using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.AI;
using UnityEngine.Events;

public class Enemy : MonoBehaviour {

    private GameObject target;

    private NavMeshAgent agent;

    private Health health;

    private Animator animator;

    private Collider collider;

    private Health targetHealth;

    private Player player;

    [HideInInspector] public bool isAttacking = false;

    [HideInInspector] public bool isDead = false;

    public float speed = 1.0f;

    public float angularSpeed = 120;

    public float damage = 20;

    public float attackAngle = 45;

    [HideInInspector] public UnityEvent onDead;

    void Start() {
        target = GameObject.Find("Player");
        targetHealth = target.GetComponent<Health>();

        if (target == null){
            throw new System.Exception("Target dosen't have Health Component.");
        }

        player = target.GetComponent<Player>();

        if (player == null)
        {
            throw new System.Exception("Player dosen't have Player Component.");
        }

        agent = GetComponent<NavMeshAgent>();
        health = GetComponent<Health>();
        animator = GetComponent<Animator>();
        collider = GetComponent<Collider>();
    }

    void Update() {
        CheckHealth();
        Chase();
        CheckAttack();
    }

    void CheckHealth() {
        if (isDead) return;

        if (health.value <= 0) {
            onDead.Invoke();

            isDead = true;
            agent.isStopped = true;
            collider.enabled = false;

            animator.CrossFadeInFixedTime("Death", 0.1f);
            Destroy(gameObject, 3f);
        }
    }

    void Chase() {
        if (isDead) return;
        else if (player.isDead) return;

        agent.destination = target.transform.position;
    }

    void CheckAttack() {
        if (isDead) return;
        else if (isAttacking) return;
        else if (player.isDead) return;

        float distanceFromTarget = Vector3.Distance(target.transform.position, transform.position);

        if (distanceFromTarget <= 1.8f) {
            Vector3 directionToTarget = target.transform.position - transform.position;
            float angle = Vector3.Angle(directionToTarget, transform.forward);

            if(angle <= attackAngle) {
                Attack();
            }
        }
    }

    void Attack() {
        targetHealth.TakeDamage(damage);

        agent.speed = 0;
        agent.angularSpeed = 0;
        isAttacking = true;
        animator.SetTrigger("ShouldAttack");

        Invoke("ResetAttacking", 1.5f);
    }

    void ResetAttacking() {
        isAttacking = false;
        agent.speed = speed;
        agent.angularSpeed = angularSpeed;
    }
}