using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace bbiwarg.Recognition.FingerRecognition
{
    public enum TrackingState
    {
        None,
        Detected,
        Tracked,
        Lost,
    }

    class FingerHistory
    {
        private static List<int> usedIDs = new List<int>();
        public int ID { get; private set; }
        public List<Finger> Fingers { get; private set; }
        public List<TrackingState> States { get; private set; }
        public Finger LastFinger { get; private set; }
        public Finger CurrentFinger { get { return Fingers[Fingers.Count - 1]; } }
        public TrackingState CurrentState { get { return States[States.Count - 1]; } }


        public FingerHistory(Finger finger)
        {
            ID = FingerHistory.getNextUnusedID();

            Fingers = new List<Finger>();
            States = new List<TrackingState>();

            Fingers.Add(finger);
            States.Add(TrackingState.Detected);
            LastFinger = finger;
        }

        ~FingerHistory() {
            FingerHistory.setIDUnused(ID);
        }

        public void addFinger(Finger finger)
        {
            TrackingState previousState = CurrentState;
            TrackingState newState = TrackingState.None;
            int numFramesInCurrentState = getNumFramesInCurrentState();

            if (finger == null)
                newState = TrackingState.Lost;
            else if (previousState == TrackingState.Tracked)
                newState = TrackingState.Tracked;
            else if (previousState == TrackingState.Detected)
            {
                if (numFramesInCurrentState == Constants.FingerNumFramesUntilTracked)
                    newState = TrackingState.Tracked;
                else
                    newState = TrackingState.Detected;
            }

            Fingers.Add(finger);
            States.Add(newState);
            if (finger != null)
                LastFinger = finger;
        }

        public int getNumFramesInCurrentState()
        {
            TrackingState currentState = CurrentState;
            int count = 0;
            for (int i = States.Count - 1; i >= 0; i--)
            {
                if (States[i] == currentState)
                    count++;
                else
                    break;
            }
            return count;
        }

        public static int getNextUnusedID() {
            int id = 1;
            while (usedIDs.Contains(id))
                id++;
            usedIDs.Add(id);
            return id;
        }

        public static void setIDUnused(int id) {
            usedIDs.Remove(id);
        }
    }
}