visitor.go

// Copyright (c) 2020 Uber Technologies, Inc.
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// THE SOFTWARE.

package ast

// Walker provides acccess to information about the state of the AST walker.
type Walker interface {
	// Ancestors returns a copy of a slice containing all the ancestor nodes
	// of the current node. The first node in the slice is the immediate
	// parent of the current node, the node after that its parent, and so on.
	Ancestors() []Node

	// Parent returns the parent node of the current node or nil if this node
	// does not have a parent node.
	Parent() Node
}

//go:generate mockgen -destination mock_visitor_test.go -package ast -self_package go.uber.org/thriftrw/ast go.uber.org/thriftrw/ast Visitor

// Visitor walks an AST. The Visit function is called on each node of the AST.
// If the function returns a non-nil visitor for any node, that visitor is
// called on the chilren of that node.
type Visitor interface {
	Visit(w Walker, n Node) Visitor
}

// VisitorFunc is a Visitor which visits all the nodes of the AST.
type VisitorFunc func(Walker, Node)

// Visit the given node and its descendants.
func (f VisitorFunc) Visit(w Walker, n Node) Visitor {
	f(w, n)
	return f
}

// MultiVisitor merges the given visitors into a single Visitor.
func MultiVisitor(visitors ...Visitor) Visitor {
	return multiVisitor(visitors)
}

type multiVisitor []Visitor

func (vs multiVisitor) Visit(w Walker, n Node) Visitor {
	newVS := make(multiVisitor, 0, len(vs))
	for _, v := range vs {
		if v := v.Visit(w, n); v != nil {
			newVS = append(newVS, v)
		}
	}
	return newVS
}