1 files changed, 67 insertions, 0 deletions
diff --git a/src/main/kotlin/io/dico/parcels2/blockvisitor/RegionTraverser.kt b/src/main/kotlin/io/dico/parcels2/blockvisitor/RegionTraverser.kt
new file mode 100644
index 0000000..1cac5f9
--- /dev/null
+++ b/src/main/kotlin/io/dico/parcels2/blockvisitor/RegionTraverser.kt
@@ -0,0 +1,67 @@
+package io.dico.parcels2.blockvisitor
+
+import io.dico.parcels2.util.Region
+import io.dico.parcels2.util.Vec3i
+import kotlin.coroutines.experimental.SequenceBuilder
+import kotlin.coroutines.experimental.buildIterator
+
+abstract class RegionTraverser {
+    fun traverseRegion(region: Region): Iterable<Vec3i> = Iterable { buildIterator { build(region) } }
+
+    protected abstract suspend fun SequenceBuilder<Vec3i>.build(region: Region)
+
+    companion object {
+        val upward = create { traverseUpward(it) }
+        val downward = create { traverseDownward(it) }
+        val forClearing get() = downward
+        val forFilling get() = upward
+
+        inline fun create(crossinline builder: suspend SequenceBuilder<Vec3i>.(Region) -> Unit) = object : RegionTraverser() {
+            override suspend fun SequenceBuilder<Vec3i>.build(region: Region) {
+                builder(region)
+            }
+        }
+
+        private suspend fun SequenceBuilder<Vec3i>.traverseDownward(region: Region) {
+            val origin = region.origin
+            val size = region.size
+            repeat(size.y) { y ->
+                repeat(size.z) { z ->
+                    repeat(size.x) { x ->
+                        yield(origin.add(x, size.y - y - 1, z))
+                    }
+                }
+            }
+        }
+
+        private suspend fun SequenceBuilder<Vec3i>.traverseUpward(region: Region) {
+            val origin = region.origin
+            val size = region.size
+            repeat(size.y) { y ->
+                repeat(size.z) { z ->
+                    repeat(size.x) { x ->
+                        yield(origin.add(x, size.y - y - 1, z))
+                    }
+                }
+            }
+        }
+
+        private fun slice(region: Region, atY: Int): Pair<Region, Region?> {
+            if (atY < region.size.y + 1) {
+                val first = Region(region.origin, region.size.withY(atY + 1))
+                val second = Region(region.origin.withY(atY), region.size.addY(-atY-1))
+                return first to second
+            }
+            return region to null
+        }
+
+        fun upToAndDownUntil(y: Int) = create { region ->
+            val (bottom, top) = slice(region, y)
+            traverseUpward(bottom)
+            top?.let { traverseDownward(it) }
+        }
+
+    }
+
+
+}