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using System;
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using System.Threading;
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namespace Implab {
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public class ActionChainTaskBase : AbstractPromise {
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readonly Func<Exception, IPromise> m_error;
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readonly Func<Exception, IPromise> m_cancel;
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int m_cancelationLock;
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protected ActionChainTaskBase( Func<Exception, IPromise> error, Func<Exception, IPromise> cancel) {
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m_error = error;
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m_cancel = cancel;
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}
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public void Reject(Exception error) {
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if (LockCancelation())
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HandleErrorInternal(error);
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}
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public override void CancelOperation(Exception reason) {
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if (m_cancel != null && LockCancelation()) {
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try {
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Observe(m_cancel(reason));
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} catch(Exception err) {
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HandleErrorInternal(err);
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}
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}
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}
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protected void HandleErrorInternal(Exception error) {
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if (m_error != null) {
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try {
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Observe(m_error(error));
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} catch(Exception err) {
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SetError(err);
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}
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} else {
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SetError(error);
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}
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}
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protected void Observe(IPromise operation) {
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if (operation == null)
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throw new NullReferenceException("The task returned null promise");
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// pass operation results to the current promise
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operation.On(SetResult, SetError, SetCancelled);
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// pass the cancelation request
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CancellationRequested(operation.Cancel);
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}
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protected bool LockCancelation() {
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return 0 == Interlocked.CompareExchange(ref m_cancelationLock, 1, 0);
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}
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}
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}
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