using UnityEngine;

namespace ECM2
{
    /// <summary>
    ///
    /// RootMotionController.
    /// 
    /// Helper component to get Animator root motion velocity vector (animRootMotionVelocity).
    /// 
    /// This must be attached to a game object with an Animator component.
    /// </summary>

    [RequireComponent(typeof(Animator))]
    public class RootMotionController : MonoBehaviour
    {
        #region FIELDS

        protected Animator _animator;

        protected Vector3 _rootMotionDeltaPosition;
        protected Quaternion _rootMotionDeltaRotation;

        #endregion

        #region METHOD

        /// <summary>
        /// Flush any accumulated deltas. This prevents accumulation while character is toggling root motion.
        /// </summary>

        public virtual void FlushAccumulatedDeltas()
        {
            _rootMotionDeltaPosition = Vector3.zero;
            _rootMotionDeltaRotation = Quaternion.identity;
        }

        /// <summary>
        /// Return current root motion rotation and clears accumulated delta rotation.
        /// </summary>

        public virtual Quaternion ConsumeRootMotionRotation()
        {
            Quaternion rootMotionRotation = _rootMotionDeltaRotation;
            _rootMotionDeltaRotation = Quaternion.identity;

            return rootMotionRotation;
        }

        /// <summary>
        /// Get the calculated root motion velocity.
        /// </summary>

        public virtual Vector3 GetRootMotionVelocity(float deltaTime)
        {
            if (deltaTime == 0.0f)
                return Vector3.zero;

            Vector3 rootMotionVelocity = _rootMotionDeltaPosition / deltaTime;
            return rootMotionVelocity;
        }

        /// <summary>
        /// Return current root motion velocity and clears accumulated delta positions.
        /// </summary>

        public virtual Vector3 ConsumeRootMotionVelocity(float deltaTime)
        {
            Vector3 rootMotionVelocity = GetRootMotionVelocity(deltaTime);
            _rootMotionDeltaPosition = Vector3.zero;

            return rootMotionVelocity;
        }

        #endregion

        #region MONOBEHAVIOUR
        
        /// <summary>
        /// If overriden, base method MUST be called.
        /// </summary>

        public virtual void Awake()
        {
            _animator = GetComponent<Animator>();

            if (_animator == null)
            {
                Debug.LogError($"RootMotionController: There is no 'Animator' attached to the '{name}' game object.\n" +
                               $"Please attach a 'Animator' to the '{name}' game object");
            }
        }
        
        /// <summary>
        /// If overriden, base method MUST be called.
        /// </summary>

        public virtual void Start()
        {
            _rootMotionDeltaPosition = Vector3.zero;
            _rootMotionDeltaRotation = Quaternion.identity;
        }
        
        /// <summary>
        /// If overriden, base method MUST be called.
        /// </summary>

        public virtual void OnAnimatorMove()
        {
            // Accumulate root motion deltas between character updates 

            _rootMotionDeltaPosition += _animator.deltaPosition;
            _rootMotionDeltaRotation = _animator.deltaRotation * _rootMotionDeltaRotation;
        }

        #endregion
    }
}