geometry-tower-defense/Assets/GameMain/Scripts/Components/ShooterBullet.cs

using UnityEngine;
using GeometryTD.Definition;
using GeometryTD.Entity.EntityData;

namespace Components
{
    [DisallowMultipleComponent]
    public class ShooterBullet : MonoBehaviour
    {
        [SerializeField] [Min(0.1f)] private float _defaultSpeed = 12f;
        [SerializeField] [Min(0.02f)] private float _hitDistance = 0.15f;
        [SerializeField] [Min(0.1f)] private float _maxLifetime = 3f;

        private Transform _target;
        private float _speed;
        private AttackPayload _attackPayload;
        private float _lifetime;
        private float _runtimeMaxLifetime;
        private bool _isRunning;
        private bool _despawnRequested;

        public void OnShow(BulletData bulletData)
        {
            _target = bulletData != null ? bulletData.Target : null;
            _attackPayload = bulletData?.AttackPayload?.Clone() ?? new AttackPayload();
            _speed = bulletData != null && bulletData.Speed > 0f ? bulletData.Speed : _defaultSpeed;
            _runtimeMaxLifetime = bulletData != null && bulletData.MaxLifetime > 0f ? bulletData.MaxLifetime : _maxLifetime;
            _lifetime = 0f;
            _despawnRequested = false;
            _isRunning = _target != null;
            if (_isRunning)
            {
                Vector2 initialDirection = (Vector2)(_target.position - transform.position);
                RotateToDirection(initialDirection);
            }

            if (!_isRunning)
            {
                _despawnRequested = true;
            }
        }

        public void OnReset()
        {
            _target = null;
            _speed = 0f;
            _attackPayload = new AttackPayload();
            _lifetime = 0f;
            _runtimeMaxLifetime = _maxLifetime;
            _isRunning = false;
            _despawnRequested = false;
        }

        public void Tick(float deltaTime)
        {
            if (!_isRunning)
            {
                return;
            }

            _lifetime += Mathf.Max(0f, deltaTime);
            if (_lifetime >= _runtimeMaxLifetime || _target == null)
            {
                _isRunning = false;
                _despawnRequested = true;
                return;
            }

            Vector3 currentPosition = transform.position;
            Vector2 toTarget = (Vector2)(_target.position - currentPosition);
            float hitDistanceSquared = _hitDistance * _hitDistance;
            if (toTarget.sqrMagnitude <= hitDistanceSquared)
            {
                HitTarget();
                return;
            }

            Vector2 direction = toTarget.normalized;
            RotateToDirection(direction);
            float moveDistance = _speed * Mathf.Max(0f, deltaTime);
            if (moveDistance * moveDistance >= toTarget.sqrMagnitude)
            {
                Vector3 targetPosition = _target.position;
                transform.position = new Vector3(targetPosition.x, targetPosition.y, currentPosition.z);
                HitTarget();
                return;
            }

            transform.position += (Vector3)(direction * moveDistance);
        }

        public bool TryConsumeDespawnRequest()
        {
            if (!_despawnRequested)
            {
                return false;
            }

            _despawnRequested = false;
            return true;
        }

        private void HitTarget()
        {
            if (_target == null)
            {
                _isRunning = false;
                _despawnRequested = true;
                return;
            }

            MonoBehaviour[] components = _target.GetComponentsInParent<MonoBehaviour>();
            foreach (var mono in components)
            {
                if (mono is IDamageReceiver damageReceiver)
                {
                    damageReceiver.TakeDamage(_attackPayload);
                    break;
                }
            }

            _isRunning = false;
            _despawnRequested = true;
        }

        private void RotateToDirection(Vector2 direction)
        {
            if (direction.sqrMagnitude <= Mathf.Epsilon)
            {
                return;
            }

            float targetZAngle = Vector2.SignedAngle(Vector2.up, direction);
            transform.rotation = Quaternion.Euler(0f, 0f, targetZAngle);
        }
    }
}