using UnityEngine;

[DisallowMultipleComponent]
[RequireComponent(typeof(Rigidbody))]
[RequireComponent(typeof(CapsuleCollider))]
public class BobberBuoyancyStable : MonoBehaviour
{
    [Header("Water")]
    public float waterLevelY = 0f;

    [Tooltip("必须至少浸入这么深才开始产生浮力（防止还没入水就被顶）")]
    public float enterWaterDepth = 0.003f; // 3mm（按你的尺度改）

    [Tooltip("在这个深度范围内做平滑过渡（越大越软）")]
    public float smoothDepth = 0.02f;

    [Header("Buoyancy Spring")]
    public float buoyancySpring = 30f;
    public float buoyancyDamping = 8f;

    [Tooltip("最大上浮加速度限制(0=不限制)")]
    public float maxUpAcceleration = 0f;

    [Header("Water Drag")]
    public float extraLinearDampingInWater = 2f;
    public float extraAngularDampingInWater = 2f;

    [Header("Center Of Mass")]
    public bool driveCenterOfMassFromCapsule = true;
    public Vector3 extraCenterOfMassOffset = new Vector3(0f, -0.01f, 0f); // 恢复原来的重心下移

    [Header("Righting")]
    public float rightingTorque = 3f; // 适中的归正扭矩
    public float rightingDamping = 0.8f;

    Rigidbody rb;
    CapsuleCollider cap;

    float airLinearDamping;
    float airAngularDamping;

    void Awake()
    {
        rb = GetComponent<Rigidbody>();
        cap = GetComponent<CapsuleCollider>();
        rb.useGravity = true;

        airLinearDamping = rb.linearDamping;
        airAngularDamping = rb.angularDamping;

        ApplyCenterOfMass();
        rb.maxAngularVelocity = 50f;
        // 移除了强制设置物理参数的代码，保留用户在Inspector中的设置
    }

    void FixedUpdate()
    {
        ApplyCenterOfMass();

        Bounds b = cap.bounds;
        float bottomY = b.min.y;
        float topY = b.max.y;

        // 用"底部点"判定是否真正入水
        float bottomSubmersion = waterLevelY - bottomY;
        if (bottomSubmersion <= enterWaterDepth)
        {
            rb.linearDamping = airLinearDamping;
            rb.angularDamping = airAngularDamping;
            return;
        }

        // 进入水中：阻尼随浸入增强
        float w = Smooth01((bottomSubmersion - enterWaterDepth) / Mathf.Max(1e-4f, smoothDepth));
        rb.linearDamping = airLinearDamping + extraLinearDampingInWater * w;
        rb.angularDamping = airAngularDamping + extraAngularDampingInWater * w;

        // 关键修正：正确的浮力计算
        float volume = Mathf.PI * cap.radius * cap.radius * cap.height;
        float submergedVolume = volume * Mathf.Clamp01(bottomSubmersion / cap.height);
        
        // 浮力 = 排开液体重量 = 体积 × 密度 × 重力
        float buoyantForce = submergedVolume * 1000f * 9.81f;
        
        // 物体重量
        float weight = rb.mass * 9.81f;
        
        // 净浮力（浮力 - 重量）
        float netBuoyancy = buoyantForce - weight;
        
        // 添加弹簧阻尼系统
        float velocity = Vector3.Dot(rb.linearVelocity, Vector3.up);
        float springForce = buoyancySpring * bottomSubmersion;
        float dampingForce = buoyancyDamping * velocity;
        
        float totalForce = netBuoyancy + springForce - dampingForce;
        totalForce *= w; // 平滑过渡
        
        // 限制向上的力
        if (totalForce < 0) totalForce = 0;
        
        // 限制最大加速度
        if (maxUpAcceleration > 0f)
        {
            float maxForce = rb.mass * maxUpAcceleration;
            if (totalForce > maxForce) totalForce = maxForce;
        }

        // 浮力作用点
        float buoyY = Mathf.Min(waterLevelY - 0.001f, topY);
        buoyY = Mathf.Max(buoyY, bottomY);
        Vector3 buoyPoint = new Vector3(b.center.x, buoyY, b.center.z);

        rb.AddForceAtPosition(Vector3.up * totalForce, buoyPoint, ForceMode.Force);

        // 简化的归正扭矩系统
        SimpleRightingSystem(w);
    }

    void SimpleRightingSystem(float weight)
    {
        Vector3 up = transform.up;
        Vector3 axis = Vector3.Cross(up, Vector3.up);
        float mag = axis.magnitude;
        
        if (mag > 1e-4f)
        {
            axis /= mag;
            float angle = Mathf.Asin(Mathf.Clamp(mag, -1f, 1f)) * Mathf.Rad2Deg;
            float angVelOnAxis = Vector3.Dot(rb.angularVelocity, axis);
            
            // 归正扭矩
            float torque = (rightingTorque * angle - rightingDamping * angVelOnAxis) * weight;
            rb.AddTorque(axis * torque, ForceMode.Acceleration);
        }
    }

    void ApplyCenterOfMass()
    {
        if (!driveCenterOfMassFromCapsule) return;
        rb.centerOfMass = cap.center + extraCenterOfMassOffset;
    }

    static float Smooth01(float t)
    {
        t = Mathf.Clamp01(t);
        return t * t * (3f - 2f * t);
    }
    
    void OnDrawGizmos()
    {
        if (cap == null) return;
        
        Gizmos.color = Color.blue;
        Bounds bounds = cap.bounds;
        
        // 绘制浸入部分
        float bottomY = bounds.min.y;
        float submergedHeight = Mathf.Max(0, waterLevelY - bottomY);
        
        Vector3 submergedCenter = new Vector3(
            bounds.center.x,
            bottomY + submergedHeight * 0.5f,
            bounds.center.z
        );
        
        Vector3 submergedSize = new Vector3(
            bounds.size.x,
            submergedHeight,
            bounds.size.z
        );
        
        Gizmos.DrawWireCube(submergedCenter, submergedSize);
        
        // 显示重心
        if (rb != null)
        {
            Gizmos.color = Color.red;
            Vector3 comWorld = transform.TransformPoint(rb.centerOfMass);
            Gizmos.DrawSphere(comWorld, 0.005f);
        }
    }
}