omit top half DOUBLE_BLOCK_HALF property holders

Author: beanbag44

common/src/main/kotlin/com/lambda/interaction/construction/processing/ProcessorRegistry.kt

@@ -28,7 +28,7 @@ import net.minecraft.util.math.BlockPos
 
 object ProcessorRegistry : Loadable {
     private val processors = getInstances<PlacementProcessor>()
-    private val processorCache = mutableMapOf<BlockState, PreProcessingInfo>()
+    private val processorCache = mutableMapOf<BlockState, PreProcessingInfo?>()
 
     val postProcessedProperties = setOf(
         Properties.EXTENDED,
@@ -107,22 +107,26 @@ object ProcessorRegistry : Loadable {
 
     override fun load() = "Loaded ${processors.size} pre processors"
 
-    fun TargetState.getProcessingInfo(pos: BlockPos): PreProcessingInfo =
-        (this as? TargetState.State)?.let { state ->
-            val get: () -> PreProcessingInfo = {
-
+    fun TargetState.getProcessingInfo(pos: BlockPos): PreProcessingInfo? {
+        return if (this is TargetState.State) {
+            val targetState = this as? TargetState.State ?: return null
+            val get: () -> PreProcessingInfo? = get@ {
                 val infoAccumulator = PreProcessingInfoAccumulator()
 
                 processors.forEach {
-                    if (!it.acceptsState(state.blockState)) return@forEach
-                    it.preProcess(state.blockState, pos, infoAccumulator)
+                    if (!it.acceptsState(targetState.blockState)) return@forEach
+                    it.preProcess(targetState.blockState, pos, infoAccumulator)
+                    if (infoAccumulator.shouldBeOmitted) {
+                        return@get null
+                    }
                 }
 
                 infoAccumulator.complete()
             }
-            if (isExemptFromCache(state)) get()
-            else processorCache.getOrPut(state.blockState, get)
-        } ?: PreProcessingInfo.DEFAULT
+            if (isExemptFromCache(targetState)) get()
+            else processorCache.getOrPut(targetState.blockState, get)
+        } else PreProcessingInfo.DEFAULT
+    }
 
     private fun isExemptFromCache(state: TargetState.State) =
         state.blockState.block is SlabBlock && state.blockState.get(Properties.SLAB_TYPE) == SlabType.DOUBLE

common/src/main/kotlin/com/lambda/interaction/construction/processing/preprocessors/OmitPreProcessor.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2025 Lambda
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.lambda.interaction.construction.processing.preprocessors
+
+import com.lambda.interaction.construction.processing.PlacementProcessor
+import com.lambda.interaction.construction.processing.PreProcessingInfoAccumulator
+import net.minecraft.block.BlockState
+import net.minecraft.block.enums.DoubleBlockHalf
+import net.minecraft.state.property.Properties
+import net.minecraft.util.math.BlockPos
+
+// Collected using reflections and then accessed from a collection in ProcessorRegistry
+@Suppress("unused")
+object OmitPreProcessor : PlacementProcessor() {
+    override fun acceptsState(state: BlockState) = true
+
+    override fun preProcess(state: BlockState, pos: BlockPos, accumulator: PreProcessingInfoAccumulator) {
+        if (Properties.DOUBLE_BLOCK_HALF in state.properties) {
+            if (state.get(Properties.DOUBLE_BLOCK_HALF) == DoubleBlockHalf.UPPER) {
+                accumulator.omitPlacement()
+            }
+        }
+    }
+}

common/src/main/kotlin/com/lambda/interaction/construction/simulation/BuildSimulator.kt

@@ -97,7 +97,7 @@ object BuildSimulator {
         build: BuildConfig = TaskFlowModule.build,
     ) = runSafe {
         structure.entries.flatMap { (pos, target) ->
-            val preProcessing = target.getProcessingInfo(pos)
+            val preProcessing = target.getProcessingInfo(pos) ?: return@flatMap emptySet()
             checkRequirements(pos, target, build).let {
                 if (it.isEmpty()) return@let
                 return@flatMap it