using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(Rigidbody2D))]
[RequireComponent(typeof(Collider2D))]
public class Bullet : MonoBehaviour
{
    [Header("Runtime Values")]
    private Vector2 direction;

    private float speed;
    private float damage;
    private float maxDistance;

    private float distanceTravelled;

    private bool initialized;

    // Speichert alle Gegner, die diese Kugel bereits getroffen hat.
    private HashSet<Enemy> hitEnemies = new HashSet<Enemy>();

    private Rigidbody2D rb;

    private void Awake()
    {
        rb = GetComponent<Rigidbody2D>();

        rb.gravityScale = 0f;
        rb.bodyType = RigidbodyType2D.Kinematic;
        rb.collisionDetectionMode =
            CollisionDetectionMode2D.Continuous;
    }

    public void Initialize(
        Vector2 shootDirection,
        float bulletSpeed,
        float bulletDamage,
        float range
    )
    {
        direction = shootDirection.normalized;

        speed = bulletSpeed;
        damage = bulletDamage;
        maxDistance = range;

        // Sprite zeigt standardmäßig mit seiner lokalen Y-Achse nach oben.
        float angle =
            Mathf.Atan2(direction.y, direction.x)
            * Mathf.Rad2Deg - 90f;

        transform.rotation =
            Quaternion.Euler(0f, 0f, angle);

        initialized = true;
    }

    private void FixedUpdate()
    {
        if (!initialized)
            return;

        float remainingDistance =
            maxDistance - distanceTravelled;

        if (remainingDistance <= 0f)
        {
            Destroy(gameObject);
            return;
        }

        float movementDistance = Mathf.Min(
            speed * Time.fixedDeltaTime,
            remainingDistance
        );

        Vector2 movement =
            direction * movementDistance;

        rb.MovePosition(rb.position + movement);

        distanceTravelled += movementDistance;

        if (distanceTravelled >= maxDistance)
        {
            Destroy(gameObject);
        }
    }

    private void OnTriggerEnter2D(Collider2D other)
    {
        Enemy enemy =
            other.GetComponentInParent<Enemy>();

        if (enemy == null)
            return;

        // Bereits getroffenen Gegner ignorieren.
        if (!hitEnemies.Add(enemy))
            return;

        // Keine weiteren Treffer auf tote Gegner.
        if (enemy.IsDead)
            return;

        enemy.TakeDamage(damage);
    }
}