// Assets/_Project/Scripts/Gameplay/EnemyHealth.cs
using Unity.Netcode;
using UnityEngine;
using TD.Core;

namespace TD.Gameplay
{
    /// <summary>
    /// Per-enemy HP component. Holds replicated HP and is the single point
    /// through which all damage flows, so resistance lookups (Phase 1.5+) can
    /// be added in one place without touching every damage source.
    /// </summary>
    /// <remarks>
    /// Lives on the enemy prefab root alongside <see cref="EnemyStatus"/> and the
    /// future <c>EnemyMovement</c> component (Phase 1.5/1.6). HP is server-written
    /// and replicated to all clients so health bars can render on any peer.
    ///
    /// <b>Death flow (server-only):</b>
    /// <c>TakeDamage</c> clamps HP to 0, fires <see cref="OnDied"/>, then calls
    /// <c>NetworkObject.Despawn</c>. Subscribers must not touch the NetworkObject
    /// after <c>OnDied</c> returns.
    /// </remarks>
    [RequireComponent(typeof(NetworkObject))]
    public class EnemyHealth : NetworkBehaviour
    {
        [SerializeField] private float maxHp = 100f;

        private readonly NetworkVariable<float> hp = new NetworkVariable<float>(
            0f,
            NetworkVariableReadPermission.Everyone,
            NetworkVariableWritePermission.Server);

        // ----- Public state -----------------------------------------------

        public float CurrentHp => hp.Value;
        public float MaxHp     => maxHp;
        public bool  IsDead    => hp.Value <= 0f;

        // Stub: set by EnemyMovement or spawner in Phase 1.5/1.6.
        // TowerCombat reads this to honour the GroundedOnly tower flag.
        public bool IsFlying => false;

        // ----- Events -----------------------------------------------------

        /// <summary>
        /// Fired on the server immediately before the enemy NetworkObject is despawned.
        /// <see cref="TD.Combat.TowerCombat"/> subscribes to clear its target reference.
        /// Do not access the NetworkObject after this event returns.
        /// </summary>
        public event System.Action<EnemyHealth> OnDied;

        // ----- NGO lifecycle ----------------------------------------------

        public override void OnNetworkSpawn()
        {
            if (IsServer)
                hp.Value = maxHp;
        }

        // ----- Server API -------------------------------------------------

        /// <summary>
        /// Applies <paramref name="damage"/> to this enemy. Server-only; no-op on clients.
        /// <paramref name="type"/> is recorded for future resistance/weakness lookups —
        /// all damage is full-value until the resistance table is implemented (Phase 1.5+).
        /// </summary>
        public void TakeDamage(float damage, DamageType type)
        {
            if (!IsServer) return;
            if (IsDead)    return;

            // STUB — resistance table slot:
            // float modified = ResistanceTable.Apply(damage, type, this);
            float modified = damage;

            hp.Value = Mathf.Max(0f, hp.Value - modified);

            if (hp.Value <= 0f)
                HandleDeath();
        }

        // ----- Private ----------------------------------------------------

        private void HandleDeath()
        {
            OnDied?.Invoke(this);
            NetworkObject.Despawn();
        }
    }
}