PlayerTabTargeting.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using Mirror;

namespace uMMORPG
{
    [RequireComponent(typeof(Player))]
    [RequireComponent(typeof(PlayerIndicator))]
    [DisallowMultipleComponent]
    public class PlayerTabTargeting : NetworkBehaviour
    {
        [Header("Components")]
        public Player player;
        public PlayerIndicator indicator;

        [Header("Targeting")]
        public KeyCode key = KeyCode.Tab;

        void Update()
        {
            // only for local player
            if (!isLocalPlayer) return;

            // in a state where tab targeting is allowed?
            if (player.state == "IDLE" ||
                player.state == "MOVING" ||
                player.state == "CASTING" ||
                player.state == "STUNNED")
            {
                // key pressed?
                if (Input.GetKeyDown(key))
                    TargetNearest();
            }
        }

        [Client]
        void TargetNearest()
        {
            // find all monsters that are alive, sort by distance
            // (NetworkIdentity.spawned is available on client too for those it sees)
            // note: uses Linq, but this only happens on the client when pressing Tab
            List<Monster> monsters = NetworkClient.spawned.Values
                .Select(ni => ni.GetComponent<Monster>())
                .Where(m => m != null && m.health.current > 0)
                .ToList();
            List<Monster> sorted = monsters.OrderBy(m => Vector3.Distance(transform.position, m.transform.position)).ToList();

            // target nearest one
            if (sorted.Count > 0)
            {
                indicator.SetViaParent(sorted[0].transform);
                player.CmdSetTarget(sorted[0].netIdentity);
            }
        }
    }
}