using System;
using System.Collections.Generic;
using UnityEngine;

public class Bullet : Entity, IColliderChecker
{
    [SerializeField] float speed = 10.0f;
    [SerializeField] float lifeTime = 5.0f;
    [SerializeField] float maxDistance = 0f;

    Vector2 headDirection;
    float flyingDistance = 0.0f;
    float elapsedLifeTime = 0.0f;
    HashSet<string> collideFilter = new HashSet<string>();
    HashSet<Collider2D> currentColliders = new HashSet<Collider2D>();

    public event Action<Bullet> OnBeforeDestroy;
    public event Action<Collider2D> OnEnterCollider;

    public float Speed { get => speed; set => speed = value; }

    public Vector2 HeadDirection
    {
        get
        {
            if (headDirection == default)
            {
                float zRad = transform.eulerAngles.z * Mathf.Deg2Rad;
                headDirection = new Vector2(Mathf.Cos(zRad), Mathf.Sin(zRad)).normalized;
            }
            return headDirection;
        }
        set
        {
            headDirection = value.normalized;
            transform.eulerAngles = new Vector3(0, 0, Mathf.Atan2(value.y, value.x) * Mathf.Rad2Deg);
        }
    }

    public bool IsFired { get; private set; } = false;

    private void LateUpdate()
    {
        if (!IsFired) return;

        float moveUnit = speed * Time.fixedDeltaTime;

        bool shouldDestroy = !UpdateLifeTime();
        shouldDestroy |= !UpdateFlyingDistance(moveUnit);

        if (shouldDestroy)
        {
            OnBeforeDestroy?.Invoke(this);
            Destroy(gameObject);
        }
        else
        {
            transform.position += (Vector3)HeadDirection * moveUnit;
        }
    }

    private bool UpdateLifeTime()
    {
        elapsedLifeTime += Time.fixedUnscaledDeltaTime;
        return elapsedLifeTime < lifeTime;
    }

    private bool UpdateFlyingDistance(float moveUnit)
    {
        if(flyingDistance <= 0) return true;
        flyingDistance += moveUnit;
        return flyingDistance < maxDistance;
    }

    public void Fire()
    {
        elapsedLifeTime = 0;
        flyingDistance = 0;

        IsFired = true;
    }

    public void Fire(Transform target)
    {
        HeadDirection = target.position - transform.position;
        elapsedLifeTime = 0;
        flyingDistance = 0;

        IsFired = true;
    }

    public void AddTagFilter(params string[] tags) => collideFilter.UnionWith(tags);
    public void RemoveTagFilter(params string[] tags) => collideFilter.ExceptWith(tags);
    public void ClearTagFilter() => collideFilter.Clear();
    public void CheckColliding(Action<Collider2D> collided)
    {
        foreach (var target in currentColliders)
        {
            collided.Invoke(target);
        }
    }

    private void OnTriggerEnter2D(Collider2D other)
    {
        if (collideFilter.Contains(other.tag))
        {
            currentColliders.Add(other);
            OnEnterCollider?.Invoke(other);
        }
    }

    private void OnTriggerExit2D(Collider2D collision)
    {
        currentColliders.Remove(collision);
    }
}