Add pattern that randomly chooses states.

Also works with fuzzy states.

Syntax is `*type`, e.g. `//set *stone_slab` or with states,
`//set *oak_fence[waterlogged=false]`

worldedit-core/src/main/java/com/sk89q/worldedit/function/pattern/RandomStatePattern.java

@@ -0,0 +1,45 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser 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 Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.function.pattern;
+
+import com.sk89q.worldedit.math.BlockVector3;
+import com.sk89q.worldedit.world.block.BaseBlock;
+import com.sk89q.worldedit.world.block.BlockState;
+import com.sk89q.worldedit.world.block.FuzzyBlockState;
+
+import java.util.List;
+import java.util.Random;
+import java.util.stream.Collectors;
+
+public class RandomStatePattern implements Pattern {
+
+    private final Random rand = new Random();
+    private final List<BaseBlock> blocks;
+
+    public RandomStatePattern(FuzzyBlockState state) {
+        blocks = state.getBlockType().getAllStates().stream().filter(state::equalsFuzzy)
+                .map(BlockState::toBaseBlock).collect(Collectors.toList());
+    }
+
+    @Override
+    public BaseBlock apply(BlockVector3 position) {
+        return blocks.get(rand.nextInt(blocks.size()));
+    }
+}