1 files changed, 144 insertions, 0 deletions

diff --git a/src/Items/ItemEyeOfEnder.h b/src/Items/ItemEyeOfEnder.h
index 3849feb00..6a636cb12 100644
--- a/src/Items/ItemEyeOfEnder.h
+++ b/src/Items/ItemEyeOfEnder.h
@@ -46,6 +46,11 @@ public:
 					{
 						a_Player->GetInventory().RemoveOneEquippedItem();
 					}
+
+					cChunkInterface ChunkInterface(a_World->GetChunkMap());
+
+					// Try to spawn portal:
+					FindAndSetPortal(a_ClickedBlockPos, FacingMeta & 3, ChunkInterface, *a_World);
 					return true;
 				}
 			}
@@ -58,6 +63,145 @@ public:
 		return false;
 	}
 
+
+
+
+	/** Returns false if portal cannot be made, true if portal was made. */
+	static bool FindAndSetPortal(Vector3i a_FirstFrame, NIBBLETYPE a_Direction, cChunkInterface & a_ChunkInterface, cWorldInterface & a_WorldInterface)
+	{
+		/*
+		PORTAL FINDING ALGORITH
+		=======================
+		- Get clicked base block
+		- Check diagonally (clockwise) for another portal block
+			- if exists, and has eye, Continue. Abort if any are facing the wrong direction.
+			- if doesn't exist, check horizontally (the block to the left of this block). Abort if there is no horizontal block.
+		- After a corner has been met, traverse the portal clockwise, ensuring valid portal frames connect the rectangle.
+		- Track the NorthWest Corner, and the dimensions.
+		- If dimensions are valid, create the portal.
+		*/
+
+		static_assert((E_META_END_PORTAL_FRAME_ZM - E_META_END_PORTAL_FRAME_XM) == 1, "Should be going clockwise");
+
+		const int MIN_PORTAL_WIDTH = 3;
+		const int MAX_PORTAL_WIDTH = 4;
+
+		// Directions to use for the clockwise traversal.
+		static const Vector3i Left[] =
+		{
+			{ 1, 0,  0},  // 0, South, left block is East  / XP
+			{ 0, 0,  1},  // 1, West,  left block is South / ZP
+			{-1, 0,  0},  // 2, North, left block is West  / XM
+			{ 0, 0, -1},  // 3, East,  left block is North / ZM
+		};
+		static const Vector3i LeftForward[] =
+		{
+			{ 1, 0,  1},  // 0, South, left block is SouthEast / XP ZP
+			{-1, 0,  1},  // 1, West,  left block is SouthWest / XM ZP
+			{-1, 0, -1},  // 2, North, left block is NorthWest / XM ZM
+			{ 1, 0, -1},  // 3, East,  left block is NorthEast / XP ZM
+		};
+
+
+		int EdgesComplete = -1;  // We start search _before_ finding the first edge
+		Vector3i NorthWestCorner;
+		int EdgeWidth[4] = { 1, 1, 1, 1 };
+		NIBBLETYPE CurrentDirection = a_Direction;
+		Vector3i CurrentPos = a_FirstFrame;
+
+		// Scan clockwise until we have seen all 4 edges
+		while (EdgesComplete < 4)
+		{
+			// Check if we are at a corner
+			Vector3i NextPos = CurrentPos + LeftForward[CurrentDirection];
+			if (IsPortalFrame(a_ChunkInterface.GetBlock(NextPos)))
+			{
+				// We have found the corner, move clockwise to next edge
+				if (CurrentDirection == E_META_END_PORTAL_FRAME_XP)
+				{
+					// We are on the NW (XM, ZM) Corner
+					// Relative to the previous frame, the portal should appear to the right of this portal frame.
+					NorthWestCorner = NextPos - Left[CurrentDirection];
+				}
+
+				if (EdgesComplete == -1)
+				{
+					// Reset current width, we will revisit it last
+					EdgeWidth[CurrentDirection] = 1;
+				}
+
+				// Rotate 90 degrees clockwise
+				CurrentDirection = (CurrentDirection + 1) % 4;
+				EdgesComplete++;
+			}
+			else
+			{
+				// We are not at a corner, keep walking the edge
+				NextPos = CurrentPos + Left[CurrentDirection];
+
+				EdgeWidth[CurrentDirection]++;
+				if (EdgeWidth[CurrentDirection] > MAX_PORTAL_WIDTH)
+				{
+					// Don't build a portal that is too long.
+					return false;
+				}
+			}
+
+			if (!IsValidFrameAtPos(a_ChunkInterface, NextPos, CurrentDirection))
+			{
+				// Neither the edge nor the corner are valid portal blocks.
+				return false;
+			}
+
+			CurrentPos = NextPos;
+		}
+
+		if ((EdgeWidth[0] != EdgeWidth[2]) || (EdgeWidth[1] != EdgeWidth[3]))
+		{
+			// Mismatched Portal Dimensions.
+			return false;
+		}
+		if ((EdgeWidth[0] < MIN_PORTAL_WIDTH) || (EdgeWidth[1] < MIN_PORTAL_WIDTH))
+		{
+			// Portal too small.
+			return false;
+		}
+
+		for (int i = 0; i < EdgeWidth[0]; i++)
+		{
+			for (int j = 0; j < EdgeWidth[1]; j++)
+			{
+				a_ChunkInterface.SetBlock(NorthWestCorner.x + i, NorthWestCorner.y, NorthWestCorner.z + j, E_BLOCK_END_PORTAL, 0);
+			}
+		}
+		return true;
+	}
+
+
+
+
+
+	/** Return true if this block is a portal frame, has an eye, and is facing the correct direction. */
+	static bool IsValidFrameAtPos(cChunkInterface & a_ChunkInterface, Vector3i a_BlockPos, NIBBLETYPE a_ShouldFace)
+	{
+		BLOCKTYPE BlockType;
+		NIBBLETYPE BlockMeta;
+
+		return (
+			a_ChunkInterface.GetBlockTypeMeta(a_BlockPos, BlockType, BlockMeta) &&
+			(BlockType == E_BLOCK_END_PORTAL_FRAME) &&
+			(BlockMeta == (a_ShouldFace | E_META_END_PORTAL_FRAME_EYE))
+		);
+	}
+
+
+
+
+	/** Return true if this block is a portal frame. */
+	static bool IsPortalFrame(BLOCKTYPE BlockType)
+	{
+		return (BlockType == E_BLOCK_END_PORTAL_FRAME);
+	}
 } ;