Add DamagePopup, Target Entities, And Practice Laser Gun (#12317)

Content.Server/Damage/Systems/DamagePopupSystem.cs

@@ -0,0 +1,36 @@
+using Content.Server.Damage.Components;
+using Content.Server.Popups;
+using Content.Shared.Damage;
+using Robust.Shared.Player;
+
+namespace Content.Server.Damage.Systems;
+
+public sealed class DamagePopupSystem : EntitySystem
+{
+    [Dependency] private readonly PopupSystem _popupSystem = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<DamagePopupComponent, DamageChangedEvent>(OnDamageChange);
+    }
+
+    private void OnDamageChange(EntityUid uid, DamagePopupComponent component, DamageChangedEvent args)
+    {
+        if (args.DamageDelta != null)
+        {
+            var damageTotal = args.Damageable.TotalDamage;
+            var damageDelta = args.DamageDelta.Total;
+
+            var msg = component.Type switch
+            {
+                DamagePopupType.Delta => damageDelta.ToString(),
+                DamagePopupType.Total => damageTotal.ToString(),
+                DamagePopupType.Combined => damageDelta + " | " + damageTotal,
+                DamagePopupType.Hit => "!",
+                _ => "Invalid type",
+            };
+            _popupSystem.PopupEntity(msg, uid, Filter.Pvs(uid, 2F, EntityManager));
+        }
+    }
+}