using UnityEngine;

public class Projectile : MonoBehaviour
{
    private GameObject target;
    private GameObject owner;
    private float damage;
    private float speed;
    private float lifetime;
    private bool registerEnergyOnHit;
    private bool initialized;
    private bool hasHit;

    public void Initialize(
        GameObject targetObject,
        float damageAmount,
        GameObject ownerObject,
        float moveSpeed,
        float lifeTime,
        bool registerEnergy = true)
    {
        target = targetObject;
        damage = damageAmount;
        owner = ownerObject;
        speed = moveSpeed;
        lifetime = lifeTime;
        registerEnergyOnHit = registerEnergy;
        initialized = true;
        hasHit = false;

        // The projectile uses its own raycast hit check. Disable the collider so
        // it cannot be destroyed or disturbed by the owner's launch socket.
        foreach (var collider in GetComponentsInChildren<Collider>(true))
        {
            collider.enabled = false;
        }

        if (lifetime > 0f)
        {
            Destroy(gameObject, lifetime);
        }
    }

    private void Update()
    {
        if (!initialized)
        {
            return;
        }

        if (target == null)
        {
            Destroy(gameObject);
            return;
        }

        // 目标根节点位于脚底，只取水平差值，让箭保持当前高度平行飞行。
        Vector3 offset = target.transform.position - transform.position;
        offset.y = 0f;
        if (offset.sqrMagnitude <= 0.01f)
        {
            HitTarget(target);
            return;
        }

        Vector3 direction = offset.normalized;
        float distance = speed * Time.deltaTime;
        if (distance >= offset.magnitude)
        {
            HitTarget(target);
            return;
        }

        if (Physics.Raycast(transform.position, direction, out RaycastHit hit, distance))
        {
            TryHit(hit.collider.gameObject);
            if (hit.collider.transform.root == target.transform.root)
            {
                return;
            }
        }

        transform.forward = direction;
        transform.position += direction * distance;
    }

    private void OnTriggerEnter(Collider other)
    {
        TryHit(other.gameObject);
    }

    private void OnCollisionEnter(Collision collision)
    {
        TryHit(collision.gameObject);
    }

    private void TryHit(GameObject hitObject)
    {
        if (!initialized || hitObject == null || target == null || IsOwner(hitObject))
        {
            return;
        }

        if (hitObject.transform.root == target.transform.root)
        {
            HitTarget(hitObject);
        }
    }

    private void HitTarget(GameObject hitObject)
    {
        if (hasHit)
        {
            return;
        }

        UnitBase targetUnit = hitObject.GetComponentInParent<UnitBase>();
        BuildingHealth targetBuilding = hitObject.GetComponentInParent<BuildingHealth>();
        WorldHealthBar targetHealthBar = hitObject.GetComponentInParent<WorldHealthBar>();
        
        if (targetUnit == null && targetBuilding == null && targetHealthBar == null)
        {
            return;
        }

        hasHit = true;
        
        if (targetUnit != null)
        {
            targetUnit.ReceiveDamage(damage, owner);
        }
        else if (targetBuilding != null)
        {
            targetBuilding.ReceiveDamage(damage, owner);
        }
        else if (targetHealthBar != null)
        {
            // 召唤师等特殊单位（有 WorldHealthBar 但没有 UnitBase）
            targetHealthBar.TakeDamage(damage, owner);
        }
        
        if (registerEnergyOnHit && owner != null)
        {
            UnitBase unit = owner.GetComponent<UnitBase>();
            if (unit != null)
            {
                unit.RegisterAttackHit();
            }
        }

        Destroy(gameObject);
    }

    private bool IsOwner(GameObject hitObject)
    {
        return owner != null &&
            (hitObject == owner || hitObject.transform.root == owner.transform.root);
    }
}