Partially Fixed Exit Doors

Added code so that exit doors will search for a destination and place a
platform for the player on the other side. However, the search function
only searches upward, not downward. I'd like to discuss some details
about this before completing the implementation:
1. How should the search work?
2. What should be the likelihood of a dungeon exit leading to a
different root dimension than the dungeon's actual root?

I've tested the exits and they're working well.

StevenDimDoors/mod_pocketDim/core/DDTeleporter.java

@@ -18,6 +18,11 @@ import net.minecraft.world.World;
 import net.minecraft.world.WorldServer;
 import net.minecraftforge.common.DimensionManager;
 import StevenDimDoors.mod_pocketDim.DDProperties;
+import StevenDimDoors.mod_pocketDim.Point3D;
+import StevenDimDoors.mod_pocketDim.mod_pocketDim;
+import StevenDimDoors.mod_pocketDim.helpers.yCoordHelper;
+import StevenDimDoors.mod_pocketDim.items.ItemDimensionalDoor;
+import StevenDimDoors.mod_pocketDim.schematic.BlockRotator;
 import StevenDimDoors.mod_pocketDim.util.Point4D;
 import StevenDimDoors.mod_pocketDim.world.PocketBuilder;
 import cpw.mods.fml.common.registry.GameRegistry;
@@ -472,19 +477,63 @@ public class DDTeleporter
 		return false;
 	}
 	
-	private static boolean generateSafeExit(NewDimData target, DimLink link, DDProperties properties)
+	private static boolean generateSafeExit(NewDimData destinationDim, DimLink link, DDProperties properties)
 	{
 		// A safe exit attempts to place a Warp Door in a dimension with
 		// some precautions to protect the player. The X and Z coordinates
-		// are fixed to match the source, but the Y coordinate is chosen by
-		// searching for a safe location to place the door. The direction of
-		// the vertical search is away from the map boundary closest to
-		// the source Y. In other words, if a player is really high up, the
-		// search proceeds down. If a player is near the bottom of the map,
-		// the search proceeds up. If a safe destination cannot be found,
-		// then we return false and the source-side door slams shut.
+		// are fixed to match the source (mostly - may be shifted a little),
+		// but the Y coordinate is chosen by searching for a safe location
+		// to place the door.
 		
-		// FIXME: Add code here!
-		return false;
+		// The direction of the vertical search is away from the map boundary
+		// closest to the source Y. In other words, if a player is really
+		// high up, the search goes down. If a player is near the bottom
+		// of the map, the search goes up. If a safe destination cannot be
+		// found, then we return false and the source-side door slams shut.
+		
+		Point3D destination;
+		Point4D source = link.source();
+		World world = PocketManager.loadDimension(destinationDim.id());
+		if (world == null)
+		{
+			return false;
+		}
+		
+		boolean searchDown = (source.getY() >= world.getActualHeight() / 2);
+		destination = yCoordHelper.findSafeCube(world, source.getX(), source.getY() - 2, source.getZ(), searchDown);
+		if (destination == null)
+		{
+			destination = yCoordHelper.findSafeCube(world, source.getX(), source.getY() - 2, source.getZ(), !searchDown);			
+		}
+		if (destination != null)
+		{
+			// Set up a 3x3 platform at the destination
+			int x = destination.getX();
+			int y = destination.getY();
+			int z = destination.getZ();
+			for (int dx = -1; dx <= 1; dx++)
+			{
+				for (int dz = -1; dz <= 1; dz++)
+				{
+					world.setBlock(x + dx, y, z + dz, properties.FabricBlockID);
+				}
+			}
+			
+			// Create a reverse link for returning
+			NewDimData sourceDim = PocketManager.getDimensionData(link.source().getDimension());
+			DimLink reverse = destinationDim.createLink(x, y + 2, z, LinkTypes.REVERSE);
+			sourceDim.setDestination(reverse, source.getX(), source.getY(), source.getZ());
+			
+			// Set up the warp door at the destination
+			int orientation = getDestinationOrientation(source, properties);
+			orientation = BlockRotator.transformMetadata(orientation, 2, properties.WarpDoorID);
+			ItemDimensionalDoor.placeDoorBlock(world, x, y + 1, z, orientation, mod_pocketDim.warpDoor);
+			
+			// Complete the link to the destination
+			// This comes last so the destination isn't set unless everything else works first
+			destinationDim.setDestination(link, x, y + 2, z);
+		}
+		
+		return (destination != null);
 	}
 }

StevenDimDoors/mod_pocketDim/helpers/yCoordHelper.java

@@ -2,8 +2,10 @@ package StevenDimDoors.mod_pocketDim.helpers;
 
 import net.minecraft.block.Block;
 import net.minecraft.block.material.Material;
+import net.minecraft.util.MathHelper;
 import net.minecraft.world.World;
 import net.minecraft.world.chunk.Chunk;
+import StevenDimDoors.mod_pocketDim.Point3D;
 
 public class yCoordHelper 
 {
@@ -67,6 +69,76 @@ public class yCoordHelper
 		material = block.blockMaterial;
 		return (material.isLiquid() || !material.isReplaceable());
 	}
+	
+	public static Point3D findSafeCube(World world, int x, int startY, int z, boolean searchDown)
+	{
+		// Search for a 3x3x3 cube of air with blocks underneath
+		// We can also match against a 3x2x3 box with 
+		// We shift the search area into the bounds of a chunk for the sake of simplicity,
+		// so that we don't need to worry about working across chunks.
+		
+		int localX = x < 0 ? (x % 16) + 16 : (x % 16);
+		int localZ = z < 0 ? (z % 16) + 16 : (z % 16);
+		int cornerX = x - localX;
+		int cornerZ = z - localZ;
+		localX = MathHelper.clamp_int(localX, 1, 14);
+		localZ = MathHelper.clamp_int(localZ, 1, 14);
+		
+		Chunk chunk = world.getChunkProvider().loadChunk(x >> 4, z >> 4);
+		
+		int layers = 0;
+		int height = world.getActualHeight();
+		int y, dx, dz, blockID;
+		boolean filled;
+		Block block;
+		Point3D location = null;
+		
+		if (searchDown)
+		{
+			/*for (y = startY; y >= 0; y--)
+			{
+				blockID = chunk.getBlockID(localX, y, localZ);
+				
+			}*/
+		}
+		else
+		{
+			// Check if a 3x3 layer of blocks is empty
+			// If we find a layer that contains replaceable blocks, it can
+			// serve as the base where we'll place the player and door.
+			for (y = Math.max(startY, 0); y < height; y++)
+			{
+				filled = false;
+				for (dx = -1; dx <= 1 && !filled; dx++)
+				{
+					for (dz = -1; dz <= 1 && !filled; dz++)
+					{
+						blockID = chunk.getBlockID(localX  + dx, y, localZ + dz);
+						if (blockID != 0)
+						{
+							block = Block.blocksList[blockID];
+							if (block != null && !block.blockMaterial.isReplaceable())
+							{
+								filled = true;
+							}
+							layers = 0;
+						}
+					}
+				}
+				if (!filled)
+				{
+					layers++;
+					if (layers == 3)
+					{
+						location = new Point3D(localX + cornerX, y - 2, localZ + cornerZ);
+						break;
+					}
+				}
+			}
+		}
+
+		return location;
+	}
 
 	public static int adjustDestinationY(int y, int worldHeight, int entranceY, int dungeonHeight)
 	{