/*
 *
 * (c) Copyright Ascensio System Limited 2010-2018
 *
 * This program is freeware. You can redistribute it and/or modify it under the terms of the GNU 
 * General Public License (GPL) version 3 as published by the Free Software Foundation (https://www.gnu.org/copyleft/gpl.html). 
 * In accordance with Section 7(a) of the GNU GPL its Section 15 shall be amended to the effect that 
 * Ascensio System SIA expressly excludes the warranty of non-infringement of any third-party rights.
 *
 * THIS PROGRAM IS DISTRIBUTED WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE. For more details, see GNU GPL at https://www.gnu.org/copyleft/gpl.html
 *
 * You can contact Ascensio System SIA by email at sales@onlyoffice.com
 *
 * The interactive user interfaces in modified source and object code versions of ONLYOFFICE must display 
 * Appropriate Legal Notices, as required under Section 5 of the GNU GPL version 3.
 *
 * Pursuant to Section 7 § 3(b) of the GNU GPL you must retain the original ONLYOFFICE logo which contains 
 * relevant author attributions when distributing the software. If the display of the logo in its graphic 
 * form is not reasonably feasible for technical reasons, you must include the words "Powered by ONLYOFFICE" 
 * in every copy of the program you distribute. 
 * Pursuant to Section 7 § 3(e) we decline to grant you any rights under trademark law for use of our trademarks.
 *
*/

namespace ASC.Common.Threading;

[Singletone]
public class DistributedTaskCacheNotify
{
    public ConcurrentDictionary<string, CancellationTokenSource> Cancelations { get; }
    public ICache Cache { get; }

    private readonly IEventBus<DistributedTaskCancelation> _eventBusNotify;
    private readonly IEventBus<DistributedTaskCache> _eventBusCache;

    public DistributedTaskCacheNotify(
        IEventBus<DistributedTaskCancelation> eventBusNotify,
        IEventBus<DistributedTaskCache> eventBusCache,
        ICache cache)
    {
        Cancelations = new ConcurrentDictionary<string, CancellationTokenSource>();

        Cache = cache;

        _eventBusNotify = eventBusNotify;

        eventBusNotify.Subscribe((c) =>
        {
            if (Cancelations.TryGetValue(c.Id, out var s)) s.Cancel();

        }, EventType.Remove);

        _eventBusCache = eventBusCache;

        eventBusCache.Subscribe((c) =>
        {
            Cache.HashSet(c.Key, c.Id, (DistributedTaskCache)null);
        }, EventType.Remove);

        eventBusCache.Subscribe((c) =>
        {
            Cache.HashSet(c.Key, c.Id, c);
        }, EventType.InsertOrUpdate);
    }

    public void CancelTask(string id) =>
        _eventBusNotify.Publish(new DistributedTaskCancelation() { Id = id }, EventType.Remove);

    public void SetTask(DistributedTask task) =>
        _eventBusCache.Publish(task.DistributedTaskCache, EventType.InsertOrUpdate);

    public void RemoveTask(string id, string key) =>
        _eventBusCache.Publish(new DistributedTaskCache() { Id = id, Key = key }, EventType.Remove);
}

[Singletone(typeof(ConfigureDistributedTaskQueue))]
public class DistributedTaskQueueOptionsManager : OptionsManager<DistributedTaskQueue>
{
    public DistributedTaskQueueOptionsManager(IOptionsFactory<DistributedTaskQueue> factory) : base(factory) { }

    public DistributedTaskQueue Get<T>() where T : DistributedTask => Get(typeof(T).FullName);
}

[Scope]
public class ConfigureDistributedTaskQueue : IConfigureNamedOptions<DistributedTaskQueue>
{
    private DistributedTaskCacheNotify DistributedTaskCacheNotify { get; }
    public IServiceProvider ServiceProvider { get; }
    public IServiceScopeFactory ServiceScopeFactory { get; }

    public ConfigureDistributedTaskQueue(
        DistributedTaskCacheNotify distributedTaskCacheNotify, 
        IServiceProvider serviceProvider,
        IServiceScopeFactory serviceScopeFactory)
    {
        DistributedTaskCacheNotify = distributedTaskCacheNotify;
        ServiceProvider = serviceProvider;
        ServiceScopeFactory = serviceScopeFactory;
    }

    public void Configure(DistributedTaskQueue queue)
    {
        queue.DistributedTaskCacheNotify = DistributedTaskCacheNotify;
        queue.ServiceProvider = ServiceProvider;
    }

    public void Configure(string name, DistributedTaskQueue options)
    {
        Configure(options);
        options.Name = name;
    }
}

public class DistributedTaskQueue
{
    public IServiceProvider ServiceProvider { get; set; }
    public IServiceScopeFactory ServiceScopeFactory { get; set; }
    public DistributedTaskCacheNotify DistributedTaskCacheNotify { get; set; }
    public string Name
    {
        get => _name;
        set => _name = value + GetType().Name;
    }
    public int MaxThreadsCount
    {
        set => Scheduler = value <= 0
                ? TaskScheduler.Default
                : new ConcurrentExclusiveSchedulerPair(TaskScheduler.Default, value).ConcurrentScheduler;
    }

    private ICache Cache => DistributedTaskCacheNotify.Cache;
    private TaskScheduler Scheduler { get; set; } = TaskScheduler.Default;

    public static readonly int InstanceId;
    private string _name;

    private ConcurrentDictionary<string, CancellationTokenSource> Cancelations =>
        DistributedTaskCacheNotify.Cancelations;

    static DistributedTaskQueue() => InstanceId = Process.GetCurrentProcess().Id;

    public void QueueTask(DistributedTaskProgress taskProgress) =>
         QueueTask((a, b) => taskProgress.RunJob(), taskProgress);

    public void QueueTask(Action<DistributedTask, CancellationToken> action, DistributedTask distributedTask = null)
    {
        if (distributedTask == null) distributedTask = new DistributedTask();

        distributedTask.InstanceId = InstanceId;

        var cancelation = new CancellationTokenSource();
        var token = cancelation.Token;
        Cancelations[distributedTask.Id] = cancelation;

        var task = new Task(() => { action(distributedTask, token); }, token, TaskCreationOptions.LongRunning);

        task.ConfigureAwait(false)
            .GetAwaiter()
            .OnCompleted(() => OnCompleted(task, distributedTask.Id));

        distributedTask.Status = DistributedTaskStatus.Running;

        if (distributedTask.Publication == null)
            distributedTask.Publication = GetPublication();

        distributedTask.PublishChanges();

        task.Start(Scheduler);
    }

    public IEnumerable<DistributedTask> GetTasks()
    {
        var tasks = Cache.HashGetAll<DistributedTaskCache>(_name).Values.Select(r => new DistributedTask(r)).ToList();

        tasks.ForEach(t =>
        {
            if (t.Publication == null) t.Publication = GetPublication();
        });

        return tasks;
    }

    public IEnumerable<T> GetTasks<T>() where T : DistributedTask
    {
        var tasks = Cache.HashGetAll<DistributedTaskCache>(_name).Values.Select(r =>
        {
            var result = ServiceProvider.GetService<T>();
            result.DistributedTaskCache = r;

            return result;
        }).ToList();

        tasks.ForEach(t =>
        {
            if (t.Publication == null) t.Publication = GetPublication();
        });

        return tasks;
    }

    public T GetTask<T>(string id) where T : DistributedTask
    {
        var cache = Cache.HashGet<DistributedTaskCache>(_name, id);
        if (cache != null)
        {
            using var scope = ServiceScopeFactory.CreateScope();
            var task = scope.ServiceProvider.GetService<T>();
            task.DistributedTaskCache = cache;

            if (task != null && task.Publication == null)
                task.Publication = GetPublication();

            return task;
        }

        return null;
    }

    public DistributedTask GetTask(string id)
    {
        var cache = Cache.HashGet<DistributedTaskCache>(_name, id);
        if (cache != null)
        {
            var task = new DistributedTask();
            task.DistributedTaskCache = cache;

            if (task != null && task.Publication == null) task.Publication = GetPublication();

            return task;
        }

        return null;
    }

    public void SetTask(DistributedTask task) => DistributedTaskCacheNotify.SetTask(task);

    public void RemoveTask(string id) => DistributedTaskCacheNotify.RemoveTask(id, _name);

    public void CancelTask(string id) => DistributedTaskCacheNotify.CancelTask(id);

    private void OnCompleted(Task task, string id)
    {
        var distributedTask = GetTask(id);
        if (distributedTask != null)
        {
            distributedTask.Status = DistributedTaskStatus.Completed;
            distributedTask.Exception = task.Exception;

            if (task.IsFaulted) distributedTask.Status = DistributedTaskStatus.Failted;

            if (task.IsCanceled) distributedTask.Status = DistributedTaskStatus.Canceled;

            Cancelations.TryRemove(id, out _);

            distributedTask.PublishChanges();
        }
    }

    private Action<DistributedTask> GetPublication()
    {
        return (t) =>
        {
            if (t.DistributedTaskCache != null) t.DistributedTaskCache.Key = _name;

            DistributedTaskCacheNotify.SetTask(t);
        };
    }
}

public static class DistributedTaskQueueExtention
{
    public static DIHelper AddDistributedTaskQueueService<T>(this DIHelper services, int maxThreadsCount) where T : DistributedTask
    {
        services.TryAdd<DistributedTaskCacheNotify>();
        services.TryAdd<DistributedTaskQueueOptionsManager>();
        services.TryAdd<DistributedTaskQueue>();

        var type = typeof(T);

        if (!type.IsAbstract) services.TryAdd<T>();

        services.TryAddSingleton<IConfigureOptions<DistributedTaskQueue>, ConfigureDistributedTaskQueue>();

        _ = services.Configure<DistributedTaskQueue>(type.Name, r =>
        {
            r.MaxThreadsCount = maxThreadsCount;
                //r.errorCount = 1;
            });

        return services;
    }
}