cirnogodot/GTweensGodot/GTweens/Source/Tweeners/Tweener.cs

using System;
using GTweens.Delegates;
using GTweens.Easings;
using GTweens.Enums;
using GTweens.Extensions;
using GTweens.Interpolators;

namespace GTweens.Tweeners
{
    public abstract class Tweener<T> : ITweener
    {
        public delegate void Setter(T currentValue);
        public delegate T Getter();
        
        public bool IsPlaying { get; private set; }
        public bool IsCompleted { get; private set; }
        public bool IsKilled { get; private set; }
        public bool IsCompletedOrKilled => IsCompleted || IsKilled;

        public float Duration { get; }
        public float Elapsed { get; private set; }
        public float Remaining => Math.Max(Duration - Elapsed, 0f);
        
        readonly Getter _getter;
        readonly Setter _setter;
        readonly Getter _to;
        readonly ValidationDelegates.Validation _validation;
        
        readonly IInterpolator<T> _interpolator;

        bool _hasFirstTimeValues;
        T _firstTimeInitialValue = default!;
        T _firstTimeFinalValue = default!;

        T _initialValue = default!;
        T _finalValue = default!;
        T _currentValue = default!;

        EasingDelegate _easingFunction = PresetEasingDelegateFactory.GetEaseDelegate(Easing.Linear);

        public Tweener(
            Getter getter, 
            Setter setter, 
            Getter to, 
            float duration, 
            IInterpolator<T> interpolator,
            ValidationDelegates.Validation validation
            )
        {
            _getter = getter;
            _setter = setter;
            _to = to;
            _interpolator = interpolator;
            _validation = validation;
            
            Duration = Math.Max(duration, 0.0f);
        }

        public void Start()
        {
            if (IsPlaying)
            {
                return;
            }

            IsPlaying = true;
            IsCompleted = false;
            IsKilled = false;

            Elapsed = 0.0f;

            bool valid = Validate();

            if(!valid)
            {
                Kill();
                return;
            }

            _initialValue = _getter.Invoke();

            GetFirstTimeValues();

            CompleteIfInstant();
        }

        public void Reset(ResetMode mode)
        {
            bool valid = Validate();

            if (!valid)
            {
                Kill();
                return;
            }
            
            GetFirstTimeValues();

            IsCompleted = false;
            IsKilled = false;
            Elapsed = 0.0f;

            switch (mode)
            {
                default:
                case ResetMode.InitialValues:
                    {
                        _setter(_firstTimeInitialValue);
                        _finalValue = _firstTimeFinalValue;
                    }
                    break;

                case ResetMode.IncrementalValues:
                    {
                        T difference = _interpolator.Subtract(_firstTimeInitialValue, _firstTimeFinalValue);
                        _finalValue = _interpolator.Add(_currentValue, difference);
                    }
                    break;
                
                case ResetMode.PingPong:
                    {
                        _finalValue = _initialValue;
                    } 
                    break;
            }
        }

        public void Tick(float deltaTime)
        {
            if (!IsPlaying)
            {
                return;
            }

            bool valid = Validate();

            if (!valid)
            {
                Kill();
                return;
            }
            
            Elapsed = Math.Min(Duration, Elapsed + deltaTime);

            if (Elapsed < Duration)
            {
                float timeNormalized = MathExtensions.SafeDivide(Elapsed, Duration);

                _currentValue = _interpolator.Evaluate(
                    _initialValue,
                    _finalValue,
                    timeNormalized,
                    _easingFunction
                );

                _setter(_currentValue);
            }
            else
            {
                Complete();
            }
        }

        public void Complete()
        {
            bool valid = Validate();

            if (!valid)
            {
                return;
            }
            
            GetFirstTimeValues();

            T newValue = _interpolator.Evaluate(
                _initialValue,
                _finalValue,
                1.0f,
                _easingFunction
            );

            _setter(newValue);

            IsPlaying = false;
            IsCompleted = true;
        }

        public void Kill()
        {
            IsKilled = true;
            IsPlaying = false;
        }

        public void SetEasing(EasingDelegate easingFunction)
        {
            _easingFunction = easingFunction;
        }

        void CompleteIfInstant()
        {
            if (!IsPlaying)
            {
                return;
            }

            bool isInstant = Duration == 0.0f;

            if (isInstant)
            {
                Complete();
            }
        }

        bool Validate()
        {
            return _validation.Invoke();
        }

        void GetFirstTimeValues()
        {
            if (_hasFirstTimeValues)
            {
                return;
            }

            _hasFirstTimeValues = true;

            _finalValue = _to.Invoke();
            
            _firstTimeInitialValue = _initialValue;
            _firstTimeFinalValue = _finalValue;
        }
    }
}