using UnityEngine;

/// <summary>
/// 鱼线张力参考模型
/// 
/// 这个脚本不负责真正的鱼线渲染，也不负责完整鱼AI，
/// 只负责根据“竿尖 - 鱼”的关系，计算一个较合理的张力模型。
///
/// 适合先拿来验证：
/// 1. 当前张力是否合理
/// 2. 鱼竿弯曲是否合理
/// 3. 卸力出线是否自然
/// 4. 断线判定是否符合预期
/// </summary>
public class FishingLineTensionModel : MonoBehaviour
{
    [Header("References")] [Tooltip("鱼竿竿尖挂点")]
    public Transform rodTip;

    [Tooltip("鱼对象（位置来源）")] public Transform fishTarget;

    [Tooltip("鱼刚体，用来取速度并施加线的拉力")] public Rigidbody fishRb;

    [Tooltip("玩家/竿尖所在刚体，可选。若为空则竿尖速度按0处理")] public Rigidbody rodTipRb;

    [Header("Line State")] [Tooltip("当前放线长度（米）")]
    public float lineLength = 5f;

    [Tooltip("最短允许线长，防止收线收到过小")] public float minLineLength = 0.5f;

    [Tooltip("最长允许线长")] public float maxLineLength = 100f;

    [Tooltip("手动收线速度（米/秒），这里只是参考参数")] public float reelInSpeed = 1.5f;

    [Tooltip("手动放线速度（米/秒），这里只是参考参数")] public float reelOutSpeed = 3f;

    [Header("Line Tension")] [Tooltip("鱼线系统等效刚度。越大，拉直后越硬")]
    public float lineStiffness = 120f;

    [Tooltip("沿鱼线方向的阻尼。鱼外冲越快，附加张力越大")] public float lineDamping = 20f;

    [Tooltip("接近绷直时保留的一点最小张力，避免完全没手感")] public float minTensionWhenNearTight = 1f;

    [Tooltip("进入预张力区域的比例。比如0.95表示距离达到线长95%就开始有一点点手感")] [Range(0.7f, 1f)]
    public float nearTightRatio = 0.95f;

    [Header("Rod Buffer / Flex")] [Tooltip("鱼竿最大承载参考值。张力越接近这个值，竿越弯")]
    public float rodMaxLoad = 40f;

    [Tooltip("鱼竿最大缓冲长度（米）。竿越弯，等效可多“吃掉”一些长度")]
    public float rodFlexMax = 0.35f;

    [Header("Drag / Spool")] [Tooltip("绕线轮卸力阈值。张力超过它就开始自动出线")]
    public float dragThreshold = 18f;

    [Tooltip("超过卸力阈值后，每多1单位张力，对应的自动出线速度倍率")]
    public float dragSpoolFactor = 0.08f;

    [Header("Break / Damage")] [Tooltip("安全张力。超过它开始累计损伤")]
    public float safeTension = 22f;

    [Tooltip("绝对极限张力。超过它可以直接判定断线")] public float breakTension = 35f;

    [Tooltip("超安全张力时的损伤累计速度倍率")] public float lineDamageRate = 1.5f;

    [Tooltip("累计损伤达到此值后断线")] public float lineDamageLimit = 10f;

    [Header("Fish Force")] [Tooltip("是否把张力反向施加给鱼刚体")]
    public bool applyForceToFish = true;

    [Tooltip("对鱼施加拉力时的倍率，用来调手感")] public float forceToFishScale = 1f;

    [Header("Runtime Debug (Read Only)")] [SerializeField]
    private float currentDistance;

    [SerializeField] private float currentRelativeSpeedAlongLine;
    [SerializeField] private float currentRodFlexOffset;
    [SerializeField] private float currentOverStretch;
    [SerializeField] private float currentTension;
    [SerializeField] private float currentRodBend01;
    [SerializeField] private float currentLineDamage;
    [SerializeField] private bool isLineBroken;
    [SerializeField] private bool isAutoSpooling;

    /// <summary> 当前张力，对外只读 </summary>
    public float CurrentTension => currentTension;

    /// <summary> 当前鱼竿弯曲比例（0~1） </summary>
    public float CurrentRodBend01 => currentRodBend01;

    /// <summary> 当前是否断线 </summary>
    public bool IsLineBroken => isLineBroken;

    /// <summary> 当前累计损伤 </summary>
    public float CurrentLineDamage => currentLineDamage;

    private void Reset()
    {
        lineLength = 5f;
        minLineLength = 0.5f;
        maxLineLength = 100f;

        lineStiffness = 120f;
        lineDamping = 20f;
        minTensionWhenNearTight = 1f;
        nearTightRatio = 0.95f;

        rodMaxLoad = 40f;
        rodFlexMax = 0.35f;

        dragThreshold = 18f;
        dragSpoolFactor = 0.08f;

        safeTension = 22f;
        breakTension = 35f;
        lineDamageRate = 1.5f;
        lineDamageLimit = 10f;

        applyForceToFish = true;
        forceToFishScale = 1f;
    }

    private void Update()
    {
        // 这里只演示输入，实际项目你可能会改成输入系统控制
        HandleManualLineInput();
    }

    private void FixedUpdate()
    {
        if (isLineBroken)
        {
            currentTension = 0f;
            currentRodBend01 = 0f;
            currentRodFlexOffset = 0f;
            currentOverStretch = 0f;
            currentRelativeSpeedAlongLine = 0f;
            isAutoSpooling = false;
            return;
        }

        if (rodTip == null || fishTarget == null)
            return;

        // --------------------------------------------------
        // 1. 计算竿尖到鱼的几何关系
        // --------------------------------------------------
        Vector3 delta = fishTarget.position - rodTip.position;
        float distance = delta.magnitude;
        Vector3 lineDir = distance > 0.0001f ? delta / distance : Vector3.forward;

        currentDistance = distance;

        // --------------------------------------------------
        // 2. 计算沿鱼线方向的相对速度
        //    > 0 代表鱼在远离竿尖，拉力应增加
        //    < 0 代表鱼在靠近竿尖，拉力应减小
        // --------------------------------------------------
        Vector3 fishVel = fishRb != null ? fishRb.linearVelocity : Vector3.zero;
        Vector3 tipVel = rodTipRb != null ? rodTipRb.linearVelocity : Vector3.zero;

        float relativeSpeedAlongLine = Vector3.Dot(fishVel - tipVel, lineDir);
        currentRelativeSpeedAlongLine = relativeSpeedAlongLine;

        // --------------------------------------------------
        // 3. 根据“上一帧张力”估算当前鱼竿弯曲带来的缓冲长度
        //    张力越大，竿越弯，可额外缓冲一些长度
        // --------------------------------------------------
        currentRodBend01 = rodMaxLoad > 0.0001f
            ? Mathf.Clamp01(currentTension / rodMaxLoad)
            : 0f;

        currentRodFlexOffset = currentRodBend01 * rodFlexMax;

        // --------------------------------------------------
        // 4. 计算“超限量”
        //    当距离 <= 线长 + 竿缓冲时，认为线没有真正被硬拉伸
        //    当距离 > 线长 + 竿缓冲时，多出来的部分转化为张力
        // --------------------------------------------------
        float effectiveLength = lineLength + currentRodFlexOffset;
        float overStretch = Mathf.Max(0f, distance - effectiveLength);
        currentOverStretch = overStretch;

        // --------------------------------------------------
        // 5. 计算基础张力
        //    T = 刚度项 + 阻尼项
        // --------------------------------------------------
        float tension = 0f;

        // 刚度项：超过可承受长度才会产生明显张力
        tension += lineStiffness * overStretch;

        // 阻尼项：只有“往外冲”的速度才增加张力
        if (relativeSpeedAlongLine > 0f)
        {
            tension += lineDamping * relativeSpeedAlongLine;
        }

        // --------------------------------------------------
        // 6. 接近绷直时给一点最小预张力
        //    避免 D 接近 lineLength 时，手感突然从0跳到有力
        // --------------------------------------------------
        float nearTightDistance = lineLength * nearTightRatio;
        if (distance >= nearTightDistance)
        {
            tension = Mathf.Max(tension, minTensionWhenNearTight);
        }

        // 线完全松很多时，可直接视为无有效张力
        if (distance < nearTightDistance && overStretch <= 0f)
        {
            tension = 0f;
        }

        currentTension = Mathf.Max(0f, tension);

        // --------------------------------------------------
        // 7. 卸力：当张力超过绕线轮设定值时，自动出线
        //    这样大鱼冲刺时不会硬顶到瞬间爆线
        // --------------------------------------------------
        isAutoSpooling = false;

        if (currentTension > dragThreshold)
        {
            float extraTension = currentTension - dragThreshold;
            float autoSpoolSpeed = extraTension * dragSpoolFactor;

            lineLength += autoSpoolSpeed * Time.fixedDeltaTime;
            lineLength = Mathf.Clamp(lineLength, minLineLength, maxLineLength);

            isAutoSpooling = true;
        }

        // --------------------------------------------------
        // 8. 断线逻辑
        //    8.1 超过极限值：可直接断
        //    8.2 超过安全值：持续累计损伤
        // --------------------------------------------------
        if (currentTension >= breakTension)
        {
            BreakLine();
            return;
        }

        if (currentTension > safeTension)
        {
            float overload = currentTension - safeTension;
            currentLineDamage += overload * lineDamageRate * Time.fixedDeltaTime;

            if (currentLineDamage >= lineDamageLimit)
            {
                BreakLine();
                return;
            }
        }
        else
        {
            // 张力安全时，损伤缓慢恢复一点
            currentLineDamage -= Time.fixedDeltaTime;
            currentLineDamage = Mathf.Max(0f, currentLineDamage);
        }

        // --------------------------------------------------
        // 9. 把鱼线张力反向施加给鱼
        //    鱼越往外冲，线张力越大，反向拉回鱼的力也越大
        // --------------------------------------------------
        if (applyForceToFish && fishRb != null && currentTension > 0f)
        {
            Vector3 pullForce = -lineDir * currentTension * forceToFishScale;
            fishRb.AddForce(pullForce, ForceMode.Force);
        }

        // --------------------------------------------------
        // 10. 重新根据当前张力更新鱼竿弯曲值（给外部表现层用）
        // --------------------------------------------------
        currentRodBend01 = rodMaxLoad > 0.0001f
            ? Mathf.Clamp01(currentTension / rodMaxLoad)
            : 0f;
    }

    /// <summary>
    /// 示例输入：
    /// R = 收线
    /// F = 放线
    /// 实际项目建议接你自己的输入系统
    /// </summary>
    private void HandleManualLineInput()
    {
        if (isLineBroken)
            return;

        if (Input.GetKey(KeyCode.R))
        {
            lineLength -= reelInSpeed * Time.deltaTime;
        }

        if (Input.GetKey(KeyCode.F))
        {
            lineLength += reelOutSpeed * Time.deltaTime;
        }

        lineLength = Mathf.Clamp(lineLength, minLineLength, maxLineLength);
    }

    /// <summary>
    /// 断线
    /// </summary>
    private void BreakLine()
    {
        isLineBroken = true;
        currentTension = 0f;
        currentRodBend01 = 0f;
        currentRodFlexOffset = 0f;
        currentOverStretch = 0f;
        isAutoSpooling = false;

        Debug.Log("鱼线断了");
    }

    /// <summary>
    /// 外部调用：修复鱼线
    /// </summary>
    public void RepairLine(float repairedLength)
    {
        isLineBroken = false;
        currentLineDamage = 0f;
        lineLength = Mathf.Clamp(repairedLength, minLineLength, maxLineLength);
    }

    /// <summary>
    /// 外部调用：直接设置线长
    /// </summary>
    public void SetLineLength(float length)
    {
        lineLength = Mathf.Clamp(length, minLineLength, maxLineLength);
    }
}