using UnityEngine;

namespace Vanguard.Battle
{
    /// <summary>
    /// Единственный владелец кинематографичного движения камеры.
    /// Снимок исходного pose берётся один раз на цепочку и
    /// восстанавливается идемпотентно.
    /// </summary>
    public sealed class CameraDirector
    {
        private struct Pose
        {
            public Vector3 Position;
            public Quaternion Rotation;
            public float FieldOfView;
        }

        private readonly Camera _camera;
        private Pose _origin;
        private Pose _from;
        private Pose _to;
        private float _duration;
        private float _elapsed;
        private bool _moving;
        private bool _hasOrigin;

        public CameraDirector(Camera camera)
        {
            _camera = camera;
        }

        public bool IsActive => _hasOrigin && _camera != null;
        public bool IsMoving => _moving;

        public void BeginChain()
        {
            if (_camera == null || _hasOrigin)
                return;

            _origin = Capture();
            _hasOrigin = true;
        }

        public void ZoomTo(
            Vector3 target,
            float duration,
            float fieldOfView = 34f)
        {
            if (_camera == null)
                return;

            BeginChain();
            var current = Capture();
            var targetPosition = target
                + (Vector3.back * 3.4f)
                + (Vector3.up * 2.6f);
            var targetRotation = Quaternion.LookRotation(
                target - targetPosition,
                Vector3.up);
            AnimateTo(
                new Pose
                {
                    Position = targetPosition,
                    Rotation = targetRotation,
                    FieldOfView = fieldOfView,
                },
                duration);
        }

        public void ReturnToOrigin(float duration)
        {
            if (!_hasOrigin)
                return;

            AnimateTo(_origin, duration);
        }

        public void Restore()
        {
            if (_camera == null || !_hasOrigin)
                return;

            _moving = false;
            Apply(_origin);
            _hasOrigin = false;
        }

        public void Tick(float deltaTime)
        {
            if (!_moving || _camera == null)
                return;

            _elapsed += deltaTime;
            var t = Mathf.Clamp01(_elapsed / Mathf.Max(0.01f, _duration));
            var eased = t * t * (3f - (2f * t));
            Apply(new Pose
            {
                Position = Vector3.Lerp(_from.Position, _to.Position, eased),
                Rotation = Quaternion.Slerp(
                    _from.Rotation,
                    _to.Rotation,
                    eased),
                FieldOfView = Mathf.Lerp(
                    _from.FieldOfView,
                    _to.FieldOfView,
                    eased),
            });

            if (t >= 1f)
                _moving = false;
        }

        private void AnimateTo(Pose target, float duration)
        {
            if (_camera == null)
                return;

            _from = Capture();
            _to = target;
            _duration = Mathf.Max(0.01f, duration);
            _elapsed = 0f;
            _moving = true;
        }

        private Pose Capture() => new Pose
        {
            Position = _camera.transform.position,
            Rotation = _camera.transform.rotation,
            FieldOfView = _camera.fieldOfView,
        };

        private void Apply(Pose pose)
        {
            if (_camera == null)
                return;

            _camera.transform.position = pose.Position;
            _camera.transform.rotation = pose.Rotation;
            _camera.fieldOfView = pose.FieldOfView;
        }
    }
}