[BREAKING] Make `ArchiCacheable` support `CancellationToken`

[Łukasz Domeradzki]

Checklist

• I read and understood ASF's Contributing guidelines
• I also read Setting-up and FAQ, I don't need help, this is an enhancement idea
• My idea doesn't duplicate existing ASF functionality described on the wiki
• I believe that my idea falls into ASF's scope and should be offered as part of ASF built-in functionality
• My idea doesn't violate the Steam Subscriber Agreement
• My idea doesn't violate the Steam Online Conduct
• This is not ASF-ui suggestion

Enhancement purpose

ArchiCacheable doesn't support CancellationToken for now, making it impossible to cancel the task before given delay or signal.

Solution

//     _                _      _  ____   _                           _____
//    / \    _ __  ___ | |__  (_)/ ___| | |_  ___   __ _  _ __ ___  |  ___|__ _  _ __  _ __ ___
//   / _ \  | '__|/ __|| '_ \ | |\___ \ | __|/ _ \ / _` || '_ ` _ \ | |_  / _` || '__|| '_ ` _ \
//  / ___ \ | |  | (__ | | | || | ___) || |_|  __/| (_| || | | | | ||  _|| (_| || |   | | | | | |
// /_/   \_\|_|   \___||_| |_||_||____/  \__|\___| \__,_||_| |_| |_||_|   \__,_||_|   |_| |_| |_|
// |
// Copyright 2022-2023 Łukasz "JustArchi" Domeradzki
// Contact: [e-mail]

using System;
using System.ComponentModel;
using System.Threading;
using System.Threading.Tasks;

namespace ArchiSteamFarmBackend.Helpers;

internal sealed class ArchiCacheable<T> : IDisposable {
	private readonly TimeSpan CacheLifetime;
	private readonly SemaphoreSlim InitSemaphore = new(1, 1);
	private readonly Func<CancellationToken, Task<(bool Success, T? Result)>> ResolveFunction;

	private bool IsInitialized => InitializedAt > DateTime.MinValue;
	private bool IsPermanentCache => CacheLifetime == Timeout.InfiniteTimeSpan;
	private bool IsRecent => IsPermanentCache || (DateTime.UtcNow.Subtract(InitializedAt) < CacheLifetime);

	private DateTime InitializedAt;
	private T? InitializedValue;

	internal ArchiCacheable(Func<CancellationToken, Task<(bool Success, T? Result)>> resolveFunction, TimeSpan? cacheLifetime = null) {
		ResolveFunction = resolveFunction ?? throw new ArgumentNullException(nameof(resolveFunction));
		CacheLifetime = cacheLifetime ?? Timeout.InfiniteTimeSpan;
	}

	public void Dispose() => InitSemaphore.Dispose();

	internal async Task<(bool Success, T? Result)> GetValue(EFallback fallback = EFallback.DefaultForType, CancellationToken cancellationToken = default) {
		if (!Enum.IsDefined(typeof(EFallback), fallback)) {
			throw new InvalidEnumArgumentException(nameof(fallback), (int) fallback, typeof(EFallback));
		}

		if (IsInitialized && IsRecent) {
			return (true, InitializedValue);
		}

		try {
			await InitSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
		} catch (OperationCanceledException e) {
			Program.ArchiLogger.LogGenericDebuggingException(e);

			return ReturnFailedValueFor(fallback);
		}

		try {
			if (IsInitialized && IsRecent) {
				return (true, InitializedValue);
			}

			(bool success, T? result) = await ResolveFunction(cancellationToken).ConfigureAwait(false);

			if (!success) {
				return ReturnFailedValueFor(fallback, result);
			}

			InitializedValue = result;
			InitializedAt = DateTime.UtcNow;

			return (true, result);
		} catch (OperationCanceledException e) {
			Program.ArchiLogger.LogGenericDebuggingException(e);

			return ReturnFailedValueFor(fallback);
		} finally {
			InitSemaphore.Release();
		}
	}

	internal async Task Reset() {
		if (!IsInitialized) {
			return;
		}

		await InitSemaphore.WaitAsync().ConfigureAwait(false);

		try {
			if (!IsInitialized) {
				return;
			}

			InitializedAt = DateTime.MinValue;
		} finally {
			InitSemaphore.Release();
		}
	}

	private (bool Success, T? Result) ReturnFailedValueFor(EFallback fallback, T? result = default) {
		if (!Enum.IsDefined(typeof(EFallback), fallback)) {
			throw new InvalidEnumArgumentException(nameof(fallback), (int) fallback, typeof(EFallback));
		}

		return fallback switch {
			EFallback.DefaultForType => (false, default(T?)),
			EFallback.FailedNow => (false, result),
			EFallback.SuccessPreviously => (false, InitializedValue),
			_ => throw new InvalidOperationException(nameof(fallback))
		};
	}
}

Or equivalent.

Why currently available solutions are not sufficient?

Usually those calls are expensive, allow inheritors to implement their own cancellation if needed.

Can you help us with this enhancement idea?

Yes, I can code the solution myself and send a pull request

Additional info

Breaking change for all inheritors, don't ship before .NET 8 when we break more things.