using System.Globalization;
using System.Text.Json.Serialization;
using Logging;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using Tranga.TrangaTasks;
using JsonConverter = Newtonsoft.Json.JsonConverter;

namespace Tranga;

/// <summary>
/// Stores information on Task, when implementing new Tasks also update the serializer
/// </summary>
[JsonDerivedType(typeof(DownloadNewChaptersTask), 2)]
[JsonDerivedType(typeof(UpdateLibrariesTask), 3)]
[JsonDerivedType(typeof(DownloadChapterTask), 4)]
public abstract class TrangaTask
{
    // ReSharper disable once CommentTypo ...Tell me why!
    // ReSharper disable once MemberCanBePrivate.Global I want it thaaat way
    public TimeSpan reoccurrence { get; }
    public DateTime lastExecuted { get; set; }
    public Task task { get; }
    public string taskId { get; set; }
    [Newtonsoft.Json.JsonIgnore] public ExecutionState state { get; set; }
    [Newtonsoft.Json.JsonIgnore] protected HashSet<TrangaTask> childTasks { get; }
    [Newtonsoft.Json.JsonIgnore] public TrangaTask? parentTask { get; set; }
    public string? parentTaskId { get; set; }
    [Newtonsoft.Json.JsonIgnore]public double progress { get; private set; }
    [Newtonsoft.Json.JsonIgnore]public DateTime executionStarted { get; private set; }
    [Newtonsoft.Json.JsonIgnore]public DateTime lastChange { get; private set; }
    [Newtonsoft.Json.JsonIgnore]public DateTime executionApproximatelyFinished => progress != 0 ? lastChange.Add(GetRemainingTime()) : DateTime.MaxValue;
    [Newtonsoft.Json.JsonIgnore]public TimeSpan executionApproximatelyRemaining => executionApproximatelyFinished.Subtract(DateTime.Now);
    [Newtonsoft.Json.JsonIgnore]public DateTime nextExecution => lastExecuted.Add(reoccurrence);

    public enum ExecutionState { Waiting, Enqueued, Running }

    protected TrangaTask(Task task, TimeSpan reoccurrence, TrangaTask? parentTask = null)
    {
        this.reoccurrence = reoccurrence;
        this.lastExecuted = DateTime.Now.Subtract(reoccurrence);
        this.task = task;
        this.executionStarted = DateTime.Now;
        this.lastChange = DateTime.MaxValue;
        this.taskId = Convert.ToBase64String(System.Text.Encoding.ASCII.GetBytes(this.executionStarted.ToString(CultureInfo.InvariantCulture)));
        this.childTasks = new();
        this.parentTask = parentTask;
        this.parentTaskId = parentTask?.taskId;
    }
    
    /// <summary>
    /// BL for concrete Tasks
    /// </summary>
    /// <param name="taskManager"></param>
    /// <param name="logger"></param>
    /// <param name="cancellationToken"></param>
    protected abstract void ExecuteTask(TaskManager taskManager, Logger? logger, CancellationToken? cancellationToken = null);

    /// <summary>
    /// Execute the task
    /// </summary>
    /// <param name="taskManager">Should be the parent taskManager</param>
    /// <param name="logger"></param>
    /// <param name="cancellationToken"></param>
    public void Execute(TaskManager taskManager, Logger? logger, CancellationToken? cancellationToken = null)
    {
        logger?.WriteLine(this.GetType().ToString(), $"Executing Task {this}");
        this.state = ExecutionState.Running;
        this.executionStarted = DateTime.Now;
        this.lastChange = DateTime.Now;
        ExecuteTask(taskManager, logger, cancellationToken);
        this.lastExecuted = DateTime.Now;
        this.state = ExecutionState.Waiting;
        logger?.WriteLine(this.GetType().ToString(), $"Finished Executing Task {this}");
    }

    public void ReplaceFailedChildTask(DownloadChapterTask failed, DownloadChapterTask newTask)
    {
        if (!this.childTasks.Contains(failed))
            throw new ArgumentException($"Task {failed} is not childTask of {this}");
        this.childTasks.Remove(failed);
        this.childTasks.Add(newTask);
        this.DecrementProgress(failed.progress);
    }

    public void AddChildTask(TrangaTask childTask)
    {
        this.childTasks.Add(childTask);
    }

    public void IncrementProgress(double amount)
    {
        this.lastChange = DateTime.Now;
        this.progress += amount / (childTasks.Count > 0 ? childTasks.Count : 1);
        if (parentTask is not null)
        {
            parentTask.IncrementProgress(amount);
            parentTask.state = ExecutionState.Running;
        }
    }

    public void DecrementProgress(double amount)
    {
        this.lastChange = DateTime.Now;
        this.progress -= amount / childTasks.Count > 0 ? childTasks.Count : 1;
        parentTask?.DecrementProgress(amount);
    }

    private TimeSpan GetRemainingTime()
    {
        if(progress == 0)
            return DateTime.MaxValue.Subtract(DateTime.Now);
        TimeSpan elapsed = lastChange.Subtract(executionStarted);
        return elapsed.Divide(progress).Subtract(elapsed);
    }

    public enum Task : byte
    {
        DownloadNewChapters = 2,
        UpdateLibraries = 3,
        DownloadChapter = 4
    }

    public override string ToString()
    {
        return $"{task}, {lastExecuted}, {reoccurrence}, {state}, {progress:P2}, {executionApproximatelyFinished}, {executionApproximatelyRemaining}";
    }
    
    public class TrangaTaskJsonConverter : JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return (objectType == typeof(TrangaTask));
        }

        public override object ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
        {
            JObject jo = JObject.Load(reader);
            if (jo["task"]!.Value<Int64>() == (Int64)Task.DownloadNewChapters)
                return jo.ToObject<DownloadNewChaptersTask>(serializer)!;

            if (jo["task"]!.Value<Int64>() == (Int64)Task.UpdateLibraries)
                return jo.ToObject<UpdateLibrariesTask>(serializer)!;
            
            if (jo["task"]!.Value<Int64>() == (Int64)Task.DownloadChapter)
                return jo.ToObject<DownloadChapterTask>(serializer)!;

            throw new Exception();
        }

        public override bool CanWrite => false;

        /// <summary>
        /// Don't call this
        /// </summary>
        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
        {
            throw new Exception("Dont call this");
        }
    }
}