Race_fields/Assets/_Project/Scripts/Harvesters/AI/HarvesterChaseController.cs

using RaceFields.Vehicles;
using UnityEngine;

namespace RaceFields.Harvesters.AI
{
    [RequireComponent(typeof(Rigidbody))]
    public sealed class HarvesterChaseController : MonoBehaviour
    {
        [Header("Target")]
        [SerializeField] private Transform target;
        [SerializeField] private bool autoFindPlayer = true;
        [SerializeField] private float targetSearchInterval = 0.35f;

        [Header("Wheel Colliders")]
        [SerializeField] private WheelCollider frontLeftCollider;
        [SerializeField] private WheelCollider frontRightCollider;
        [SerializeField] private WheelCollider rearLeftCollider;
        [SerializeField] private WheelCollider rearRightCollider;

        [Header("Wheel Visuals")]
        [SerializeField] private Transform frontLeftVisual;
        [SerializeField] private Transform frontRightVisual;
        [SerializeField] private Transform rearLeftVisual;
        [SerializeField] private Transform rearRightVisual;

        [Header("Movement")]
        [SerializeField] private float maxSpeedKmh = 55f;
        [SerializeField] private float motorTorque = 30000f;
        [SerializeField] private float brakeTorque = 6500f;
        [SerializeField] private float maxSteerAngle = 28f;
        [SerializeField] private float steeringResponse = 4f;
        [SerializeField] private float stoppingDistance = 1.4f;
        [SerializeField] private float reverseDistance = 0.7f;
        [SerializeField] private float downforce = 45f;

        [Header("Stability")]
        [SerializeField] private Vector3 centerOfMass = new Vector3(0f, -0.65f, 0.2f);

        private Rigidbody body;
        private float nextTargetSearchTime;
        private float currentSteerAngle;

        private void Awake()
        {
            body = GetComponent<Rigidbody>();
            AutoFindReferences();

            body.centerOfMass = centerOfMass;
            body.interpolation = RigidbodyInterpolation.Interpolate;
            body.collisionDetectionMode = CollisionDetectionMode.ContinuousDynamic;
        }

        private void FixedUpdate()
        {
            ResolveTarget();
            UpdateDriving();
            ApplyDownforce();
        }

        private void Update()
        {
            UpdateWheelVisuals();
        }

        public void SetTarget(Transform newTarget)
        {
            target = newTarget;
            nextTargetSearchTime = Time.time + targetSearchInterval;
        }

        private void UpdateDriving()
        {
            if (target == null)
            {
                ApplyBrake(brakeTorque);
                ApplyMotor(0f);
                SetSteering(0f);
                return;
            }

            Vector3 localTarget = transform.InverseTransformPoint(target.position);
            localTarget.y = 0f;
            float distance = localTarget.magnitude;
            if (distance < 0.1f)
            {
                ApplyBrake(brakeTorque);
                ApplyMotor(0f);
                return;
            }

            float speedKmh = body.linearVelocity.magnitude * 3.6f;
            float targetAngle = Mathf.Atan2(localTarget.x, localTarget.z) * Mathf.Rad2Deg;
            float desiredSteer = Mathf.Clamp(targetAngle, -maxSteerAngle, maxSteerAngle);
            if (localTarget.z < 0f && Mathf.Abs(localTarget.x) < 0.5f)
                desiredSteer = currentSteerAngle >= 0f ? maxSteerAngle : -maxSteerAngle;

            SetSteering(desiredSteer);

            if (distance <= reverseDistance)
            {
                ApplyBrake(0f);
                ApplyMotor(-motorTorque * 0.45f);
                return;
            }

            if (distance <= stoppingDistance)
            {
                ApplyBrake(brakeTorque);
                ApplyMotor(0f);
                return;
            }

            float angleFactor = Mathf.Clamp(1f - Mathf.Abs(targetAngle) / 130f * 0.5f, 0.65f, 1f);
            float speedFactor = speedKmh < maxSpeedKmh ? 1f : 0f;
            float torque = motorTorque * angleFactor * speedFactor;

            ApplyBrake(0f);
            ApplyMotor(torque);
        }

        private void SetSteering(float desiredAngle)
        {
            currentSteerAngle = Mathf.Lerp(currentSteerAngle, desiredAngle, steeringResponse * Time.fixedDeltaTime);
            if (frontLeftCollider != null)
                frontLeftCollider.steerAngle = currentSteerAngle;
            if (frontRightCollider != null)
                frontRightCollider.steerAngle = currentSteerAngle;
        }

        private void ApplyMotor(float torque)
        {
            SetMotorTorque(frontLeftCollider, torque * 0.5f);
            SetMotorTorque(frontRightCollider, torque * 0.5f);
            SetMotorTorque(rearLeftCollider, torque);
            SetMotorTorque(rearRightCollider, torque);
        }

        private void ApplyBrake(float torque)
        {
            SetBrakeTorque(frontLeftCollider, torque);
            SetBrakeTorque(frontRightCollider, torque);
            SetBrakeTorque(rearLeftCollider, torque);
            SetBrakeTorque(rearRightCollider, torque);
        }

        private void ApplyDownforce()
        {
            body.AddForce(-transform.up * downforce * body.linearVelocity.magnitude, ForceMode.Force);
        }

        private void UpdateWheelVisuals()
        {
            SyncWheelVisual(frontLeftCollider, frontLeftVisual);
            SyncWheelVisual(frontRightCollider, frontRightVisual);
            SyncWheelVisual(rearLeftCollider, rearLeftVisual);
            SyncWheelVisual(rearRightCollider, rearRightVisual);
        }

        private void ResolveTarget()
        {
            if (target != null || !autoFindPlayer)
                return;

            if (Time.time < nextTargetSearchTime)
                return;

            nextTargetSearchTime = Time.time + targetSearchInterval;
            ArcadeBuggyController player = Object.FindFirstObjectByType<ArcadeBuggyController>();
            if (player != null)
                target = player.transform;
        }

        private void AutoFindReferences()
        {
            frontLeftCollider ??= FindChildComponent<WheelCollider>("WheelCollider_FL");
            frontRightCollider ??= FindChildComponent<WheelCollider>("WheelCollider_FR");
            rearLeftCollider ??= FindChildComponent<WheelCollider>("WheelCollider_RL");
            rearRightCollider ??= FindChildComponent<WheelCollider>("WheelCollider_RR");

            frontLeftVisual ??= FindChildTransform("H_Wheel_FL");
            frontRightVisual ??= FindChildTransform("H_Wheel_FR");
            rearLeftVisual ??= FindChildTransform("H_Wheel_RL");
            rearRightVisual ??= FindChildTransform("H_Wheel_RR");
        }

        private T FindChildComponent<T>(string childName) where T : Component
        {
            Transform child = FindChildTransform(childName);
            return child != null ? child.GetComponent<T>() : null;
        }

        private Transform FindChildTransform(string childName)
        {
            Transform[] children = GetComponentsInChildren<Transform>(true);
            for (int i = 0; i < children.Length; i++)
            {
                if (children[i].name == childName)
                    return children[i];
            }

            return null;
        }

        private static void SetMotorTorque(WheelCollider wheel, float torque)
        {
            if (wheel != null)
                wheel.motorTorque = torque;
        }

        private static void SetBrakeTorque(WheelCollider wheel, float torque)
        {
            if (wheel != null)
                wheel.brakeTorque = torque;
        }

        private static void SyncWheelVisual(WheelCollider collider, Transform visual)
        {
            if (collider == null || visual == null)
                return;

            collider.GetWorldPose(out Vector3 position, out Quaternion rotation);
            visual.SetPositionAndRotation(position, rotation);
        }
    }
}