century digit 1 = 2000s, year 24, day 001)
        // Time 120000 = 12:00:00
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, 124001m, 120000m, "Test" });
        source.Read().Returns(true);

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);
        reader.Read();

        var expectedDate = new DateTime(2024, 1, 1, 12, 0, 0);
        Assert.Equal(expectedDate, reader.GetValue(1));
    }

    [Fact]
    public void GetValue_NullDate_ReturnsDbNull()
    {
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, DBNull.Value, DBNull.Value, "Test" });
        source.Read().Returns(true);

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);
        reader.Read();

        Assert.Equal(DBNull.Value, reader.GetValue(1));
    }

    [Fact]
    public void GetFieldType_DateColumn_ReturnsDateTime()
    {
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, 124001m, 120000m, "Test" });

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);

        Assert.Equal(typeof(DateTime), reader.GetFieldType(1));
    }

    [Fact]
    public void GetOrdinal_NewDateColumn_ReturnsCorrectOrdinal()
    {
        var source = CreateMockReader(
            new[] { "Id", "UPMJ", "TDAY", "Name" },
            new object[] { 1, 124001m, 120000m, "Test" });

        var transformer = new JdeDateTransformer("UPMJ", "TDAY", "UpdatedAt");
        var reader = transformer.Transform(source);

        Assert.Equal(1, reader.GetOrdinal("UpdatedAt"));
    }

    private static IDataReader CreateMockReader(string[] columns, object[] values)
    {
        var reader = Substitute.For<IDataReader>();
        reader.FieldCount.Returns(columns.Length);

        for (int i = 0; i < columns.Length; i++)
        {
            var index = i;
            reader.GetName(index).Returns(columns[index]);
            reader.GetOrdinal(columns[index]).Returns(index);
            reader.GetValue(index).Returns(values[index]);
            reader.IsDBNull(index).Returns(values[index] == DBNull.Value);
            reader.GetFieldType(index).Returns(values[index]?.GetType() ?? typeof(object));
        }

        return reader;
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~JdeDateTransformerTests" --verbosity normal`
Expected: FAIL - JdeDateTransformer does not exist

**Step 3: Implement JdeDateTransformer**

```csharp
// src/JdeScoping.DataSync/Etl/Transformers/JdeDateTransformer.cs
using System.Data;

namespace JdeScoping.DataSync.Etl.Transformers;

/// <summary>
/// Transforms JDE Julian date (UPMJ) and time (TDAY) columns into a single DateTime column.
/// JDE Julian date format: CYYDDD where C=century (0=1900s, 1=2000s), YY=year, DDD=day of year.
/// JDE time format: HHMMSS as decimal.
/// </summary>
public class JdeDateTransformer : DataTransformerBase
{
    private readonly string _dateColumn;
    private readonly string _timeColumn;
    private readonly string _outputColumn;

    private int _dateOrdinal;
    private int _timeOrdinal;
    private int[]? _ordinalMap;
    private string[]? _outputNames;
    private Dictionary<string, int>? _nameToOrdinal;

    public override string TransformerName => $"JdeDate:{_outputColumn}";

    public JdeDateTransformer(string dateColumn, string timeColumn, string outputColumn)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(dateColumn);
        ArgumentException.ThrowIfNullOrWhiteSpace(timeColumn);
        ArgumentException.ThrowIfNullOrWhiteSpace(outputColumn);

        _dateColumn = dateColumn;
        _timeColumn = timeColumn;
        _outputColumn = outputColumn;
    }

    protected override void OnInitialize(IDataReader source)
    {
        _dateOrdinal = source.GetOrdinal(_dateColumn);
        _timeOrdinal = source.GetOrdinal(_timeColumn);

        var ordinalList = new List<int>();
        var nameList = new List<string>();
        _nameToOrdinal = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);

        for (int i = 0; i < source.FieldCount; i++)
        {
            if (i == _timeOrdinal)
                continue; // Skip time column

            if (i == _dateOrdinal)
            {
                _nameToOrdinal[_outputColumn] = ordinalList.Count;
                nameList.Add(_outputColumn);
            }
            else
            {
                var name = source.GetName(i);
                _nameToOrdinal[name] = ordinalList.Count;
                nameList.Add(name);
            }
            ordinalList.Add(i);
        }

        _ordinalMap = ordinalList.ToArray();
        _outputNames = nameList.ToArray();
    }

    public override int GetFieldCount(IDataReader source) => _ordinalMap!.Length;

    public override string GetName(int ordinal, IDataReader source) => _outputNames![ordinal];

    public override Type GetFieldType(int ordinal, IDataReader source)
    {
        var sourceOrdinal = _ordinalMap![ordinal];
        return sourceOrdinal == _dateOrdinal ? typeof(DateTime) : source.GetFieldType(sourceOrdinal);
    }

    public override object GetValue(int ordinal, IDataReader source)
    {
        var sourceOrdinal = _ordinalMap![ordinal];

        if (sourceOrdinal == _dateOrdinal)
            return ParseJdeDateTime(source);

        return source.GetValue(sourceOrdinal);
    }

    public override int GetOrdinal(string name, IDataReader source)
    {
        if (_nameToOrdinal!.TryGetValue(name, out var ordinal))
            return ordinal;
        throw new IndexOutOfRangeException($"Column '{name}' not found.");
    }

    public override bool IsDBNull(int ordinal, IDataReader source)
    {
        var sourceOrdinal = _ordinalMap![ordinal];
        if (sourceOrdinal == _dateOrdinal)
            return source.IsDBNull(_dateOrdinal);
        return source.IsDBNull(sourceOrdinal);
    }

    private object ParseJdeDateTime(IDataReader source)
    {
        if (source.IsDBNull(_dateOrdinal))
            return DBNull.Value;

        var julianDate = Convert.ToDecimal(source.GetValue(_dateOrdinal));
        var timeValue = source.IsDBNull(_timeOrdinal) ? 0m : Convert.ToDecimal(source.GetValue(_timeOrdinal));

        return ParseJdeDateTime(julianDate, timeValue);
    }

    /// <summary>
    /// Parses JDE Julian date and time into DateTime.
    /// </summary>
    public static DateTime ParseJdeDateTime(decimal julianDate, decimal time)
    {
        // CYYDDD format
        var dateInt = (int)julianDate;
        var century = dateInt / 100000;
        var year = (dateInt / 1000) % 100;
        var dayOfYear = dateInt % 1000;

        var fullYear = (century == 0 ? 1900 : 2000) + year;
        var date = new DateTime(fullYear, 1, 1).AddDays(dayOfYear - 1);

        // HHMMSS format
        var timeInt = (int)time;
        var hours = timeInt / 10000;
        var minutes = (timeInt / 100) % 100;
        var seconds = timeInt % 100;

        return date.AddHours(hours).AddMinutes(minutes).AddSeconds(seconds);
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~JdeDateTransformerTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Transformers/JdeDateTransformer.cs tests/JdeScoping.DataSync.Tests/Etl/Transformers/JdeDateTransformerTests.cs
git commit -m "feat(etl): implement JdeDateTransformer for Julian date parsing"
```

---

## Phase 4: Source Implementations

### Task 9: Implement DbQuerySource

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Sources/DbQuerySource.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Sources/DbQuerySourceTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Sources/DbQuerySourceTests.cs
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Sources;
using Microsoft.Data.SqlClient;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Sources;

public class DbQuerySourceTests
{
    [Fact]
    public void Constructor_SetsSourceName()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var source = new DbQuerySource(factory, "SELECT 1", "TestSource");

        Assert.Equal("DbQuery:TestSource", source.SourceName);
    }

    [Fact]
    public void Constructor_NullName_UsesDefault()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var source = new DbQuerySource(factory, "SELECT 1");

        Assert.Equal("DbQuery:Query", source.SourceName);
    }

    [Fact]
    public void Constructor_NullFactory_ThrowsArgumentNullException()
    {
        Assert.Throws<ArgumentNullException>(() =>
            new DbQuerySource(null!, "SELECT 1"));
    }

    [Fact]
    public void Constructor_NullSql_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbQuerySource(factory, null!));
    }

    [Fact]
    public void Constructor_EmptySql_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbQuerySource(factory, ""));
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbQuerySourceTests" --verbosity normal`
Expected: FAIL - DbQuerySource does not exist

**Step 3: Implement DbQuerySource**

```csharp
// src/JdeScoping.DataSync/Etl/Sources/DbQuerySource.cs
using System.Data;
using System.Data.Common;
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Contracts;
using Microsoft.Data.SqlClient;

namespace JdeScoping.DataSync.Etl.Sources;

/// <summary>
/// Import source that executes a SQL query and returns results as IDataReader.
/// </summary>
public class DbQuerySource : IImportSource
{
    private readonly IDbConnectionFactory _connectionFactory;
    private readonly string _sql;
    private readonly object? _parameters;
    private readonly int _commandTimeout;

    private SqlConnection? _connection;
    private SqlCommand? _command;

    public string SourceName { get; }

    public DbQuerySource(
        IDbConnectionFactory connectionFactory,
        string sql,
        string? name = null,
        object? parameters = null,
        int commandTimeout = 3600)
    {
        ArgumentNullException.ThrowIfNull(connectionFactory);
        ArgumentException.ThrowIfNullOrWhiteSpace(sql);

        _connectionFactory = connectionFactory;
        _sql = sql;
        _parameters = parameters;
        _commandTimeout = commandTimeout;
        SourceName = $"DbQuery:{name ?? "Query"}";
    }

    public async Task<IDataReader> ReadDataAsync(CancellationToken cancellationToken = default)
    {
        _connection = await _connectionFactory.CreateLotFinderConnectionAsync(cancellationToken);
        _command = _connection.CreateCommand();
        _command.CommandText = _sql;
        _command.CommandTimeout = _commandTimeout;

        AddParameters(_command, _parameters);

        return await _command.ExecuteReaderAsync(cancellationToken);
    }

    private static void AddParameters(SqlCommand command, object? parameters)
    {
        if (parameters == null)
            return;

        var properties = parameters.GetType().GetProperties();
        foreach (var prop in properties)
        {
            var value = prop.GetValue(parameters) ?? DBNull.Value;
            command.Parameters.AddWithValue($"@{prop.Name}", value);
        }
    }

    public async ValueTask DisposeAsync()
    {
        if (_command != null)
        {
            await _command.DisposeAsync();
            _command = null;
        }
        if (_connection != null)
        {
            await _connection.DisposeAsync();
            _connection = null;
        }
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbQuerySourceTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Sources/DbQuerySource.cs tests/JdeScoping.DataSync.Tests/Etl/Sources/
git commit -m "feat(etl): implement DbQuerySource for database queries"
```

---

## Phase 5: Destination Implementations

### Task 10: Implement DbBulkImportDestination

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Destinations/DbBulkImportDestination.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Destinations/DbBulkImportDestinationTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Destinations/DbBulkImportDestinationTests.cs
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Destinations;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Destinations;

public class DbBulkImportDestinationTests
{
    [Fact]
    public void Constructor_SetsDestinationName()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var dest = new DbBulkImportDestination(factory, "WorkOrder");

        Assert.Equal("BulkImport:WorkOrder", dest.DestinationName);
    }

    [Fact]
    public void Constructor_NullFactory_ThrowsArgumentNullException()
    {
        Assert.Throws<ArgumentNullException>(() =>
            new DbBulkImportDestination(null!, "WorkOrder"));
    }

    [Fact]
    public void Constructor_NullTableName_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbBulkImportDestination(factory, null!));
    }

    [Fact]
    public void Constructor_EmptyTableName_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbBulkImportDestination(factory, ""));
    }

    [Theory]
    [InlineData(0, 10000)]  // 0 means default
    [InlineData(5000, 5000)]
    [InlineData(50000, 50000)]
    public void Constructor_BatchSize_SetsCorrectly(int input, int expected)
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var dest = new DbBulkImportDestination(factory, "WorkOrder", batchSize: input);

        // We can't easily test internal batch size, but construction should succeed
        Assert.NotNull(dest);
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbBulkImportDestinationTests" --verbosity normal`
Expected: FAIL - DbBulkImportDestination does not exist

**Step 3: Implement DbBulkImportDestination**

```csharp
// src/JdeScoping.DataSync/Etl/Destinations/DbBulkImportDestination.cs
using System.Data;
using System.Diagnostics;
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Contracts;
using JdeScoping.DataSync.Etl.Results;
using Microsoft.Data.SqlClient;

namespace JdeScoping.DataSync.Etl.Destinations;

/// <summary>
/// Destination that truncates the target table and bulk loads all data.
/// </summary>
public class DbBulkImportDestination : IImportDestination
{
    private const int DefaultBatchSize = 10000;

    private readonly IDbConnectionFactory _connectionFactory;
    private readonly string _tableName;
    private readonly int _batchSize;

    public string DestinationName => $"BulkImport:{_tableName}";

    public DbBulkImportDestination(
        IDbConnectionFactory connectionFactory,
        string tableName,
        int batchSize = 0)
    {
        ArgumentNullException.ThrowIfNull(connectionFactory);
        ArgumentException.ThrowIfNullOrWhiteSpace(tableName);

        _connectionFactory = connectionFactory;
        _tableName = tableName;
        _batchSize = batchSize > 0 ? batchSize : DefaultBatchSize;
    }

    public async Task<DestinationResult> WriteAsync(
        IDataReader source,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(source);

        var stopwatch = Stopwatch.StartNew();
        long totalRows = 0;
        int batchCount = 0;

        await using var connection = await _connectionFactory.CreateLotFinderConnectionAsync(cancellationToken);

        // Truncate destination table
        await using (var truncateCmd = connection.CreateCommand())
        {
            truncateCmd.CommandText = $"TRUNCATE TABLE [{_tableName}]";
            await truncateCmd.ExecuteNonQueryAsync(cancellationToken);
        }

        // Bulk copy data
        using var bulkCopy = new SqlBulkCopy(connection)
        {
            DestinationTableName = $"[{_tableName}]",
            BatchSize = _batchSize,
            BulkCopyTimeout = 3600,
            EnableStreaming = true
        };

        // Map columns by name
        for (int i = 0; i < source.FieldCount; i++)
        {
            bulkCopy.ColumnMappings.Add(source.GetName(i), source.GetName(i));
        }

        // Track rows via event
        bulkCopy.NotifyAfter = _batchSize;
        bulkCopy.SqlRowsCopied += (_, e) =>
        {
            totalRows = e.RowsCopied;
            batchCount++;
        };

        await bulkCopy.WriteToServerAsync(source, cancellationToken);

        // Final count (in case NotifyAfter didn't fire for last partial batch)
        if (bulkCopy.RowsCopied > totalRows)
        {
            totalRows = bulkCopy.RowsCopied;
            batchCount++;
        }

        stopwatch.Stop();
        return new DestinationResult(totalRows, batchCount, stopwatch.Elapsed);
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbBulkImportDestinationTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Destinations/DbBulkImportDestination.cs tests/JdeScoping.DataSync.Tests/Etl/Destinations/
git commit -m "feat(etl): implement DbBulkImportDestination for full table refresh"
```

---

### Task 11: Implement DbBulkMergeDestination

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Destinations/DbBulkMergeDestination.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Destinations/DbBulkMergeDestinationTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Destinations/DbBulkMergeDestinationTests.cs
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Destinations;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Destinations;

public class DbBulkMergeDestinationTests
{
    [Fact]
    public void Constructor_SetsDestinationName()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        var dest = new DbBulkMergeDestination(factory, "WorkOrder", new[] { "OrderNumber" });

        Assert.Equal("BulkMerge:WorkOrder", dest.DestinationName);
    }

    [Fact]
    public void Constructor_NullFactory_ThrowsArgumentNullException()
    {
        Assert.Throws<ArgumentNullException>(() =>
            new DbBulkMergeDestination(null!, "WorkOrder", new[] { "Id" }));
    }

    [Fact]
    public void Constructor_NullTableName_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbBulkMergeDestination(factory, null!, new[] { "Id" }));
    }

    [Fact]
    public void Constructor_EmptyMatchColumns_ThrowsArgumentException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentException>(() =>
            new DbBulkMergeDestination(factory, "WorkOrder", Array.Empty<string>()));
    }

    [Fact]
    public void Constructor_NullMatchColumns_ThrowsArgumentNullException()
    {
        var factory = Substitute.For<IDbConnectionFactory>();

        Assert.Throws<ArgumentNullException>(() =>
            new DbBulkMergeDestination(factory, "WorkOrder", null!));
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbBulkMergeDestinationTests" --verbosity normal`
Expected: FAIL - DbBulkMergeDestination does not exist

**Step 3: Implement DbBulkMergeDestination**

```csharp
// src/JdeScoping.DataSync/Etl/Destinations/DbBulkMergeDestination.cs
using System.Data;
using System.Diagnostics;
using System.Text;
using JdeScoping.DataAccess.Interfaces;
using JdeScoping.DataSync.Etl.Contracts;
using JdeScoping.DataSync.Etl.Results;
using Microsoft.Data.SqlClient;

namespace JdeScoping.DataSync.Etl.Destinations;

/// <summary>
/// Destination that uses temp table + MERGE for incremental updates.
/// </summary>
public class DbBulkMergeDestination : IImportDestination
{
    private const int DefaultBatchSize = 10000;

    private readonly IDbConnectionFactory _connectionFactory;
    private readonly string _tableName;
    private readonly string[] _matchColumns;
    private readonly string[]? _updateColumns;
    private readonly int _batchSize;

    public string DestinationName => $"BulkMerge:{_tableName}";

    public DbBulkMergeDestination(
        IDbConnectionFactory connectionFactory,
        string tableName,
        string[] matchColumns,
        string[]? updateColumns = null,
        int batchSize = 0)
    {
        ArgumentNullException.ThrowIfNull(connectionFactory);
        ArgumentException.ThrowIfNullOrWhiteSpace(tableName);
        ArgumentNullException.ThrowIfNull(matchColumns);
        if (matchColumns.Length == 0)
            throw new ArgumentException("At least one match column is required.", nameof(matchColumns));

        _connectionFactory = connectionFactory;
        _tableName = tableName;
        _matchColumns = matchColumns;
        _updateColumns = updateColumns;
        _batchSize = batchSize > 0 ? batchSize : DefaultBatchSize;
    }

    public async Task<DestinationResult> WriteAsync(
        IDataReader source,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(source);

        var stopwatch = Stopwatch.StartNew();
        long totalRows = 0;
        int batchCount = 0;

        var tempTableName = $"#ETL_{_tableName.Replace(".", "_").Replace("[", "").Replace("]", "")}";

        await using var connection = await _connectionFactory.CreateLotFinderConnectionAsync(cancellationToken);

        try
        {
            // Create temp table from destination schema
            await CreateTempTableAsync(connection, tempTableName, cancellationToken);

            // Get all column names from source
            var allColumns = new List<string>();
            for (int i = 0; i < source.FieldCount; i++)
                allColumns.Add(source.GetName(i));

            // Determine update columns (all non-match columns if not specified)
            var matchSet = new HashSet<string>(_matchColumns, StringComparer.OrdinalIgnoreCase);
            var updateCols = _updateColumns ?? allColumns.Where(c => !matchSet.Contains(c)).ToArray();

            // Build MERGE SQL
            var mergeSql = BuildMergeSql(allColumns, updateCols);

            // Process in batches using DataTable buffer
            var batch = new DataTable();
            SetupDataTable(batch, source);

            while (source.Read())
            {
                var row = batch.NewRow();
                for (int i = 0; i < source.FieldCount; i++)
                    row[i] = source.GetValue(i);
                batch.Rows.Add(row);

                if (batch.Rows.Count >= _batchSize)
                {
                    batchCount++;
                    await ProcessBatchAsync(connection, batch, tempTableName, mergeSql, cancellationToken);
                    totalRows += batch.Rows.Count;
                    batch.Clear();
                }
            }

            // Process remaining rows
            if (batch.Rows.Count > 0)
            {
                batchCount++;
                await ProcessBatchAsync(connection, batch, tempTableName, mergeSql, cancellationToken);
                totalRows += batch.Rows.Count;
            }

            stopwatch.Stop();
            return new DestinationResult(totalRows, batchCount, stopwatch.Elapsed);
        }
        finally
        {
            await DropTempTableAsync(connection, tempTableName);
        }
    }

    private async Task CreateTempTableAsync(SqlConnection connection, string tempTableName, CancellationToken ct)
    {
        var sql = $"SELECT TOP 0 * INTO [{tempTableName}] FROM [{_tableName}]";
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = sql;
        await cmd.ExecuteNonQueryAsync(ct);
    }

    private async Task DropTempTableAsync(SqlConnection connection, string tempTableName)
    {
        try
        {
            var sql = $"IF OBJECT_ID('tempdb..{tempTableName}') IS NOT NULL DROP TABLE [{tempTableName}]";
            await using var cmd = connection.CreateCommand();
            cmd.CommandText = sql;
            await cmd.ExecuteNonQueryAsync();
        }
        catch { /* Ignore cleanup errors */ }
    }

    private async Task ProcessBatchAsync(
        SqlConnection connection,
        DataTable batch,
        string tempTableName,
        string mergeSql,
        CancellationToken ct)
    {
        // Bulk copy to temp table
        using var bulkCopy = new SqlBulkCopy(connection)
        {
            DestinationTableName = tempTableName,
            BatchSize = batch.Rows.Count
        };
        await bulkCopy.WriteToServerAsync(batch, ct);

        // Execute MERGE
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = mergeSql;
        await cmd.ExecuteNonQueryAsync(ct);

        // Truncate temp table
        cmd.CommandText = $"TRUNCATE TABLE [{tempTableName}]";
        await cmd.ExecuteNonQueryAsync(ct);
    }

    private string BuildMergeSql(IReadOnlyList<string> allColumns, IReadOnlyList<string> updateColumns)
    {
        var tempTableName = $"#ETL_{_tableName.Replace(".", "_").Replace("[", "").Replace("]", "")}";
        var sb = new StringBuilder();

        sb.AppendLine($"MERGE INTO [{_tableName}] AS target");
        sb.AppendLine($"USING [{tempTableName}] AS source");
        sb.Append("ON ");
        sb.AppendLine(string.Join(" AND ", _matchColumns.Select(c => $"target.[{c}] = source.[{c}]")));

        if (updateColumns.Count > 0)
        {
            sb.AppendLine("WHEN MATCHED THEN UPDATE SET");
            sb.AppendLine(string.Join(", ", updateColumns.Select(c => $"target.[{c}] = source.[{c}]")));
        }

        sb.AppendLine("WHEN NOT MATCHED THEN INSERT");
        sb.AppendLine($"({string.Join(", ", allColumns.Select(c => $"[{c}]"))})");
        sb.AppendLine($"VALUES ({string.Join(", ", allColumns.Select(c => $"source.[{c}]"))});");

        return sb.ToString();
    }

    private static void SetupDataTable(DataTable table, IDataReader source)
    {
        for (int i = 0; i < source.FieldCount; i++)
        {
            var type = source.GetFieldType(i);
            // Handle nullable types
            if (type.IsValueType)
                type = typeof(Nullable<>).MakeGenericType(type);
            table.Columns.Add(source.GetName(i), Nullable.GetUnderlyingType(type) ?? type);
        }
    }
}
```

**Step 4: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~DbBulkMergeDestinationTests" --verbosity normal`
Expected: All tests pass

**Step 5: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Destinations/DbBulkMergeDestination.cs tests/JdeScoping.DataSync.Tests/Etl/Destinations/DbBulkMergeDestinationTests.cs
git commit -m "feat(etl): implement DbBulkMergeDestination for incremental updates"
```

---

## Phase 6: Pipeline Orchestration

### Task 12: Implement EtlPipeline

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/Pipeline/EtlPipeline.cs`
- Test: `tests/JdeScoping.DataSync.Tests/Etl/Pipeline/EtlPipelineTests.cs`

**Step 1: Write failing tests**

```csharp
// tests/JdeScoping.DataSync.Tests/Etl/Pipeline/EtlPipelineTests.cs
using System.Data;
using JdeScoping.DataSync.Etl.Contracts;
using JdeScoping.DataSync.Etl.Pipeline;
using JdeScoping.DataSync.Etl.Results;
using Microsoft.Extensions.Logging.Abstractions;
using NSubstitute;

namespace JdeScoping.DataSync.Tests.Etl.Pipeline;

public class EtlPipelineTests
{
    [Fact]
    public async Task ExecuteAsync_SuccessfulPipeline_ReturnsSuccessResult()
    {
        var source = CreateMockSource();
        var destination = CreateMockDestination(100);

        var pipeline = new EtlPipelineBuilder()
            .WithName("TestPipeline")
            .WithSource(source)
            .WithDestination(destination)
            .WithLogger(NullLogger<EtlPipeline>.Instance)
            .Build();

        var result = await pipeline.ExecuteAsync();

        Assert.True(result.Success);
        Assert.Equal(100, result.TotalRows);
        Assert.Null(result.Error);
    }

    [Fact]
    public async Task ExecuteAsync_WithPreScript_RunsScriptBeforeDestination()
    {
        var callOrder = new List<string>();

        var source = CreateMockSource();
        var destination = CreateMockDestination(100);
        destination.When(d => d.WriteAsync(Arg.Any<IDataReader>(), Arg.Any<CancellationToken>()))
            .Do(_ => callOrder.Add("destination"));

        var preScript = Substitute.For<IScriptRunner>();
        preScript.ScriptName.Returns("PreScript");
        preScript.When(s => s.ExecuteAsync(Arg.Any<CancellationToken>()))
            .Do(_ => callOrder.Add("prescript"));

        var pipeline = new EtlPipelineBuilder()
            .WithName("TestPipeline")
            .WithSource(source)
            .WithDestination(destination)
            .WithPreScript(preScript)
            .WithLogger(NullLogger<EtlPipeline>.Instance)
            .Build();

        await pipeline.ExecuteAsync();

        Assert.Equal(new[] { "prescript", "destination" }, callOrder);
    }

    [Fact]
    public async Task ExecuteAsync_DestinationFails_ReturnsFailedResult()
    {
        var source = CreateMockSource();
        var destination = Substitute.For<IImportDestination>();
        destination.DestinationName.Returns("FailingDest");
        destination.WriteAsync(Arg.Any<IDataReader>(), Arg.Any<CancellationToken>())
            .ThrowsAsync(new InvalidOperationException("Destination failed"));

        var pipeline = new EtlPipelineBuilder()
            .WithName("TestPipeline")
            .WithSource(source)
            .WithDestination(destination)
            .WithLogger(NullLogger<EtlPipeline>.Instance)
            .Build();

        var result = await pipeline.ExecuteAsync();

        Assert.False(result.Success);
        Assert.NotNull(result.Error);
        Assert.IsType<InvalidOperationException>(result.Error);
    }

    [Fact]
    public async Task ExecuteAsync_TracksStepResults()
    {
        var source = CreateMockSource();
        var destination = CreateMockDestination(100);

        var pipeline = new EtlPipelineBuilder()
            .WithName("TestPipeline")
            .WithSource(source)
            .WithDestination(destination)
            .WithLogger(NullLogger<EtlPipeline>.Instance)
            .Build();

        var result = await pipeline.ExecuteAsync();

        Assert.Equal(2, result.Steps.Count);
        Assert.Equal("Source", result.Steps[0].StepType);
        Assert.Equal("Destination", result.Steps[1].StepType);
    }

    private static IImportSource CreateMockSource()
    {
        var reader = Substitute.For<IDataReader>();
        reader.Read().Returns(false);
        reader.FieldCount.Returns(0);

        var source = Substitute.For<IImportSource>();
        source.SourceName.Returns("MockSource");
        source.ReadDataAsync(Arg.Any<CancellationToken>())
            .Returns(Task.FromResult(reader));
        return source;
    }

    private static IImportDestination CreateMockDestination(long rows)
    {
        var destination = Substitute.For<IImportDestination>();
        destination.DestinationName.Returns("MockDestination");
        destination.WriteAsync(Arg.Any<IDataReader>(), Arg.Any<CancellationToken>())
            .Returns(Task.FromResult(new DestinationResult(rows, 1, TimeSpan.FromSeconds(1))));
        return destination;
    }
}
```

**Step 2: Run test to verify it fails**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~EtlPipelineTests" --verbosity normal`
Expected: FAIL - EtlPipeline and EtlPipelineBuilder do not exist

**Step 3: Implement EtlPipeline**

```csharp
// src/JdeScoping.DataSync/Etl/Pipeline/EtlPipeline.cs
using System.Data;
using System.Diagnostics;
using JdeScoping.DataSync.Etl.Contracts;
using JdeScoping.DataSync.Etl.Results;
using Microsoft.Extensions.Logging;

namespace JdeScoping.DataSync.Etl.Pipeline;

/// <summary>
/// Orchestrates ETL pipeline execution: source → transformers → destination.
/// </summary>
public class EtlPipeline
{
    private readonly IImportSource _source;
    private readonly IReadOnlyList<IDataTransformer> _transformers;
    private readonly IImportDestination _destination;
    private readonly IReadOnlyList<IScriptRunner> _preScripts;
    private readonly IReadOnlyList<IScriptRunner> _postScripts;
    private readonly ILogger<EtlPipeline> _logger;

    public string PipelineName { get; }

    internal EtlPipeline(
        string name,
        IImportSource source,
        IReadOnlyList<IDataTransformer> transformers,
        IImportDestination destination,
        IReadOnlyList<IScriptRunner> preScripts,
        IReadOnlyList<IScriptRunner> postScripts,
        ILogger<EtlPipeline> logger)
    {
        PipelineName = name;
        _source = source;
        _transformers = transformers;
        _destination = destination;
        _preScripts = preScripts;
        _postScripts = postScripts;
        _logger = logger;
    }

    public async Task<PipelineResult> ExecuteAsync(CancellationToken cancellationToken = default)
    {
        var steps = new List<StepResult>();
        var totalStopwatch = Stopwatch.StartNew();

        _logger.LogInformation("Starting pipeline {PipelineName}", PipelineName);

        try
        {
            // 1. Run pre-scripts
            foreach (var script in _preScripts)
            {
                var stepResult = await RunScriptAsync(script, cancellationToken);
                steps.Add(stepResult);
            }

            // 2. Open source
            var sourceStopwatch = Stopwatch.StartNew();
            await using (_source)
            {
                var reader = await _source.ReadDataAsync(cancellationToken);
                sourceStopwatch.Stop();
                steps.Add(new StepResult(_source.SourceName, "Source", 0, sourceStopwatch.Elapsed));

                // 3. Apply transformers (chain of decorators)
                foreach (var transformer in _transformers)
                {
                    var transformStopwatch = Stopwatch.StartNew();
                    reader = transformer.Transform(reader);
                    transformStopwatch.Stop();
                    steps.Add(new StepResult(transformer.TransformerName, "Transform", 0, transformStopwatch.Elapsed));
                }

                // 4. Write to destination
                var destResult = await _destination.WriteAsync(reader, cancellationToken);
                steps.Add(new StepResult(
                    _destination.DestinationName,
                    "Destination",
                    destResult.RowsProcessed,
                    destResult.Elapsed));
            }

            // 5. Run post-scripts
            foreach (var script in _postScripts)
            {
                var stepResult = await RunScriptAsync(script, cancellationToken);
                steps.Add(stepResult);
            }

            totalStopwatch.Stop();
            var totalRows = steps.Sum(s => s.RowsAffected);

            _logger.LogInformation(
                "Pipeline {PipelineName} completed. Rows={Rows}, Elapsed={Elapsed}ms",
                PipelineName, totalRows, totalStopwatch.ElapsedMilliseconds);

            return PipelineResult.Succeeded(totalRows, totalStopwatch.Elapsed, steps);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            totalStopwatch.Stop();
            var totalRows = steps.Sum(s => s.RowsAffected);

            _logger.LogError(ex,
                "Pipeline {PipelineName} failed at step {Step}",
                PipelineName, steps.LastOrDefault()?.StepName ?? "Unknown");

            return PipelineResult.Failed(totalRows, totalStopwatch.Elapsed, steps, ex);
        }
    }

    private async Task<StepResult> RunScriptAsync(IScriptRunner script, CancellationToken cancellationToken)
    {
        var stopwatch = Stopwatch.StartNew();
        _logger.LogDebug("Running script {ScriptName}", script.ScriptName);
        await script.ExecuteAsync(cancellationToken);
        stopwatch.Stop();
        return new StepResult(script.ScriptName, "Script", 0, stopwatch.Elapsed);
    }
}
```

**Step 4: Implement EtlPipelineBuilder**

```csharp
// src/JdeScoping.DataSync/Etl/Pipeline/EtlPipelineBuilder.cs
using JdeScoping.DataSync.Etl.Contracts;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;

namespace JdeScoping.DataSync.Etl.Pipeline;

/// <summary>
/// Fluent builder for constructing ETL pipelines.
/// </summary>
public class EtlPipelineBuilder
{
    private string _name = "Unnamed";
    private IImportSource? _source;
    private readonly List<IDataTransformer> _transformers = new();
    private IImportDestination? _destination;
    private readonly List<IScriptRunner> _preScripts = new();
    private readonly List<IScriptRunner> _postScripts = new();
    private ILogger<EtlPipeline>? _logger;

    public EtlPipelineBuilder WithName(string name)
    {
        _name = name ?? throw new ArgumentNullException(nameof(name));
        return this;
    }

    public EtlPipelineBuilder WithSource(IImportSource source)
    {
        _source = source ?? throw new ArgumentNullException(nameof(source));
        return this;
    }

    public EtlPipelineBuilder WithTransformer(IDataTransformer transformer)
    {
        ArgumentNullException.ThrowIfNull(transformer);
        _transformers.Add(transformer);
        return this;
    }

    public EtlPipelineBuilder WithDestination(IImportDestination destination)
    {
        _destination = destination ?? throw new ArgumentNullException(nameof(destination));
        return this;
    }

    public EtlPipelineBuilder WithPreScript(IScriptRunner script)
    {
        ArgumentNullException.ThrowIfNull(script);
        _preScripts.Add(script);
        return this;
    }

    public EtlPipelineBuilder WithPostScript(IScriptRunner script)
    {
        ArgumentNullException.ThrowIfNull(script);
        _postScripts.Add(script);
        return this;
    }

    public EtlPipelineBuilder WithLogger(ILogger<EtlPipeline> logger)
    {
        _logger = logger;
        return this;
    }

    public EtlPipeline Build()
    {
        if (_source == null)
            throw new InvalidOperationException("Source is required. Call WithSource() before Build().");
        if (_destination == null)
            throw new InvalidOperationException("Destination is required. Call WithDestination() before Build().");

        return new EtlPipeline(
            _name,
            _source,
            _transformers,
            _destination,
            _preScripts,
            _postScripts,
            _logger ?? NullLogger<EtlPipeline>.Instance);
    }
}
```

**Step 5: Run tests to verify they pass**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --filter "FullyQualifiedName~EtlPipelineTests" --verbosity normal`
Expected: All tests pass

**Step 6: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/Pipeline/ tests/JdeScoping.DataSync.Tests/Etl/Pipeline/
git commit -m "feat(etl): implement EtlPipeline and EtlPipelineBuilder"
```

---

## Phase 7: Configuration and DI

### Task 13: Add DI Registration

**Files:**
- Create: `src/JdeScoping.DataSync/Etl/EtlServiceCollectionExtensions.cs`
- Modify: `src/JdeScoping.DataSync/DependencyInjection.cs`

**Step 1: Create ETL DI extensions**

```csharp
// src/JdeScoping.DataSync/Etl/EtlServiceCollectionExtensions.cs
using JdeScoping.DataSync.Etl.Pipeline;
using Microsoft.Extensions.DependencyInjection;

namespace JdeScoping.DataSync.Etl;

/// <summary>
/// Extension methods for registering ETL pipeline services.
/// </summary>
public static class EtlServiceCollectionExtensions
{
    /// <summary>
    /// Adds ETL pipeline services to the service collection.
    /// </summary>
    public static IServiceCollection AddEtlPipeline(this IServiceCollection services)
    {
        // Register factory for creating pipelines
        services.AddTransient<EtlPipelineBuilder>();

        return services;
    }
}
```

**Step 2: Commit**

```bash
git add src/JdeScoping.DataSync/Etl/EtlServiceCollectionExtensions.cs
git commit -m "feat(etl): add DI registration for ETL pipeline"
```

---

### Task 14: Run Full Test Suite

**Step 1: Build the solution**

Run: `dotnet build NEW/`
Expected: Build succeeds

**Step 2: Run all DataSync tests**

Run: `dotnet test tests/JdeScoping.DataSync.Tests --verbosity normal`
Expected: All tests pass

**Step 3: Commit any fixes if needed**

---

## Summary

This implementation plan creates a complete ETL pipeline system with:

1. **Core Interfaces**: `IImportSource`, `IDataTransformer`, `IImportDestination`, `IScriptRunner`
2. **Result Models**: `PipelineResult`, `StepResult`, `DestinationResult`
3. **Transformers**: `TransformingDataReader`, `DataTransformerBase`, `ColumnDropTransformer`, `ColumnRenameTransformer`, `JdeDateTransformer`
4. **Sources**: `DbQuerySource`
5. **Destinations**: `DbBulkImportDestination`, `DbBulkMergeDestination`
6. **Scripts**: `SqlScriptRunner`, `CommonScripts`
7. **Pipeline**: `EtlPipeline`, `EtlPipelineBuilder`

Each task follows TDD with failing tests first, then implementation, then verification.