# Bulk Merge Helper Implementation Plan

**Date:** 2026-01-01
**Design:** [2026-01-01-bulk-merge-helper-design.md](./2026-01-01-bulk-merge-helper-design.md)
**Status:** Draft - Pending Review

## Prerequisites

- .NET 10 SDK installed
- SQL Server running (Docker container for tests)
- Existing DataSync project compiles

## Phase 1: Source Generator Project Setup

### Task 1.1: Create Source Generator Project

**Location:** `NEW/src/JdeScoping.DataSync.SourceGenerators/`

**Files to create:**

1. `JdeScoping.DataSync.SourceGenerators.csproj`
```xml
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <LangVersion>latest</LangVersion>
    <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
    <IsRoslynComponent>true</IsRoslynComponent>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.4" PrivateAssets="all" />
    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.8.0" PrivateAssets="all" />
  </ItemGroup>
</Project>
```

2. `DataReaderGenerator.cs` - Main incremental source generator

**Verification:** Project compiles with `dotnet build`

### Task 1.2: Add Generator Reference to DataSync

**File:** `NEW/src/JdeScoping.DataSync/JdeScoping.DataSync.csproj`

**Add:**
```xml
<ItemGroup>
  <ProjectReference Include="..\JdeScoping.DataSync.SourceGenerators\JdeScoping.DataSync.SourceGenerators.csproj"
                    OutputItemType="Analyzer"
                    ReferenceOutputAssembly="false" />
</ItemGroup>
```

**Verification:** DataSync project compiles

---

## Phase 2: Core Interfaces and Contracts

### Task 2.1: Create IDataReaderFactory Interface

**File:** `NEW/src/JdeScoping.DataSync/Contracts/IDataReaderFactory.cs`

```csharp
namespace JdeScoping.DataSync.Contracts;

public interface IDataReaderFactory
{
    IDataReader CreateReader<T>(IAsyncEnumerable<T> source);

    IReadOnlyList<string> GetColumnNames<T>();
}
```

**Verification:** Compiles

### Task 2.2: Create IBulkMergeHelper Interface

**File:** `NEW/src/JdeScoping.DataSync/Contracts/IBulkMergeHelper.cs`

```csharp
namespace JdeScoping.DataSync.Contracts;

public interface IBulkMergeHelper
{
    Task<MergeResult> MergeAsync<T>(
        IAsyncEnumerable<T> data,
        string destinationTable,
        Expression<Func<T, object>> matchOn,
        Expression<Func<T, object>>? updateColumns = null,
        Expression<Func<T, T, bool>>? updateWhen = null,
        Expression<Func<T, object>>? insertColumns = null,
        string? tempTableName = null,
        int batchSize = 0,
        bool validateBeforeCopy = false,
        CancellationToken cancellationToken = default);
}
```

**Verification:** Compiles

### Task 2.3: Create MergeResult Record

**File:** `NEW/src/JdeScoping.DataSync/Models/MergeResult.cs`

```csharp
namespace JdeScoping.DataSync.Models;

public record MergeResult(
    int TotalRowsProcessed,
    int RowsInserted,
    int RowsUpdated,
    int BatchCount,
    TimeSpan Elapsed);
```

**Verification:** Compiles

### Task 2.4: Create Exception Classes

**File:** `NEW/src/JdeScoping.DataSync/Exceptions/BulkMergeException.cs`

```csharp
namespace JdeScoping.DataSync.Exceptions;

public class BulkMergeException : Exception
{
    public string TableName { get; init; } = string.Empty;
    public int BatchNumber { get; init; }
    public int RowsInBatch { get; init; }
    public string? SqlStatement { get; init; }

    // constructors...
}

public class BulkMergeValidationException : BulkMergeException
{
    public IReadOnlyList<ValidationError> Errors { get; init; } = [];
}

public record ValidationError(
    int RowIndex,
    string ColumnName,
    object? Value,
    string Message);
```

**Verification:** Compiles

---

## Phase 3: Type Registry and Generator Implementation

### Task 3.1: Create BulkCopyTypeRegistry

**File:** `NEW/src/JdeScoping.DataSync/BulkCopyTypeRegistry.cs`

```csharp
namespace JdeScoping.DataSync;

public static class BulkCopyTypeRegistry
{
    public static readonly Type[] Types =
    [
        typeof(WorkOrder),
        typeof(Lot),
        typeof(LotUsage),
        typeof(Item),
        typeof(WorkCenter),
        typeof(ProfitCenter),
        typeof(JdeUser),
        typeof(Branch),
        typeof(MisData),
    ];
}
```

**Verification:** Compiles with correct type references

### Task 3.2: Implement DataReaderGenerator

**File:** `NEW/src/JdeScoping.DataSync.SourceGenerators/DataReaderGenerator.cs`

Generator must:
1. Find `BulkCopyTypeRegistry.Types` array in compilation
2. For each type, generate a `{TypeName}DataReader : IDataReader` class
3. Generate `DataReaderFactory` implementation
4. Generate `AddBulkCopyConverters()` extension method

**Key implementation details:**
- Use incremental generator (`IIncrementalGenerator`) for performance
- Handle nullable properties correctly (use `DBNull.Value` for null)
- Skip properties with private setters
- Order columns alphabetically for consistency

**Verification:**
- Generator compiles
- DataSync builds and generated code appears in `obj/Generated/`

### Task 3.3: Write Generator Unit Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/SourceGenerators/DataReaderGeneratorTests.cs`

Test scenarios:
- Generates reader for simple type
- Generates factory with all registered types
- Handles nullable properties
- Skips private properties
- Generates correct column ordinal mapping

**Verification:** All generator tests pass

---

## Phase 4: Expression Parsing

### Task 4.1: Create ExpressionParser

**File:** `NEW/src/JdeScoping.DataSync/Services/ExpressionParser.cs`

```csharp
namespace JdeScoping.DataSync.Services;

internal static class ExpressionParser
{
    public static IReadOnlyList<string> GetColumnNames<T>(
        Expression<Func<T, object>> expression);

    public static string BuildUpdateWhenSql<T>(
        Expression<Func<T, T, bool>>? expression,
        string sourceAlias,
        string targetAlias);
}
```

**Handles:**
- Single property: `x => x.Id` → `["Id"]`
- Anonymous type: `x => new { x.A, x.B }` → `["A", "B"]`
- Comparison expressions for `updateWhen`

**Verification:** Compiles

### Task 4.2: Write ExpressionParser Unit Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/Services/ExpressionParserTests.cs`

Test scenarios:
- Single property extraction
- Multiple properties via anonymous type
- Nested property access throws helpful error
- Comparison expression SQL generation
- Complex boolean expressions (AND, OR)

**Verification:** All tests pass

---

## Phase 5: SQL Builder

### Task 5.1: Create MergeSqlBuilder

**File:** `NEW/src/JdeScoping.DataSync/Services/MergeSqlBuilder.cs`

```csharp
namespace JdeScoping.DataSync.Services;

internal static class MergeSqlBuilder
{
    public static string BuildCreateTempTable(
        string tempTableName,
        string sourceTableName);

    public static string BuildMerge(
        string destinationTable,
        string tempTableName,
        IReadOnlyList<string> matchColumns,
        IReadOnlyList<string> updateColumns,
        string? updateWhenClause,
        IReadOnlyList<string> insertColumns);
}
```

**Verification:** Compiles

### Task 5.2: Write MergeSqlBuilder Unit Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/Services/MergeSqlBuilderTests.cs`

Test scenarios:
- Creates temp table with SELECT INTO
- MERGE with single match column
- MERGE with composite key
- MERGE with updateWhen condition
- MERGE with subset of update columns
- MERGE with all columns for insert
- Proper SQL escaping of column names

**Verification:** All tests pass

---

## Phase 6: Schema Validation

### Task 6.1: Create SchemaValidator

**File:** `NEW/src/JdeScoping.DataSync/Services/SchemaValidator.cs`

```csharp
namespace JdeScoping.DataSync.Services;

internal sealed class SchemaValidator
{
    public async Task<TableSchema> LoadSchemaAsync(
        SqlConnection connection,
        string tableName);

    public IReadOnlyList<ValidationError> Validate<T>(
        IEnumerable<T> rows,
        TableSchema schema,
        IReadOnlyList<string> columnNames);
}

internal record TableSchema(
    IReadOnlyDictionary<string, ColumnSchema> Columns);

internal record ColumnSchema(
    string Name,
    Type ClrType,
    bool IsNullable,
    int? MaxLength,
    byte? Precision,
    byte? Scale);
```

**Verification:** Compiles

### Task 6.2: Write SchemaValidator Unit Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/Services/SchemaValidatorTests.cs`

Test scenarios:
- Detects string exceeding max length
- Detects null in non-nullable column
- Detects decimal precision overflow
- Returns multiple errors for row
- Includes row index in errors

**Verification:** All tests pass

---

## Phase 7: BulkMergeHelper Implementation

### Task 7.1: Implement BulkMergeHelper

**File:** `NEW/src/JdeScoping.DataSync/Services/BulkMergeHelper.cs`

```csharp
namespace JdeScoping.DataSync.Services;

public sealed class BulkMergeHelper : IBulkMergeHelper
{
    private readonly IDataReaderFactory _readerFactory;
    private readonly IDbConnectionFactory _connectionFactory;
    private readonly ILogger<BulkMergeHelper> _logger;
    private readonly DataSyncOptions _options;

    public async Task<MergeResult> MergeAsync<T>(...) { ... }
}
```

**Implementation flow:**
1. Parse expressions
2. Open connection
3. Create temp table
4. Loop: batch → validate? → bulk copy → merge → truncate
5. Finally: drop temp table
6. Return result

**Verification:** Compiles

### Task 7.2: Write BulkMergeHelper Unit Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/Services/BulkMergeHelperTests.cs`

Test scenarios (use mocks):
- Calls factory to create reader
- Builds correct SQL from expressions
- Handles empty data source
- Respects batch size
- Wraps SqlException with context
- Invokes validation when flag set
- Drops temp table on failure

**Verification:** All tests pass

---

## Phase 8: DI Registration

### Task 8.1: Update ServiceCollectionExtensions

**File:** `NEW/src/JdeScoping.DataSync/DependencyInjection/ServiceCollectionExtensions.cs`

**Add to existing method:**
```csharp
// Add bulk copy converters (generated)
services.AddBulkCopyConverters();

// Add bulk merge helper
services.AddScoped<IBulkMergeHelper, BulkMergeHelper>();
```

**Verification:** Compiles, DI container builds correctly

---

## Phase 9: Integration Tests

### Task 9.1: Create BulkMergeHelper Integration Tests

**File:** `NEW/tests/JdeScoping.DataSync.IntegrationTests/Services/BulkMergeHelperIntegrationTests.cs`

Test scenarios:
- Inserts new records to empty table
- Updates existing records
- Conditional update respects updateWhen
- Composite primary key matching works
- Handles 10k+ records
- Temp table cleaned up on success
- Temp table cleaned up on failure

**Verification:** All integration tests pass

### Task 9.2: Create Batching Integration Tests

**File:** `NEW/tests/JdeScoping.DataSync.IntegrationTests/Services/BatchingIntegrationTests.cs`

Test scenarios:
- Processes 50k records in batches of 10k
- Each batch commits independently
- Partial failure leaves earlier batches committed
- Result contains correct batch count

**Verification:** All tests pass

### Task 9.3: Create Validation Integration Tests

**File:** `NEW/tests/JdeScoping.DataSync.IntegrationTests/Services/ValidationIntegrationTests.cs`

Test scenarios:
- Validation catches string truncation
- Validation catches null violation
- Validation error includes row details
- Without validation, gets SqlException

**Verification:** All tests pass

---

## Phase 10: Migration - Update Existing Code

### Task 10.1: Update TableSyncOperation

**File:** `NEW/src/JdeScoping.DataSync/Services/TableSyncOperation.cs`

**Changes:**
- Inject `IBulkMergeHelper` instead of `IStagingTableManager`
- Replace staging table calls with single `MergeAsync` call
- Update mass update path to use `MergeAsync` with `batchSize: 0`
- Keep post-processor invocation

**Verification:** Compiles

### Task 10.2: Update DataSourceConfig for Expressions

**File:** `NEW/src/JdeScoping.DataSync/Configuration/DataSourceConfig.cs`

**Consider:** How to store/configure match/update expressions per table.

Options:
1. Each fetcher returns its merge config
2. Convention: use primary key for match, all columns for update
3. Attribute on model classes (rejected - Core stays clean)

**Recommended:** Convention with optional override in fetcher.

**Verification:** Compiles

### Task 10.3: Update TableSyncOperation Tests

**File:** `NEW/tests/JdeScoping.DataSync.Tests/Services/TableSyncOperationTests.cs`

**Changes:**
- Mock `IBulkMergeHelper` instead of `IStagingTableManager`
- Update assertions for new call patterns

**Verification:** All tests pass

---

## Phase 11: Cleanup

### Task 11.1: Remove Old Bulk Merge Code

**Files to delete:**
- `NEW/src/JdeScoping.DataSync/Contracts/IStagingTableManager.cs`
- `NEW/src/JdeScoping.DataSync/Services/StagingTableManager.cs`
- `NEW/tests/JdeScoping.DataSync.Tests/Services/StagingTableManagerTests.cs`
- `NEW/tests/JdeScoping.DataSync.IntegrationTests/Services/StagingTableManagerTests.cs`

**Files to update:**
- `NEW/src/JdeScoping.DataSync/DependencyInjection/ServiceCollectionExtensions.cs` - Remove `IStagingTableManager` registration
- `NEW/src/JdeScoping.Data/Repositories/LotFinderRepository.DataSync.cs` - Remove unused bulk methods if any

**Verification:**
- Solution compiles
- All tests pass
- No references to deleted types

### Task 11.2: Final Verification

**Commands:**
```bash
dotnet build
dotnet test
```

**Verification:**
- Zero build warnings related to new code
- All tests pass
- Integration tests pass against SQL Server

---

## Phase 12: Codex Review

### Task 12.1: Consult Codex for Gaps

Use Codex MCP to review:
- Generated code efficiency
- Missing edge cases
- Performance considerations for large datasets
- Error handling completeness
- Thread safety concerns

**Verification:** Address any issues found

---

## Summary Checklist

| Phase | Tasks | Status |
|-------|-------|--------|
| 1. Generator Project | 1.1-1.2 | Pending |
| 2. Contracts | 2.1-2.4 | Pending |
| 3. Type Registry & Generator | 3.1-3.3 | Pending |
| 4. Expression Parsing | 4.1-4.2 | Pending |
| 5. SQL Builder | 5.1-5.2 | Pending |
| 6. Schema Validation | 6.1-6.2 | Pending |
| 7. BulkMergeHelper | 7.1-7.2 | Pending |
| 8. DI Registration | 8.1 | Pending |
| 9. Integration Tests | 9.1-9.3 | Pending |
| 10. Migration | 10.1-10.3 | Pending |
| 11. Cleanup | 11.1-11.2 | Pending |
| 12. Codex Review | 12.1 | Pending |

**Estimated total tasks:** 24