func()

in s2/cell.go [487:547]

• 45 lines of code
• 11 McCabe index (conditional complexity)

func (c Cell) distanceInternal(targetXYZ Point, toInterior bool) s1.ChordAngle {
	// All calculations are done in the (u,v,w) coordinates of this cell's face.
	target := faceXYZtoUVW(int(c.face), targetXYZ)

	// Compute dot products with all four upward or rightward-facing edge
	// normals. dirIJ is the dot product for the edge corresponding to axis
	// I, endpoint J. For example, dir01 is the right edge of the Cell
	// (corresponding to the upper endpoint of the u-axis).
	dir00 := target.X - target.Z*c.uv.X.Lo
	dir01 := target.X - target.Z*c.uv.X.Hi
	dir10 := target.Y - target.Z*c.uv.Y.Lo
	dir11 := target.Y - target.Z*c.uv.Y.Hi
	inside := true
	if dir00 < 0 {
		inside = false // Target is to the left of the cell
		if c.vEdgeIsClosest(target, false) {
			return edgeDistance(-dir00, c.uv.X.Lo)
		}
	}
	if dir01 > 0 {
		inside = false // Target is to the right of the cell
		if c.vEdgeIsClosest(target, true) {
			return edgeDistance(dir01, c.uv.X.Hi)
		}
	}
	if dir10 < 0 {
		inside = false // Target is below the cell
		if c.uEdgeIsClosest(target, false) {
			return edgeDistance(-dir10, c.uv.Y.Lo)
		}
	}
	if dir11 > 0 {
		inside = false // Target is above the cell
		if c.uEdgeIsClosest(target, true) {
			return edgeDistance(dir11, c.uv.Y.Hi)
		}
	}
	if inside {
		if toInterior {
			return s1.ChordAngle(0)
		}
		// Although you might think of Cells as rectangles, they are actually
		// arbitrary quadrilaterals after they are projected onto the sphere.
		// Therefore the simplest approach is just to find the minimum distance to
		// any of the four edges.
		return minChordAngle(edgeDistance(-dir00, c.uv.X.Lo),
			edgeDistance(dir01, c.uv.X.Hi),
			edgeDistance(-dir10, c.uv.Y.Lo),
			edgeDistance(dir11, c.uv.Y.Hi))
	}

	// Otherwise, the closest point is one of the four cell vertices. Note that
	// it is *not* trivial to narrow down the candidates based on the edge sign
	// tests above, because (1) the edges don't meet at right angles and (2)
	// there are points on the far side of the sphere that are both above *and*
	// below the cell, etc.
	return minChordAngle(c.vertexChordDist2(target, false, false),
		c.vertexChordDist2(target, true, false),
		c.vertexChordDist2(target, false, true),
		c.vertexChordDist2(target, true, true))
}