tree

Documentation

Overview

Package tree provides functions for performing operations related to tree data structures.

A website's page structure can be easily depicted as a tree, so these functions are used for storing pages in a tree structure as well as reading pages from it.

The package exclusively uses terminology for tree data structures: https://en.wikipedia.org/wiki/Tree_(data_structure)#Terminology

Index

• Constants
• Variables
• func CreateNode(path string, root Node, node Node) error
• func Edges(path string) []string
• func IsRootPath(path string) bool
• func IsValidPath(path string) bool
• func Walk(root Node, walkFn func(path string, node Node) error, maxDepth int) error
• func WalkPath(path string, root Node, walkFn func(node Node) error) error
• type Node
  • func ResolveNode(path string, root Node) (Node, error)
  • func ResolveOrInitNode(path string, root Node) (Node, error)

Constants

const (
	// RootPath represents the path of the root node in a tree.
	RootPath string = "/"
)

Variables

var (
	// ErrInvalidPath indicates that a path is not formally valid.
	ErrInvalidPath = errors.New("path is not a valid tree path")
	// ErrEdgeNotFound indicates that an edge cannot be found.
	ErrEdgeNotFound = errors.New("edge does not exist")
)

Functions

func CreateNode

func CreateNode(path string, root Node, node Node) error

CreateNode stores a node under a given tree path. It follows the path starting from the root node and creates all required children using Node.CreateChild if they don't exist yet.

Passing an invalid tree path to CreateNode will lead to undefined behavior. Check the path using IsValidPath first.

func Edges

func Edges(path string) []string

Edges returns the tree edges for a path. Those edges will be used by the tree package to traverse a node's children.

Passing an invalid path leads to undefined behavior. Check the path's validity using IsValidPath first.

func IsRootPath

func IsRootPath(path string) bool

IsRootPath checks if a path corresponds to a tree's root path.

func IsValidPath

func IsValidPath(path string) bool

IsValidPath checks if a path is considered valid by the tree package, meaning that it can be used in functions like CreateNode or ResolveNode.

func Walk

func Walk(root Node, walkFn func(path string, node Node) error, maxDepth int) error

Walk traverses all nodes in a tree, starting from the root route. For each node, walkFn will be invoked with the current node and the tree path for that node.

maxDepth is counted starting from 0, which represents the root node. Set maxDepth to -1 to walk down the entire tree.

As soon as an error arises in one of the walkFns, the error is handed up to the caller.

func WalkPath

func WalkPath(path string, root Node, walkFn func(node Node) error) error

WalkPath walks all nodes within a tree path and invokes the given walkFn on each node.

In contrast to Walk, WalkPath does not invoke the walkFn for sibling nodes with the same depth because they're not within the tree path. If you desire to take sibling nodes into account, use Walk with the depth of your path instead.

Types

type Node

type Node interface {
	// Children should return a map of child nodes. The map keys are
	// expected to be edge names that link the node to its child.
	Children() map[string]Node

	// InitChild should initialize a new child node that is linked
	// to the current node via the given edge name.
	//
	// This implies that a node initialized with InitChild can be
	// loaded with Children afterwards, and is available under the
	// edge name passed to CreateChild.
	InitChild(edge string)

	// CreateChild should create a new child node that is linked to
	// the current node via the given edge name. Its behavior should
	// be analogous to InitChild.
	CreateChild(edge string, child Node)
}

Node represents a tree node which contains a value and has zero or more child nodes connected via edges.

func ResolveNode

func ResolveNode(path string, root Node) (Node, error)

ResolveNode follows the given path starting from the root node and traverses all child nodes until the last edge is reached.

Returns the node linked to the last edge in the path or an error if it cannot be resolved. Passing an invalid tree path to ResolveNode will lead to undefined behavior. Check the path using IsValidPath first.

func ResolveOrInitNode

func ResolveOrInitNode(path string, root Node) (Node, error)

ResolveOrInitNode resolves the node under the given tree path or, if it doesn't exist yet, initializes a new node and returns that new node.

This is convenient in situations where you would create a new node if it does not exist yet or load it from the tree if it does exist - but without the need to try ResolveNode first and call CreateNode if the node cannot be resolved.

ResolveOrInitNode creates the entire path including all edges.