func()

in s2/regioncoverer.go [430:499]

• 52 lines of code
• 16 McCabe index (conditional complexity)

func (c *coverer) normalizeCovering(covering *CellUnion) {
	// If any cells are too small, or don't satisfy levelMod, then replace them with ancestors.
	if c.maxLevel < maxLevel || c.levelMod > 1 {
		for i, ci := range *covering {
			level := ci.Level()
			newLevel := c.adjustLevel(minInt(level, c.maxLevel))
			if newLevel != level {
				(*covering)[i] = ci.Parent(newLevel)
			}
		}
	}
	// Sort the cells and simplify them.
	covering.Normalize()

	// Make sure that the covering satisfies minLevel and levelMod,
	// possibly at the expense of satisfying MaxCells.
	if c.minLevel > 0 || c.levelMod > 1 {
		covering.Denormalize(c.minLevel, c.levelMod)
	}

	// If there are too many cells and the covering is very large, use the
	// RegionCoverer to compute a new covering. (This avoids possible O(n^2)
	// behavior of the simpler algorithm below.)
	excess := len(*covering) - c.maxCells
	if excess <= 0 || c.isCanonical(*covering) {
		return
	}
	if excess*len(*covering) > 10000 {
		rc := NewRegionCoverer()
		(*covering) = rc.Covering(covering)
		return
	}

	// If there are still too many cells, then repeatedly replace two adjacent
	// cells in CellID order by their lowest common ancestor.
	for len(*covering) > c.maxCells {
		bestIndex := -1
		bestLevel := -1
		for i := 0; i+1 < len(*covering); i++ {
			level, ok := (*covering)[i].CommonAncestorLevel((*covering)[i+1])
			if !ok {
				continue
			}
			level = c.adjustLevel(level)
			if level > bestLevel {
				bestLevel = level
				bestIndex = i
			}
		}

		if bestLevel < c.minLevel {
			break
		}

		// Replace all cells contained by the new ancestor cell.
		id := (*covering)[bestIndex].Parent(bestLevel)
		(*covering) = c.replaceCellsWithAncestor(*covering, id)

		// Now repeatedly check whether all children of the parent cell are
		// present, in which case we can replace those cells with their parent.
		for bestLevel > c.minLevel {
			bestLevel -= c.levelMod
			id = id.Parent(bestLevel)
			if !c.containsAllChildren(*covering, id) {
				break
			}
			(*covering) = c.replaceCellsWithAncestor(*covering, id)
		}
	}
}