Rework emergency lights (#1830)

* Implement emergency lights reacting to lost power

* Add emergency light sprites
Remove shared emergency light component

* Remove unused import

* Remove EmergencyLight NetID

* Add rich description
Change comments
Add license
Implement ExposeData

Co-authored-by: Julian Giebel <j.giebel@netrocks.info>

Content.Server/GameObjects/Components/Power/ApcNetComponents/PowerReceiverUsers/EmergencyLightComponent.cs

@@ -0,0 +1,143 @@
+using System;
+using System.Collections.Generic;
+using Content.Shared.GameObjects.EntitySystems;
+using Robust.Server.GameObjects;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Serialization;
+using Robust.Shared.Utility;
+using Robust.Shared.ViewVariables;
+
+namespace Content.Server.GameObjects.Components.Power.ApcNetComponents.PowerReceiverUsers
+{
+    /// <summary>
+    ///     Component that represents an emergency light, it has an internal battery that charges when the power is on.
+    /// </summary>
+    [RegisterComponent]
+    public class EmergencyLightComponent : Component, IExamine
+    {
+        public override string Name => "EmergencyLight";
+
+        [ViewVariables]
+        private EmergencyLightState _lightState = EmergencyLightState.Charging;
+
+        [ViewVariables]
+        private BatteryComponent Battery => Owner.GetComponent<BatteryComponent>();
+        [ViewVariables]
+        private PointLightComponent Light => Owner.GetComponent<PointLightComponent>();
+        [ViewVariables]
+        private PowerReceiverComponent PowerReceiver => Owner.GetComponent<PowerReceiverComponent>();
+        private SpriteComponent Sprite => Owner.GetComponent<SpriteComponent>();
+
+        [ViewVariables(VVAccess.ReadWrite)]
+        private float _wattage;
+        [ViewVariables(VVAccess.ReadWrite)]
+        private float _chargingWattage;
+        [ViewVariables(VVAccess.ReadWrite)]
+        private float _chargingEfficiency;
+
+        public override void ExposeData(ObjectSerializer serializer)
+        {
+            base.ExposeData(serializer);
+            serializer.DataField(ref _wattage, "wattage", 5);
+            serializer.DataField(ref _chargingWattage, "chargingWattage", 60);
+            serializer.DataField(ref _chargingEfficiency, "chargingEfficiency", 0.85f);
+        }
+
+        /// <summary>
+        ///     For attaching UpdateState() to events.
+        /// </summary>
+        public void UpdateState(object sender, EventArgs e)
+        {
+            UpdateState();
+        }
+
+        /// <summary>
+        ///     Updates the light's power drain, battery drain, sprite and actual light state.
+        /// </summary>
+        public void UpdateState()
+        {
+            if (PowerReceiver.Powered)
+            {
+                PowerReceiver.Load = (int) Math.Abs(_wattage);
+                TurnOff();
+                _lightState = EmergencyLightState.Charging;
+            }
+            else
+            {
+                TurnOn();
+                _lightState = EmergencyLightState.On;
+            }
+        }
+
+        public void OnUpdate(float frameTime)
+        {
+            if (_lightState == EmergencyLightState.Empty
+                || _lightState == EmergencyLightState.Full) return;
+
+            if(_lightState == EmergencyLightState.On)
+            {
+                if (!Battery.TryUseCharge(_wattage * frameTime))
+                {
+                    _lightState = EmergencyLightState.Empty;
+                    TurnOff();
+                }
+            }
+            else
+            {
+                Battery.CurrentCharge += _chargingWattage * frameTime * _chargingEfficiency;
+                if (Battery.BatteryState == BatteryState.Full)
+                {
+                    PowerReceiver.Load = 1;
+                    _lightState = EmergencyLightState.Full;
+                }
+            }
+        }
+
+        private void TurnOff()
+        {
+            Sprite.LayerSetState(0, "emergency_light_off");
+            Light.Enabled = false;
+        }
+
+        private void TurnOn()
+        {
+            Sprite.LayerSetState(0, "emergency_light_on");
+            Light.Enabled = true;
+        }
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            Owner.GetComponent<PowerReceiverComponent>().OnPowerStateChanged += UpdateState;
+        }
+
+        public override void OnRemove()
+        {
+            Owner.GetComponent<PowerReceiverComponent>().OnPowerStateChanged -= UpdateState;
+            base.OnRemove();
+        }
+
+        void IExamine.Examine(FormattedMessage message, bool inDetailsRange)
+        {
+            message.AddMarkup(Loc.GetString($"The battery indicator displays: {BatteryStateText[_lightState]}."));
+        }
+
+        public enum EmergencyLightState
+        {
+            Charging,
+            Full,
+            Empty,
+            On
+        }
+
+        public Dictionary<EmergencyLightState, string> BatteryStateText = new Dictionary<EmergencyLightState, String>
+        {
+            { EmergencyLightState.Full, "[color=darkgreen]Full[/color]"},
+            { EmergencyLightState.Empty, "[color=darkred]Empty[/color]"},
+            { EmergencyLightState.Charging, "[color=darkorange]Charging[/color]"},
+            { EmergencyLightState.On, "[color=darkorange]Discharging[/color]"}
+        };
+    }
+}