using UnityEngine;

namespace BrewMonster
{
    /// <summary>
    /// Parabolic trajectory movement with gravity.
    /// Mirrors C++ CGfxParabolicMove exactly (A3DSkillGfxEvent2.cpp:54-92).
    /// 抛物线轨迹移动（带重力），完全镜像C++ CGfxParabolicMove。
    /// </summary>
    public class CGfxParabolicMove : CGfxMoveBase
    {
        protected Vector3 m_vOrgPos;
        protected Vector3 m_vHorzVel;
        protected float m_fVertVel;
        protected float m_fTotalTime;
        protected float m_fCurTime;
        protected float m_fSpeed;

        private const float _fly_speed = 20.0f / 1000.0f; // units per ms, same as C++
        private const float _gravity = 9.8e-6f; // gravity constant, same as C++

        public CGfxParabolicMove(GfxMoveMode mode) : base(mode) { }

        /// <summary>
        /// Initialize parabolic trajectory from host to target.
        /// 初始化从施法者到目标的抛物线轨迹。
        /// </summary>
        public override void StartMove(Vector3 vHost, Vector3 vTarget)
        {
            if (m_bArea)
            {
                CalcRange((vTarget - vHost).normalized);
                m_vOrgPos = m_vPos = vHost + GetRandOff();
            }
            else
            {
                m_vOrgPos = m_vPos = vHost;
            }

            m_vHorzVel = vTarget - m_vPos;
            float fVert = m_vHorzVel.y;
            m_vHorzVel.y = 0;
            float fDist = Normalize(ref m_vHorzVel);
            float fMax = _fly_speed * m_dwMaxFlyTime;

            if (fMax >= fDist)
            {
                m_fSpeed = _fly_speed;
            }
            else
            {
                m_fSpeed = fDist / m_dwMaxFlyTime;
            }

            m_fTotalTime = fDist / m_fSpeed;
            m_vHorzVel *= m_fSpeed;
            m_fVertVel = fVert / m_fTotalTime + 0.5f * _gravity * m_fTotalTime;
            m_vMoveDir = (m_vHorzVel + m_fVertVel * Vector3.up).normalized;
            m_fCurTime = 0;
        }

        /// <summary>
        /// Tick parabolic movement. Returns true when target is reached.
        /// 更新抛物线移动。当到达目标时返回true。
        /// </summary>
        public override bool TickMove(uint dwDeltaTime, Vector3 vHostPos, Vector3 vTargetPos)
        {
            m_fCurTime += dwDeltaTime;
            if (m_fCurTime >= m_fTotalTime)
            {
                return true;
            }

            float fVertVel = m_fVertVel - _gravity * m_fCurTime;
            float fVertDist = 0.5f * (fVertVel + m_fVertVel) * m_fCurTime;
            m_vPos = m_vOrgPos + m_fCurTime * m_vHorzVel + fVertDist * Vector3.up;
            m_vMoveDir = (m_vHorzVel + fVertVel * Vector3.up).normalized;
            return false;
        }
    }
}