using System;
using UnityEngine;

[ExecuteInEditMode]
[RequireComponent(typeof(Rigidbody))]
public class Buoyancy : MonoBehaviour
{
    // ====== No water plugin dependency ======
    [Header("Water (No Plugin)")]
    [Tooltip("Fallback flat water level (Y). Set this to match your scene water height for now.")]
    public float waterLevel = 0f;

    [Tooltip("If false, buoyancy is disabled and rigidbody uses gravity.")]
    public bool waterAvailable = true;

    // ====== Original fields (kept) ======
    public bool includeDeformation = true;

    [Tooltip("Approxative radius of object for buoyancy.")]
    public float sphereRadiusApproximation = 0.25f;

    [Tooltip("Specifies the multiplier for the movement induced by other deformation (waves, swell... etc).")]
    public float waveForceMultiplier = 1f;

    [Tooltip("Specifies the multiplier for the movement induced by the current of the water surface.")]
    public float currentSpeedMultiplier = 1f;

    [Tooltip("Specifies the multiplier for the drag forces induced by the viscosity of the mediums.")]
    public float dragMultiplier = 1f;

    public float defaultRigidbodyDrag = 0.1f;

    public float underwaterRigidbodyAngularDrag = 1f;

    public float overwaterRigidbodyAngularDrag = 0.05f;

    [Tooltip("Specifies the value for surface tension. A high value will stop the object bouncing faster on water.")]
    public float surfaceTensionDamping = 10f;

    [Tooltip("When enabled, the net force is applied with a random offset to create an angular velocity.")]
    public bool applyForceWithRandomOffset;

    // 原脚本里这个是 HDRP 的“自定义网格水面高度偏移”，这里保留字段但不再依赖水插件
    [Tooltip("Optional extra offset added to sampled water height. Useful if your water mesh pivot isn't at surface level.")]
    public float waterHeightOffset = 0f;

    public bool drawDebug;

    private Vector3 currentDirection;
    private Vector3 A;
    private Vector3 B;
    private Vector3 C;
    private Vector3 waterPosition;
    private Vector3 normal;
    private Vector3 deformationDirection;

    private Rigidbody rigidbodyComponent;

    private float h;
    private float hNormalized;

    private bool _isEnabled = true;

    private void Start()
    {
        rigidbodyComponent = GetComponent<Rigidbody>();
        rigidbodyComponent.useGravity = false;
        rigidbodyComponent.linearDamping = defaultRigidbodyDrag;
    }

    public void EnablePhysics(bool set)
    {
        _isEnabled = set;
    }

    private void FixedUpdate()
    {
        // ✅ 关键：没有水 / 禁用时，回到“用Unity重力”
        if (!_isEnabled || !waterAvailable)
        {
            h = (hNormalized = 0f);
            rigidbodyComponent.useGravity = true;
            return;
        }

        rigidbodyComponent.useGravity = false;

        FetchWaterSurfaceData(transform.position, out waterPosition, out normal, out currentDirection);

        deformationDirection = Vector3.ProjectOnPlane(normal, Vector3.up);

        h = Mathf.Clamp(
            waterPosition.y - (transform.position.y - sphereRadiusApproximation),
            0f,
            2f * sphereRadiusApproximation
        );

        hNormalized = h * 1f / (2f * sphereRadiusApproximation);

        float num = MathF.PI * h * h / 3f * (3f * sphereRadiusApproximation - h);

        rigidbodyComponent.angularDamping = Mathf.Lerp(overwaterRigidbodyAngularDrag, underwaterRigidbodyAngularDrag, hNormalized);

        // === 以下保持原脚本单位/写法（尽量贴近原行为） ===
        Vector3 b = rigidbodyComponent.mass * Physics.gravity;
        Vector3 vector = Vector3.Lerp(Physics.gravity, b, hNormalized);

        float num2 = 997f;
        float num3 = 0.001293f;
        float num4 = 1.81E-05f;
        float num5 = 0.001f;
        float num6 = 0.47f;

        Vector3 vector2 = (0f - num2) * num * Physics.gravity;

        Vector3 a = MathF.PI * 6f * sphereRadiusApproximation * num4 * -rigidbodyComponent.linearVelocity;
        Vector3 b2 = MathF.PI * 6f * sphereRadiusApproximation * num5 * -rigidbodyComponent.linearVelocity;
        Vector3 vector3 = Vector3.Lerp(a, b2, hNormalized) * dragMultiplier;

        float num7 = Mathf.Lerp(
            b: Mathf.Sqrt(2f * rigidbodyComponent.mass * (0f - Physics.gravity.y) /
                          (num2 * MathF.PI * Mathf.Pow(sphereRadiusApproximation, 2f) * num6)),
            a: Mathf.Sqrt(2f * rigidbodyComponent.mass * (0f - Physics.gravity.y) /
                          (num3 * MathF.PI * Mathf.Pow(sphereRadiusApproximation, 2f) * num6)),
            t: hNormalized
        );

        Vector3 force = vector + vector2 + vector3;

        Vector3 vector4 = applyForceWithRandomOffset
            ? (new Vector3(
                    UnityEngine.Random.Range(-1f, 1f),
                    UnityEngine.Random.Range(-1f, 1f),
                    UnityEngine.Random.Range(-1f, 1f)
                ) * sphereRadiusApproximation / 5f)
            : Vector3.zero;

        rigidbodyComponent.AddForceAtPosition(force, transform.position + vector4, ForceMode.Acceleration);

        if (hNormalized > 0f && hNormalized < 1f)
        {
            Vector3 force2 = -(Vector3.Dot(rigidbodyComponent.linearVelocity, Physics.gravity.normalized)
                               * Physics.gravity.normalized) * surfaceTensionDamping;

            rigidbodyComponent.AddForce(force2, ForceMode.Acceleration);

            if (includeDeformation)
            {
                rigidbodyComponent.AddForce(deformationDirection * waveForceMultiplier, ForceMode.Acceleration);
                rigidbodyComponent.AddForce(currentDirection * currentSpeedMultiplier, ForceMode.Acceleration);
            }
        }

        if (rigidbodyComponent.linearVelocity.magnitude > num7)
        {
            rigidbodyComponent.linearVelocity = rigidbodyComponent.linearVelocity.normalized * num7;
        }
    }

    private Vector3 FetchWaterSurfaceData(Vector3 point, out Vector3 positionWS, out Vector3 normalWS, out Vector3 currentDirectionWS)
    {
        // ✅ 插件无关：统一从 GetWaterInfo 拿数据
        GetWaterInfo(point, out float waterHeight, out normalWS, out currentDirectionWS);

        positionWS = new Vector3(point.x, waterHeight + waterHeightOffset, point.z);

        if (normalWS == Vector3.zero) normalWS = Vector3.up;

        return positionWS;
    }

    /// <summary>
    /// Water provider (no plugin dependency).
    /// 默认：水平水面，高度 = waterLevel
    /// 以后接 Crest5：你只要改这个函数即可。
    /// </summary>
    protected virtual void GetWaterInfo(Vector3 worldPoint, out float waterHeight, out Vector3 waterNormal, out Vector3 waterCurrentDir)
    {
        waterHeight = waterLevel;        // 默认水面高度（可在Inspector里调对齐）
        waterNormal = Vector3.up;        // 默认法线
        waterCurrentDir = Vector3.zero;  // 默认水流方向
    }

    public Vector3 GetCurrentWaterPosition() => waterPosition;

    public float GetNormalizedHeightOfSphereBelowSurface() => hNormalized;

    private void OnDrawGizmosSelected()
    {
        if (!drawDebug) return;

        Gizmos.color = Color.magenta;
        Gizmos.DrawLine(transform.position, transform.position + normal);

        Gizmos.color = Color.green;
        Gizmos.DrawLine(transform.position, transform.position + deformationDirection * 10f);

        Gizmos.color = Color.red;
        Gizmos.DrawLine(transform.position, transform.position + currentDirection);

        Gizmos.color = Color.yellow;
        Gizmos.DrawSphere(transform.position, sphereRadiusApproximation);

        Gizmos.color = Color.blue;
        Gizmos.DrawSphere(A, sphereRadiusApproximation / 10f);
        Gizmos.DrawSphere(B, sphereRadiusApproximation / 10f);
        Gizmos.DrawSphere(C, sphereRadiusApproximation / 10f);
    }
}