ECS guns (#6229)

Co-authored-by: ShadowCommander <10494922+ShadowCommander@users.noreply.github.com>

Content.Server/Weapon/Ranged/GunSystem.Battery.cs

@@ -0,0 +1,119 @@
+using System;
+using Content.Server.PowerCell;
+using Content.Server.Projectiles.Components;
+using Content.Server.Weapon.Ranged.Barrels.Components;
+using Content.Shared.PowerCell.Components;
+using Content.Shared.Weapons.Ranged.Barrels.Components;
+using Robust.Shared.Containers;
+using Robust.Shared.GameObjects;
+using Robust.Shared.GameStates;
+using Robust.Shared.Map;
+
+namespace Content.Server.Weapon.Ranged;
+
+public sealed partial class GunSystem
+{
+    private void OnBatteryInit(EntityUid uid, BatteryBarrelComponent component, ComponentInit args)
+    {
+        if (component.AmmoPrototype != null)
+        {
+            component.AmmoContainer = uid.EnsureContainer<ContainerSlot>($"{component.GetType()}-ammo-container");
+        }
+
+        component.Dirty(EntityManager);
+    }
+
+    private void OnBatteryMapInit(EntityUid uid, BatteryBarrelComponent component, MapInitEvent args)
+    {
+        UpdateBatteryAppearance(component);
+    }
+
+    private void OnBatteryGetState(EntityUid uid, BatteryBarrelComponent component, ref ComponentGetState args)
+    {
+        (int, int)? count = (component.ShotsLeft, component.Capacity);
+
+        args.State = new BatteryBarrelComponentState(
+            component.FireRateSelector,
+            count);
+    }
+
+    private void OnCellSlotUpdated(EntityUid uid, BatteryBarrelComponent component, PowerCellChangedEvent args)
+    {
+        UpdateBatteryAppearance(component);
+    }
+
+    public void UpdateBatteryAppearance(BatteryBarrelComponent component)
+    {
+        if (!EntityManager.TryGetComponent(component.Owner, out AppearanceComponent? appearanceComponent)) return;
+
+        appearanceComponent.SetData(MagazineBarrelVisuals.MagLoaded, _cell.TryGetBatteryFromSlot(component.Owner, out _));
+        appearanceComponent.SetData(AmmoVisuals.AmmoCount, component.ShotsLeft);
+        appearanceComponent.SetData(AmmoVisuals.AmmoMax, component.Capacity);
+    }
+
+    public EntityUid? PeekAmmo(BatteryBarrelComponent component)
+    {
+        // Spawn a dummy entity because it's easier to work with I guess
+        // This will get re-used for the projectile
+        var ammo = component.AmmoContainer.ContainedEntity;
+        if (ammo == null)
+        {
+            ammo = EntityManager.SpawnEntity(component.AmmoPrototype, Transform(component.Owner).Coordinates);
+            component.AmmoContainer.Insert(ammo.Value);
+        }
+
+        return ammo.Value;
+    }
+
+    public EntityUid? TakeProjectile(BatteryBarrelComponent component, EntityCoordinates spawnAt)
+    {
+        if (!_cell.TryGetBatteryFromSlot(component.Owner, out var capacitor))
+            return null;
+
+        if (capacitor.CurrentCharge < component.LowerChargeLimit)
+            return null;
+
+        // Can fire confirmed
+        // Multiply the entity's damage / whatever by the percentage of charge the shot has.
+        EntityUid? entity;
+        var chargeChange = Math.Min(capacitor.CurrentCharge, component.BaseFireCost);
+        if (capacitor.UseCharge(chargeChange) < component.LowerChargeLimit)
+        {
+            // Handling of funny exploding cells.
+            return null;
+        }
+        var energyRatio = chargeChange / component.BaseFireCost;
+
+        if (component.AmmoContainer.ContainedEntity != null)
+        {
+            entity = component.AmmoContainer.ContainedEntity;
+            component.AmmoContainer.Remove(entity.Value);
+            Transform(entity.Value).Coordinates = spawnAt;
+        }
+        else
+        {
+            entity = EntityManager.SpawnEntity(component.AmmoPrototype, spawnAt);
+        }
+
+        if (TryComp(entity.Value, out ProjectileComponent? projectileComponent))
+        {
+            if (energyRatio < 1.0)
+            {
+                projectileComponent.Damage *= energyRatio;
+            }
+        }
+        else if (TryComp(entity.Value, out HitscanComponent? hitscanComponent))
+        {
+            hitscanComponent.Damage *= energyRatio;
+            hitscanComponent.ColorModifier = energyRatio;
+        }
+        else
+        {
+            throw new InvalidOperationException("Ammo doesn't have hitscan or projectile?");
+        }
+
+        // capacitor.UseCharge() triggers a PowerCellChangedEvent which will cause appearance to be updated.
+        // So let's not double-call UpdateAppearance() here.
+        return entity.Value;
+    }
+}