WaveDefender/Assets/Scripts/AIBehaviour.cs

using UnityEngine;
using UnityEngine.AI;

/// <summary>
/// Call of Duty Zombies-style enemy AI.
/// States: Seeking (chase player) → BreakingBarrier (hammer a blocked door/window) → Attacking (melee the player)
///
/// Setup requirements:
///   - NavMeshAgent on this GameObject
///   - Player GameObject tagged "Player" with a PlayerHealth component
///   - Barrier objects on a layer assigned to barrierLayer, with a Barrier component + NavMeshObstacle (carving on)
/// </summary>
[RequireComponent(typeof(NavMeshAgent))]
public class AIBehaviour : MonoBehaviour
{
    public enum ZombieState { Seeking, BreakingBarrier, Attacking, Dead }

    // -------------------------------------------------------------------------
    //  Inspector
    // -------------------------------------------------------------------------
    [Header("Movement")]
    public float moveSpeed = 3.5f;
    public float acceleration = 12f;

    [Header("Attack — Player")]
    public float attackRange = 1.8f;
    public float attackDamage = 15f;
    [Tooltip("Attacks per second")] public float attackRate = 1f;

    [Header("Attack — Barrier")]
    public float barrierDetectRange = 1.6f;
    public float barrierDamage = 25f;
    [Tooltip("Barrier hits per second")] public float barrierAttackRate = 1.5f;
    public LayerMask barrierLayer;

    [Header("Health")]
    public float maxHealth = 100f;

    [Header("Animation (optional)")]
    public Animator animator;

    // -------------------------------------------------------------------------
    //  Private state
    // -------------------------------------------------------------------------
    private NavMeshAgent _agent;
    private Transform _player;
    private PlayerHealth _playerHealth;
    private ZombieState _state = ZombieState.Seeking;
    private float _health;
    private float _attackTimer;
    private float _barrierTimer;
    private Barrier _targetBarrier;

    // -------------------------------------------------------------------------
    //  Lifecycle
    // -------------------------------------------------------------------------
    void Awake()
    {
        _agent = GetComponent<NavMeshAgent>();
        _agent.speed = moveSpeed;
        _agent.acceleration = acceleration;
        _agent.stoppingDistance = attackRange * 0.85f;
        _agent.autoBraking = true;
        _health = maxHealth;
    }

    void Start()
    {
        GameObject playerObj = GameObject.FindGameObjectWithTag("Player");
        if (playerObj != null)
        {
            _player       = playerObj.transform;
            _playerHealth = playerObj.GetComponent<PlayerHealth>();
        }
        else
        {
            Debug.LogWarning("[ZombieAI] No GameObject tagged 'Player' found.");
        }
    }

    void Update()
    {
        if (_state == ZombieState.Dead || _player == null) return;

        _attackTimer  -= Time.deltaTime;
        _barrierTimer -= Time.deltaTime;

        switch (_state)
        {
            case ZombieState.Seeking:         UpdateSeeking();         break;
            case ZombieState.BreakingBarrier: UpdateBreakingBarrier(); break;
            case ZombieState.Attacking:       UpdateAttacking();       break;
        }

        UpdateAnimator();
    }

    // -------------------------------------------------------------------------
    //  Seeking — navigate toward the player, detect barriers blocking the path
    // -------------------------------------------------------------------------
    void UpdateSeeking()
    {
        float dist = Vector3.Distance(transform.position, _player.position);

        // Close enough to swing
        if (dist <= attackRange)
        {
            _agent.ResetPath();
            TransitionTo(ZombieState.Attacking);
            return;
        }

        // Keep chasing
        _agent.SetDestination(_player.position);

        // If the NavMesh path can't reach the player, a barrier may be blocking
        if (_agent.pathStatus == NavMeshPathStatus.PathPartial ||
            _agent.pathStatus == NavMeshPathStatus.PathInvalid)
        {
            Barrier b = ScanForBarrierAhead();
            if (b != null)
            {
                _targetBarrier = b;
                _agent.ResetPath();
                TransitionTo(ZombieState.BreakingBarrier);
                return;
            }
        }

        // Also do a short spherecast while moving in case the path is briefly valid
        // but a barrier is right in front of us (tight corridor)
        if (_agent.velocity.magnitude > 0.2f)
        {
            Barrier bAhead = ScanForBarrierAhead();
            if (bAhead != null)
            {
                _targetBarrier = bAhead;
                _agent.ResetPath();
                TransitionTo(ZombieState.BreakingBarrier);
            }
        }
    }

    // -------------------------------------------------------------------------
    //  Breaking barrier — face it and hammer until it falls
    // -------------------------------------------------------------------------
    void UpdateBreakingBarrier()
    {
        // Barrier was destroyed (by us or another zombie)
        if (_targetBarrier == null || _targetBarrier.IsDestroyed)
        {
            _targetBarrier = null;
            TransitionTo(ZombieState.Seeking);
            return;
        }

        // Face the barrier
        FaceTarget(_targetBarrier.transform.position);

        // Hit on cooldown
        if (_barrierTimer <= 0f)
        {
            _targetBarrier.TakeDamage(barrierDamage);
            _barrierTimer = 1f / barrierAttackRate;
            TriggerAnimatorTrigger("BarrierHit");
        }
    }

    // -------------------------------------------------------------------------
    //  Attacking — melee the player
    // -------------------------------------------------------------------------
    void UpdateAttacking()
    {
        float dist = Vector3.Distance(transform.position, _player.position);

        // Player escaped melee range — resume chase
        if (dist > attackRange + 0.6f)
        {
            TransitionTo(ZombieState.Seeking);
            return;
        }

        FaceTarget(_player.position);

        if (_attackTimer <= 0f)
        {
            PlayerHealth ph = _player.GetComponent<PlayerHealth>();
            if (ph != null) ph.TakeDamage(attackDamage);
            _attackTimer = 1f / attackRate;
            TriggerAnimatorTrigger("Attack");
        }
    }

    // -------------------------------------------------------------------------
    //  Public API — take damage / die
    // -------------------------------------------------------------------------
    public void TakeDamage(float damage)
    {
        if (_state == ZombieState.Dead) return;
        _health -= damage;
        if (_health <= 0f) Die();
    }

    void Die()
    {
        TransitionTo(ZombieState.Dead);
        _agent.ResetPath();
        _agent.enabled = false;
        TriggerAnimatorTrigger("Die");
        Destroy(gameObject, 3f);
    }

    // -------------------------------------------------------------------------
    //  Helpers
    // -------------------------------------------------------------------------

    /// Spherecast in the direction of movement to find a Barrier collider.
    Barrier ScanForBarrierAhead()
    {
        Vector3 origin = transform.position + Vector3.up * 0.8f;
        Vector3 dir    = _agent.desiredVelocity.magnitude > 0.1f
                         ? _agent.desiredVelocity.normalized
                         : transform.forward;

        if (Physics.SphereCast(origin, 0.45f, dir, out RaycastHit hit,
                               barrierDetectRange, barrierLayer,
                               QueryTriggerInteraction.Ignore))
        {
            Barrier b = hit.collider.GetComponentInParent<Barrier>();
            if (b != null && !b.IsDestroyed)
                return b;
        }
        return null;
    }

    void FaceTarget(Vector3 targetPos)
    {
        Vector3 dir = (targetPos - transform.position);
        dir.y = 0f;
        if (dir.sqrMagnitude < 0.001f) return;
        Quaternion target = Quaternion.LookRotation(dir);
        transform.rotation = Quaternion.Slerp(transform.rotation, target, 10f * Time.deltaTime);
    }

    void TransitionTo(ZombieState next)
    {
        _state = next;
    }

    // -------------------------------------------------------------------------
    //  Animator bridge — all parameters are optional; missing params are ignored
    // -------------------------------------------------------------------------
    void UpdateAnimator()
    {
        if (animator == null) return;
        SetAnimFloat("Speed",   _agent.velocity.magnitude);
        SetAnimBool("IsAttacking",      _state == ZombieState.Attacking);
        SetAnimBool("IsBreakingBarrier",_state == ZombieState.BreakingBarrier);
        SetAnimBool("IsDead",           _state == ZombieState.Dead);
    }

    void SetAnimFloat(string name, float value)
    {
        if (animator.HasParameterByName(name)) animator.SetFloat(name, value);
    }

    void SetAnimBool(string name, bool value)
    {
        if (animator.HasParameterByName(name)) animator.SetBool(name, value);
    }

    void TriggerAnimatorTrigger(string name)
    {
        if (animator != null && animator.HasParameterByName(name))
            animator.SetTrigger(name);
    }

#if UNITY_EDITOR
    void OnDrawGizmosSelected()
    {
        Gizmos.color = Color.red;
        Gizmos.DrawWireSphere(transform.position, attackRange);
        Gizmos.color = Color.yellow;
        Gizmos.DrawWireSphere(transform.position, barrierDetectRange);
    }
#endif
}

/// Extension to safely check Animator parameter existence
public static class AnimatorExtensions
{
    public static bool HasParameterByName(this Animator animator, string name)
    {
        foreach (AnimatorControllerParameter p in animator.parameters)
            if (p.name == name) return true;
        return false;
    }
}