Added oxygen damage and an oxygen damage source

src/main/java/net/xevianlight/aphelion/core/init/ModDamageSources.java

@@ -0,0 +1,19 @@
+package net.xevianlight.aphelion.core.init;
+
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.damagesource.DamageSource;
+import net.minecraft.world.damagesource.DamageType;
+import net.minecraft.world.level.Level;
+import net.xevianlight.aphelion.Aphelion;
+
+public class ModDamageSources {
+
+    // Relatively sure this is right
+    public static final ResourceKey<DamageType> OXYGEN = ResourceKey.create(Registries.DAMAGE_TYPE, ResourceLocation.fromNamespaceAndPath(Aphelion.MOD_ID, "oxygen"));
+
+    public static DamageSource create(Level level, ResourceKey<DamageType> key) {
+        return new DamageSource(level.registryAccess().registryOrThrow(Registries.DAMAGE_TYPE).getHolderOrThrow(key));
+    }
+}

src/main/java/net/xevianlight/aphelion/mixins/common/LivingEntityMixin.java

@@ -0,0 +1,29 @@
+package net.xevianlight.aphelion.mixins.common;
+
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.level.Level;
+import net.xevianlight.aphelion.systems.OxygenService;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+//
+@Mixin(LivingEntity.class)
+public abstract class LivingEntityMixin extends Entity {
+
+    public LivingEntityMixin(EntityType<?> type, Level level) { super(type, level); }
+
+    @Inject(method= "tick", at = @At("TAIL"))
+    public void aphelion$tick(CallbackInfo ci) {
+        if ((level() instanceof ServerLevel level)) {
+            LivingEntity entity = (LivingEntity) (Object) this;
+
+            // Oxygen system
+            OxygenService.entityTick(level, entity);
+        }
+    }
+}

src/main/java/net/xevianlight/aphelion/systems/OxygenService.java

@@ -0,0 +1,38 @@
+package net.xevianlight.aphelion.systems;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.level.Level;
+import net.xevianlight.aphelion.Aphelion;
+import net.xevianlight.aphelion.core.init.ModDamageSources;
+import net.xevianlight.aphelion.core.saveddata.EnvironmentSavedData;
+
+public class OxygenService {
+    public static boolean hasOxygen(Level level, BlockPos pos) {
+        if (level.isClientSide) {
+            // We can't pull oxygen data from the client side, so just, uhh, don't!
+            Aphelion.LOGGER.warn("Tried to get server oxygen data from client side!");
+            return false;
+        }
+        boolean positionHasOxygen = EnvironmentSavedData.get((ServerLevel) level).hasOxygen(level, pos);
+
+        return positionHasOxygen;
+    }
+
+    public static boolean hasOxygen(Entity entity) {
+        // Not sure if this is at the entity's feet, head, or the middle... research later
+        BlockPos entityBlockPos = BlockPos.containing(entity.getX(), entity.getY(), entity.getZ());
+        return hasOxygen(entity.level(), entityBlockPos);
+    }
+
+    public static int OXYGEN_DAMAGE_TICK_AMT = 2;
+    public static int OXYGEN_DAMAGE_TICK_FREQ = 20;
+    /// Called by LivingEntity.entityTick mixin
+    public static void entityTick(ServerLevel level, LivingEntity entity) {
+        if (entity.tickCount % OXYGEN_DAMAGE_TICK_FREQ != 0) return;
+        if (hasOxygen(entity)) return;
+        entity.hurt(ModDamageSources.create(level, ModDamageSources.OXYGEN), OXYGEN_DAMAGE_TICK_AMT);
+    }
+}