using UnityEngine;

namespace XGame.Framework.Map
{
    /// <summary>
    /// 平行相机跟随范围
    /// 相机跟随目标限制在该范围内
    /// </summary>
    [RequireComponent(typeof(Camera))]
    public class ParallelCamera : MonoBehaviour
    {
        private struct Positions
        {
            public Vector3 leftDown;
            public Vector3 leftUp;
            public Vector3 rightDown;
            public Vector3 rightUp;
            public Vector3 CenterUp => (leftUp + rightUp) * 0.5f;
            public Vector3 CenterDown => (leftDown + rightDown) * 0.5f;
            public override string ToString()
            {
                return $"Positions leftDown:{leftDown} leftUp:{leftUp} rightDown:{rightDown} rightUp:{rightUp}";
            }
        }
        /// <summary>
        /// 目标平面垂直于相机的直线距离
        /// </summary>
        [SerializeField]
        private float _distance = 16;
        /// <summary>
        /// 可移动区域相对于视口的缩放
        /// </summary>
        [SerializeField]
        private Vector2 _viewportScale = Vector2.one;
        /// <summary>
        /// 可移动区域对齐点
        /// </summary>
        [SerializeField]
        private Vector2 _viewportPivot = Vector2.one * 0.5f;
        /// <summary>
        /// 指定距离对应的视口大小
        /// 下负上正，左负右正
        /// 不可修改
        /// </summary>
        //[SerializeField]
        private Rect _viewportRect;
        /// <summary>
        /// 目标移动区域
        /// 下负上正，左负右正
        /// 不可修改
        /// </summary>
        //[SerializeField]
        private Rect _targetRect;
        //[SerializeField]
        private Camera _camera;
        //[SerializeField]
        private IParallelTarget _target;

        //[SerializeField]
        private Vector3 _offsetUp;
        //[SerializeField]
        private Vector3 _offsetDown;
        /// <summary>
        /// 目标的屏幕区域
        /// 左下(0,0)，右上(width,height)
        /// </summary>
        private Rect _screenRect;
        /// <summary>
        /// 显示区域顶部中心位置转世界坐标
        /// </summary>
        /// <returns></returns>
        public Vector3 TopCenterToWorldPosition()
        {
            var screenPos = _screenRect.center;
            screenPos.y = _screenRect.yMax;
            return _camera.ScreenToWorldPoint(screenPos);
        }
        public IParallelTarget Target
        {
            get => _target;
            set
            {
                if (_target != value)
                {
                    _target = value;
                    OnSetTarget();
                }
            }
        }

        private void Awake()
        {
            _camera = GetComponent<Camera>();
            CalculateViewport();
        }
        //private void LateUpdate()
        //{
        //    if (_target != null)
        //    {
        //        if (_offset ==  Vector3.zero)
        //        {
        //            _offset = transform.position - _target.position;
        //        }
        //        transform.position = _target.position + _offset;
        //        //Debug.Log($"LateUpdate distance: {PointToPlaneDistance(transform.position, target.position, Vector3.back)}");
        //    }
        //}
        public void OnLateUpdate(int millisecond)
        {
            if (_target == null)
                return;
            var tarPosition = _target.Position;
            var tarScreenPos = _camera.WorldToScreenPoint(tarPosition);
            if (_target.IsMoving)
            {
                var moveDir = _target.MoveDir;
                if (tarScreenPos.y > _screenRect.yMax && moveDir.y > 0)
                { // 小于
                  //Debug.Log($"OnLateUpdate Up :{tarScreenPos} _offsetUp:{_offsetUp}");
                    transform.position = tarPosition + _offsetUp;
                }
                else if (tarScreenPos.y < _screenRect.y && moveDir.y < 0)
                {
                    //Debug.Log($"OnLateUpdate Down :{tarScreenPos} _offsetDown:{_offsetDown}");
                    transform.position = tarPosition + _offsetDown;
                }
            }
            else
            {// 没有移动
                if (tarScreenPos.y > _screenRect.y)
                { // 自动移动到显示区域底部
                    var pos = transform.position;
                    pos.y += millisecond * 0.001f * 2;
                    transform.position = pos;
                }
            }
            //Debug.Log($"OnLateUpdate Screen:{tarScreenPos} tarPosition:{tarPosition}");

        }
        private void OnSetTarget()
        {
            if (_target == null)
                return;
            //_offset = transform.position - _target.position;
            _distance = PointToPlaneDistance(transform.position, _target.Position, Vector3.back);
            CalculateViewport();
        }
        private void CalculateViewport()
        {
            //Debug.Log($"Camera pixelRect:{_camera.pixelRect} rect:{_camera.rect} pixelWidth:{_camera.pixelWidth} pixelHeight:{_camera.pixelHeight}");

            var fovRadians = Mathf.Deg2Rad * _camera.fieldOfView; //fov从度数转弧度
            var viewportH = 2 * Mathf.Tan(fovRadians * 0.5f) * _distance;
            var viewportW = viewportH * _camera.aspect;
            _viewportRect = new Rect(-viewportW * 0.5f, -viewportH * 0.5f, viewportW, viewportH);

            _targetRect = new Rect(_viewportRect);
            _targetRect.size *= _viewportScale;
            _targetRect.center = _viewportRect.center + (_viewportPivot - Vector2.one * 0.5f) * _targetRect.size;

            var positions = RectToWorldPositions(_targetRect);

            _offsetUp = transform.position - positions.CenterUp;
            _offsetDown = transform.position - positions.CenterDown;

            var leftDown = _camera.WorldToScreenPoint(positions.leftDown);
            var rightUp = _camera.WorldToScreenPoint(positions.rightUp);
            _screenRect = new Rect(leftDown.x, leftDown.y, rightUp.x - leftDown.x, rightUp.y - leftDown.y);
            //Debug.Log($"World leftDown:{positions.leftDown} leftUp:{positions.leftUp} rightDown:{positions.rightDown} rightUp:{positions.rightUp}");
            //Log.Debug($"Screen leftDown:{leftDown} rightUp:{rightUp} screenRect:{_screenRect}");
        }
        private Positions RectToWorldPositions(Rect rect)
        {
            var normal = transform.forward;
            var center = transform.position + normal * _distance;
            var halfSize = rect.size * 0.5f;
            var offset = rect.center;
            var xAxis = Vector3.Normalize(Vector3.Cross(normal, Vector3.up));
            //Debug.Log($"center:{center} halfSize:{halfSize} offset:{offset} xAxis:{xAxis}");
            if (xAxis == Vector3.zero)
            { //预防当前方向与Y轴平行
                xAxis = Vector3.Cross(normal, Vector3.right);
            }
            var yAxis = Vector3.Cross(normal, xAxis);
            center = center - xAxis * offset.x - yAxis * offset.y;
            var positions = new Positions();
            positions.leftDown = center + xAxis * halfSize.x + yAxis * halfSize.y;
            positions.leftUp = center + xAxis * halfSize.x - yAxis * halfSize.y;
            positions.rightDown = center - xAxis * halfSize.x + yAxis * halfSize.y;
            positions.rightUp = center - xAxis * halfSize.x - yAxis * halfSize.y;
            //Log.Debug(positions);
            return positions;
        }
        /// <summary>
        /// 计算点到平面的垂直距离
        /// 法线向量不能为零
        /// </summary>
        /// <param name="point">待计算距离的点</param>
        /// <param name="pointOnPlane">平面上的一个点</param>
        /// <param name="planeNormal">平面的法线向量</param>
        /// <returns></returns>
        private float PointToPlaneDistance(Vector3 point, Vector3 pointOnPlane, Vector3 planeNormal)
        {
            var distance = Vector3.Dot(planeNormal, (point - pointOnPlane)) / planeNormal.magnitude;
            return distance;
        }

        public Vector3 WorldToScreenPoint(Vector3 point)
        {
            return _camera.WorldToScreenPoint(point);
        }

#if UNITY_EDITOR
        void OnDrawGizmos()
        { //下负上正，左负右正
            //if (Physics.Raycast(transform.position, transform.forward, out var hitInfo))
            //{
            //}
            _camera = GetComponent<Camera>();
            CalculateViewport();
            var positions_1 = RectToWorldPositions(_viewportRect);
            Gizmos.color = Color.blue;
            Gizmos.DrawLine(positions_1.leftDown, positions_1.rightDown);
            Gizmos.DrawLine(positions_1.rightDown, positions_1.rightUp);
            Gizmos.DrawLine(positions_1.rightUp, positions_1.leftUp);
            Gizmos.DrawLine(positions_1.leftUp, positions_1.leftDown);

            Gizmos.color = Color.red;
            var positions_2 = RectToWorldPositions(_targetRect);
            Gizmos.DrawLine(positions_2.leftDown, positions_2.rightDown);
            Gizmos.DrawLine(positions_2.rightDown, positions_2.rightUp);
            Gizmos.DrawLine(positions_2.rightUp, positions_2.leftUp);
            Gizmos.DrawLine(positions_2.leftUp, positions_2.leftDown);
            Gizmos.DrawLine(transform.position, positions_2.CenterUp);
            Gizmos.DrawLine(transform.position, positions_2.CenterDown);

            //Gizmos.color = Color.green;
            //Vector3[] frustumCorners = new Vector3[4];
            //camera.CalculateFrustumCorners(new Rect(0, 0, 1, 1), distance, Camera.MonoOrStereoscopicEye.Mono, frustumCorners);
            //var offsetZ = transform.position.z;
            //for ( int i = 0; i < frustumCorners.Length; i++)
            //{
            //    var pos = frustumCorners[i];
            //    pos.z += offsetZ;
            //    frustumCorners[i] = pos;
            //}
            //Gizmos.DrawLine(frustumCorners[0], frustumCorners[1]);
            //Gizmos.DrawLine(frustumCorners[1], frustumCorners[2]);
            //Gizmos.DrawLine(frustumCorners[2], frustumCorners[3]);
            //Gizmos.DrawLine(frustumCorners[3], frustumCorners[0]);
            //Gizmos.DrawFrustum(transform.position, fovRadians, camera.farClipPlane, camera.nearClipPlane, camera.aspect);
            //var ray = camera.ScreenPointToRay(Vector3.zero);
            //Gizmos.DrawRay(ray);
            //Debug.Log($"PointToScreen LD:{PointToScreen(leftDown)} LU:{PointToScreen(leftUp)} RD:{PointToScreen(rightDown)} RU:{PointToScreen(rightUp)}");
        }

#endif
    }
}