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using System;
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using System.Threading;
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using Implab.Diagnostics;
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namespace Implab.Components {
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public class PollingRunnableComponent : RunnableComponent {
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readonly Timer m_timer;
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readonly Func<Func<IPromise>, IPromise> m_dispatcher;
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readonly TimeSpan m_interval;
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int m_processing;
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Promise m_pending;
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protected PollingRunnableComponent(TimeSpan interval, Func<Func<IPromise>, IPromise> dispatcher, bool initialized) : base(initialized) {
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m_timer = new Timer(OnInternalTick);
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m_interval = interval;
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m_dispatcher = dispatcher;
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}
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protected override IPromise OnStart() {
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m_timer.Change(TimeSpan.Zero, m_interval);
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return base.OnStart();
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}
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void OnInternalTick(object state) {
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if (StartTick()) {
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try {
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AwaitTick(m_dispatcher != null ? m_dispatcher(OnTick) : OnTick());
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} catch (Exception error) {
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HandleTickError(error);
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}
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}
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}
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/// <summary>
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/// Starts the tick handler.
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/// </summary>
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/// <returns>boolean value, true - the new tick handler may be invoked, false - a tick handler is already running or a component isn't running.</returns>
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/// <remarks>
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/// If the component is stopping no new handlers can be run. Every successful call to this method must be completed with either AwaitTick or HandleTickError handlers.
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/// </remarks>
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protected virtual bool StartTick() {
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if (State == ExecutionState.Running && Interlocked.CompareExchange(ref m_processing, 1, 0) == 0) {
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m_pending = new Promise();
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m_pending
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.On(() => m_processing = 0, PromiseEventType.All)
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.On(null, LogTickError);
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return true;
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}
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return false;
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}
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protected virtual void AwaitTick(IPromise tick) {
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if (tick == null) {
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m_pending.Resolve();
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} else {
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tick.On(
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m_pending.Resolve,
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m_pending.Reject,
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m_pending.CancelOperation
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);
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m_pending.CancellationRequested(tick.Cancel);
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}
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}
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protected virtual void HandleTickError(Exception error) {
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m_pending.Reject(error);
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}
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protected virtual void LogTickError(Exception error) {
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}
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protected virtual IPromise OnTick() {
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return Promise.SUCCESS;
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}
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protected override IPromise OnStop() {
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m_timer.Change(-1, -1);
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if (m_pending != null) {
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m_pending.Cancel();
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return m_pending.Then(base.OnStop);
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}
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return base.OnStop();
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}
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protected override void Dispose(bool disposing, Exception lastError) {
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if (disposing)
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Safe.Dispose(m_timer);
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base.Dispose(disposing, lastError);
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}
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}
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}
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