AutoZoom

using System.Collections.Generic;
using cAlgo.API;

namespace cAlgo
{
    [Indicator(AccessRights = AccessRights.None, IsOverlay = true)]
    public class AutoZoom : Indicator
    {
        private record TimeFrameTransition(TimeFrame Less, TimeFrame Greater);

        private const int MinZoomLevel = 5;
        private const int MaxZoomLevel = 500;

        private readonly Dictionary<TimeFrame, TimeFrameTransition> Transitions = new();

        [Parameter(DefaultValue = "m1,m5,m15,m30,h1,h4,h12,D1")]
        public string TimeOrder { get; set; }

        [Parameter(DefaultValue = "t1,t5,t20,t100,t200,t500,t1000")]
        public string TickOrder { get; set; }

        [Parameter(DefaultValue = "re1,re2,re5,re20,re100,re200,re500,re1000")]
        public string RenkoOrder { get; set; }

        [Parameter(DefaultValue = "ra1,ra2,ra5,ra20,ra100,ra200,ra500,ra1000")]
        public string RangeOrder { get; set; }

        [Parameter(MinValue = 160, MaxValue = MaxZoomLevel, Step = 5, DefaultValue = 320)]
        public int MaxZoom { get; set; }

        [Parameter(MinValue = MinZoomLevel, MaxValue = 160, Step = 5, DefaultValue = 80)]
        public int MinZoom { get; set; }

        protected override void Initialize()
        {
            ApplyTransitions(TimeOrder);
            ApplyTransitions(TickOrder);
            ApplyTransitions(RenkoOrder);
            ApplyTransitions(RangeOrder);

            Chart.ZoomChanged += Chart_ZoomChanged;
        }

        public override void Calculate(int index)
        {
            // DO NOTHING
        }

        private void Chart_ZoomChanged(ChartZoomEventArgs args)
        {
            TimeFrame nextTimeFrame = null;
            int nextZoomLevel = 0;

            if (Chart.ZoomLevel >= MaxZoom && TryGetLessTimeFrame(Chart.TimeFrame, out nextTimeFrame))
                nextZoomLevel = MinZoom;

            if (Chart.ZoomLevel <= MinZoom && TryGetGreaterTimeFrame(Chart.TimeFrame, out nextTimeFrame))
                nextZoomLevel = MaxZoom;

            if (nextTimeFrame != null)
            {
                Chart.ZoomLevel = nextZoomLevel;
                Chart.TryChangeTimeFrame(nextTimeFrame);
            }
        }
        
        private bool TryGetLessTimeFrame(TimeFrame timeFrame, out TimeFrame lessTimeFrame) {
            if (Transitions.TryGetValue(timeFrame, out var transition) && transition.Less != null)
            {
                lessTimeFrame = transition.Less;
                return true;
            }

            lessTimeFrame = null;
            return false;
        }
        
        private bool TryGetGreaterTimeFrame(TimeFrame timeFrame, out TimeFrame greaterTimeFrame) {
            if (Transitions.TryGetValue(timeFrame, out var transition) && transition.Greater != null)
            {
                greaterTimeFrame = transition.Greater;
                return true;
            }

            greaterTimeFrame = null;
            return false;
        }
        
        private void ApplyTransitions(string order)
        {
            var tfNames = order.Split(',');

            if (tfNames.Length == 0)
                return;

            var i = 0;

            TimeFrame less;
            TimeFrame current = null;
            TimeFrame greater = TimeFrame.Parse(tfNames[i]);            

            while (++i <= tfNames.Length) {
                less = current;
                current = greater;
                greater = i < tfNames.Length ? TimeFrame.Parse(tfNames[i]) : null;

                Transitions.Add(current, new TimeFrameTransition(less, greater));
            }
        }
    }
}