using System; using System.Threading; using System.Threading.Tasks; namespace Polly.Fallback { internal class AsyncFallbackEngine { internal static async Task<TResult> ImplementationAsync<TResult>(Func<Context, CancellationToken, Task<TResult>> action, Context context, CancellationToken cancellationToken, ExceptionPredicates shouldHandleExceptionPredicates, ResultPredicates<TResult> shouldHandleResultPredicates, Func<DelegateResult<TResult>, Context, Task> onFallbackAsync, Func<DelegateResult<TResult>, Context, CancellationToken, Task<TResult>> fallbackAction, bool continueOnCapturedContext) { DelegateResult<TResult> delegateOutcome; try { cancellationToken.ThrowIfCancellationRequested(); TResult result = await action(context, cancellationToken).ConfigureAwait(continueOnCapturedContext); if (!shouldHandleResultPredicates.AnyMatch(result)) return result; delegateOutcome = new DelegateResult<TResult>(result); } catch (Exception ex) { Exception ex2 = shouldHandleExceptionPredicates.FirstMatchOrDefault(ex); if (ex2 == null) throw; delegateOutcome = new DelegateResult<TResult>(ex2); } await onFallbackAsync(delegateOutcome, context).ConfigureAwait(continueOnCapturedContext); return await fallbackAction(delegateOutcome, context, cancellationToken).ConfigureAwait(continueOnCapturedContext); } } }