Added FlatRegionFunction and GroundFindingFunction.

FlatRegionFunction takes apply(Vector2D) and GroundFindingFunction is an implementation of FlatRegionFunction that searches for the first ground block.

src/main/java/com/sk89q/worldedit/operation/FlatRegionFunction.java

@@ -0,0 +1,39 @@
+/*
+ * 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 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.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.Vector2D;
+import com.sk89q.worldedit.WorldEditException;
+
+/**
+ * Performs a function on points in a flat region.
+ */
+public interface FlatRegionFunction {
+
+    /**
+     * Apply the function to the given point.
+     *
+     * @param pt the point
+     * @return true if something was changed
+     * @throws WorldEditException thrown on an error
+     */
+    public boolean apply(Vector2D pt) throws WorldEditException;
+
+}

src/main/java/com/sk89q/worldedit/operation/GroundFindingFunction.java

@@ -0,0 +1,140 @@
+/*
+ * 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 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.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.*;
+import com.sk89q.worldedit.blocks.BaseBlock;
+import com.sk89q.worldedit.blocks.BlockID;
+
+/**
+ * An abstract implementation of {@link com.sk89q.worldedit.operation.FlatRegionFunction}
+ * that searches for the ground, which is considered to be any non-air block.
+ */
+public abstract class GroundFindingFunction implements FlatRegionFunction {
+
+    private final EditSession editSession;
+    private int lowerY;
+    private int upperY;
+
+    /**
+     * Create a new instance.
+     *
+     * @param editSession the edit session
+     * @param lowerY the lower Y
+     * @param upperY the upper Y (lowerY <= upperY)
+     */
+    protected GroundFindingFunction(EditSession editSession, int lowerY, int upperY) {
+        this.editSession = editSession;
+        this.lowerY = lowerY;
+        this.upperY = upperY;
+        checkYBounds();
+    }
+
+    /**
+     * Check whether upperY is >= lowerY.
+     */
+    private void checkYBounds() {
+        if (upperY < lowerY) {
+            throw new IllegalArgumentException("upperY must be greater than or equal to lowerY");
+        }
+    }
+
+    /**
+     * Get the upper Y coordinate to start the ground search from.
+     *
+     * @return the upper Y coordinate
+     */
+    public int getUpperY() {
+        return upperY;
+    }
+
+    /**
+     * Set the upper Y coordinate to start the ground search from.
+     *
+     * @param upperY the upper Y coordinate
+     */
+    public void setUpperY(int upperY) {
+        this.upperY = upperY;
+        checkYBounds();
+    }
+
+    /**
+     * Get the lower Y coordinate to end the ground search at.
+     *
+     * @return lowerY the lower Y coordinate
+     */
+    public int getLowerY() {
+        return lowerY;
+    }
+
+    /**
+     * Set the lower Y coordinate to end the ground search at.
+     *
+     * @return lowerY the lower Y coordinate
+     */
+    public void setLowerY(int lowerY) {
+        this.lowerY = lowerY;
+        checkYBounds();
+    }
+
+    @Override
+    public final boolean apply(Vector2D pt) throws WorldEditException {
+        // Don't want to be in the ground
+        if (!editSession.getBlock(pt.toVector(upperY)).isAir()) {
+            return false;
+        }
+
+        if (!shouldContinue(pt)) {
+            return false;
+        }
+
+        for (int y = upperY; y >= lowerY; --y) {
+            Vector testPt = pt.toVector(y);
+            BaseBlock block = editSession.getBlock(testPt);
+
+            if (block.getType() != BlockID.AIR) {
+                return apply(testPt, block);
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Returns whether a search for the ground should be performed for the given point.
+     *
+     * @param pt the point
+     * @return true if the search should begin
+     */
+    protected boolean shouldContinue(Vector2D pt) {
+        return true;
+    }
+
+    /**
+     * Apply the function to the given ground block.
+     *
+     * @param pt the position
+     * @param block the block
+     * @return true if something was changed
+     * @throws WorldEditException thrown on an error
+     */
+    protected abstract boolean apply(Vector pt, BaseBlock block) throws WorldEditException;
+
+}