using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;

namespace Sony.Filtr.Tasks.Helpers
{
    public class ProgressTracker
    {
        private readonly ConcurrentBag<ProgressItem> items;
        private readonly ActionBlock<int> ProcessBlock;

        private int CurrentProgress = 0;
        public readonly int Total;

        public class ProgressItem
        {
            public static readonly ProgressItem Empty = new ProgressItem(0, DateTime.Now);

            public readonly DateTime DT;
            public readonly int Current;

            public ProgressItem(int current, DateTime dt)
            {
                this.Current = current;
                this.DT = dt;
            }

            public string ToPercentage(int total)
            {
                return $"{((double)this.Current / total * 100).ToString("0.00")}%";
            }

            public double HourlyProcessingSpeed(DateTime startTime)
            {
                if ((this.DT - startTime).TotalSeconds < 2) { return this.Current; }

                return (double)this.Current / (this.DT - startTime).TotalSeconds * 3600;
            }

            public double HourShift(DateTime startTime)
            {
                return (this.DT - startTime).TotalHours;
            }
        }

        public ProgressTracker(int total)
        {
            this.items = new ConcurrentBag<ProgressItem>();

            this.ProcessBlock = new ActionBlock<int>(
                delta => this.items.Add(new ProgressItem(Interlocked.Add(ref this.CurrentProgress, delta), DateTime.Now)),
                new ExecutionDataflowBlockOptions() { MaxDegreeOfParallelism = 1, EnsureOrdered = true });

            this.Total = total;
        }

        public int GetCurrentProgress() { return this.CurrentProgress; }

        public IEnumerable<ProgressItem> Items { get { return this.items.ToArray(); } }

        public async Task NextAsync(int delta)
        {
            await this.ProcessBlock.SendAsync(delta);
        }

        public void Next(int delta, DateTime dt)
        {
            this.items.Add(new ProgressItem(Interlocked.Add(ref this.CurrentProgress, delta), dt));
        }
    }
}