using System;
using System.Collections.Generic;
using UnityEngine;

namespace BF
{
    public class BFFingerSnapshot
    {
        public float age;
        public Vector2 screenPos;

        public static List<BFFingerSnapshot> InactiveSnapshots = new List<BFFingerSnapshot>(1000);

        public static BFFingerSnapshot Pop()
        {
            if (InactiveSnapshots.Count > 0)
            {
                var index = InactiveSnapshots.Count - 1;
                var snapshot = InactiveSnapshots[index];
                InactiveSnapshots.RemoveAt(index);
                return snapshot;
            }
            return new BFFingerSnapshot();
        }

        public static void Push(BFFingerSnapshot snapshot)
        {
            InactiveSnapshots.Add(snapshot);
        }

        public static bool TryGetScreenPos(List<BFFingerSnapshot> snapshots, float targetAge, ref Vector2 screenPos)
        {
            if (snapshots != null && snapshots.Count > 0)
            {
                var snapshot = snapshots[0];
                if (targetAge <= snapshot.age)
                {
                    screenPos = snapshot.screenPos;
                    return true;
                }

                snapshot = snapshots[snapshots.Count - 1];
                if (targetAge >= snapshot.age)
                {
                    screenPos = snapshot.screenPos;
                    return true;
                }

                var lowerIndex = GetLowerIndex(snapshots, targetAge);
                var upperIndex = lowerIndex + 1;
                var lower = snapshots[lowerIndex];
                var upper = upperIndex < snapshots.Count ? snapshots[upperIndex] : lower;
                var across = Mathf.InverseLerp(lower.age, upper.age, targetAge);
                screenPos = Vector2.Lerp(lower.screenPos, upper.screenPos, across);
                return true;
            }
            return false;
        }

        public static int GetLowerIndex(List<BFFingerSnapshot> snapshots, float targetAge)
        {
            if (snapshots != null)
            {
                var count = snapshots.Count;
                if (count > 0)
                {
                    for (int i = count - 1; i >= 0; i--)
                    {
                        if (snapshots[i].age <= targetAge)
                        {
                            return i;
                        }
                    }
                }
                return 0;
            }
            return -1;
        }
    }
}