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package ast
import "io"
// Print prints the given AST node to the given output. This operation
// basically walks the AST and, for each TerminalNode, prints the node's
// leading comments, leading whitespace, the node's raw text, and then
// any trailing comments. If the given node is a *FileNode, it will then
// also print the file's FinalComments and FinalWhitespace.
func Print(w io.Writer, node Node) error {
sw, ok := w.(stringWriter)
if !ok {
sw = &strWriter{w}
}
var err error
Walk(node, func(n Node) (bool, VisitFunc) {
if err != nil {
return false, nil
}
token, ok := n.(TerminalNode)
if !ok {
return true, nil
}
err = printComments(sw, token.LeadingComments())
if err != nil {
return false, nil
}
_, err = sw.WriteString(token.LeadingWhitespace())
if err != nil {
return false, nil
}
_, err = sw.WriteString(token.RawText())
if err != nil {
return false, nil
}
err = printComments(sw, token.TrailingComments())
return false, nil
})
if err != nil {
return err
}
if file, ok := node.(*FileNode); ok {
err = printComments(sw, file.FinalComments)
if err != nil {
return err
}
_, err = sw.WriteString(file.FinalWhitespace)
return err
}
return nil
}
func printComments(sw stringWriter, comments []Comment) error {
for _, comment := range comments {
if _, err := sw.WriteString(comment.LeadingWhitespace); err != nil {
return err
}
if _, err := sw.WriteString(comment.Text); err != nil {
return err
}
}
return nil
}
// many io.Writer impls also provide a string-based method
type stringWriter interface {
WriteString(s string) (n int, err error)
}
// adapter, in case the given writer does NOT provide a string-based method
type strWriter struct {
io.Writer
}
func (s *strWriter) WriteString(str string) (int, error) {
if str == "" {
return 0, nil
}
return s.Write([]byte(str))
}
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