using System.Runtime.InteropServices;
using Polly;
using Polly.Retry;
namespace Sbroenne.ExcelMcp.ComInterop.Session;
/// <summary>
/// Provides pre-configured resilience pipelines for Excel COM interop operations.
/// </summary>
public static class ResiliencePipelines
{
#region COM HResult Constants
/// <summary>
/// RPC_E_SERVERCALL_RETRYLATER - COM server is busy, retry later.
/// </summary>
public const int RPC_E_SERVERCALL_RETRYLATER = unchecked((int)0x8001010A); // -2147417846
/// <summary>
/// RPC_E_CALL_REJECTED - COM call was rejected.
/// </summary>
public const int RPC_E_CALL_REJECTED = unchecked((int)0x80010001); // -2147418111
/// <summary>
/// Data Model specific error - intermittent failure during measure/table operations.
/// See GitHub Issue #315.
/// </summary>
public const int DATA_MODEL_BUSY = unchecked((int)0x800AC472); // -2146827150
#endregion
#region Pipeline Configuration
/// <summary>
/// Default retry configuration for standard COM busy operations.
/// </summary>
private static readonly PipelineConfig DefaultComConfig = new(
MaxRetryAttempts: 6,
DelayMs: 500,
AdditionalHResults: []);
/// <summary>
/// Retry configuration for Data Model operations.
/// </summary>
private static readonly PipelineConfig DataModelConfig = new(
MaxRetryAttempts: 5,
DelayMs: 1000,
AdditionalHResults: [DATA_MODEL_BUSY]);
#endregion
#region Factory Methods
/// <summary>
/// Creates a retry pipeline for Excel.Quit() operations.
/// Handles transient COM busy conditions with exponential backoff + jitter.
/// </summary>
/// <returns>Configured resilience pipeline</returns>
public static ResiliencePipeline CreateExcelQuitPipeline() => CreatePipeline(DefaultComConfig);
/// <summary>
/// Creates a retry pipeline for Data Model operations (measures, relationships, tables).
/// Handles intermittent 0x800AC472 errors with exponential backoff + jitter.
/// </summary>
/// <remarks>
/// The 0x800AC472 error occurs intermittently when performing Data Model operations
/// on workbooks with active Power Pivot models. The operation typically succeeds on retry.
/// See GitHub Issue #315 for details.
/// </remarks>
/// <returns>Configured resilience pipeline</returns>
public static ResiliencePipeline CreateDataModelPipeline() => CreatePipeline(DataModelConfig);
#endregion
#region Private Implementation
/// <summary>
/// Creates a resilience pipeline with the specified configuration.
/// </summary>
private static ResiliencePipeline CreatePipeline(PipelineConfig config)
{
return new ResiliencePipelineBuilder()
.AddRetry(new RetryStrategyOptions
{
MaxRetryAttempts = config.MaxRetryAttempts,
BackoffType = DelayBackoffType.Exponential,
UseJitter = true,
Delay = TimeSpan.FromMilliseconds(config.DelayMs),
ShouldHandle = new PredicateBuilder().Handle<COMException>(ex =>
ex.HResult == RPC_E_SERVERCALL_RETRYLATER ||
ex.HResult == RPC_E_CALL_REJECTED ||
config.AdditionalHResults.Contains(ex.HResult)),
OnRetry = static _ => ValueTask.CompletedTask
})
.Build();
}
/// <summary>
/// Configuration record for pipeline creation.
/// </summary>
private sealed record PipelineConfig(
int MaxRetryAttempts,
int DelayMs,
int[] AdditionalHResults);
#endregion
}
