//     _                _      _  ____   _                           _____
//    / \    _ __  ___ | |__  (_)/ ___| | |_  ___   __ _  _ __ ___  |  ___|__ _  _ __  _ __ ___
//   / _ \  | '__|/ __|| '_ \ | |\___ \ | __|/ _ \ / _` || '_ ` _ \ | |_  / _` || '__|| '_ ` _ \
//  / ___ \ | |  | (__ | | | || | ___) || |_|  __/| (_| || | | | | ||  _|| (_| || |   | | | | | |
// /_/   \_\|_|   \___||_| |_||_||____/  \__|\___| \__,_||_| |_| |_||_|   \__,_||_|   |_| |_| |_|
// 
//  Copyright 2015-2018 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.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace ArchiSteamFarm {
	internal sealed class GlobalDatabase : IDisposable {
		[JsonProperty(Required = Required.DisallowNull)]
		internal readonly Guid Guid = Guid.NewGuid();

		[JsonProperty(Required = Required.DisallowNull)]
		internal readonly ConcurrentDictionary<uint, (uint ChangeNumber, HashSet<uint> AppIDs)> PackagesData = new ConcurrentDictionary<uint, (uint ChangeNumber, HashSet<uint> AppIDs)>();

		[JsonProperty(Required = Required.DisallowNull)]
		internal readonly InMemoryServerListProvider ServerListProvider = new InMemoryServerListProvider();

		private readonly SemaphoreSlim FileSemaphore = new SemaphoreSlim(1, 1);
		private readonly SemaphoreSlim PackagesRefreshSemaphore = new SemaphoreSlim(1, 1);

		[JsonProperty(PropertyName = "_CellID", Required = Required.DisallowNull)]
		internal uint CellID { get; private set; }

		private string FilePath;

		// This constructor is used when creating new database
		private GlobalDatabase(string filePath) : this() {
			if (string.IsNullOrEmpty(filePath)) {
				throw new ArgumentNullException(nameof(filePath));
			}

			FilePath = filePath;
			Save().Wait();
		}

		// This constructor is used only by deserializer
		private GlobalDatabase() => ServerListProvider.ServerListUpdated += OnServerListUpdated;

		public void Dispose() {
			// Events we registered
			ServerListProvider.ServerListUpdated -= OnServerListUpdated;

			// Those are objects that are always being created if constructor doesn't throw exception
			FileSemaphore.Dispose();
			PackagesRefreshSemaphore.Dispose();
		}

		internal HashSet<uint> GetPackageIDs(uint appID) {
			if (appID == 0) {
				ASF.ArchiLogger.LogNullError(nameof(appID));
				return null;
			}

			HashSet<uint> result = new HashSet<uint>(PackagesData.Where(package => (package.Value.AppIDs != null) && package.Value.AppIDs.Contains(appID)).Select(package => package.Key));
			return result;
		}

		internal static GlobalDatabase Load(string filePath) {
			if (string.IsNullOrEmpty(filePath)) {
				ASF.ArchiLogger.LogNullError(nameof(filePath));
				return null;
			}

			if (!File.Exists(filePath)) {
				return new GlobalDatabase(filePath);
			}

			GlobalDatabase globalDatabase;

			try {
				globalDatabase = JsonConvert.DeserializeObject<GlobalDatabase>(File.ReadAllText(filePath));
			} catch (Exception e) {
				ASF.ArchiLogger.LogGenericException(e);
				return null;
			}

			if (globalDatabase == null) {
				ASF.ArchiLogger.LogNullError(nameof(globalDatabase));
				return null;
			}

			globalDatabase.FilePath = filePath;
			return globalDatabase;
		}

		internal async Task RefreshPackages(Bot bot, IReadOnlyDictionary<uint, uint> packages) {
			if ((bot == null) || (packages == null) || (packages.Count == 0)) {
				ASF.ArchiLogger.LogNullError(nameof(bot) + " || " + nameof(packages));
				return;
			}

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

			try {
				HashSet<uint> packageIDs = new HashSet<uint>();

				foreach (KeyValuePair<uint, uint> package in packages) {
					if (!PackagesData.TryGetValue(package.Key, out (uint ChangeNumber, HashSet<uint> _) packageData) || (packageData.ChangeNumber < package.Value)) {
						packageIDs.Add(package.Key);
					}
				}

				if (packageIDs.Count == 0) {
					return;
				}

				Dictionary<uint, (uint ChangeNumber, HashSet<uint> AppIDs)> packagesData = await bot.GetPackagesData(packageIDs).ConfigureAwait(false);
				if ((packagesData == null) || (packagesData.Count == 0)) {
					return;
				}

				foreach (KeyValuePair<uint, (uint ChangeNumber, HashSet<uint> AppIDs)> packageData in packagesData) {
					PackagesData[packageData.Key] = packageData.Value;
				}

				await Save().ConfigureAwait(false);
			} finally {
				PackagesRefreshSemaphore.Release();
			}
		}

		internal async Task SetCellID(uint value = 0) {
			if (value == CellID) {
				return;
			}

			CellID = value;
			await Save().ConfigureAwait(false);
		}

		private async void OnServerListUpdated(object sender, EventArgs e) => await Save().ConfigureAwait(false);

		private async Task Save() {
			string json = JsonConvert.SerializeObject(this);
			if (string.IsNullOrEmpty(json)) {
				ASF.ArchiLogger.LogNullError(nameof(json));
				return;
			}

			string newFilePath = FilePath + ".new";

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

			try {
				// We always want to write entire content to temporary file first, in order to never load corrupted data, also when target file doesn't exist
				await File.WriteAllTextAsync(newFilePath, json).ConfigureAwait(false);

				if (File.Exists(FilePath)) {
					File.Replace(newFilePath, FilePath, null);
				} else {
					File.Move(newFilePath, FilePath);
				}
			} catch (Exception e) {
				ASF.ArchiLogger.LogGenericException(e);
			} finally {
				FileSemaphore.Release();
			}
		}
	}
}