up3

server/block/cube/face.go

@@ -0,0 +1,124 @@
+package cube
+
+const (
+	// FaceDown represents the bottom face of a block.
+	FaceDown Face = iota
+	// FaceUp represents the top face of a block.
+	FaceUp
+	// FaceNorth represents the north face of a block.
+	FaceNorth
+	// FaceSouth represents the south face of a block.
+	FaceSouth
+	// FaceWest represents the west face of the block.
+	FaceWest
+	// FaceEast represents the east face of the block.
+	FaceEast
+)
+
+// Face represents the face of a block or entity.
+type Face int
+
+// Direction converts the Face to a Direction and returns it, assuming the Face
+// is horizontal and not FaceUp or FaceDown.
+func (f Face) Direction() Direction {
+	return Direction(f - 2)
+}
+
+// Opposite returns the opposite Face. FaceDown will return FaceUp, FaceNorth
+// will return FaceSouth, FaceWest will return FaceEast, and vice versa.
+func (f Face) Opposite() Face {
+	switch f {
+	default:
+		return FaceUp
+	case FaceUp:
+		return FaceDown
+	case FaceNorth:
+		return FaceSouth
+	case FaceSouth:
+		return FaceNorth
+	case FaceWest:
+		return FaceEast
+	case FaceEast:
+		return FaceWest
+	}
+}
+
+// Axis returns the Axis the face is facing. FaceEast and FaceWest correspond
+// to the X Axis, FaceNorth and FaceSouth to the Z Axis and FaceUp and FaceDown
+// to the Y Axis.
+func (f Face) Axis() Axis {
+	switch f {
+	default:
+		return Y
+	case FaceEast, FaceWest:
+		return X
+	case FaceNorth, FaceSouth:
+		return Z
+	}
+}
+
+// RotateRight rotates the face 90 degrees to the right horizontally
+// (clockwise) and returns the new Face.
+func (f Face) RotateRight() Face {
+	switch f {
+	case FaceNorth:
+		return FaceEast
+	case FaceEast:
+		return FaceSouth
+	case FaceSouth:
+		return FaceWest
+	case FaceWest:
+		return FaceNorth
+	}
+	return f
+}
+
+// RotateLeft rotates the face 90 degrees to the left horizontally
+// (counter-clockwise) and returns the new Face.
+func (f Face) RotateLeft() Face {
+	switch f {
+	case FaceNorth:
+		return FaceWest
+	case FaceEast:
+		return FaceNorth
+	case FaceSouth:
+		return FaceEast
+	case FaceWest:
+		return FaceSouth
+	}
+	return f
+}
+
+// String returns the Face as a string.
+func (f Face) String() string {
+	switch f {
+	case FaceUp:
+		return "up"
+	case FaceDown:
+		return "down"
+	case FaceNorth:
+		return "north"
+	case FaceSouth:
+		return "south"
+	case FaceWest:
+		return "west"
+	case FaceEast:
+		return "east"
+	}
+	panic("invalid face")
+}
+
+// Faces returns a list of all faces, starting with down, then up, then north
+// to west.
+func Faces() []Face {
+	return faces[:]
+}
+
+// HorizontalFaces returns a list of all horizontal faces, from north to west.
+func HorizontalFaces() []Face {
+	return hFaces[:]
+}
+
+var hFaces = [...]Face{FaceNorth, FaceEast, FaceSouth, FaceWest}
+
+var faces = [...]Face{FaceDown, FaceUp, FaceNorth, FaceEast, FaceSouth, FaceWest}