new: added events.on (and other related commands) to trigger specific actions when an events happens

vendor/github.com/antchfx/xpath/xpath.go

@@ -0,0 +1,157 @@
+package xpath
+
+import (
+	"errors"
+)
+
+// NodeType represents a type of XPath node.
+type NodeType int
+
+const (
+	// RootNode is a root node of the XML document or node tree.
+	RootNode NodeType = iota
+
+	// ElementNode is an element, such as <element>.
+	ElementNode
+
+	// AttributeNode is an attribute, such as id='123'.
+	AttributeNode
+
+	// TextNode is the text content of a node.
+	TextNode
+
+	// CommentNode is a comment node, such as <!-- my comment -->
+	CommentNode
+
+	// allNode is any types of node, used by xpath package only to predicate match.
+	allNode
+)
+
+// NodeNavigator provides cursor model for navigating XML data.
+type NodeNavigator interface {
+	// NodeType returns the XPathNodeType of the current node.
+	NodeType() NodeType
+
+	// LocalName gets the Name of the current node.
+	LocalName() string
+
+	// Prefix returns namespace prefix associated with the current node.
+	Prefix() string
+
+	// Value gets the value of current node.
+	Value() string
+
+	// Copy does a deep copy of the NodeNavigator and all its components.
+	Copy() NodeNavigator
+
+	// MoveToRoot moves the NodeNavigator to the root node of the current node.
+	MoveToRoot()
+
+	// MoveToParent moves the NodeNavigator to the parent node of the current node.
+	MoveToParent() bool
+
+	// MoveToNextAttribute moves the NodeNavigator to the next attribute on current node.
+	MoveToNextAttribute() bool
+
+	// MoveToChild moves the NodeNavigator to the first child node of the current node.
+	MoveToChild() bool
+
+	// MoveToFirst moves the NodeNavigator to the first sibling node of the current node.
+	MoveToFirst() bool
+
+	// MoveToNext moves the NodeNavigator to the next sibling node of the current node.
+	MoveToNext() bool
+
+	// MoveToPrevious moves the NodeNavigator to the previous sibling node of the current node.
+	MoveToPrevious() bool
+
+	// MoveTo moves the NodeNavigator to the same position as the specified NodeNavigator.
+	MoveTo(NodeNavigator) bool
+}
+
+// NodeIterator holds all matched Node object.
+type NodeIterator struct {
+	node  NodeNavigator
+	query query
+}
+
+// Current returns current node which matched.
+func (t *NodeIterator) Current() NodeNavigator {
+	return t.node
+}
+
+// MoveNext moves Navigator to the next match node.
+func (t *NodeIterator) MoveNext() bool {
+	n := t.query.Select(t)
+	if n != nil {
+		if !t.node.MoveTo(n) {
+			t.node = n.Copy()
+		}
+		return true
+	}
+	return false
+}
+
+// Select selects a node set using the specified XPath expression.
+// This method is deprecated, recommend using Expr.Select() method instead.
+func Select(root NodeNavigator, expr string) *NodeIterator {
+	exp, err := Compile(expr)
+	if err != nil {
+		panic(err)
+	}
+	return exp.Select(root)
+}
+
+// Expr is an XPath expression for query.
+type Expr struct {
+	s string
+	q query
+}
+
+type iteratorFunc func() NodeNavigator
+
+func (f iteratorFunc) Current() NodeNavigator {
+	return f()
+}
+
+// Evaluate returns the result of the expression.
+// The result type of the expression is one of the follow: bool,float64,string,NodeIterator).
+func (expr *Expr) Evaluate(root NodeNavigator) interface{} {
+	val := expr.q.Evaluate(iteratorFunc(func() NodeNavigator { return root }))
+	switch val.(type) {
+	case query:
+		return &NodeIterator{query: expr.q.Clone(), node: root}
+	}
+	return val
+}
+
+// Select selects a node set using the specified XPath expression.
+func (expr *Expr) Select(root NodeNavigator) *NodeIterator {
+	return &NodeIterator{query: expr.q.Clone(), node: root}
+}
+
+// String returns XPath expression string.
+func (expr *Expr) String() string {
+	return expr.s
+}
+
+// Compile compiles an XPath expression string.
+func Compile(expr string) (*Expr, error) {
+	if expr == "" {
+		return nil, errors.New("expr expression is nil")
+	}
+	qy, err := build(expr)
+	if err != nil {
+		return nil, err
+	}
+	return &Expr{s: expr, q: qy}, nil
+}
+
+// MustCompile compiles an XPath expression string and ignored error.
+func MustCompile(expr string) *Expr {
+	exp, err := Compile(expr)
+	if err != nil {
+		return nil
+	}
+	return exp
+}