Closes #3073 (#3077)

* Initial implementation of announce with diff

* Add missing logic pieces

* Change in logic

* Fix checksums

* Add deduplication logic

* Update SetPart.cs

* Use standalone endpoint for diff

* Use different hashcode impl

* Update AssetForListing.cs

* Misc

* Push all the changes for this to finally work

* Use original index rather than self-calculated

ASFB makes some calculations based on index, it's better for us to have holes rather than hiding skipped items.

* Handle edge case of no assets after deduplication

* Remove dead code

* Address trim warnings

* Misc optimization

ArchiSteamFarm.OfficialPlugins.ItemsMatcher/BotCache.cs

@@ -0,0 +1,124 @@
+//     _                _      _  ____   _                           _____
+//    / \    _ __  ___ | |__  (_)/ ___| | |_  ___   __ _  _ __ ___  |  ___|__ _  _ __  _ __ ___
+//   / _ \  | '__|/ __|| '_ \ | |\___ \ | __|/ _ \ / _` || '_ ` _ \ | |_  / _` || '__|| '_ ` _ \
+//  / ___ \ | |  | (__ | | | || | ___) || |_|  __/| (_| || | | | | ||  _|| (_| || |   | | | | | |
+// /_/   \_\|_|   \___||_| |_||_||____/  \__|\___| \__,_||_| |_| |_||_|   \__,_||_|   |_| |_| |_|
+// |
+// Copyright 2015-2023 Łukasz "JustArchi" Domeradzki
+// Contact: JustArchi@JustArchi.net
+// |
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// |
+// http://www.apache.org/licenses/LICENSE-2.0
+// |
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using System;
+using System.Globalization;
+using System.IO;
+using System.Threading.Tasks;
+using ArchiSteamFarm.Collections;
+using ArchiSteamFarm.Core;
+using ArchiSteamFarm.Helpers;
+using ArchiSteamFarm.Localization;
+using ArchiSteamFarm.OfficialPlugins.ItemsMatcher.Data;
+using JetBrains.Annotations;
+using Newtonsoft.Json;
+
+namespace ArchiSteamFarm.OfficialPlugins.ItemsMatcher;
+
+internal sealed class BotCache : SerializableFile {
+	[JsonProperty(Required = Required.DisallowNull)]
+	internal readonly ConcurrentList<AssetForListing> LastAnnouncedAssetsForListing = new();
+
+	internal string? LastAnnouncedTradeToken {
+		get => BackingLastAnnouncedTradeToken;
+
+		set {
+			if (BackingLastAnnouncedTradeToken == value) {
+				return;
+			}
+
+			BackingLastAnnouncedTradeToken = value;
+			Utilities.InBackground(Save);
+		}
+	}
+
+	[JsonProperty]
+	private string? BackingLastAnnouncedTradeToken;
+
+	private BotCache(string filePath) : this() {
+		ArgumentException.ThrowIfNullOrEmpty(filePath);
+
+		FilePath = filePath;
+	}
+
+	[JsonConstructor]
+	private BotCache() => LastAnnouncedAssetsForListing.OnModified += OnObjectModified;
+
+	[UsedImplicitly]
+	public bool ShouldSerializeBackingLastAnnouncedTradeToken() => !string.IsNullOrEmpty(BackingLastAnnouncedTradeToken);
+
+	[UsedImplicitly]
+	public bool ShouldSerializeLastAnnouncedAssetsForListing() => LastAnnouncedAssetsForListing.Count > 0;
+
+	protected override void Dispose(bool disposing) {
+		if (disposing) {
+			// Events we registered
+			LastAnnouncedAssetsForListing.OnModified -= OnObjectModified;
+		}
+
+		// Base dispose
+		base.Dispose(disposing);
+	}
+
+	internal static async Task<BotCache> CreateOrLoad(string filePath) {
+		ArgumentException.ThrowIfNullOrEmpty(filePath);
+
+		if (!File.Exists(filePath)) {
+			return new BotCache(filePath);
+		}
+
+		BotCache? botCache;
+
+		try {
+			string json = await File.ReadAllTextAsync(filePath).ConfigureAwait(false);
+
+			if (string.IsNullOrEmpty(json)) {
+				ASF.ArchiLogger.LogGenericError(string.Format(CultureInfo.CurrentCulture, Strings.ErrorIsEmpty, nameof(json)));
+
+				return new BotCache(filePath);
+			}
+
+			botCache = JsonConvert.DeserializeObject<BotCache>(json);
+		} catch (Exception e) {
+			ASF.ArchiLogger.LogGenericException(e);
+
+			return new BotCache(filePath);
+		}
+
+		if (botCache == null) {
+			ASF.ArchiLogger.LogNullError(botCache);
+
+			return new BotCache(filePath);
+		}
+
+		botCache.FilePath = filePath;
+
+		return botCache;
+	}
+
+	private async void OnObjectModified(object? sender, EventArgs e) {
+		if (string.IsNullOrEmpty(FilePath)) {
+			return;
+		}
+
+		await Save().ConfigureAwait(false);
+	}
+}