port Native EU to FE

src/main/java/gregtech/api/capability/GregtechCapabilities.java

@@ -1,12 +1,20 @@
 package gregtech.api.capability;
 
+import gregtech.api.GTValues;
+import gregtech.api.capability.impl.EUToFEProvider;
 import gregtech.api.capability.tool.ICutterItem;
 import gregtech.api.capability.tool.IScrewdriverItem;
 import gregtech.api.capability.tool.ISoftHammerItem;
 import gregtech.api.capability.tool.IWrenchItem;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.ResourceLocation;
 import net.minecraftforge.common.capabilities.Capability;
 import net.minecraftforge.common.capabilities.CapabilityInject;
+import net.minecraftforge.event.AttachCapabilitiesEvent;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 
+@Mod.EventBusSubscriber(modid = GTValues.MODID)
 public class GregtechCapabilities {
 
     @CapabilityInject(IEnergyContainer.class)
@@ -33,4 +41,10 @@ public class GregtechCapabilities {
     @CapabilityInject(IMultiblockController.class)
     public static Capability<IMultiblockController> CAPABILITY_MULTIBLOCK_CONTROLLER = null;
 
+    private static final ResourceLocation CAPABILITY_EU_TO_FE = new ResourceLocation(GTValues.MODID, "fe_capability");
+
+    @SubscribeEvent
+    public static void attachTileCapability(AttachCapabilitiesEvent<TileEntity> event) {
+        event.addCapability(CAPABILITY_EU_TO_FE, new EUToFEProvider(event.getObject()));
+    }
 }

src/main/java/gregtech/api/capability/impl/EUToFEProvider.java

@@ -0,0 +1,67 @@
+package gregtech.api.capability.impl;
+
+import gregtech.api.capability.GregtechCapabilities;
+import gregtech.common.ConfigHolder;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.EnumFacing;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import net.minecraftforge.energy.CapabilityEnergy;
+
+import javax.annotation.Nonnull;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class EUToFEProvider implements ICapabilityProvider {
+
+    private final TileEntity tileEntity;
+    private GTEnergyWrapper wrapper;
+
+    /**
+     * Lock used for concurrency protection between hasCapability and getCapability.
+     */
+    ReentrantLock lock = new ReentrantLock();
+
+    public EUToFEProvider(TileEntity tileEntity) {
+        this.tileEntity = tileEntity;
+    }
+
+    @Override
+    public boolean hasCapability(@Nonnull Capability<?> capability, EnumFacing facing) {
+
+        if (!ConfigHolder.U.energyOptions.nativeEUToFE)
+            return false;
+
+        if (lock.isLocked() || (capability != CapabilityEnergy.ENERGY && capability != GregtechCapabilities.CAPABILITY_ENERGY_CONTAINER))
+            return false;
+
+        // Wrap FE Machines with a GTEU EnergyContainer
+        if (wrapper == null) wrapper = new GTEnergyWrapper(tileEntity);
+
+        lock.lock();
+        try {
+            return wrapper.isValid(facing);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> T getCapability(@Nonnull Capability<T> capability, EnumFacing facing) {
+
+        if (!ConfigHolder.U.energyOptions.nativeEUToFE)
+            return null;
+
+        if (lock.isLocked() || !hasCapability(capability, facing))
+            return null;
+
+        if (wrapper == null) wrapper = new GTEnergyWrapper(tileEntity);
+
+        lock.lock();
+        try {
+            return wrapper.isValid(facing) ? (T) wrapper : null;
+        } finally {
+            lock.unlock();
+        }
+    }
+}