Add //line command and EditSession method

The EditSession method comes with javadoc.

src/main/java/com/sk89q/worldedit/EditSession.java

@@ -2996,6 +2996,73 @@ public class EditSession {
         return affected;
     }
 
+    /**
+     * Draws a line (out of blocks) between two vectors.
+     *
+     * @param pattern The block pattern used to draw the line
+     * @param pos1 One of the points that define the line.
+     * @param pos2 The other point that defines the line.
+     *
+     * @return number of blocks affected
+     * @throws MaxChangedBlocksException
+     */
+    public int drawLine(Pattern pattern, Vector pos1, Vector pos2)
+        throws MaxChangedBlocksException {
+
+        int affected = 0;
+        boolean notdrawn = true;
+
+        int x1 = pos1.getBlockX(), y1 = pos1.getBlockY(), z1 = pos1.getBlockZ();
+        int x2 = pos2.getBlockX(), y2 = pos2.getBlockY(), z2 = pos2.getBlockZ();
+        int tipx = x1, tipy = y1, tipz = z1;
+        int dx = Math.abs(x2 - x1), dy = Math.abs(y2 - y1), dz = Math.abs(z2 - z1);
+
+        if (dx + dy + dz == 0) {
+            return setBlock(new Vector(tipx, tipy, tipz), pattern) ? 1 : 0;
+        }
+
+        if (Math.max(Math.max(dx, dy), dz) == dx && notdrawn) {
+            for (int domstep = 0; domstep <= dx; domstep++) {
+                tipx = x1 + domstep * (x2 - x1 > 0 ? 1 : -1);
+                tipy = (int) Math.round(y1 + domstep * ((double) dy) / ((double) dx) * (y2 - y1 > 0 ? 1 : -1));
+                tipz = (int) Math.round(z1 + domstep * ((double) dz) / ((double) dx) * (z2 - z1 > 0 ? 1 : -1));
+
+                if (setBlock(new Vector(tipx, tipy, tipz), pattern)) {
+                    affected++;
+                }
+            }
+            notdrawn = false;
+        }
+
+        if (Math.max(Math.max(dx, dy), dz) == dy && notdrawn) {
+            for (int domstep = 0; domstep <= dy; domstep++) {
+                tipy = y1 + domstep * (y2 - y1 > 0 ? 1 : -1);
+                tipx = (int) Math.round(x1 + domstep * ((double) dx) / ((double) dy) * (x2 - x1 > 0 ? 1 : -1));
+                tipz = (int) Math.round(z1 + domstep * ((double) dz) / ((double) dy) * (z2 - z1 > 0 ? 1 : -1));
+
+                if (setBlock(new Vector(tipx, tipy, tipz), pattern)) {
+                    affected++;
+                }
+            }
+            notdrawn = false;
+        }
+
+        if (Math.max(Math.max(dx, dy), dz) == dz && notdrawn) {
+            for (int domstep = 0; domstep <= dz; domstep++) {
+                tipz = z1 + domstep * (z2 - z1 > 0 ? 1 : -1);
+                tipy = (int) Math.round(y1 + domstep * ((double) dy) / ((double) dz) * (y2-y1>0 ? 1 : -1));
+                tipx = (int) Math.round(x1 + domstep * ((double) dx) / ((double) dz) * (x2-x1>0 ? 1 : -1));
+
+                if (setBlock(new Vector(tipx, tipy, tipz), pattern)) {
+                    affected++;
+                }
+            }
+            notdrawn = false;
+        }
+
+        return affected;
+    }
+
     private void recurseHollow(Region region, BlockVector origin, Set<BlockVector> outside) {
         final LinkedList<BlockVector> queue = new LinkedList<BlockVector>();
         queue.addLast(origin);

src/main/java/com/sk89q/worldedit/commands/RegionCommands.java

@@ -86,6 +86,32 @@ public class RegionCommands {
         player.print(affected + " block(s) have been changed.");
     }
 
+    @Command(
+            aliases = { "/line" },
+            usage = "<block>",
+            desc = "Draw a line segment between selection corners.",
+            min = 1,
+            max = 1
+    )
+    @CommandPermissions("worldedit.region.line")
+    @Logging(REGION)
+    public void line(CommandContext args, LocalSession session, LocalPlayer player,
+            EditSession editSession) throws WorldEditException {
+
+        Region region = session.getSelection(session.getSelectionWorld());
+        if (!(region instanceof CuboidRegion)) {
+            player.printError("Invalid region type");
+            return;
+        }
+
+        Pattern pattern = we.getBlockPattern(player, args.getString(0));
+        Vector pos1 = ((CuboidRegion) region).getPos1();
+        Vector pos2 = ((CuboidRegion) region).getPos2();
+        int blocksChanged = editSession.drawLine(pattern, pos1, pos2);
+
+        player.print(blocksChanged + " block(s) have been changed.");
+    }
+
     @Command(
         aliases = { "/replace", "/re", "/rep" },
         usage = "[from-block] <to-block>",