package workflow

// Splits a flat map representing a graph's parent > children relationships
// into an ordered slice of levels.
func SplitFlatTreeIntoGroups(flatTree map[string][]string) [][]string {
	type TreeNode struct {
		name  string
		level int
	}

	nodes := map[string]TreeNode{}

	deepestLevel := 0
	next := []string{""}

	for len(next) > 0 {
		current := next[0]
		next = next[1:]
		children := flatTree[current]

		currentNode, found := nodes[current]

		// The negative value represents the graph root.
		currentLevel := -1

		if found {
			currentLevel = currentNode.level
		}

		for _, child := range children {
			nodes[child] = TreeNode{
				name:  child,
				level: currentLevel + 1,
			}
		}

		if deepestLevel < currentLevel {
			deepestLevel = currentLevel
		}

		next = append(next, children...)
	}

	levels := make([][]string, deepestLevel+1)

	for _, node := range nodes {
		levels[node.level] = append(levels[node.level], node.name)
	}

	return levels
}