using UnityEngine;

[RequireComponent(typeof(Rigidbody))]
public class BobberBuoyancy : MonoBehaviour
{
    [Header("Water")]
    public float waterLevel = 0f;            // 水面是 0
    public Vector3 waterFlow = Vector3.zero;

    [Header("Bobber Size (origin at bottom)")]
    public float bobberHeight = 0.18f;        // 浮漂总高度（底部原点 → 顶部）

    [Header("Buoyancy")]
    public float maxBuoyancy = 12f;           // 完全浸没浮力
    public float buoyancyMultiplier = 1.0f;
    public float waterDrag = 0.7f;
    public float waterAngularDrag = 0.4f;

    [Header("Vertical Damping（控制“慢慢上浮”，避免弹跳）")]
    public float verticalDamping = 4.0f;      // 数值越大，上浮越慢、越不弹

    [Header("Upright")]
    public float uprightStrength = 8f;        // 站漂恢复力
    public float uprightDamping = 1.2f;

    [Header("Lay Down (躺漂)")]
    public float layDownThreshold = 0.15f;    // 低于 15% 浸没 → 转入躺漂模式
    public float layDownUprightMultiplier = 0.2f;  // 躺漂时保留多少站立力度（越小越“翘头”）

    private Rigidbody rb;

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

        // 重心稍微靠上，配合 AddForceAtPosition，才能让“底在水里、头上翘”
        rb.centerOfMass = new Vector3(0, bobberHeight * 0.4f, 0);
    }

    private void FixedUpdate()
    {
        ApplyBuoyancy();
        ApplyFlowForce();
        ApplyOrientationControl();
    }

    void ApplyBuoyancy()
    {
        float bottom = rb.position.y;                      // 原点就是最底部
        float depth = waterLevel - bottom;                 // 浸入深度 = 水面 - 底部

        if (depth <= 0f) return;                           // 完全在水面上方，无浮力

        // 当前浸没比例
        float submersionRatio = Mathf.Clamp01(depth / bobberHeight);

        // 基础浮力（和你之前一致）
        float baseForce = maxBuoyancy * submersionRatio * buoyancyMultiplier;

        // ⭐ 竖直速度（用你原来习惯的 linearVelocity）
        float vy = rb.linearVelocity.y;

        // ⭐ 阻尼项：速度越快，反向力越大
        //   下沉很快 → 给一个向上的阻尼（减缓下沉）
        //   向上很快 → 给一个向下的阻尼（防止弹出水面）
        float damping = -vy * verticalDamping;

        // 总的向上力：基础浮力 + 阻尼修正
        float totalUpForce = baseForce + damping;

        // 物理上浮力不能把它“往下按”，所以最少为 0
        if (totalUpForce < 0f) totalUpForce = 0f;

        // ⭐ 浮力作用点 = 浸没体积中心（不动，保持你之前的设计）
        float clampedDepth = Mathf.Clamp(depth, 0, bobberHeight);
        float centerY = bottom + clampedDepth * 0.5f;
        Vector3 buoyancyPoint = new Vector3(rb.position.x, centerY, rb.position.z);

        rb.AddForceAtPosition(Vector3.up * totalUpForce, buoyancyPoint, ForceMode.Acceleration);

        // 水中阻力（保留原逻辑）
        rb.AddForce(-rb.linearVelocity * waterDrag, ForceMode.Acceleration);
        rb.AddTorque(-rb.angularVelocity * waterAngularDrag, ForceMode.Acceleration);
    }

    void ApplyFlowForce()
    {
        if (waterFlow.sqrMagnitude <= 0.0001f) return;
        rb.AddForce((waterFlow - rb.linearVelocity) * 0.3f, ForceMode.Acceleration);
    }

    void ApplyOrientationControl()
    {
        float bottom = rb.position.y;
        float depth = waterLevel - bottom;
        float submersionRatio = Mathf.Clamp01(depth / bobberHeight);

        Vector3 up = transform.up;
        Vector3 worldUp = Vector3.up;

        if (submersionRatio > layDownThreshold)
        {
            // 深浸 → 正常站漂
            Vector3 uprightTorqueVec =
                Vector3.Cross(up, worldUp) * uprightStrength
                - rb.angularVelocity * uprightDamping;

            rb.AddTorque(uprightTorqueVec, ForceMode.Acceleration);
        }
        else
        {
            // 浅浸 → “躺漂”，只保留少量站立力，让它自然斜、头上翘
            float reduced = uprightStrength * layDownUprightMultiplier;

            Vector3 uprightTorqueVec =
                Vector3.Cross(up, worldUp) * reduced
                - rb.angularVelocity * uprightDamping;

            rb.AddTorque(uprightTorqueVec, ForceMode.Acceleration);
        }
    }
}